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[Guile-commits] GNU Guile branch, master, updated. v2.1.0-18-g510ca12


From: Andy Wingo
Subject: [Guile-commits] GNU Guile branch, master, updated. v2.1.0-18-g510ca12
Date: Fri, 31 May 2013 14:44:08 +0000

This is an automated email from the git hooks/post-receive script. It was
generated because a ref change was pushed to the repository containing
the project "GNU Guile".

http://git.savannah.gnu.org/cgit/guile.git/commit/?id=510ca12687b2137031d537be7b99bcf6d5306e41

The branch, master has been updated
       via  510ca12687b2137031d537be7b99bcf6d5306e41 (commit)
      from  1701a68920cf1b83d320711a4d47806ba089c148 (commit)

Those revisions listed above that are new to this repository have
not appeared on any other notification email; so we list those
revisions in full, below.

- Log -----------------------------------------------------------------
commit 510ca12687b2137031d537be7b99bcf6d5306e41
Author: Andy Wingo <address@hidden>
Date:   Thu May 23 14:52:29 2013 +0200

    add new rtl vm
    
    * libguile/vm-engine.c (rtl_vm_engine): Add new VM.
      (vm_engine): Add support for calling RTL programs.
    
    * libguile/tags.h (scm_tc7_rtl_program): New type for procedures that
      run on the new VM.
    * libguile/evalext.c (scm_self_evaluating_p):
    * libguile/goops.c (scm_class_of):
    * libguile/print.c (iprin1):
    * libguile/procprop.c (scm_i_procedure_arity):
    * libguile/procs.c (scm_procedure_p): Add hooks for the new tc7.
    
    * libguile/programs.h:
    * libguile/programs.c (scm_make_rtl_program, scm_i_rtl_program_print)
      (scm_rtl_program_p, scm_rtl_program_code):
    * module/system/vm/program.scm: Add constructors and accessors for the
      new "RTL programs".
    
    * libguile/vm.c (rtl_boot_continuation): Define a boot program.
      (rtl_apply, rtl_values): New static RTL programs.
    
    * libguile/frames.c (scm_frame_num_locals): Adapt for frames of RTL
      programs.
    
    * libguile/frames.h: Add description of RTL frames.
    
    * libguile/Makefile.am: Add rules to generate vm-operations.h.
    * .gitignore: Ignore vm-operations.h.
    * module/system/vm/instruction.scm:
    * libguile/instructions.c:
    * libguile/instructions.h: Use vm-operations.h to define enumerated
      values for the new RTL opcodes.  Define some helper macros to pack and
      unpack 32-bit instruction words.
      (rtl-instruction-list): New function, exported by (system vm
      instruction).
    
    * libguile/objcodes.c: Wire up the bits needed to detect the new RTL
      bytecode and load it, as appropriate.

-----------------------------------------------------------------------

Summary of changes:
 .gitignore                       |    1 +
 libguile/Makefile.am             |   11 +-
 libguile/evalext.c               |    3 +-
 libguile/frames.c                |   12 +-
 libguile/frames.h                |   33 +-
 libguile/goops.c                 |    3 +
 libguile/instructions.c          |  166 ++-
 libguile/instructions.h          |   57 +-
 libguile/objcodes.c              |   54 +-
 libguile/print.c                 |    3 +
 libguile/procprop.c              |    8 +
 libguile/procs.c                 |    3 +-
 libguile/programs.c              |   63 +-
 libguile/programs.h              |   27 +-
 libguile/tags.h                  |    2 +-
 libguile/vm-engine.c             | 3170 +++++++++++++++++++++++++++++++++++++-
 libguile/vm.c                    |   32 +
 module/system/vm/instruction.scm |    5 +-
 module/system/vm/program.scm     |    2 +
 19 files changed, 3626 insertions(+), 29 deletions(-)

diff --git a/.gitignore b/.gitignore
index 90bacbe..b136c7a 100644
--- a/.gitignore
+++ b/.gitignore
@@ -156,3 +156,4 @@ INSTALL
 /test-suite/standalone/test-smob-mark
 /test-suite/standalone/test-scm-values
 /test-suite/standalone/test-scm-to-latin1-string
+/libguile/vm-operations.h
diff --git a/libguile/Makefile.am b/libguile/Makefile.am
index 7c7a34b..ce437e4 100644
--- a/libguile/Makefile.am
+++ b/libguile/Makefile.am
@@ -433,9 +433,18 @@ DOT_I_FILES = vm-i-system.i vm-i-scheme.i vm-i-loader.i
 .c.i:
        $(AM_V_GEN)$(GREP) '^VM_DEFINE' $< > $@
 
+vm-operations.h: vm-engine.c
+       @echo '/* This file was generated automatically from $<; do not' > $@
+       @echo '   edit.  See the source file for copyright information.  */' >> 
$@
+       @echo '' >> $@
+       @echo "#define FOR_EACH_VM_OPERATION(M) \\" >> $@
+       $(AM_V_GEN)$(GREP) '^ *VM_DEFINE_OP' $< \
+       | sed -e 's,VM_DEFINE_OP (\(.*\)).*,  M (\1) \\,' >> $@
+       @echo '' >> $@
+
 BUILT_SOURCES = cpp-E.c cpp-SIG.c libpath.h \
     scmconfig.h \
-    $(DOT_I_FILES) $(DOT_X_FILES) $(EXTRA_DOT_X_FILES)
+    $(DOT_I_FILES) vm-operations.h $(DOT_X_FILES) $(EXTRA_DOT_X_FILES)
 
 # Force the generation of `guile-procedures.texi' because the top-level
 # Makefile expects it to be built.
diff --git a/libguile/evalext.c b/libguile/evalext.c
index 3e04a7a..f955cee 100644
--- a/libguile/evalext.c
+++ b/libguile/evalext.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998,1999,2000,2001,2002,2003, 2006, 2008, 2009, 2010, 2011 
Free Software Foundation, Inc.
+/* Copyright (C) 1998,1999,2000,2001,2002,2003, 2006, 2008, 2009, 2010, 2011, 
2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -87,6 +87,7 @@ SCM_DEFINE (scm_self_evaluating_p, "self-evaluating?", 1, 0, 
0,
        case scm_tc7_number:
        case scm_tc7_string:
        case scm_tc7_smob:
+       case scm_tc7_rtl_program:
        case scm_tc7_program:
        case scm_tc7_bytevector:
        case scm_tc7_array:
diff --git a/libguile/frames.c b/libguile/frames.c
index 0338d18..8ce5aa0 100644
--- a/libguile/frames.c
+++ b/libguile/frames.c
@@ -129,11 +129,21 @@ SCM_DEFINE (scm_frame_num_locals, "frame-num-locals", 1, 
0, 0,
            "")
 #define FUNC_NAME s_scm_frame_num_locals
 {
-  SCM *sp, *p;
+  SCM *fp, *sp, *p;
   unsigned int n = 0;
 
   SCM_VALIDATE_VM_FRAME (1, frame);
 
+  fp = SCM_VM_FRAME_FP (frame);
+  sp = SCM_VM_FRAME_SP (frame);
+  p = SCM_FRAME_STACK_ADDRESS (SCM_VM_FRAME_FP (frame));
+
+  if (SCM_RTL_PROGRAM_P (fp[-1]))
+    /* The frame size of an RTL program is fixed, except in the case of
+       passing a wrong number of arguments to the program.  So we do
+       need to use an SP for determining the number of locals.  */
+    return scm_from_uint32 (sp + 1 - p);
+
   sp = SCM_VM_FRAME_SP (frame);
   p = SCM_FRAME_STACK_ADDRESS (SCM_VM_FRAME_FP (frame));
   while (p <= sp)
diff --git a/libguile/frames.h b/libguile/frames.h
index 71d5b12..9105311 100644
--- a/libguile/frames.h
+++ b/libguile/frames.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012 Free Software Foundation, Inc.
  * * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -100,6 +100,37 @@ struct scm_vm_frame
 
 
 /*
+ * RTL frames
+ */
+
+/* The frame format for the new RTL programs is almost like that for the
+   stack-vm programs.  They differ in their handling of MV returns,
+   however.  For RTL, every call is an MV call: every call has an MVRA.
+   Unlike the stack-vm programs, the MVRA for RTL programs is computable
+   from the RA -- it's always one word (4 bytes) before the RA.
+
+   Until we completely migrate to the RTL VM, we will also write the
+   MVRA to the stack.
+
+   When an RTL program returns multiple values, it will shuffle them
+   down to start contiguously from slot 0, as for a tail call.  This
+   means that when the caller goes to access them, there are 2 or 3
+   empty words between the top of the caller stack and the bottom of the
+   values, corresponding to the frame that was just popped.
+*/
+
+#define SCM_FRAME_RTL_RETURN_ADDRESS(fp)                \
+  ((scm_t_uint32 *) SCM_FRAME_RETURN_ADDRESS (fp))
+#define SCM_FRAME_SET_RTL_RETURN_ADDRESS(fp, ip)        \
+  SCM_FRAME_SET_RETURN_ADDRESS (fp, (scm_t_uint8 *) (ip))
+
+#define SCM_FRAME_RTL_MV_RETURN_ADDRESS(fp)             \
+  ((scm_t_uint32 *) SCM_FRAME_MV_RETURN_ADDRESS (fp))
+#define SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS(fp, ip)     \
+  SCM_FRAME_SET_MV_RETURN_ADDRESS (fp, (scm_t_uint8 *) (ip))
+
+
+/*
  * Heap frames
  */
 
diff --git a/libguile/goops.c b/libguile/goops.c
index 355e5ef..74ded73 100644
--- a/libguile/goops.c
+++ b/libguile/goops.c
@@ -301,6 +301,9 @@ SCM_DEFINE (scm_class_of, "class-of", 1, 0, 0,
          else
            return scm_class_procedure;
 
+       case scm_tc7_rtl_program:
+          return scm_class_procedure;
+
        case scm_tc7_smob:
          {
            scm_t_bits type = SCM_TYP16 (x);
diff --git a/libguile/instructions.c b/libguile/instructions.c
index f3b8963..08f7cd6 100644
--- a/libguile/instructions.c
+++ b/libguile/instructions.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, 
Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -40,6 +40,83 @@ struct scm_instruction {
   SCM symname;                  /* filled in later */
 };
 
+
+#define OP_HAS_ARITY (1U << 0)
+
+#define FOR_EACH_INSTRUCTION_WORD_TYPE(M)       \
+    M(X32)                                      \
+    M(U8_X24)                                   \
+    M(U8_U24)                                   \
+    M(U8_L24)                                   \
+    M(U8_R24)                                   \
+    M(U8_U8_I16)                                \
+    M(U8_U8_U8_U8)                              \
+    M(U8_U12_U12)                               \
+    M(U32) /* Unsigned. */                      \
+    M(I32) /* Immediate. */                     \
+    M(A32) /* Immediate, high bits. */          \
+    M(B32) /* Immediate, low bits. */           \
+    M(N32) /* Non-immediate. */                 \
+    M(S32) /* Scheme value (indirected). */     \
+    M(L32) /* Label. */                         \
+    M(LO32) /* Label with offset. */            \
+    M(X8_U24)                                   \
+    M(X8_U12_U12)                               \
+    M(X8_R24)                                   \
+    M(X8_L24)                                   \
+    M(B1_X7_L24)                                \
+    M(B1_U7_L24)
+
+#define TYPE_WIDTH 5
+
+enum word_type
+  {
+#define ENUM(type) type,
+    FOR_EACH_INSTRUCTION_WORD_TYPE (ENUM)
+#undef ENUM
+  };
+
+static SCM word_type_symbols[] =
+  {
+#define FALSE(type) SCM_BOOL_F,
+    FOR_EACH_INSTRUCTION_WORD_TYPE (FALSE)
+#undef FALSE
+  };
+
+#define OP(n,type) ((type) << (n*TYPE_WIDTH))
+
+/* The VM_DEFINE_OP macro uses a CPP-based DSL to describe what kinds of
+   arguments each RTL instruction takes.  This piece of code is the only
+   bit that actually interprets that language.  These macro definitions
+   encode the operand types into bits in a 32-bit integer.
+
+   (rtl-instruction-list) parses those encoded values into lists of
+   symbols, one for each 32-bit word that the operator takes.  (system
+   vm rtl) uses those word types to generate assemblers and
+   disassemblers for the instructions.  */
+
+#define OP1(type0) \
+  (OP (0, type0))
+#define OP2(type0, type1) \
+  (OP (0, type0) | OP (1, type1))
+#define OP3(type0, type1, type2) \
+  (OP (0, type0) | OP (1, type1) | OP (2, type2))
+#define OP4(type0, type1, type2, type3) \
+  (OP (0, type0) | OP (1, type1) | OP (2, type2) | OP (3, type3))
+
+#define OP_DST (1 << (TYPE_WIDTH * 5))
+
+#define WORD_TYPE(n, word) \
+  (((word) >> ((n) * TYPE_WIDTH)) & ((1 << TYPE_WIDTH) - 1))
+
+struct scm_rtl_instruction {
+  enum scm_rtl_opcode opcode;  /* opcode */
+  const char *name;            /* instruction name */
+  scm_t_uint32 meta;
+  SCM symname;                  /* filled in later */
+};
+
+
 #define SCM_VALIDATE_LOOKUP_INSTRUCTION(pos, var, cvar)               \
   do {                                                                \
     cvar = scm_lookup_instruction_by_name (var);                      \
@@ -82,6 +159,37 @@ fetch_instruction_table ()
   return table;
 }
 
+static struct scm_rtl_instruction*
+fetch_rtl_instruction_table ()
+{
+  static struct scm_rtl_instruction *table = NULL;
+
+  scm_i_pthread_mutex_lock (&itable_lock);
+  if (SCM_UNLIKELY (!table))
+    {
+      size_t bytes = SCM_VM_NUM_INSTRUCTIONS * sizeof(struct 
scm_rtl_instruction);
+      int i;
+      table = malloc (bytes);
+      memset (table, 0, bytes);
+
+#define INIT(opcode, tag, name_, meta_) table[opcode].name = name_; 
table[opcode].meta = meta_;
+      FOR_EACH_VM_OPERATION (INIT);
+#undef INIT
+
+      for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+        {
+          table[i].opcode = i;
+          if (table[i].name)
+            table[i].symname = scm_from_utf8_symbol (table[i].name);
+          else
+            table[i].symname = SCM_BOOL_F;
+        }
+    }
+  scm_i_pthread_mutex_unlock (&itable_lock);
+
+  return table;
+}
+
 static struct scm_instruction *
 scm_lookup_instruction_by_name (SCM name)
 {
@@ -127,6 +235,57 @@ SCM_DEFINE (scm_instruction_list, "instruction-list", 0, 
0, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_rtl_instruction_list, "rtl-instruction-list", 0, 0, 0,
+           (void),
+           "")
+#define FUNC_NAME s_scm_rtl_instruction_list
+{
+  SCM list = SCM_EOL;
+  int i;
+  struct scm_rtl_instruction *ip = fetch_rtl_instruction_table ();
+  for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+    if (ip[i].name)
+      {
+        scm_t_uint32 meta = ip[i].meta;
+        SCM tail = SCM_EOL;
+        int len;
+
+        /* Format: (name opcode len rest? out br in) */
+
+        if (WORD_TYPE (3, meta))
+          len = 4;
+        else if (WORD_TYPE (2, meta))
+          len = 3;
+        else if (WORD_TYPE (1, meta))
+          len = 2;
+        else if (WORD_TYPE (0, meta))
+          len = 1;
+        else
+          abort ();
+
+        switch (len)
+          {
+          case 4:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (3, meta)], tail);
+          case 3:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (2, meta)], tail);
+          case 2:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (1, meta)], tail);
+          case 1:
+            tail = scm_cons (word_type_symbols[WORD_TYPE (0, meta)], tail);
+          default:
+            tail = scm_cons (scm_from_int (ip[i].opcode), tail);
+            tail = scm_cons (ip[i].symname, tail);
+            break;
+          }
+
+        list = scm_cons (tail, list);
+      }
+
+  return scm_reverse_x (list, SCM_EOL);
+}
+#undef FUNC_NAME
+
 SCM_DEFINE (scm_instruction_p, "instruction?", 1, 0, 0,
            (SCM obj),
            "")
@@ -208,6 +367,11 @@ scm_bootstrap_instructions (void)
                             "scm_init_instructions",
                             (scm_t_extension_init_func)scm_init_instructions,
                             NULL);
+
+#define INIT(type) \
+  word_type_symbols[type] = scm_from_utf8_symbol (#type);
+    FOR_EACH_INSTRUCTION_WORD_TYPE (INIT)
+#undef INIT
 }
 
 void
diff --git a/libguile/instructions.h b/libguile/instructions.h
index a226322..bf27afa 100644
--- a/libguile/instructions.h
+++ b/libguile/instructions.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2012 Free Software Foundation, Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -20,6 +20,59 @@
 #define _SCM_INSTRUCTIONS_H_
 
 #include <libguile.h>
+#include <libguile/vm-operations.h>
+
+enum scm_rtl_opcode
+  {
+#define ENUM(opcode, tag, name, meta) scm_rtl_op_##tag = opcode,
+    FOR_EACH_VM_OPERATION(ENUM)
+#undef ENUM
+  };
+
+#define SCM_PACK_RTL_8_8_8(op,a,b,c) ((op) | ((a) << 8) | ((b) << 16) | ((d) 
<< 24))
+#define SCM_PACK_RTL_8_16(op,a,b) ((op) | ((a) << 8) | ((b) << 16))
+#define SCM_PACK_RTL_16_8(op,a,b) ((op) | ((a) << 16) | ((b) << 24))
+#define SCM_PACK_RTL_24(op,a) ((op) | ((a) << 8))
+
+#define SCM_UNPACK_RTL_8_8_8(op,a,b,c)    \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xff;               \
+      b = (op >> 16) & 0xff;              \
+      c = op >> 24;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_8_16(op,a,b)       \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xff;               \
+      b = op >> 16;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_16_8(op,a,b)       \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xffff;             \
+      b = op >> 24;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_12_12(op,a,b)      \
+  do                                      \
+    {                                     \
+      a = (op >> 8) & 0xfff;              \
+      b = op >> 20;                       \
+    }                                     \
+  while (0)
+
+#define SCM_UNPACK_RTL_24(op,a)           \
+  do                                      \
+    {                                     \
+      a = op >> 8;                        \
+    }                                     \
+  while (0)
 
 #define SCM_VM_NUM_INSTRUCTIONS (1<<8)
 #define SCM_VM_INSTRUCTION_MASK (SCM_VM_NUM_INSTRUCTIONS-1)
@@ -33,6 +86,8 @@ enum scm_opcode {
 #undef VM_INSTRUCTION_TO_OPCODE
 };
 
+SCM_INTERNAL SCM scm_rtl_instruction_list (void);
+
 SCM_API SCM scm_instruction_list (void);
 SCM_API SCM scm_instruction_p (SCM obj);
 SCM_API SCM scm_instruction_length (SCM inst);
diff --git a/libguile/objcodes.c b/libguile/objcodes.c
index 4daba55..734bdde 100644
--- a/libguile/objcodes.c
+++ b/libguile/objcodes.c
@@ -94,7 +94,8 @@ static void register_elf (char *data, size_t len);
 enum bytecode_kind
   {
     BYTECODE_KIND_NONE,
-    BYTECODE_KIND_GUILE_2_0
+    BYTECODE_KIND_GUILE_2_0,
+    BYTECODE_KIND_GUILE_2_2
   };
 
 static SCM
@@ -110,6 +111,10 @@ pointer_to_procedure (enum bytecode_kind bytecode_kind, 
char *ptr)
         objcode = scm_double_cell (tag, (scm_t_bits) ptr, SCM_BOOL_F_BITS, 0);
         return scm_make_program (objcode, SCM_BOOL_F, SCM_UNDEFINED);
       }
+    case BYTECODE_KIND_GUILE_2_2:
+      {
+        return scm_i_make_rtl_program ((scm_t_uint32 *) ptr);
+      }
     case BYTECODE_KIND_NONE:
     default:
       abort ();
@@ -302,29 +307,52 @@ process_dynamic_segment (char *base, Elf_Phdr *dyn_phdr,
           {
             scm_t_uint16 major = dyn[i].d_un.d_val >> 16;
             scm_t_uint16 minor = dyn[i].d_un.d_val & 0xffff;
-            if (major != 0x0200)
-              return "incompatible bytecode kind";
-            if (minor > SCM_OBJCODE_MINOR_VERSION)
-              return "incompatible bytecode version";
-            bytecode_kind = BYTECODE_KIND_GUILE_2_0;
+            switch (major)
+              {
+              case 0x0200:
+                bytecode_kind = BYTECODE_KIND_GUILE_2_0;
+                if (minor > SCM_OBJCODE_MINOR_VERSION)
+                  return "incompatible bytecode version";
+                break;
+              case 0x0202:
+                bytecode_kind = BYTECODE_KIND_GUILE_2_2;
+                if (minor)
+                  return "incompatible bytecode version";
+                break;
+              default:
+                return "incompatible bytecode kind";
+              }
             break;
           }
         }
     }
 
-  if (bytecode_kind != BYTECODE_KIND_GUILE_2_0)
-    return "missing DT_GUILE_RTL_VERSION";
-  if (init)
-    return "unexpected DT_INIT";
-  if ((scm_t_uintptr) entry % 8)
-    return "unaligned DT_GUILE_ENTRY";
   if (!entry)
     return "missing DT_GUILE_ENTRY";
 
+  switch (bytecode_kind)
+    {
+    case BYTECODE_KIND_GUILE_2_0:
+      if (init)
+        return "unexpected DT_INIT";
+      if ((scm_t_uintptr) entry % 8)
+        return "unaligned DT_GUILE_ENTRY";
+      break;
+    case BYTECODE_KIND_GUILE_2_2:
+      if ((scm_t_uintptr) init % 4)
+        return "unaligned DT_INIT";
+      if ((scm_t_uintptr) entry % 4)
+        return "unaligned DT_GUILE_ENTRY";
+      break;
+    case BYTECODE_KIND_NONE:
+    default:
+      return "missing DT_GUILE_RTL_VERSION";
+    }
+
   if (gc_root)
     GC_add_roots (gc_root, gc_root + gc_root_size);
 
-  *init_out = SCM_BOOL_F;
+  *init_out = init ? pointer_to_procedure (bytecode_kind, init) : SCM_BOOL_F;
   *entry_out = pointer_to_procedure (bytecode_kind, entry);
   return NULL;
 }
diff --git a/libguile/print.c b/libguile/print.c
index 6524091..f912a35 100644
--- a/libguile/print.c
+++ b/libguile/print.c
@@ -656,6 +656,9 @@ iprin1 (SCM exp, SCM port, scm_print_state *pstate)
        case scm_tc7_variable:
          scm_i_variable_print (exp, port, pstate);
          break;
+       case scm_tc7_rtl_program:
+         scm_i_rtl_program_print (exp, port, pstate);
+         break;
        case scm_tc7_program:
          scm_i_program_print (exp, port, pstate);
          break;
diff --git a/libguile/procprop.c b/libguile/procprop.c
index ff4648d..d37495b 100644
--- a/libguile/procprop.c
+++ b/libguile/procprop.c
@@ -82,6 +82,14 @@ scm_i_procedure_arity (SCM proc, int *req, int *opt, int 
*rest)
 
           return 1;
         }
+      else if (SCM_RTL_PROGRAM_P (proc))
+        {
+          *req = 0;
+          *opt = 0;
+          *rest = 1;
+
+          return 1;
+        }
       else
         return 0;
     }
diff --git a/libguile/procs.c b/libguile/procs.c
index 5899df0..bda6d34 100644
--- a/libguile/procs.c
+++ b/libguile/procs.c
@@ -1,5 +1,5 @@
 /* Copyright (C) 1995, 1996, 1997, 1999, 2000, 2001, 2006, 2008, 2009,
- *   2010, 2011, 2012 Free Software Foundation, Inc.
+ *   2010, 2011, 2012, 2013 Free Software Foundation, Inc.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -48,6 +48,7 @@ SCM_DEFINE (scm_procedure_p, "procedure?", 1, 0, 0,
 #define FUNC_NAME s_scm_procedure_p
 {
   return scm_from_bool (SCM_PROGRAM_P (obj)
+                        || SCM_RTL_PROGRAM_P (obj)
                         || (SCM_STRUCTP (obj) && SCM_STRUCT_APPLICABLE_P (obj))
                         || (SCM_HAS_TYP7 (obj, scm_tc7_smob)
                             && SCM_SMOB_APPLICABLE_P (obj)));
diff --git a/libguile/programs.c b/libguile/programs.c
index 128e031..eb5972a 100644
--- a/libguile/programs.c
+++ b/libguile/programs.c
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, 
Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -69,6 +69,58 @@ SCM_DEFINE (scm_make_program, "make-program", 1, 2, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_make_rtl_program, "make-rtl-program", 1, 2, 0,
+           (SCM bytevector, SCM byte_offset, SCM free_variables),
+           "")
+#define FUNC_NAME s_scm_make_rtl_program
+{
+  scm_t_uint8 *code;
+  scm_t_uint32 offset;
+
+  if (!scm_is_bytevector (bytevector))
+    scm_wrong_type_arg (FUNC_NAME, 1, bytevector);
+  if (SCM_UNBNDP (byte_offset))
+    offset = 0;
+  else
+    {
+      offset = scm_to_uint32 (byte_offset);
+      if (offset > SCM_BYTEVECTOR_LENGTH (bytevector))
+        SCM_OUT_OF_RANGE (2, byte_offset);
+    }
+
+  code = (scm_t_uint8*) SCM_BYTEVECTOR_CONTENTS (bytevector) + offset;
+  if (((scm_t_uintptr) code) % 4)
+    SCM_OUT_OF_RANGE (2, byte_offset);
+
+  if (SCM_UNBNDP (free_variables) || scm_is_false (free_variables))
+    return scm_cell (scm_tc7_rtl_program, (scm_t_bits) code);
+  else
+    abort ();
+}
+#undef FUNC_NAME
+
+SCM_DEFINE (scm_rtl_program_code, "rtl-program-code", 1, 0, 0,
+            (SCM program),
+            "")
+#define FUNC_NAME s_scm_rtl_program_code
+{
+  SCM_VALIDATE_RTL_PROGRAM (1, program);
+
+  /* FIXME: we need scm_from_uintptr ().  */
+  return scm_from_size_t ((size_t) SCM_RTL_PROGRAM_CODE (program));
+}
+#undef FUNC_NAME
+
+void
+scm_i_rtl_program_print (SCM program, SCM port, scm_print_state *pstate)
+{
+  scm_puts_unlocked ("#<rtl-program ", port);
+  scm_uintprint (SCM_UNPACK (program), 16, port);
+  scm_putc_unlocked (' ', port);
+  scm_uintprint ((scm_t_uintptr) SCM_RTL_PROGRAM_CODE (program), 16, port);
+  scm_putc_unlocked ('>', port);
+}
+
 void
 scm_i_program_print (SCM program, SCM port, scm_print_state *pstate)
 {
@@ -121,6 +173,15 @@ SCM_DEFINE (scm_program_p, "program?", 1, 0, 0,
 }
 #undef FUNC_NAME
 
+SCM_DEFINE (scm_rtl_program_p, "rtl-program?", 1, 0, 0,
+           (SCM obj),
+           "")
+#define FUNC_NAME s_scm_rtl_program_p
+{
+  return scm_from_bool (SCM_RTL_PROGRAM_P (obj));
+}
+#undef FUNC_NAME
+
 SCM_DEFINE (scm_program_base, "program-base", 1, 0, 0,
            (SCM program),
            "")
diff --git a/libguile/programs.h b/libguile/programs.h
index d53fd8f..732594c 100644
--- a/libguile/programs.h
+++ b/libguile/programs.h
@@ -1,4 +1,4 @@
-/* Copyright (C) 2001, 2009, 2010, 2011 Free Software Foundation, Inc.
+/* Copyright (C) 2001, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, 
Inc.
  * 
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public License
@@ -23,6 +23,31 @@
 #include <libguile/objcodes.h>
 
 /*
+ * The new RTL programs.
+ */
+
+#define SCM_RTL_PROGRAM_P(x) (SCM_HAS_TYP7 (x, scm_tc7_rtl_program))
+#define SCM_RTL_PROGRAM_CODE(x) ((scm_t_uint32 *) SCM_CELL_WORD_1 (x))
+#define SCM_RTL_PROGRAM_FREE_VARIABLES(x) (SCM_CELL_OBJECT_LOC (x, 2))
+#define SCM_RTL_PROGRAM_FREE_VARIABLE_REF(x,i) (SCM_RTL_PROGRAM_FREE_VARIABLES 
(x)[i])
+#define SCM_RTL_PROGRAM_FREE_VARIABLE_SET(x,i,v) 
(SCM_RTL_PROGRAM_FREE_VARIABLES (x)[i]=(v))
+#define SCM_RTL_PROGRAM_NUM_FREE_VARIABLES(x) (SCM_CELL_WORD_0 (x) >> 16)
+#define SCM_VALIDATE_RTL_PROGRAM(p,x) SCM_MAKE_VALIDATE (p, x, RTL_PROGRAM_P)
+
+static inline SCM
+scm_i_make_rtl_program (const scm_t_uint32 *code)
+{
+  return scm_cell (scm_tc7_rtl_program, (scm_t_bits)code);
+}
+
+SCM_INTERNAL SCM scm_make_rtl_program (SCM bytevector, SCM byte_offset, SCM 
free_variables);
+SCM_INTERNAL SCM scm_rtl_program_p (SCM obj);
+SCM_INTERNAL SCM scm_rtl_program_code (SCM program);
+
+SCM_INTERNAL void scm_i_rtl_program_print (SCM program, SCM port,
+                                           scm_print_state *pstate);
+
+/*
  * Programs
  */
 
diff --git a/libguile/tags.h b/libguile/tags.h
index a194ea0..fcfc014 100644
--- a/libguile/tags.h
+++ b/libguile/tags.h
@@ -425,7 +425,7 @@ typedef union SCM { struct { scm_t_bits n; } n; } SCM;
 
 #define scm_tc7_unused_17      61
 #define scm_tc7_unused_21      63
-#define scm_tc7_unused_19      69
+#define scm_tc7_rtl_program    69
 #define scm_tc7_program                79
 #define scm_tc7_weak_set       85
 #define scm_tc7_weak_table     87
diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 4454632..d070823 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -16,7 +16,34 @@
  * 02110-1301 USA
  */
 
-/* This file is included in vm.c multiple times */
+/* This file is included in vm.c multiple times.  */
+
+
+/* Virtual Machine
+
+   This file contains two virtual machines.  First, the old one -- the
+   one that is currently used, and corresponds to Guile 2.0.  It's a
+   stack machine, meaning that most instructions pop their operands from
+   the top of the stack, and push results there too.
+
+   Following it is the new virtual machine.  It's a register machine,
+   meaning that intructions address their operands by index, and store
+   results in indexed slots as well.  Those slots are on the stack.
+   It's somewhat confusing to call it a register machine, given that the
+   values are on the stack.  Perhaps it needs a new name.
+
+   Anyway, things are in a transitional state.  We're going to try to
+   avoid munging the old VM very much while we flesh out the new one.
+   We're also going to try to make them interoperable, as much as
+   possible -- to have the old VM be able to call procedures for the new
+   VM, and vice versa.  This should ease the bootstrapping process.  */
+
+
+/* The old VM.  */
+static SCM VM_NAME (SCM, SCM, SCM*, int);
+/* The new VM.  */
+static SCM RTL_VM_NAME (SCM, SCM, SCM*, size_t);
+
 
 #if (VM_ENGINE == SCM_VM_REGULAR_ENGINE)
 # define VM_USE_HOOKS          0       /* Various hooks */
@@ -379,6 +406,29 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
     {
       if (SCM_STRUCTP (program) && SCM_STRUCT_APPLICABLE_P (program))
         fp[-1] = SCM_STRUCT_PROCEDURE (program);
+      else if (SCM_HAS_TYP7 (program, scm_tc7_rtl_program))
+        {
+          SCM ret;
+          SYNC_ALL ();
+
+          ret = RTL_VM_NAME (vm, program, fp, sp - fp + 1);
+
+          NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+          if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+            {
+              /* multiple values returned to continuation */
+              ret = scm_struct_ref (ret, SCM_INUM0);
+              nvalues = scm_ilength (ret);
+              PUSH_LIST (ret, scm_is_null);
+              goto vm_return_values;
+            }
+          else
+            {
+              PUSH (ret);
+              goto vm_return;
+            }
+        }
       else if (SCM_HAS_TYP7 (program, scm_tc7_smob)
                && SCM_SMOB_APPLICABLE_P (program))
         {
@@ -450,8 +500,6 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 #undef RETURN
 #undef RETURN_ONE_VALUE
 #undef RETURN_VALUE_LIST
-#undef RUN_HOOK
-#undef RUN_HOOK1
 #undef SYNC_ALL
 #undef SYNC_BEFORE_GC
 #undef SYNC_IP
@@ -461,8 +509,3122 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 #undef VARIABLE_SET
 #undef VM_DEFINE_OP
 #undef VM_INSTRUCTION_TO_LABEL
-#undef VM_USE_HOOKS
 
+
+
+
+/* Virtual Machine
+
+   This is Guile's new virtual machine.  When I say "new", I mean
+   relative to the current virtual machine.  At some point it will
+   become "the" virtual machine, and we'll delete this paragraph.  As
+   such, the rest of the comments speak as if there's only one VM.
+
+   <more overview here>
+ */
+
+
+/* The VM has three state bits: the instruction pointer (IP), the frame
+   pointer (FP), and the top-of-stack pointer (SP).  We cache the first
+   two of these in machine registers, local to the VM, because they are
+   used extensively by the VM.  As the SP is used more by code outside
+   the VM than by the VM itself, we don't bother caching it locally.
+
+   Since the FP changes infrequently, relative to the IP, we keep vp->fp
+   in sync with the local FP.  This would be a big lose for the IP,
+   though, so instead of updating vp->ip all the time, we call SYNC_IP
+   whenever we would need to know the IP of the top frame.  In practice,
+   we need to SYNC_IP whenever we call out of the VM to a function that
+   would like to walk the stack, perhaps as the result of an
+   exception.  */
+
+#define SYNC_IP() \
+  vp->ip = (scm_t_uint8 *) (ip)
+
+#define SYNC_REGISTER() \
+  SYNC_IP()
+#define SYNC_BEFORE_GC() /* Only SP and FP needed to trace GC */
+#define SYNC_ALL() /* FP already saved */ \
+  SYNC_IP()
+
+#define CHECK_OVERFLOW(sp)                      \
+  do {                                          \
+    if (SCM_UNLIKELY ((sp) >= stack_limit))     \
+      vm_error_stack_overflow (vp);             \
+  } while (0)
+
+/* Reserve stack space for a frame.  Will check that there is sufficient
+   stack space for N locals, not including the procedure, in addition to
+   4 words to set up the next frame.  Invoke after preparing the new
+   frame and setting the fp and ip.  */
+#define ALLOC_FRAME(n)                                              \
+  do {                                                              \
+    SCM *new_sp = vp->sp = fp - 1 + n;                              \
+    CHECK_OVERFLOW (new_sp + 4);                                    \
+  } while (0)
+
+/* Reset the current frame to hold N locals.  Used when we know that no
+   stack expansion is needed.  */
+#define RESET_FRAME(n)                                              \
+  do {                                                              \
+    vp->sp = fp - 1 + n;                                            \
+  } while (0)
+
+/* Compute the number of locals in the frame.  This is equal to the
+   number of actual arguments when a function is first called.  */
+#define FRAME_LOCALS_COUNT()                                        \
+  (vp->sp + 1 - fp)
+
+/* Restore registers after returning from a frame.  */
+#define RESTORE_FRAME()                                             \
+  do {                                                              \
+  } while (0)
+
+
+#define CACHE_REGISTER()                        \
+  do {                                          \
+    ip = (scm_t_uint32 *) vp->ip;               \
+    fp = vp->fp;                                \
+  } while (0)
+
+#ifdef HAVE_LABELS_AS_VALUES
+# define BEGIN_DISPATCH_SWITCH /* */
+# define END_DISPATCH_SWITCH /* */
+# define NEXT(n)                                \
+  do                                            \
+    {                                           \
+      ip += n;                                  \
+      NEXT_HOOK ();                             \
+      op = *ip;                                 \
+      goto *jump_table[op & 0xff];              \
+    }                                           \
+  while (0)
+# define VM_DEFINE_OP(opcode, tag, name, meta)  \
+  op_##tag:
+#else
+# define BEGIN_DISPATCH_SWITCH                  \
+  vm_start:                                     \
+    NEXT_HOOK ();                               \
+    op = *ip;                                   \
+  switch (op & 0xff)                            \
+    {
+# define END_DISPATCH_SWITCH                    \
+  default:                                      \
+    goto vm_error_bad_instruction;              \
+    }
+# define NEXT(n)                                \
+  do                                            \
+    {                                           \
+      ip += n;                                  \
+      goto vm_start;                            \
+    }                                           \
+  while (0)
+# define VM_DEFINE_OP(opcode, tag, name, meta)  \
+  op_##tag:                                     \
+  case opcode:
+#endif
+
+#define LOCAL_REF(i)           SCM_FRAME_VARIABLE (fp, i)
+#define LOCAL_SET(i,o)         SCM_FRAME_VARIABLE (fp, i) = o
+
+#define VARIABLE_REF(v)                SCM_VARIABLE_REF (v)
+#define VARIABLE_SET(v,o)      SCM_VARIABLE_SET (v, o)
+#define VARIABLE_BOUNDP(v)      (!scm_is_eq (VARIABLE_REF (v), SCM_UNDEFINED))
+#define FREE_VARIABLE_REF(i)   SCM_RTL_PROGRAM_FREE_VARIABLE_REF 
(SCM_FRAME_PROGRAM (fp), i)
+
+#define RETURN_ONE_VALUE(ret)                           \
+  do {                                                  \
+    SCM val = ret;                                      \
+    SCM *sp = SCM_FRAME_LOWER_ADDRESS (fp);             \
+    VM_HANDLE_INTERRUPTS;                               \
+    ip = SCM_FRAME_RTL_RETURN_ADDRESS (fp);             \
+    vp->sp = sp;                                        \
+    fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);          \
+    *sp = val;                                          \
+    POP_CONTINUATION_HOOK (sp, 1);                      \
+    NEXT (0);                                           \
+  } while (0)
+
+/* While we could generate the list-unrolling code here, it's fine for
+   now to just tail-call (apply values vals).  */
+#define RETURN_VALUE_LIST(vals_)                        \
+  do {                                                  \
+    SCM vals = vals_;                                   \
+    VM_HANDLE_INTERRUPTS;                               \
+    fp[-1] = rtl_apply;                                 \
+    fp[0] = rtl_values;                                 \
+    fp[1] = vals;                                       \
+    RESET_FRAME (2);                                    \
+    ip = (scm_t_uint32 *) rtl_apply_code;               \
+    goto op_apply;                                      \
+  } while (0)
+
+#define BR_NARGS(rel)                           \
+  scm_t_uint16 expected;                        \
+  SCM_UNPACK_RTL_24 (op, expected);             \
+  if (FRAME_LOCALS_COUNT() rel expected)        \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_UNARY(x, exp)                        \
+  scm_t_uint32 test;                            \
+  SCM x;                                        \
+  SCM_UNPACK_RTL_24 (op, test);                 \
+  x = LOCAL_REF (test);                         \
+  if ((ip[1] & 0x1) ? !(exp) : (exp))           \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      if (offset < 0)                           \
+        VM_HANDLE_INTERRUPTS;                   \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_BINARY(x, y, exp)                    \
+  scm_t_uint16 a, b;                            \
+  SCM x, y;                                     \
+  SCM_UNPACK_RTL_12_12 (op, a, b);              \
+  x = LOCAL_REF (a);                            \
+  y = LOCAL_REF (b);                            \
+  if ((ip[1] & 0x1) ? !(exp) : (exp))           \
+    {                                           \
+      scm_t_int32 offset = ip[1];               \
+      offset >>= 8; /* Sign-extending shift. */ \
+      if (offset < 0)                           \
+        VM_HANDLE_INTERRUPTS;                   \
+      NEXT (offset);                            \
+    }                                           \
+  NEXT (2)
+
+#define BR_ARITHMETIC(crel,srel)                                        \
+  {                                                                     \
+    scm_t_uint16 a, b;                                                  \
+    SCM x, y;                                                           \
+    SCM_UNPACK_RTL_12_12 (op, a, b);                                    \
+    x = LOCAL_REF (a);                                                  \
+    y = LOCAL_REF (b);                                                  \
+    if (SCM_I_INUMP (x) && SCM_I_INUMP (y))                             \
+      {                                                                 \
+        scm_t_signed_bits x_bits = SCM_UNPACK (x);                      \
+        scm_t_signed_bits y_bits = SCM_UNPACK (y);                      \
+        if (x_bits crel y_bits)                                         \
+          {                                                             \
+            scm_t_int32 offset = ip[1];                                 \
+            offset >>= 8; /* Sign-extending shift. */                   \
+            if (offset < 0)                                             \
+              VM_HANDLE_INTERRUPTS;                                     \
+            NEXT (offset);                                              \
+          }                                                             \
+        NEXT (2);                                                       \
+      }                                                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        if (scm_is_true (srel (x, y)))                                  \
+          {                                                             \
+            scm_t_int32 offset = ip[1];                                 \
+            offset >>= 8; /* Sign-extending shift. */                   \
+            if (offset < 0)                                             \
+              VM_HANDLE_INTERRUPTS;                                     \
+            NEXT (offset);                                              \
+          }                                                             \
+        NEXT (2);                                                       \
+      }                                                                 \
+  }
+
+#define ARGS1(a1)                               \
+  scm_t_uint16 dst, src;                        \
+  SCM a1;                                       \
+  SCM_UNPACK_RTL_12_12 (op, dst, src);          \
+  a1 = LOCAL_REF (src)
+#define ARGS2(a1, a2)                           \
+  scm_t_uint8 dst, src1, src2;                  \
+  SCM a1, a2;                                   \
+  SCM_UNPACK_RTL_8_8_8 (op, dst, src1, src2);   \
+  a1 = LOCAL_REF (src1);                        \
+  a2 = LOCAL_REF (src2)
+#define RETURN(x)                               \
+  do { LOCAL_SET (dst, x); NEXT (1); } while (0)
+
+/* The maximum/minimum tagged integers.  */
+#define INUM_MAX (INTPTR_MAX - 1)
+#define INUM_MIN (INTPTR_MIN + scm_tc2_int)
+
+#define BINARY_INTEGER_OP(CFUNC,SFUNC)                                      \
+  {                                                             \
+    ARGS2 (x, y);                                              \
+    if (SCM_I_INUMP (x) && SCM_I_INUMP (y))                     \
+      {                                                         \
+        scm_t_int64 n = SCM_I_INUM (x) CFUNC SCM_I_INUM (y);    \
+        if (SCM_FIXABLE (n))                                    \
+          RETURN (SCM_I_MAKINUM (n));                           \
+      }                                                         \
+    SYNC_IP ();                                                 \
+    RETURN (SFUNC (x, y));                                      \
+  }
+
+#define VM_VALIDATE_PAIR(x, proc)              \
+  VM_ASSERT (scm_is_pair (x), vm_error_not_a_pair (proc, x))
+  
+#define VM_VALIDATE_STRUCT(obj, proc)           \
+  VM_ASSERT (SCM_STRUCTP (obj), vm_error_not_a_pair (proc, obj))
+
+#define VM_VALIDATE_BYTEVECTOR(x, proc)                \
+  VM_ASSERT (SCM_BYTEVECTOR_P (x), vm_error_not_a_bytevector (proc, x))
+
+/* Return true (non-zero) if PTR has suitable alignment for TYPE.  */
+#define ALIGNED_P(ptr, type)                   \
+  ((scm_t_uintptr) (ptr) % alignof_type (type) == 0)
+
+static SCM
+RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t nargs_)
+{
+  /* Instruction pointer: A pointer to the opcode that is currently
+     running.  */
+  register scm_t_uint32 *ip IP_REG;
+
+  /* Frame pointer: A pointer into the stack, off of which we index
+     arguments and local variables.  Pushed at function calls, popped on
+     returns.  */
+  register SCM *fp FP_REG;
+
+  /* Current opcode: A cache of *ip.  */
+  register scm_t_uint32 op;
+
+  /* Cached variables. */
+  struct scm_vm *vp = SCM_VM_DATA (vm);
+  SCM *stack_limit = vp->stack_limit;  /* stack limit address */
+  scm_i_thread *current_thread = SCM_I_CURRENT_THREAD;
+  scm_i_jmp_buf registers;              /* used for prompts */
+
+#ifdef HAVE_LABELS_AS_VALUES
+  static const void **jump_table_pointer = NULL;
+  register const void **jump_table JT_REG;
+
+  if (SCM_UNLIKELY (!jump_table_pointer))
+    {
+      int i;
+      jump_table_pointer = malloc (SCM_VM_NUM_INSTRUCTIONS * sizeof (void*));
+      for (i = 0; i < SCM_VM_NUM_INSTRUCTIONS; i++)
+        jump_table_pointer[i] = &&vm_error_bad_instruction;
+#define INIT(opcode, tag, name, meta) jump_table_pointer[opcode] = &&op_##tag;
+      FOR_EACH_VM_OPERATION(INIT);
+#undef INIT
+    }
+
+  /* Attempt to keep JUMP_TABLE_POINTER in a register.  This saves one
+     load instruction at each instruction dispatch.  */
+  jump_table = jump_table_pointer;
+#endif
+
+  if (SCM_I_SETJMP (registers))
+    {
+      /* Non-local return.  The values are on the stack, on a new frame
+         set up to call `values' to return the values to the handler.
+         Cache the VM registers back from the vp, and dispatch to the
+         body of `values'.
+
+         Note, at this point, we must assume that any variable local to
+         vm_engine that can be assigned *has* been assigned. So we need
+         to pull all our state back from the ip/fp/sp.
+      */
+      CACHE_REGISTER ();
+      ABORT_CONTINUATION_HOOK (fp, FRAME_LOCALS_COUNT());
+      NEXT (0);
+    }
+
+  /* Load previous VM registers. */
+  CACHE_REGISTER ();
+
+  VM_HANDLE_INTERRUPTS;
+
+  /* Initialization */
+  {
+    SCM *base;
+
+    /* Check that we have enough space: 4 words for the boot
+       continuation, 4 + nargs for the procedure application, and 4 for
+       setting up a new frame.  */
+    base = vp->sp + 1;
+    CHECK_OVERFLOW (vp->sp + 4 + 4 + nargs_ + 4);
+
+    /* Since it's possible to receive the arguments on the stack itself,
+       and indeed the regular VM invokes us that way, shuffle up the
+       arguments first.  */
+    {
+      int i;
+      for (i = nargs_ - 1; i >= 0; i--)
+        base[8 + i] = argv[i];
+    }
+
+    /* Initial frame, saving previous fp and ip, with the boot
+       continuation.  */
+    base[0] = SCM_PACK (fp); /* dynamic link */
+    base[1] = SCM_PACK (0); /* the boot continuation does not return to scheme 
*/
+    base[2] = SCM_PACK (ip); /* ra */
+    base[3] = rtl_boot_continuation;
+    fp = &base[4];
+    ip = rtl_boot_single_value_continuation_code;
+    if (ip - 1 != rtl_boot_multiple_value_continuation_code)
+      abort();
+
+    /* MV-call frame, function & arguments */
+    base[4] = SCM_PACK (fp); /* dynamic link */
+    base[5] = SCM_PACK (ip - 1); /* in RTL programs, MVRA precedes RA by one */
+    base[6] = SCM_PACK (ip); /* ra */
+    base[7] = program;
+    fp = vp->fp = &base[8];
+    RESET_FRAME (nargs_);
+  }
+
+ apply:
+  while (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp)))
+    {
+#if 0
+      SCM proc = SCM_FRAME_PROGRAM (fp);
+
+      if (SCM_STRUCTP (proc) && SCM_STRUCT_APPLICABLE_P (proc))
+        {
+          fp[-1] = SCM_STRUCT_PROCEDURE (proc);
+          continue;
+        }
+      if (SCM_HAS_TYP7 (proc, scm_tc7_smob) && SCM_SMOB_APPLICABLE_P (proc))
+        {
+          scm_t_uint32 n = FRAME_LOCALS_COUNT();
+
+          /* Shuffle args up, place smob in local 0. */
+          CHECK_OVERFLOW (vp->sp + 1);
+          vp->sp++;
+          while (n--)
+            LOCAL_SET (n + 1, LOCAL_REF (n));
+          LOCAL_SET (0, proc);
+
+          fp[-1] = SCM_SMOB_DESCRIPTOR (proc).apply_trampoline;
+          continue;
+        }
+
+      SYNC_IP();
+      vm_error_wrong_type_apply (proc);
+#else
+      SCM ret;
+      SYNC_ALL ();
+
+      ret = VM_NAME (vm, fp[-1], fp, FRAME_LOCALS_COUNT ());
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+#endif
+    }
+
+  /* Let's go! */
+  ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+  NEXT (0);
+
+  BEGIN_DISPATCH_SWITCH;
+  
+
+  
+
+  /*
+   * Call and return
+   */
+
+  /* halt _:24
+   *
+   * Bring the VM to a halt, returning the single value from r0.
+   */
+  VM_DEFINE_OP (0, halt, "halt", OP1 (U8_X24))
+    {
+      SCM ret = LOCAL_REF (0);
+
+      vp->ip = SCM_FRAME_RETURN_ADDRESS (fp);
+      vp->sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
+      vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      return ret;
+    }
+
+  /* halt/values _:24
+   *
+   * Bring the VM to a halt, returning all the values on the stack.
+   */
+  VM_DEFINE_OP (1, halt_values, "halt/values", OP1 (U8_X24))
+    {
+      scm_t_ptrdiff n;
+      SCM *base;
+      SCM ret = SCM_EOL;
+
+      SYNC_BEFORE_GC();
+
+      base = fp + 4;
+      n = FRAME_LOCALS_COUNT ();
+      while (n--)
+        ret = scm_cons (base[n], ret);
+
+      vp->ip = SCM_FRAME_RETURN_ADDRESS (fp);
+      vp->sp = SCM_FRAME_LOWER_ADDRESS (fp) - 1;
+      vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      return scm_values (ret);
+    }
+
+  /* call from:24 _:8 proc:24 _:8 nargs:24 arg0:24 0:8 ...
+   *
+   * Call a procedure.  Push a call frame on at FROM, saving the return
+   * address and the fp.  Parse out NARGS, and push the procedure and
+   * arguments.  All arguments except for RETURN-LOC are 24-bit values.
+   * FROM, PROC, and NARGS are in the upper 24 bits of the words.  The
+   * ARGN... are in the lower 24 bits, with the upper 8 bits being 0.
+   *
+   * The MVRA of the new frame is set to point to the next instruction
+   * after the end of the `call' instruction.  The word following that
+   * is the RA.
+   */
+  VM_DEFINE_OP (2, call, "call", OP3 (U8_U24, X8_U24, X8_R24))
+    {
+      scm_t_uint32 from, proc, nargs, n;
+      SCM *old_fp = fp;
+
+      SCM_UNPACK_RTL_24 (op, from);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+      SCM_UNPACK_RTL_24 (ip[2], nargs);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp = vp->fp = old_fp + from + 4;
+      SCM_FRAME_SET_DYNAMIC_LINK (fp, old_fp);
+      SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS (fp, ip + 3 + nargs);
+      SCM_FRAME_SET_RTL_RETURN_ADDRESS (fp, ip + 4 + nargs);
+      fp[-1] = old_fp[proc];
+      ALLOC_FRAME (nargs);
+
+      for (n = 0; n < nargs; n++)
+        LOCAL_SET (n, old_fp[ip[3 + n]]);
+
+      PUSH_CONTINUATION_HOOK ();
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* call/values from:24 _:8 proc:24
+   *
+   * Call a procedure, with the values already pushed above a call frame
+   * at FROM.  This instruction is used to handle MV returns in the case
+   * that we can't inline the handler.
+   *
+   * As with `call', the next instruction after the call/values will be
+   * the MVRA, and the word after that instruction is the RA.
+   */
+  VM_DEFINE_OP (3, call_values, "call/values", OP2 (U8_U24, X8_U24))
+    {
+      scm_t_uint32 from, proc;
+      SCM *old_fp = fp;
+
+      SCM_UNPACK_RTL_24 (op, from);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp = vp->fp = old_fp + from + 4;
+      SCM_FRAME_SET_DYNAMIC_LINK (fp, old_fp);
+      SCM_FRAME_SET_RTL_MV_RETURN_ADDRESS (fp, ip + 2);
+      SCM_FRAME_SET_RTL_RETURN_ADDRESS (fp, ip + 3);
+      fp[-1] = old_fp[proc];
+
+      PUSH_CONTINUATION_HOOK ();
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* tail-call nargs:24 _:8 proc:24
+   *
+   * Tail-call a procedure.  Requires that all of the arguments have
+   * already been shuffled into position.
+   */
+  VM_DEFINE_OP (4, tail_call, "tail-call", OP2 (U8_U24, X8_U24))
+    {
+      scm_t_uint32 nargs, proc;
+
+      SCM_UNPACK_RTL_24 (op, nargs);
+      SCM_UNPACK_RTL_24 (ip[1], proc);
+
+      VM_HANDLE_INTERRUPTS;
+
+      fp[-1] = LOCAL_REF (proc);
+      /* No need to check for overflow, as the compiler has already
+         ensured that this frame has enough space.  */
+      RESET_FRAME (nargs);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* return src:24
+   *
+   * Return a value.
+   */
+  VM_DEFINE_OP (5, return, "return", OP1 (U8_U24))
+    {
+      scm_t_uint32 src;
+      SCM_UNPACK_RTL_24 (op, src);
+      RETURN_ONE_VALUE (LOCAL_REF (src));
+    }
+
+  /* return-values nvalues:24
+   *
+   * Return a number of values from a call frame.  This opcode
+   * corresponds to an application of `values' in tail position.  As
+   * with tail calls, we expect that the NVALUES values have already
+   * been shuffled down to a contiguous array starting at slot 0.
+   */
+  VM_DEFINE_OP (6, return_values, "return/values", OP1 (U8_U24))
+    {
+      scm_t_uint32 nargs;
+      SCM_UNPACK_RTL_24 (op, nargs);
+      RESET_FRAME (nargs);
+      fp[-1] = rtl_values;
+      goto op_values;
+    }
+
+
+  
+
+  /*
+   * Specialized call stubs
+   */
+
+  /* subr-call ptr-idx:24
+   *
+   * Call a subr, passing all locals in this frame as arguments.  Fetch
+   * the foreign pointer from PTR-IDX, a free variable.  Return from the
+   * calling frame.  This instruction is part of the trampolines
+   * created in gsubr.c, and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (7, subr_call, "subr-call", OP1 (U8_U24))
+    {
+      scm_t_uint32 ptr_idx;
+      SCM pointer, ret;
+      SCM (*subr)();
+
+      SCM_UNPACK_RTL_24 (op, ptr_idx);
+
+      pointer = FREE_VARIABLE_REF (ptr_idx);
+      subr = SCM_POINTER_VALUE (pointer);
+
+      VM_HANDLE_INTERRUPTS;
+      SYNC_IP ();
+
+      switch (FRAME_LOCALS_COUNT ())
+        {
+        case 0:
+          ret = subr ();
+          break;
+        case 1:
+          ret = subr (fp[0]);
+          break;
+        case 2:
+          ret = subr (fp[0], fp[1]);
+          break;
+        case 3:
+          ret = subr (fp[0], fp[1], fp[2]);
+          break;
+        case 4:
+          ret = subr (fp[0], fp[1], fp[2], fp[3]);
+          break;
+        case 5:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4]);
+          break;
+        case 6:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5]);
+          break;
+        case 7:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6]);
+          break;
+        case 8:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7]);
+          break;
+        case 9:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], 
fp[8]);
+          break;
+        case 10:
+          ret = subr (fp[0], fp[1], fp[2], fp[3], fp[4], fp[5], fp[6], fp[7], 
fp[8], fp[9]);
+          break;
+        default:
+          abort ();
+        }
+
+      // NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        /* multiple values returned to continuation */
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+    }
+
+  /* foreign-call cif-idx:12 ptr-idx:12
+   *
+   * Call a foreign function.  Fetch the CIF and foreign pointer from
+   * CIF-IDX and PTR-IDX, both free variables.  Return from the calling
+   * frame.  Arguments are taken from the stack.  This instruction is
+   * part of the trampolines created by the FFI, and is not generated by
+   * the compiler.
+   */
+  VM_DEFINE_OP (8, foreign_call, "foreign-call", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 cif_idx, ptr_idx;
+      SCM cif, pointer, ret;
+
+      SCM_UNPACK_RTL_12_12 (op, cif_idx, ptr_idx);
+
+      cif = FREE_VARIABLE_REF (cif_idx);
+      pointer = FREE_VARIABLE_REF (ptr_idx);
+
+      SYNC_IP ();
+      VM_HANDLE_INTERRUPTS;
+
+      // FIXME: separate args
+      ret = scm_i_foreign_call (scm_cons (cif, pointer), fp);
+
+      // NULLSTACK_FOR_NONLOCAL_EXIT ();
+
+      if (SCM_UNLIKELY (SCM_VALUESP (ret)))
+        /* multiple values returned to continuation */
+        RETURN_VALUE_LIST (scm_struct_ref (ret, SCM_INUM0));
+      else
+        RETURN_ONE_VALUE (ret);
+    }
+
+  /* continuation-call contregs:24
+   *
+   * Return to a continuation, nonlocally.  The arguments to the
+   * continuation are taken from the stack.  CONTREGS is a free variable
+   * containing the reified continuation.  This instruction is part of
+   * the implementation of undelimited continuations, and is not
+   * generated by the compiler.
+   */
+  VM_DEFINE_OP (9, continuation_call, "continuation-call", OP1 (U8_U24))
+    {
+      SCM contregs;
+      scm_t_uint32 contregs_idx;
+
+      SCM_UNPACK_RTL_24 (op, contregs_idx);
+
+      contregs = FREE_VARIABLE_REF (contregs_idx);
+
+      SYNC_IP ();
+      scm_i_check_continuation (contregs);
+      vm_return_to_continuation (scm_i_contregs_vm (contregs),
+                                 scm_i_contregs_vm_cont (contregs),
+                                 FRAME_LOCALS_COUNT (), fp);
+      scm_i_reinstate_continuation (contregs);
+
+      /* no NEXT */
+      abort ();
+    }
+
+  /* compose-continuation cont:24
+   *
+   * Compose a partial continution with the current continuation.  The
+   * arguments to the continuation are taken from the stack.  CONT is a
+   * free variable containing the reified continuation.  This
+   * instruction is part of the implementation of partial continuations,
+   * and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (10, compose_continuation, "compose-continuation", OP1 (U8_U24))
+    {
+      SCM vmcont;
+      scm_t_uint32 cont_idx;
+
+      SCM_UNPACK_RTL_24 (op, cont_idx);
+      vmcont = LOCAL_REF (cont_idx);
+
+      SYNC_IP ();
+      VM_ASSERT (SCM_VM_CONT_REWINDABLE_P (vmcont),
+                 vm_error_continuation_not_rewindable (vmcont));
+      vm_reinstate_partial_continuation (vm, vmcont, FRAME_LOCALS_COUNT (), fp,
+                                         &current_thread->dynstack,
+                                         &registers);
+      CACHE_REGISTER ();
+      NEXT (0);
+    }
+
+  /* apply _:24
+   *
+   * Tail-apply the procedure in local slot 0 to the rest of the
+   * arguments.  This instruction is part of the implementation of
+   * `apply', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (11, apply, "apply", OP1 (U8_X24))
+    {
+      int i, list_idx, list_len, nargs;
+      SCM list;
+
+      VM_HANDLE_INTERRUPTS;
+
+      VM_ASSERT (FRAME_LOCALS_COUNT () >= 2, abort ());
+      nargs = FRAME_LOCALS_COUNT ();
+      list_idx = nargs - 1;
+      list = LOCAL_REF (list_idx);
+      list_len = scm_ilength (list);
+
+      VM_ASSERT (list_len >= 0, vm_error_apply_to_non_list (list));
+
+      nargs = nargs - 2 + list_len;
+      ALLOC_FRAME (nargs);
+
+      for (i = 0; i < list_idx; i++)
+        fp[i - 1] = fp[i];
+
+      /* Null out these slots, just in case there are less than 2 elements
+         in the list. */
+      fp[list_idx - 1] = SCM_UNDEFINED;
+      fp[list_idx] = SCM_UNDEFINED;
+
+      for (i = 0; i < list_len; i++, list = SCM_CDR (list))
+        fp[list_idx - 1 + i] = SCM_CAR (list);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+
+  /* call/cc _:24
+   *
+   * Capture the current continuation, and tail-apply the procedure in
+   * local slot 0 to it.  This instruction is part of the implementation
+   * of `call/cc', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (12, call_cc, "call/cc", OP1 (U8_X24))
+#if 0
+    {
+      SCM vm_cont, cont;
+      scm_t_dynstack *dynstack;
+
+      VM_HANDLE_INTERRUPTS;
+
+      SYNC_IP ();
+      dynstack = scm_dynstack_capture_all (&current_thread->dynstack);
+      vm_cont = scm_i_vm_capture_stack (vp->stack_base,
+                                        SCM_FRAME_DYNAMIC_LINK (fp),
+                                        SCM_FRAME_LOWER_ADDRESS (fp) - 1,
+                                        SCM_FRAME_RETURN_ADDRESS (fp),
+                                        SCM_FRAME_MV_RETURN_ADDRESS (fp),
+                                        dynstack,
+                                        0);
+      cont = scm_i_make_continuation (&registers, vm, vm_cont);
+
+      fp[-1] = fp[0];
+      fp[0] = cont;
+      RESET_FRAME (1);
+
+      APPLY_HOOK ();
+
+      if (SCM_UNLIKELY (!SCM_RTL_PROGRAM_P (SCM_FRAME_PROGRAM (fp))))
+        goto apply;
+
+      ip = SCM_RTL_PROGRAM_CODE (SCM_FRAME_PROGRAM (fp));
+      NEXT (0);
+    }
+#else
+  abort();
+#endif
+
+  /* values _:24
+   *
+   * Return all values on the stack to the current continuation.
+   * This instruction is part of the implementation of
+   * `values', and is not generated by the compiler.
+   */
+  VM_DEFINE_OP (13, values, "values", OP1 (U8_X24))
+    {
+      SCM *base = fp;
+#if VM_USE_HOOKS
+      int nargs = FRAME_LOCALS_COUNT ();
+#endif
+
+      /* We don't do much; it's the caller that's responsible for
+         shuffling values and resetting the stack.  */
+
+      VM_HANDLE_INTERRUPTS;
+      ip = SCM_FRAME_RTL_MV_RETURN_ADDRESS (fp);
+      fp = vp->fp = SCM_FRAME_DYNAMIC_LINK (fp);
+
+      /* Clear stack frame.  */
+      base[-1] = SCM_BOOL_F;
+      base[-2] = SCM_BOOL_F;
+      base[-3] = SCM_BOOL_F;
+      base[-4] = SCM_BOOL_F;
+
+      POP_CONTINUATION_HOOK (base, nargs);
+
+      NEXT (0);
+    }
+
+
+  
+
+  /*
+   * Function prologues
+   */
+
+  /* br-if-nargs-ne expected:24 _:8 offset:24
+   * br-if-nargs-lt expected:24 _:8 offset:24
+   * br-if-nargs-gt expected:24 _:8 offset:24
+   *
+   * If the number of actual arguments is not equal, less than, or greater
+   * than EXPECTED, respectively, add OFFSET, a signed 24-bit number, to
+   * the current instruction pointer.
+   */
+  VM_DEFINE_OP (14, br_if_nargs_ne, "br-if-nargs-ne", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (!=);
+    }
+  VM_DEFINE_OP (15, br_if_nargs_lt, "br-if-nargs-lt", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (<);
+    }
+  VM_DEFINE_OP (16, br_if_nargs_gt, "br-if-nargs-gt", OP2 (U8_U24, X8_L24))
+    {
+      BR_NARGS (>);
+    }
+
+  /* assert-nargs-ee expected:24
+   * assert-nargs-ge expected:24
+   * assert-nargs-le expected:24
+   *
+   * If the number of actual arguments is not ==, >=, or <= EXPECTED,
+   * respectively, signal an error.
+   */
+  VM_DEFINE_OP (17, assert_nargs_ee, "assert-nargs-ee", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () == expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+  VM_DEFINE_OP (18, assert_nargs_ge, "assert-nargs-ge", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () >= expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+  VM_DEFINE_OP (19, assert_nargs_le, "assert-nargs-le", OP1 (U8_U24))
+    {
+      scm_t_uint32 expected;
+      SCM_UNPACK_RTL_24 (op, expected);
+      VM_ASSERT (FRAME_LOCALS_COUNT () <= expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      NEXT (1);
+    }
+
+  /* reserve-locals nlocals:24
+   *
+   * Ensure that there is space on the stack for NLOCALS local variables,
+   * setting them all to SCM_UNDEFINED, except those nargs values that
+   * were passed as arguments.
+   */
+  VM_DEFINE_OP (20, reserve_locals, "reserve-locals", OP1 (U8_U24))
+    {
+      scm_t_uint32 nlocals, nargs;
+      SCM_UNPACK_RTL_24 (op, nlocals);
+
+      nargs = FRAME_LOCALS_COUNT ();
+      ALLOC_FRAME (nlocals);
+      while (nlocals-- > nargs)
+        LOCAL_SET (nlocals, SCM_UNDEFINED);
+
+      NEXT (1);
+    }
+
+  /* assert-nargs-ee/locals expected:12 nlocals:12
+   *
+   * Equivalent to a sequence of assert-nargs-ee and reserve-locals.  The
+   * number of locals reserved is EXPECTED + NLOCALS.
+   */
+  VM_DEFINE_OP (21, assert_nargs_ee_locals, "assert-nargs-ee/locals", OP1 
(U8_U12_U12))
+    {
+      scm_t_uint16 expected, nlocals;
+      SCM_UNPACK_RTL_12_12 (op, expected, nlocals);
+      VM_ASSERT (FRAME_LOCALS_COUNT () == expected,
+                 vm_error_wrong_num_args (SCM_FRAME_PROGRAM (fp)));
+      ALLOC_FRAME (expected + nlocals);
+      while (nlocals--)
+        LOCAL_SET (expected + nlocals, SCM_UNDEFINED);
+
+      NEXT (1);
+    }
+
+  /* bind-kwargs nreq:24 allow-other-keys:1 has-rest:1 _:6 nreq-and-opt:24
+   * _:8 ntotal:24 kw-offset:32
+   *
+   * Find the last positional argument, and shuffle all the rest above
+   * NTOTAL.  Initialize the intervening locals to SCM_UNDEFINED.  Then
+   * load the constant at KW-OFFSET words from the current IP, and use it
+   * to bind keyword arguments.  If HAS-REST, collect all shuffled
+   * arguments into a list, and store it in NREQ-AND-OPT.  Finally, clear
+   * the arguments that we shuffled up.
+   *
+   * A macro-mega-instruction.
+   */
+  VM_DEFINE_OP (22, bind_kwargs, "bind-kwargs", OP4 (U8_U24, U8_U24, X8_U24, 
N32))
+    {
+      scm_t_uint32 nreq, nreq_and_opt, ntotal, npositional, nkw, n, nargs;
+      scm_t_int32 kw_offset;
+      scm_t_bits kw_bits;
+      SCM kw;
+      char allow_other_keys, has_rest;
+
+      SCM_UNPACK_RTL_24 (op, nreq);
+      allow_other_keys = ip[1] & 0x1;
+      has_rest = ip[1] & 0x2;
+      SCM_UNPACK_RTL_24 (ip[1], nreq_and_opt);
+      SCM_UNPACK_RTL_24 (ip[2], ntotal);
+      kw_offset = ip[3];
+      kw_bits = (scm_t_bits) (ip + kw_offset);
+      VM_ASSERT (!(kw_bits & 0x7), abort());
+      kw = SCM_PACK (kw_bits);
+
+      nargs = FRAME_LOCALS_COUNT ();
+
+      /* look in optionals for first keyword or last positional */
+      /* starting after the last required positional arg */
+      npositional = nreq;
+      while (/* while we have args */
+             npositional < nargs
+             /* and we still have positionals to fill */
+             && npositional < nreq_and_opt
+             /* and we haven't reached a keyword yet */
+             && !scm_is_keyword (LOCAL_REF (npositional)))
+        /* bind this optional arg (by leaving it in place) */
+        npositional++;
+      nkw = nargs - npositional;
+      /* shuffle non-positional arguments above ntotal */
+      ALLOC_FRAME (ntotal + nkw);
+      n = nkw;
+      while (n--)
+        LOCAL_SET (ntotal + n, LOCAL_REF (npositional + n));
+      /* and fill optionals & keyword args with SCM_UNDEFINED */
+      n = npositional;
+      while (n < ntotal)
+        LOCAL_SET (n++, SCM_UNDEFINED);
+
+      VM_ASSERT (has_rest || (nkw % 2) == 0,
+                 vm_error_kwargs_length_not_even (SCM_FRAME_PROGRAM (fp)));
+
+      /* Now bind keywords, in the order given.  */
+      for (n = 0; n < nkw; n++)
+        if (scm_is_keyword (LOCAL_REF (ntotal + n)))
+          {
+            SCM walk;
+            for (walk = kw; scm_is_pair (walk); walk = SCM_CDR (walk))
+              if (scm_is_eq (SCM_CAAR (walk), LOCAL_REF (ntotal + n)))
+                {
+                  SCM si = SCM_CDAR (walk);
+                  LOCAL_SET (SCM_I_INUMP (si) ? SCM_I_INUM (si) : 
scm_to_uint32 (si),
+                             LOCAL_REF (ntotal + n + 1));
+                  break;
+                }
+            VM_ASSERT (scm_is_pair (walk) || allow_other_keys,
+                       vm_error_kwargs_unrecognized_keyword (SCM_FRAME_PROGRAM 
(fp)));
+            n++;
+          }
+        else
+          VM_ASSERT (has_rest, vm_error_kwargs_invalid_keyword 
(SCM_FRAME_PROGRAM (fp)));
+
+      if (has_rest)
+        {
+          SCM rest = SCM_EOL;
+          n = nkw;
+          while (n--)
+            rest = scm_cons (LOCAL_REF (ntotal + n), rest);
+          LOCAL_SET (nreq_and_opt, rest);
+        }
+
+      RESET_FRAME (ntotal);
+
+      NEXT (4);
+    }
+
+  /* bind-rest dst:24
+   *
+   * Collect any arguments at or above DST into a list, and store that
+   * list at DST.
+   */
+  VM_DEFINE_OP (23, bind_rest, "bind-rest", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst, nargs;
+      SCM rest = SCM_EOL;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      nargs = FRAME_LOCALS_COUNT ();
+
+      while (nargs-- > dst)
+        {
+          rest = scm_cons (LOCAL_REF (nargs), rest);
+          LOCAL_SET (nargs, SCM_UNDEFINED);
+        }
+
+      LOCAL_SET (dst, rest);
+
+      RESET_FRAME (dst + 1);
+
+      NEXT (1);
+    }
+
+  /* drop-values nlocals:24
+   *
+   * Reset the stack pointer to only have space for NLOCALS values.
+   * Used after extracting values from an MV return.
+   */
+  VM_DEFINE_OP (24, drop_values, "drop-values", OP1 (U8_U24))
+    {
+      scm_t_bits nlocals;
+
+      SCM_UNPACK_RTL_24 (op, nlocals);
+
+      RESET_FRAME (nlocals);
+
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Branching instructions
+   */
+
+  /* br offset:24
+   *
+   * Add OFFSET, a signed 24-bit number, to the current instruction
+   * pointer.
+   */
+  VM_DEFINE_OP (25, br, "br", OP1 (U8_L24))
+    {
+      scm_t_int32 offset = op;
+      offset >>= 8; /* Sign-extending shift. */
+      NEXT (offset);
+    }
+
+  /* br-if-true test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is true for the purposes of Scheme, add
+   * OFFSET, a signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (26, br_if_true, "br-if-true", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_true (x));
+    }
+
+  /* br-if-null test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is the end-of-list or Lisp nil, add OFFSET, a
+   * signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (27, br_if_null, "br-if-null", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_null (x));
+    }
+
+  /* br-if-nil test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is false to Lisp, add OFFSET, a signed 24-bit
+   * number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (28, br_if_nil, "br-if-nil", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_lisp_false (x));
+    }
+
+  /* br-if-pair test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a pair, add OFFSET, a signed 24-bit number,
+   * to the current instruction pointer.
+   */
+  VM_DEFINE_OP (29, br_if_pair, "br-if-pair", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, scm_is_pair (x));
+    }
+
+  /* br-if-struct test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a struct, add OFFSET, a signed 24-bit
+   * number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (30, br_if_struct, "br-if-struct", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, SCM_STRUCTP (x));
+    }
+
+  /* br-if-char test:24 invert:1 _:7 offset:24
+   *
+   * If the value in TEST is a char, add OFFSET, a signed 24-bit number,
+   * to the current instruction pointer.
+   */
+  VM_DEFINE_OP (31, br_if_char, "br-if-char", OP2 (U8_U24, B1_X7_L24))
+    {
+      BR_UNARY (x, SCM_CHARP (x));
+    }
+
+  /* br-if-tc7 test:24 invert:1 tc7:7 offset:24
+   *
+   * If the value in TEST has the TC7 given in the second word, add
+   * OFFSET, a signed 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (32, br_if_tc7, "br-if-tc7", OP2 (U8_U24, B1_U7_L24))
+    {
+      BR_UNARY (x, SCM_HAS_TYP7 (x, (ip[1] >> 1) & 0x7f));
+    }
+
+  /* br-if-eq a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is eq? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (33, br_if_eq, "br-if-eq", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y, scm_is_eq (x, y));
+    }
+
+  /* br-if-eqv a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is eqv? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (34, br_if_eqv, "br-if-eqv", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y,
+                 scm_is_eq (x, y)
+                 || (SCM_NIMP (x) && SCM_NIMP (y)
+                     && scm_is_true (scm_eqv_p (x, y))));
+    }
+
+  /* br-if-equal a:12 b:12 invert:1 _:7 offset:24
+   *
+   * If the value in A is equal? to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  // FIXME: should sync_ip before calling out?
+  VM_DEFINE_OP (35, br_if_equal, "br-if-equal", OP2 (U8_U12_U12, B1_X7_L24))
+    {
+      BR_BINARY (x, y,
+                 scm_is_eq (x, y)
+                 || (SCM_NIMP (x) && SCM_NIMP (y)
+                     && scm_is_true (scm_equal_p (x, y))));
+    }
+
+  /* br-if-= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is = to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (36, br_if_ee, "br-if-=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (==, scm_num_eq_p);
+    }
+
+  /* br-if-< a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is < to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (37, br_if_lt, "br-if-<", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (<, scm_less_p);
+    }
+
+  /* br-if-<= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is <= to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (38, br_if_le, "br-if-<=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (<=, scm_leq_p);
+    }
+
+  /* br-if-> a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is > to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (39, br_if_gt, "br-if->", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (>, scm_gr_p);
+    }
+
+  /* br-if->= a:12 b:12 _:8 offset:24
+   *
+   * If the value in A is >= to the value in B, add OFFSET, a signed
+   * 24-bit number, to the current instruction pointer.
+   */
+  VM_DEFINE_OP (40, br_if_ge, "br-if->=", OP2 (U8_U12_U12, X8_L24))
+    {
+      BR_ARITHMETIC (>=, scm_geq_p);
+    }
+
+
+  
+
+  /*
+   * Lexical binding instructions
+   */
+
+  /* mov dst:12 src:12
+   *
+   * Copy a value from one local slot to another.
+   */
+  VM_DEFINE_OP (41, mov, "mov", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst;
+      scm_t_uint16 src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      LOCAL_SET (dst, LOCAL_REF (src));
+
+      NEXT (1);
+    }
+
+  /* long-mov dst:24 _:8 src:24
+   *
+   * Copy a value from one local slot to another.
+   */
+  VM_DEFINE_OP (42, long_mov, "long-mov", OP2 (U8_U24, X8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_uint32 src;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      SCM_UNPACK_RTL_24 (ip[1], src);
+      LOCAL_SET (dst, LOCAL_REF (src));
+
+      NEXT (2);
+    }
+
+  /* box dst:12 src:12
+   *
+   * Create a new variable holding SRC, and place it in DST.
+   */
+  VM_DEFINE_OP (43, box, "box", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      LOCAL_SET (dst, scm_cell (scm_tc7_variable, SCM_UNPACK (LOCAL_REF 
(src))));
+      NEXT (1);
+    }
+
+  /* empty-box dst:24
+   *
+   * Create a new unbound variable, and place it in DST.  Used in the
+   * general implementation of `letrec', in those cases that fix-letrec
+   * fails to fix.
+   */
+  VM_DEFINE_OP (44, empty_box, "empty-box", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      SCM_UNPACK_RTL_24 (op, dst);
+      LOCAL_SET (dst, scm_cell (scm_tc7_variable, SCM_UNPACK (SCM_UNDEFINED)));
+      NEXT (1);
+    }
+
+  /* box-ref dst:12 src:12
+   *
+   * Unpack the variable at SRC into DST, asserting that the variable is
+   * actually bound.
+   */
+  VM_DEFINE_OP (45, box_ref, "box-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM var;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      var = LOCAL_REF (src);
+      VM_ASSERT (SCM_VARIABLEP (var), abort ());
+      if (SCM_UNLIKELY (!VARIABLE_BOUNDP (var)))
+        {
+          SCM var_name;
+          /* Attempt to provide the variable name in the error message.  */
+          SYNC_IP ();
+          var_name = scm_module_reverse_lookup (scm_current_module (), var);
+          vm_error_unbound (SCM_FRAME_PROGRAM (fp), scm_is_true (var_name) ? 
var_name : var);
+        }
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (1);
+    }
+
+  /* box-set! dst:12 src:12
+   *
+   * Set the contents of the variable at DST to SET.
+   */
+  VM_DEFINE_OP (46, box_set, "box-set!", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM var;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      var = LOCAL_REF (dst);
+      VM_ASSERT (SCM_VARIABLEP (var), abort ());
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (1);
+    }
+
+  /* free-ref dst:12 src:12
+   *
+   * Load free variable SRC into local slot DST.
+   */
+  VM_DEFINE_OP (47, free_ref, "free-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      CHECK_FREE_VARIABLE (src);
+      LOCAL_SET (dst, FREE_VARIABLE_REF (src));
+      NEXT (1);
+    }
+
+  /* make-closure dst:24 offset:32 _:8 nfree:24 free0:24 0:8 ...
+   *
+   * Make a new closure, and write it to DST.  The code for the closure
+   * will be found at OFFSET words from the current IP.  OFFSET is a
+   * signed 32-bit integer.  The registers for the NFREE free variables
+   * follow.
+   */
+  VM_DEFINE_OP (48, make_closure, "make-closure", OP3 (U8_U24, L32, X8_R24) | 
OP_DST)
+    {
+      scm_t_uint32 dst, nfree, n;
+      scm_t_int32 offset;
+      SCM closure;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      SCM_UNPACK_RTL_24 (ip[2], nfree);
+
+      // FIXME: Assert range of nfree?
+      closure = scm_words (scm_tc7_rtl_program | (nfree << 16), nfree + 2);
+      SCM_SET_CELL_WORD_1 (closure, ip + offset);
+      for (n = 0; n < nfree; n++)
+        SCM_RTL_PROGRAM_FREE_VARIABLE_SET (closure, n, LOCAL_REF (ip[n + 3]));
+      LOCAL_SET (dst, closure);
+      NEXT (nfree + 3);
+    }
+
+  /* fix-closure dst:24 _:8 nfree:24 free0:24 0:8 ...
+   *
+   * "Fix" a closure.  This is used for lambda expressions bound in a
+   * <fix>, but which are not always called in tail position.  In that
+   * case we allocate the closures first, then destructively update their
+   * free variables to point to each other.  NFREE and the locals FREE0...
+   * are as in make-closure.
+   */
+  VM_DEFINE_OP (49, fix_closure, "fix-closure", OP2 (U8_U24, X8_R24))
+    {
+      scm_t_uint32 dst, nfree, n;
+      SCM closure;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      SCM_UNPACK_RTL_24 (ip[1], nfree);
+      closure = LOCAL_REF (dst);
+      for (n = 0; n < nfree; n++)
+        SCM_RTL_PROGRAM_FREE_VARIABLE_SET (closure, n, LOCAL_REF (ip[n + 2]));
+      NEXT (nfree + 2);
+    }
+
+
+  
+
+  /*
+   * Immediates and statically allocated non-immediates
+   */
+
+  /* make-short-immediate dst:8 low-bits:16
+   *
+   * Make an immediate whose low bits are LOW-BITS, and whose top bits are
+   * 0.
+   */
+  VM_DEFINE_OP (50, make_short_immediate, "make-short-immediate", OP1 
(U8_U8_I16) | OP_DST)
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_8_16 (op, dst, val);
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (1);
+    }
+
+  /* make-long-immediate dst:24 low-bits:32
+   *
+   * Make an immediate whose low bits are LOW-BITS, and whose top bits are
+   * 0.
+   */
+  VM_DEFINE_OP (51, make_long_immediate, "make-long-immediate", OP2 (U8_U24, 
I32))
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      val = ip[1];
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (2);
+    }
+
+  /* make-long-long-immediate dst:24 high-bits:32 low-bits:32
+   *
+   * Make an immediate with HIGH-BITS and LOW-BITS.
+   */
+  VM_DEFINE_OP (52, make_long_long_immediate, "make-long-long-immediate", OP3 
(U8_U24, A32, B32) | OP_DST)
+    {
+      scm_t_uint8 dst;
+      scm_t_bits val;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+#if SIZEOF_SCM_T_BITS > 4
+      val = ip[1];
+      val <<= 32;
+      val |= ip[2];
+#else
+      ASSERT (ip[1] == 0);
+      val = ip[2];
+#endif
+      LOCAL_SET (dst, SCM_PACK (val));
+      NEXT (3);
+    }
+
+  /* make-non-immediate dst:24 offset:32
+   *
+   * Load a pointer to statically allocated memory into DST.  The
+   * object's memory is will be found OFFSET 32-bit words away from the
+   * current instruction pointer.  OFFSET is a signed value.  The
+   * intention here is that the compiler would produce an object file
+   * containing the words of a non-immediate object, and this
+   * instruction creates a pointer to that memory, effectively
+   * resurrecting that object.
+   *
+   * Whether the object is mutable or immutable depends on where it was
+   * allocated by the compiler, and loaded by the loader.
+   */
+  VM_DEFINE_OP (53, make_non_immediate, "make-non-immediate", OP2 (U8_U24, 
N32) | OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+      scm_t_bits unpacked;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      loc = ip + offset;
+      unpacked = (scm_t_bits) loc;
+
+      VM_ASSERT (!(unpacked & 0x7), abort());
+
+      LOCAL_SET (dst, SCM_PACK (unpacked));
+
+      NEXT (2);
+    }
+
+  /* static-ref dst:24 offset:32
+   *
+   * Load a SCM value into DST.  The SCM value will be fetched from
+   * memory, OFFSET 32-bit words away from the current instruction
+   * pointer.  OFFSET is a signed value.
+   *
+   * The intention is for this instruction to be used to load constants
+   * that the compiler is unable to statically allocate, like symbols.
+   * These values would be initialized when the object file loads.
+   */
+  VM_DEFINE_OP (54, static_ref, "static-ref", OP2 (U8_U24, S32))
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+      scm_t_uintptr loc_bits;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      offset = ip[1];
+      loc = ip + offset;
+      loc_bits = (scm_t_uintptr) loc;
+      VM_ASSERT (ALIGNED_P (loc, SCM), abort());
+
+      LOCAL_SET (dst, *((SCM *) loc_bits));
+
+      NEXT (2);
+    }
+
+  /* static-set! src:24 offset:32
+   *
+   * Store a SCM value into memory, OFFSET 32-bit words away from the
+   * current instruction pointer.  OFFSET is a signed value.
+   */
+  VM_DEFINE_OP (55, static_set, "static-set!", OP2 (U8_U24, LO32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      offset = ip[1];
+      loc = ip + offset;
+      VM_ASSERT (ALIGNED_P (loc, SCM), abort());
+
+      *((SCM *) loc) = LOCAL_REF (src);
+
+      NEXT (2);
+    }
+
+  /* link-procedure! src:24 offset:32
+   *
+   * Set the code pointer of the procedure in SRC to point OFFSET 32-bit
+   * words away from the current instruction pointer.  OFFSET is a
+   * signed value.
+   */
+  VM_DEFINE_OP (56, link_procedure, "link-procedure!", OP2 (U8_U24, L32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 offset;
+      scm_t_uint32* loc;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      offset = ip[1];
+      loc = ip + offset;
+
+      SCM_SET_CELL_WORD_1 (LOCAL_REF (src), (scm_t_bits) loc);
+
+      NEXT (2);
+    }
+
+  
+
+  /*
+   * Mutable top-level bindings
+   */
+
+  /* There are three slightly different ways to resolve toplevel
+     variables.
+
+     1. A toplevel reference outside of a function.  These need to be
+        looked up when the expression is evaluated -- no later, and no
+        before.  They are looked up relative to the module that is
+        current when the expression is evaluated.  For example:
+
+          (if (foo) a b)
+
+        The "resolve" instruction resolves the variable (box), and then
+        access is via box-ref or box-set!.
+
+     2. A toplevel reference inside a function.  These are looked up
+        relative to the module that was current when the function was
+        defined.  Unlike code at the toplevel, which is usually run only
+        once, these bindings benefit from memoized lookup, in which the
+        variable resulting from the lookup is cached in the function.
+
+          (lambda () (if (foo) a b))
+
+        Although one can use resolve and box-ref, the toplevel-ref and
+        toplevel-set! instructions are better for references.
+
+     3. A reference to an identifier with respect to a particular
+        module.  This can happen for primitive references, and
+        references residualized by macro expansions.  These can be
+        cached or not, depending on whether they are in a lambda or not.
+
+          (@ (foo bar) a)
+          (@@ (foo bar) a)
+
+        For these, one can use resolve-module, resolve, and the box
+        interface, though there is also module-ref as a shortcut.
+     */
+
+  /* current-module dst:24
+   *
+   * Store the current module in DST.
+   */
+  VM_DEFINE_OP (57, current_module, "current-module", OP1 (U8_U24) | OP_DST)
+    {
+      scm_t_uint32 dst;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_current_module ());
+
+      NEXT (1);
+    }
+
+  /* resolve dst:8 mod:8 sym:8
+   *
+   * Resolve SYM in MOD, and place the resulting variable in DST.
+   */
+  VM_DEFINE_OP (58, resolve, "resolve", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, mod, sym;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, mod, sym);
+
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_module_lookup (LOCAL_REF (mod), LOCAL_REF (sym)));
+
+      NEXT (1);
+    }
+
+  /* resolve-module dst:8 name:8 public:8
+   *
+   * Resolve a module with name NAME, placing it in DST.  If PUBLIC is
+   * nonzero, resolve the public interface, otherwise use the private
+   * interface.
+   */
+  VM_DEFINE_OP (59, resolve_module, "resolve-module", OP1 (U8_U8_U8_U8) | 
OP_DST)
+    {
+      scm_t_uint8 dst, name, public;
+      SCM mod;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, name, public);
+
+      SYNC_IP ();
+      mod = scm_resolve_module (LOCAL_REF (name));
+      if (public)
+        mod = scm_module_public_interface (mod);
+      LOCAL_SET (dst, mod);
+
+      NEXT (1);
+    }
+
+  /* define sym:12 val:12
+   *
+   * Look up a binding for SYM in the current module, creating it if
+   * necessary.  Set its value to VAL.
+   */
+  VM_DEFINE_OP (60, define, "define", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 sym, val;
+      SCM_UNPACK_RTL_12_12 (op, sym, val);
+      SYNC_IP ();
+      scm_define (LOCAL_REF (sym), LOCAL_REF (val));
+      NEXT (1);
+    }
+
+  /* toplevel-ref dst:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Load a SCM value.  The SCM value will be fetched from memory,
+   * VAR-OFFSET 32-bit words away from the current instruction pointer.
+   * VAR-OFFSET is a signed value.  Up to here, toplevel-ref is like
+   * static-ref.
+   *
+   * Then, if the loaded value is a variable, the value of the variable
+   * is placed in DST, and control flow continues.
+   *
+   * Otherwise, we have to resolve the variable.  In that case we load
+   * the module from MOD-OFFSET, just as we loaded the variable.
+   * Usually the module gets set when the closure is created.  The name
+   * is an offset to a symbol.
+   *
+   * We use the module and the string to resolve the variable, raising
+   * an error if it is unbound, unbox it into DST, and cache the
+   * resolved variable so that we will hit the cache next time.
+   */
+  VM_DEFINE_OP (61, toplevel_ref, "toplevel-ref", OP4 (U8_U24, S32, S32, N32) 
| OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM mod, sym;
+          scm_t_int32 mod_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *mod_loc = ip + mod_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+          
+          SYNC_IP ();
+
+          VM_ASSERT (ALIGNED_P (mod_loc, SCM), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          mod = *((SCM *) mod_loc);
+          sym = *((SCM *) sym_loc);
+
+          var = scm_module_lookup (mod, sym);
+          VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+
+          *var_loc = var;
+        }
+
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (4);
+    }
+
+  /* toplevel-set! src:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Set a top-level variable from a variable cache cell.  The variable
+   * is resolved as in toplevel-ref.
+   */
+  VM_DEFINE_OP (62, toplevel_set, "toplevel-set!", OP4 (U8_U24, S32, S32, N32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM mod, sym;
+          scm_t_int32 mod_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *mod_loc = ip + mod_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+          
+          SYNC_IP ();
+
+          VM_ASSERT (ALIGNED_P (mod_loc, SCM), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          mod = *((SCM *) mod_loc);
+          sym = *((SCM *) sym_loc);
+
+          var = scm_module_lookup (mod, sym);
+
+          *var_loc = var;
+        }
+
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (4);
+    }
+
+  /* module-ref dst:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Like toplevel-ref, except MOD-OFFSET points at the name of a module
+   * instead of the module itself.
+   */
+  VM_DEFINE_OP (63, module_ref, "module-ref", OP4 (U8_U24, S32, N32, N32) | 
OP_DST)
+    {
+      scm_t_uint32 dst;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, dst);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM modname, sym;
+          scm_t_int32 modname_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *modname_words = ip + modname_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+
+          SYNC_IP ();
+
+          VM_ASSERT (!(((scm_t_uintptr) modname_words) & 0x7), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          modname = SCM_PACK ((scm_t_bits) modname_words);
+          sym = *((SCM *) sym_loc);
+
+          if (scm_is_true (SCM_CAR (modname)))
+            var = scm_public_lookup (SCM_CDR (modname), sym);
+          else
+            var = scm_private_lookup (SCM_CDR (modname), sym);
+
+          VM_ASSERT (VARIABLE_BOUNDP (var), vm_error_unbound (fp[-1], sym));
+
+          *var_loc = var;
+        }
+
+      LOCAL_SET (dst, VARIABLE_REF (var));
+      NEXT (4);
+    }
+
+  /* module-set! src:24 var-offset:32 mod-offset:32 sym-offset:32
+   *
+   * Like toplevel-set!, except MOD-OFFSET points at the name of a module
+   * instead of the module itself.
+   */
+  VM_DEFINE_OP (64, module_set, "module-set!", OP4 (U8_U24, S32, N32, N32))
+    {
+      scm_t_uint32 src;
+      scm_t_int32 var_offset;
+      scm_t_uint32* var_loc_u32;
+      SCM *var_loc;
+      SCM var;
+
+      SCM_UNPACK_RTL_24 (op, src);
+      var_offset = ip[1];
+      var_loc_u32 = ip + var_offset;
+      VM_ASSERT (ALIGNED_P (var_loc_u32, SCM), abort());
+      var_loc = (SCM *) var_loc_u32;
+      var = *var_loc;
+
+      if (SCM_UNLIKELY (!SCM_VARIABLEP (var)))
+        {
+          SCM modname, sym;
+          scm_t_int32 modname_offset = ip[2]; /* signed */
+          scm_t_int32 sym_offset = ip[3]; /* signed */
+          scm_t_uint32 *modname_words = ip + modname_offset;
+          scm_t_uint32 *sym_loc = ip + sym_offset;
+
+          SYNC_IP ();
+
+          VM_ASSERT (!(((scm_t_uintptr) modname_words) & 0x7), abort());
+          VM_ASSERT (ALIGNED_P (sym_loc, SCM), abort());
+
+          modname = SCM_PACK ((scm_t_bits) modname_words);
+          sym = *((SCM *) sym_loc);
+
+          if (scm_is_true (SCM_CAR (modname)))
+            var = scm_public_lookup (SCM_CDR (modname), sym);
+          else
+            var = scm_private_lookup (SCM_CDR (modname), sym);
+
+          *var_loc = var;
+        }
+
+      VARIABLE_SET (var, LOCAL_REF (src));
+      NEXT (4);
+    }
+
+  
+
+  /*
+   * The dynamic environment
+   */
+
+  /* prompt tag:24 flags:8 handler-offset:24
+   *
+   * Push a new prompt on the dynamic stack, with a tag from TAG and a
+   * handler at HANDLER-OFFSET words from the current IP.  The handler
+   * will expect a multiple-value return.
+   */
+  VM_DEFINE_OP (65, prompt, "prompt", OP2 (U8_U24, U8_L24))
+#if 0
+    {
+      scm_t_uint32 tag;
+      scm_t_int32 offset;
+      scm_t_uint8 escape_only_p;
+      scm_t_dynstack_prompt_flags flags;
+
+      SCM_UNPACK_RTL_24 (op, tag);
+      escape_only_p = ip[1] & 0xff;
+      offset = ip[1];
+      offset >>= 8; /* Sign extension */
+  
+      /* Push the prompt onto the dynamic stack. */
+      flags = escape_only_p ? SCM_F_DYNSTACK_PROMPT_ESCAPE_ONLY : 0;
+      scm_dynstack_push_prompt (&current_thread->dynstack, flags,
+                                LOCAL_REF (tag),
+                                fp, vp->sp, ip + offset, &registers);
+      NEXT (2);
+    }
+#else
+  abort();
+#endif
+
+  /* wind winder:12 unwinder:12
+   *
+   * Push wind and unwind procedures onto the dynamic stack. Note that
+   * neither are actually called; the compiler should emit calls to wind
+   * and unwind for the normal dynamic-wind control flow.  Also note that
+   * the compiler should have inserted checks that they wind and unwind
+   * procs are thunks, if it could not prove that to be the case.
+   */
+  VM_DEFINE_OP (66, wind, "wind", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 winder, unwinder;
+      SCM_UNPACK_RTL_12_12 (op, winder, unwinder);
+      scm_dynstack_push_dynwind (&current_thread->dynstack,
+                                 LOCAL_REF (winder), LOCAL_REF (unwinder));
+      NEXT (1);
+    }
+
+  /* abort tag:24 _:8 nvalues:24 val0:24 0:8 val1:24 0:8 ...
+   *
+   * Return a number of values to a prompt handler.  The values VAL0,
+   * VAL1, etc are 24-bit values, in the lower 24 bits of their words.
+   * The upper 8 bits are 0.
+   */
+  VM_DEFINE_OP (67, abort, "abort", OP2 (U8_U24, X8_R24))
+#if 0
+    {
+      scm_t_uint32 tag, nvalues;
+
+      SCM_UNPACK_RTL_24 (op, tag);
+      SCM_UNPACK_RTL_24 (ip[1], nvalues);
+
+      SYNC_IP ();
+      vm_abort (vm, LOCAL_REF (tag), nvalues, &ip[2], &registers);
+
+      /* vm_abort should not return */
+      abort ();
+    }
+#else
+  abort();
+#endif
+
+  /* unwind _:24
+   *
+   * A normal exit from the dynamic extent of an expression. Pop the top
+   * entry off of the dynamic stack.
+   */
+  VM_DEFINE_OP (68, unwind, "unwind", OP1 (U8_X24))
+    {
+      scm_dynstack_pop (&current_thread->dynstack);
+      NEXT (1);
+    }
+
+  /* wind-fluids fluid-base:24 _:8 n:24 value0:24 0:8 ...
+   *
+   * Dynamically bind N fluids to values.  The fluids are expected to be
+   * allocated in a continguous range on the stack, starting from
+   * FLUID-BASE.  The values do not have this restriction.
+   */
+  VM_DEFINE_OP (69, wind_fluids, "wind-fluids", OP2 (U8_U24, X8_R24))
+#if 0
+    {
+      scm_t_uint32 fluid_base, n;
+
+      SCM_UNPACK_RTL_24 (op, fluid_base);
+      SCM_UNPACK_RTL_24 (ip[1], n);
+
+      scm_dynstack_push_fluids_shuffled (&current_thread->dynstack, n,
+                                         &fp[fluid_base], fp, &ip[2],
+                                         current_thread->dynamic_state);
+      NEXT (n + 2);
+    }
+#else
+  abort();
+#endif
+
+  /* unwind-fluids _:24
+   *
+   * Leave the dynamic extent of a with-fluids expression, restoring the
+   * fluids to their previous values.
+   */
+  VM_DEFINE_OP (70, unwind_fluids, "unwind-fluids", OP1 (U8_X24))
+    {
+      /* This function must not allocate.  */
+      scm_dynstack_unwind_fluids (&current_thread->dynstack,
+                                  current_thread->dynamic_state);
+      NEXT (1);
+    }
+
+  /* fluid-ref dst:12 src:12
+   *
+   * Reference the fluid in SRC, and place the value in DST.
+   */
+  VM_DEFINE_OP (71, fluid_ref, "fluid-ref", OP1 (U8_U12_U12) | OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      size_t num;
+      SCM fluid, fluids;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      fluid = LOCAL_REF (src);
+      fluids = SCM_I_DYNAMIC_STATE_FLUIDS (current_thread->dynamic_state);
+      if (SCM_UNLIKELY (!SCM_FLUID_P (fluid))
+          || ((num = SCM_I_FLUID_NUM (fluid)) >= SCM_SIMPLE_VECTOR_LENGTH 
(fluids)))
+        {
+          /* Punt dynstate expansion and error handling to the C proc. */
+          SYNC_IP ();
+          LOCAL_SET (dst, scm_fluid_ref (fluid));
+        }
+      else
+        {
+          SCM val = SCM_SIMPLE_VECTOR_REF (fluids, num);
+          if (scm_is_eq (val, SCM_UNDEFINED))
+            val = SCM_I_FLUID_DEFAULT (fluid);
+          VM_ASSERT (!scm_is_eq (val, SCM_UNDEFINED),
+                     vm_error_unbound_fluid (program, fluid));
+          LOCAL_SET (dst, val);
+        }
+
+      NEXT (1);
+    }
+
+  /* fluid-set fluid:12 val:12
+   *
+   * Set the value of the fluid in DST to the value in SRC.
+   */
+  VM_DEFINE_OP (72, fluid_set, "fluid-set", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      size_t num;
+      SCM fluid, fluids;
+
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      fluid = LOCAL_REF (a);
+      fluids = SCM_I_DYNAMIC_STATE_FLUIDS (current_thread->dynamic_state);
+      if (SCM_UNLIKELY (!SCM_FLUID_P (fluid))
+          || ((num = SCM_I_FLUID_NUM (fluid)) >= SCM_SIMPLE_VECTOR_LENGTH 
(fluids)))
+        {
+          /* Punt dynstate expansion and error handling to the C proc. */
+          SYNC_IP ();
+          scm_fluid_set_x (fluid, LOCAL_REF (b));
+        }
+      else
+        SCM_SIMPLE_VECTOR_SET (fluids, num, LOCAL_REF (b));
+
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Strings, symbols, and keywords
+   */
+
+  /* string-length dst:12 src:12
+   *
+   * Store the length of the string in SRC in DST.
+   */
+  VM_DEFINE_OP (73, string_length, "string-length", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (str);
+      if (SCM_LIKELY (scm_is_string (str)))
+        RETURN (SCM_I_MAKINUM (scm_i_string_length (str)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_string_length (str));
+        }
+    }
+
+  /* string-ref dst:8 src:8 idx:8
+   *
+   * Fetch the character at position IDX in the string in SRC, and store
+   * it in DST.
+   */
+  VM_DEFINE_OP (74, string_ref, "string-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_signed_bits i = 0;
+      ARGS2 (str, idx);
+      if (SCM_LIKELY (scm_is_string (str)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < scm_i_string_length (str)))
+        RETURN (SCM_MAKE_CHAR (scm_i_string_ref (str, i)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_string_ref (str, idx));
+        }
+    }
+
+  /* No string-set! instruction, as there is no good fast path there.  */
+
+  /* string-to-number dst:12 src:12
+   *
+   * Parse a string in SRC to a number, and store in DST.
+   */
+  VM_DEFINE_OP (75, string_to_number, "string->number", OP1 (U8_U12_U12) | 
OP_DST)
+    {
+      scm_t_uint16 dst, src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst,
+                 scm_string_to_number (LOCAL_REF (src),
+                                       SCM_UNDEFINED /* radix = 10 */));
+      NEXT (1);
+    }
+
+  /* string-to-symbol dst:12 src:12
+   *
+   * Parse a string in SRC to a symbol, and store in DST.
+   */
+  VM_DEFINE_OP (76, string_to_symbol, "string->symbol", OP1 (U8_U12_U12) | 
OP_DST)
+    {
+      scm_t_uint16 dst, src;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_string_to_symbol (LOCAL_REF (src)));
+      NEXT (1);
+    }
+
+  /* symbol->keyword dst:12 src:12
+   *
+   * Make a keyword from the symbol in SRC, and store it in DST.
+   */
+  VM_DEFINE_OP (77, symbol_to_keyword, "symbol->keyword", OP1 (U8_U12_U12) | 
OP_DST)
+    {
+      scm_t_uint16 dst, src;
+      SCM_UNPACK_RTL_12_12 (op, dst, src);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_symbol_to_keyword (LOCAL_REF (src)));
+      NEXT (1);
+    }
+
+  
+
+  /*
+   * Pairs
+   */
+
+  /* cons dst:8 car:8 cdr:8
+   *
+   * Cons CAR and CDR, and store the result in DST.
+   */
+  VM_DEFINE_OP (78, cons, "cons", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      RETURN (scm_cons (x, y));
+    }
+
+  /* car dst:12 src:12
+   *
+   * Place the car of SRC in DST.
+   */
+  VM_DEFINE_OP (79, car, "car", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+      VM_VALIDATE_PAIR (x, "car");
+      RETURN (SCM_CAR (x));
+    }
+
+  /* cdr dst:12 src:12
+   *
+   * Place the cdr of SRC in DST.
+   */
+  VM_DEFINE_OP (80, cdr, "cdr", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+      VM_VALIDATE_PAIR (x, "cdr");
+      RETURN (SCM_CDR (x));
+    }
+
+  /* set-car! pair:12 car:12
+   *
+   * Set the car of DST to SRC.
+   */
+  VM_DEFINE_OP (81, set_car, "set-car!", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      SCM x, y;
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      x = LOCAL_REF (a);
+      y = LOCAL_REF (b);
+      VM_VALIDATE_PAIR (x, "set-car!");
+      SCM_SETCAR (x, y);
+      NEXT (1);
+    }
+
+  /* set-cdr! pair:12 cdr:12
+   *
+   * Set the cdr of DST to SRC.
+   */
+  VM_DEFINE_OP (82, set_cdr, "set-cdr!", OP1 (U8_U12_U12))
+    {
+      scm_t_uint16 a, b;
+      SCM x, y;
+      SCM_UNPACK_RTL_12_12 (op, a, b);
+      x = LOCAL_REF (a);
+      y = LOCAL_REF (b);
+      VM_VALIDATE_PAIR (x, "set-car!");
+      SCM_SETCDR (x, y);
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Numeric operations
+   */
+
+  /* add dst:8 a:8 b:8
+   *
+   * Add A to B, and place the result in DST.
+   */
+  VM_DEFINE_OP (83, add, "add", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      BINARY_INTEGER_OP (+, scm_sum);
+    }
+
+  /* add1 dst:12 src:12
+   *
+   * Add 1 to the value in SRC, and place the result in DST.
+   */
+  VM_DEFINE_OP (84, add1, "add1", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+
+      /* Check for overflow.  */
+      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) < INUM_MAX))
+        {
+          SCM result;
+
+          /* Add the integers without untagging.  */
+          result = SCM_PACK ((scm_t_intptr) SCM_UNPACK (x)
+                             + (scm_t_intptr) SCM_UNPACK (SCM_I_MAKINUM (1))
+                             - scm_tc2_int);
+
+          if (SCM_LIKELY (SCM_I_INUMP (result)))
+            RETURN (result);
+        }
+
+      SYNC_IP ();
+      RETURN (scm_sum (x, SCM_I_MAKINUM (1)));
+    }
+
+  /* sub dst:8 a:8 b:8
+   *
+   * Subtract B from A, and place the result in DST.
+   */
+  VM_DEFINE_OP (85, sub, "sub", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      BINARY_INTEGER_OP (-, scm_difference);
+    }
+
+  /* sub1 dst:12 src:12
+   *
+   * Subtract 1 from SRC, and place the result in DST.
+   */
+  VM_DEFINE_OP (86, sub1, "sub1", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (x);
+
+      /* Check for underflow.  */
+      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) > INUM_MIN))
+        {
+          SCM result;
+
+          /* Substract the integers without untagging.  */
+          result = SCM_PACK ((scm_t_intptr) SCM_UNPACK (x)
+                             - (scm_t_intptr) SCM_UNPACK (SCM_I_MAKINUM (1))
+                             + scm_tc2_int);
+
+          if (SCM_LIKELY (SCM_I_INUMP (result)))
+            RETURN (result);
+        }
+
+      SYNC_IP ();
+      RETURN (scm_difference (x, SCM_I_MAKINUM (1)));
+    }
+
+  /* mul dst:8 a:8 b:8
+   *
+   * Multiply A and B, and place the result in DST.
+   */
+  VM_DEFINE_OP (87, mul, "mul", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_product (x, y));
+    }
+
+  /* div dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the result in DST.
+   */
+  VM_DEFINE_OP (88, div, "div", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_divide (x, y));
+    }
+
+  /* quo dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the quotient in DST.
+   */
+  VM_DEFINE_OP (89, quo, "quo", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_quotient (x, y));
+    }
+
+  /* rem dst:8 a:8 b:8
+   *
+   * Divide A by B, and place the remainder in DST.
+   */
+  VM_DEFINE_OP (90, rem, "rem", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_remainder (x, y));
+    }
+
+  /* mod dst:8 a:8 b:8
+   *
+   * Place the modulo of A by B in DST.
+   */
+  VM_DEFINE_OP (91, mod, "mod", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      SYNC_IP ();
+      RETURN (scm_modulo (x, y));
+    }
+
+  /* ash dst:8 a:8 b:8
+   *
+   * Shift A arithmetically by B bits, and place the result in DST.
+   */
+  VM_DEFINE_OP (92, ash, "ash", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        {
+          if (SCM_I_INUM (y) < 0)
+            /* Right shift, will be a fixnum. */
+            RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) >> -SCM_I_INUM (y)));
+          else
+            /* Left shift. See comments in scm_ash. */
+            {
+              scm_t_signed_bits nn, bits_to_shift;
+
+              nn = SCM_I_INUM (x);
+              bits_to_shift = SCM_I_INUM (y);
+
+              if (bits_to_shift < SCM_I_FIXNUM_BIT-1
+                  && ((scm_t_bits)
+                      (SCM_SRS (nn, (SCM_I_FIXNUM_BIT-1 - bits_to_shift)) + 1)
+                      <= 1))
+                RETURN (SCM_I_MAKINUM (nn << bits_to_shift));
+              /* fall through */
+            }
+          /* fall through */
+        }
+      SYNC_IP ();
+      RETURN (scm_ash (x, y));
+    }
+
+  /* logand dst:8 a:8 b:8
+   *
+   * Place the bitwise AND of A and B into DST.
+   */
+  VM_DEFINE_OP (93, logand, "logand", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) & SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logand (x, y));
+    }
+
+  /* logior dst:8 a:8 b:8
+   *
+   * Place the bitwise inclusive OR of A with B in DST.
+   */
+  VM_DEFINE_OP (94, logior, "logior", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) | SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logior (x, y));
+    }
+
+  /* logxor dst:8 a:8 b:8
+   *
+   * Place the bitwise exclusive OR of A with B in DST.
+   */
+  VM_DEFINE_OP (95, logxor, "logxor", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (x, y);
+      if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
+        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) ^ SCM_I_INUM (y)));
+      SYNC_IP ();
+      RETURN (scm_logxor (x, y));
+    }
+
+  /* vector-length dst:12 src:12
+   *
+   * Store the length of the vector in SRC in DST.
+   */
+  VM_DEFINE_OP (96, vector_length, "vector-length", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (vect);
+      if (SCM_LIKELY (SCM_I_IS_VECTOR (vect)))
+        RETURN (SCM_I_MAKINUM (SCM_I_VECTOR_LENGTH (vect)));
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_vector_length (vect));
+        }
+    }
+
+  /* vector-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at position IDX in the vector in SRC, and store it
+   * in DST.
+   */
+  VM_DEFINE_OP (97, vector_ref, "vector-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_signed_bits i = 0;
+      ARGS2 (vect, idx);
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (vect)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < SCM_I_VECTOR_LENGTH (vect)))
+        RETURN (SCM_I_VECTOR_ELTS (vect)[i]);
+      else
+        {
+          SYNC_IP ();
+          RETURN (scm_vector_ref (vect, idx));
+        }
+    }
+
+  /* constant-vector-ref dst:8 src:8 idx:8
+   *
+   * Fill DST with the item IDX elements into the vector at SRC.  Useful
+   * for building data types using vectors.
+   */
+  VM_DEFINE_OP (98, constant_vector_ref, "constant-vector-ref", OP1 
(U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, src, idx;
+      SCM v;
+      
+      SCM_UNPACK_RTL_8_8_8 (op, dst, src, idx);
+      v = LOCAL_REF (src);
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (v)
+                      && idx < SCM_I_VECTOR_LENGTH (v)))
+        LOCAL_SET (dst, SCM_I_VECTOR_ELTS (LOCAL_REF (src))[idx]);
+      else
+        LOCAL_SET (dst, scm_c_vector_ref (v, idx));
+      NEXT (1);
+    }
+
+  /* vector-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the vector DST at index IDX.
+   */
+  VM_DEFINE_OP (99, vector_set, "vector-set", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx_var, src;
+      SCM vect, idx, val;
+      scm_t_signed_bits i = 0;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx_var, src);
+      vect = LOCAL_REF (dst);
+      idx = LOCAL_REF (idx_var);
+      val = LOCAL_REF (src);
+
+      if (SCM_LIKELY (SCM_I_IS_NONWEAK_VECTOR (vect)
+                      && SCM_I_INUMP (idx)
+                      && ((i = SCM_I_INUM (idx)) >= 0)
+                      && i < SCM_I_VECTOR_LENGTH (vect)))
+        SCM_I_VECTOR_WELTS (vect)[i] = val;
+      else
+        {
+          SYNC_IP ();
+          scm_vector_set_x (vect, idx, val);
+        }
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Structs and GOOPS
+   */
+
+  /* struct-vtable dst:12 src:12
+   *
+   * Store the vtable of SRC into DST.
+   */
+  VM_DEFINE_OP (100, struct_vtable, "struct-vtable", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (obj);
+      VM_VALIDATE_STRUCT (obj, "struct_vtable");
+      RETURN (SCM_STRUCT_VTABLE (obj));
+    }
+
+  /* make-struct dst:12 vtable:12 _:8 n-init:24 init0:24 0:8 ...
+   *
+   * Make a new struct with VTABLE, and place it in DST.  The struct
+   * will be constructed with N-INIT initializers, which are located in
+   * the locals given by INIT0....  The format of INIT0... is as in the
+   * "call" opcode: unsigned 24-bit values, with 0 in the high byte.
+   */
+  VM_DEFINE_OP (101, make_struct, "make-struct", OP2 (U8_U12_U12, X8_R24))
+#if 0
+    {
+      scm_t_uint16 dst, vtable_r;
+      scm_t_uint32 n_init, n;
+      SCM vtable, ret;
+
+      SCM_UNPACK_RTL_12_12 (op, dst, vtable_r);
+      vtable = LOCAL_REF (vtable_r);
+      SCM_UNPACK_RTL_24 (ip[1], n_init);
+
+      SYNC_IP ();
+
+      if (SCM_LIKELY (SCM_STRUCTP (vtable)
+                      && SCM_VTABLE_FLAG_IS_SET (vtable, 
SCM_VTABLE_FLAG_SIMPLE)
+                      && (SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size)
+                          == n_init)
+                      && !SCM_VTABLE_INSTANCE_FINALIZER (vtable)))
+        {
+          /* Verily, we are making a simple struct with the right number of
+             initializers, and no finalizer. */
+          ret = scm_words ((scm_t_bits)SCM_STRUCT_DATA (vtable) | 
scm_tc3_struct,
+                           n_init + 2);
+          SCM_SET_CELL_WORD_1 (ret, (scm_t_bits)SCM_CELL_OBJECT_LOC (ret, 2));
+          
+          for (n = 0; n < n_init; n++)
+            SCM_STRUCT_DATA (ret)[n] = SCM_UNPACK (LOCAL_REF (ip[n + 1]));
+        }
+      else
+        ret = scm_c_make_structvs (vtable, fp, &ip[1], n_init);
+
+      LOCAL_SET (dst, ret);
+      NEXT (n_init + 1);
+    }
+#else
+  abort ();
+#endif
+
+  /* struct-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at slot IDX in the struct in SRC, and store it
+   * in DST.
+   */
+  VM_DEFINE_OP (102, struct_ref, "struct-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      ARGS2 (obj, pos);
+
+      if (SCM_LIKELY (SCM_STRUCTP (obj)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        SCM_VTABLE_FLAG_SIMPLE)
+                      && SCM_I_INUMP (pos)))
+        {
+          SCM vtable;
+          scm_t_bits index, len;
+
+          /* True, an inum is a signed value, but cast to unsigned it will
+             certainly be more than the length, so we will fall through if
+             index is negative. */
+          index = SCM_I_INUM (pos);
+          vtable = SCM_STRUCT_VTABLE (obj);
+          len = SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size);
+
+          if (SCM_LIKELY (index < len))
+            {
+              scm_t_bits *data = SCM_STRUCT_DATA (obj);
+              RETURN (SCM_PACK (data[index]));
+            }
+        }
+
+      SYNC_IP ();
+      RETURN (scm_struct_ref (obj, pos));
+    }
+
+  /* struct-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the struct DST at slot IDX.
+   */
+  VM_DEFINE_OP (103, struct_set, "struct-set!", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx, src;
+      SCM obj, pos, val;
+      
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);
+      obj = LOCAL_REF (dst);
+      pos = LOCAL_REF (idx);
+      val = LOCAL_REF (src);
+      
+      if (SCM_LIKELY (SCM_STRUCTP (obj)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        SCM_VTABLE_FLAG_SIMPLE)
+                      && SCM_STRUCT_VTABLE_FLAG_IS_SET (obj,
+                                                        
SCM_VTABLE_FLAG_SIMPLE_RW)
+                      && SCM_I_INUMP (pos)))
+        {
+          SCM vtable;
+          scm_t_bits index, len;
+
+          /* See above regarding index being >= 0. */
+          index = SCM_I_INUM (pos);
+          vtable = SCM_STRUCT_VTABLE (obj);
+          len = SCM_STRUCT_DATA_REF (vtable, scm_vtable_index_size);
+          if (SCM_LIKELY (index < len))
+            {
+              scm_t_bits *data = SCM_STRUCT_DATA (obj);
+              data[index] = SCM_UNPACK (val);
+              NEXT (1);
+            }
+        }
+
+      SYNC_IP ();
+      scm_struct_set_x (obj, pos, val);
+      NEXT (1);
+    }
+
+  /* class-of dst:12 type:12
+   *
+   * Store the vtable of SRC into DST.
+   */
+  VM_DEFINE_OP (104, class_of, "class-of", OP1 (U8_U12_U12) | OP_DST)
+    {
+      ARGS1 (obj);
+      if (SCM_INSTANCEP (obj))
+        RETURN (SCM_CLASS_OF (obj));
+      SYNC_IP ();
+      RETURN (scm_class_of (obj));
+    }
+
+  /* slot-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at slot IDX in the struct in SRC, and store it in
+   * DST.  Unlike struct-ref, IDX is an 8-bit immediate value, not an
+   * index into the stack.
+   */
+  VM_DEFINE_OP (105, slot_ref, "slot-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    {
+      scm_t_uint8 dst, src, idx;
+      SCM_UNPACK_RTL_8_8_8 (op, dst, src, idx);
+      LOCAL_SET (dst,
+                 SCM_PACK (SCM_STRUCT_DATA (LOCAL_REF (src))[idx]));
+      NEXT (1);
+    }
+
+  /* slot-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into slot IDX of the struct in DST.  Unlike struct-set!,
+   * IDX is an 8-bit immediate value, not an index into the stack.
+   */
+  VM_DEFINE_OP (106, slot_set, "slot-set!", OP1 (U8_U8_U8_U8))
+    {
+      scm_t_uint8 dst, idx, src;
+      SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);
+      SCM_STRUCT_DATA (LOCAL_REF (dst))[idx] = SCM_UNPACK (LOCAL_REF (src));
+      NEXT (1);
+    }
+
+
+  
+
+  /*
+   * Arrays, packed uniform arrays, and bytevectors.
+   */
+
+  /* load-typed-array dst:8 type:8 shape:8 offset:32 len:32
+   *
+   * Load the contiguous typed array located at OFFSET 32-bit words away
+   * from the instruction pointer, and store into DST.  LEN is a byte
+   * length.  OFFSET is signed.
+   */
+  VM_DEFINE_OP (107, load_typed_array, "load-typed-array", OP3 (U8_U8_U8_U8, 
N32, U32) | OP_DST)
+    {
+      scm_t_uint8 dst, type, shape;
+      scm_t_int32 offset;
+      scm_t_uint32 len;
+
+      SCM_UNPACK_RTL_8_8_8 (op, dst, type, shape);
+      offset = ip[1];
+      len = ip[2];
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_from_contiguous_typed_array (LOCAL_REF (type),
+                                                       LOCAL_REF (shape),
+                                                       ip + offset, len));
+      NEXT (3);
+    }
+
+  /* make-array dst:12 type:12 _:8 fill:12 bounds:12
+   *
+   * Make a new array with TYPE, FILL, and BOUNDS, storing it in DST.
+   */
+  VM_DEFINE_OP (108, make_array, "make-array", OP2 (U8_U12_U12, X8_U12_U12) | 
OP_DST)
+    {
+      scm_t_uint16 dst, type, fill, bounds;
+      SCM_UNPACK_RTL_12_12 (op, dst, type);
+      SCM_UNPACK_RTL_12_12 (ip[1], fill, bounds);
+      SYNC_IP ();
+      LOCAL_SET (dst, scm_make_typed_array (LOCAL_REF (type), LOCAL_REF (fill),
+                                            LOCAL_REF (bounds)));
+      NEXT (2);
+    }
+
+  /* bv-u8-ref dst:8 src:8 idx:8
+   * bv-s8-ref dst:8 src:8 idx:8
+   * bv-u16-ref dst:8 src:8 idx:8
+   * bv-s16-ref dst:8 src:8 idx:8
+   * bv-u32-ref dst:8 src:8 idx:8
+   * bv-s32-ref dst:8 src:8 idx:8
+   * bv-u64-ref dst:8 src:8 idx:8
+   * bv-s64-ref dst:8 src:8 idx:8
+   * bv-f32-ref dst:8 src:8 idx:8
+   * bv-f64-ref dst:8 src:8 idx:8
+   *
+   * Fetch the item at byte offset IDX in the bytevector SRC, and store
+   * it in DST.  All accesses use native endianness.
+   */
+#define BV_FIXABLE_INT_REF(stem, fn_stem, type, size)                  \
+  do {                                                                 \
+    scm_t_signed_bits i;                                                \
+    const scm_t_ ## type *int_ptr;                                     \
+    ARGS2 (bv, idx);                                                   \
+                                                                       \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);   \
+                                                                       \
+    if (SCM_LIKELY (SCM_I_INUMP (idx)                                  \
+                    && (i >= 0)                                                
\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))                
\
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))         \
+      RETURN (SCM_I_MAKINUM (*int_ptr));                                \
+    else                                                                \
+      {                                                                        
\
+        SYNC_IP ();                                                    \
+        RETURN (scm_bytevector_ ## fn_stem ## _ref (bv, idx));         \
+      }                                                                        
\
+  } while (0)
+
+#define BV_INT_REF(stem, type, size)                                   \
+  do {                                                                 \
+    scm_t_signed_bits i;                                                \
+    const scm_t_ ## type *int_ptr;                                     \
+    ARGS2 (bv, idx);                                                   \
+                                                                       \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);   \
+                                                                       \
+    if (SCM_LIKELY (SCM_I_INUMP (idx)                                  \
+                    && (i >= 0)                                                
\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))                
\
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))         \
+      {                                                                        
\
+        scm_t_ ## type x = *int_ptr;                                   \
+        if (SCM_FIXABLE (x))                                           \
+          RETURN (SCM_I_MAKINUM (x));                                  \
+        else                                                           \
+          {                                                            \
+            SYNC_IP ();                                                 \
+            RETURN (scm_from_ ## type (x));                            \
+          }                                                            \
+      }                                                                        
\
+    else                                                                \
+      {                                                                        
\
+        SYNC_IP ();                                                    \
+        RETURN (scm_bytevector_ ## stem ## _native_ref (bv, idx));     \
+      }                                                                        
\
+  } while (0)
+
+#define BV_FLOAT_REF(stem, fn_stem, type, size)                                
\
+  do {                                                                 \
+    scm_t_signed_bits i;                                                \
+    const type *float_ptr;                                             \
+    ARGS2 (bv, idx);                                                   \
+                                                                       \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-ref");                    \
+    i = SCM_I_INUM (idx);                                               \
+    float_ptr = (type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);           \
+                                                                       \
+    SYNC_IP ();                                                         \
+    if (SCM_LIKELY (SCM_I_INUMP (idx)                                  \
+                    && (i >= 0)                                                
\
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))                
\
+                    && (ALIGNED_P (float_ptr, type))))                 \
+      RETURN (scm_from_double (*float_ptr));                           \
+    else                                                                \
+      RETURN (scm_bytevector_ ## fn_stem ## _native_ref (bv, idx));    \
+  } while (0)
+
+  VM_DEFINE_OP (109, bv_u8_ref, "bv-u8-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (u8, u8, uint8, 1);
+
+  VM_DEFINE_OP (110, bv_s8_ref, "bv-s8-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (s8, s8, int8, 1);
+
+  VM_DEFINE_OP (111, bv_u16_ref, "bv-u16-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (u16, u16_native, uint16, 2);
+
+  VM_DEFINE_OP (112, bv_s16_ref, "bv-s16-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FIXABLE_INT_REF (s16, s16_native, int16, 2);
+
+  VM_DEFINE_OP (113, bv_u32_ref, "bv-u32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_REF (u32, u32_native, uint32, 4);
+#else
+    BV_INT_REF (u32, uint32, 4);
+#endif
+
+  VM_DEFINE_OP (114, bv_s32_ref, "bv-s32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_REF (s32, s32_native, int32, 4);
+#else
+    BV_INT_REF (s32, int32, 4);
+#endif
+
+  VM_DEFINE_OP (115, bv_u64_ref, "bv-u64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_INT_REF (u64, uint64, 8);
+
+  VM_DEFINE_OP (116, bv_s64_ref, "bv-s64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_INT_REF (s64, int64, 8);
+
+  VM_DEFINE_OP (117, bv_f32_ref, "bv-f32-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FLOAT_REF (f32, ieee_single, float, 4);
+
+  VM_DEFINE_OP (118, bv_f64_ref, "bv-f64-ref", OP1 (U8_U8_U8_U8) | OP_DST)
+    BV_FLOAT_REF (f64, ieee_double, double, 8);
+
+  /* bv-u8-set! dst:8 idx:8 src:8
+   * bv-s8-set! dst:8 idx:8 src:8
+   * bv-u16-set! dst:8 idx:8 src:8
+   * bv-s16-set! dst:8 idx:8 src:8
+   * bv-u32-set! dst:8 idx:8 src:8
+   * bv-s32-set! dst:8 idx:8 src:8
+   * bv-u64-set! dst:8 idx:8 src:8
+   * bv-s64-set! dst:8 idx:8 src:8
+   * bv-f32-set! dst:8 idx:8 src:8
+   * bv-f64-set! dst:8 idx:8 src:8
+   *
+   * Store SRC into the bytevector DST at byte offset IDX.  Multibyte
+   * values are written using native endianness.
+   */
+#define BV_FIXABLE_INT_SET(stem, fn_stem, type, min, max, size)                
\
+  do {                                                                 \
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i, j = 0;                                         \
+    SCM bv, scm_idx, val;                                               \
+    scm_t_ ## type *int_ptr;                                           \
+                                                                       \
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);   \
+                                                                       \
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))           \
+                    && (SCM_I_INUMP (val))                             \
+                    && ((j = SCM_I_INUM (val)) >= min)                  \
+                    && (j <= max)))                                    \
+      *int_ptr = (scm_t_ ## type) j;                                   \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## fn_stem ## _set_x (bv, scm_idx, val);        \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+#define BV_INT_SET(stem, type, size)                                   \
+  do {                                                                 \
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i;                                                \
+    SCM bv, scm_idx, val;                                               \
+    scm_t_ ## type *int_ptr;                                           \
+                                                                       \
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    int_ptr = (scm_t_ ## type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);   \
+                                                                       \
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (int_ptr, scm_t_ ## type))))          \
+      *int_ptr = scm_to_ ## type (val);                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## stem ## _native_set_x (bv, scm_idx, val);    \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+#define BV_FLOAT_SET(stem, fn_stem, type, size)                         \
+  do {                                                                  \
+    scm_t_uint8 dst, idx, src;                                          \
+    scm_t_signed_bits i;                                                \
+    SCM bv, scm_idx, val;                                               \
+    type *float_ptr;                                                    \
+                                                                       \
+    SCM_UNPACK_RTL_8_8_8 (op, dst, idx, src);                           \
+    bv = LOCAL_REF (dst);                                               \
+    scm_idx = LOCAL_REF (idx);                                          \
+    val = LOCAL_REF (src);                                              \
+    VM_VALIDATE_BYTEVECTOR (bv, "bv-" #stem "-set");                    \
+    i = SCM_I_INUM (scm_idx);                                           \
+    float_ptr = (type *) (SCM_BYTEVECTOR_CONTENTS (bv) + i);            \
+                                                                        \
+    if (SCM_LIKELY (SCM_I_INUMP (scm_idx)                               \
+                    && (i >= 0)                                         \
+                    && (i + size <= SCM_BYTEVECTOR_LENGTH (bv))         \
+                    && (ALIGNED_P (float_ptr, type))))                  \
+      *float_ptr = scm_to_double (val);                                 \
+    else                                                                \
+      {                                                                 \
+        SYNC_IP ();                                                     \
+        scm_bytevector_ ## fn_stem ## _native_set_x (bv, scm_idx, val); \
+      }                                                                 \
+    NEXT (1);                                                           \
+  } while (0)
+
+  VM_DEFINE_OP (119, bv_u8_set, "bv-u8-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (u8, u8, uint8, 0, SCM_T_UINT8_MAX, 1);
+
+  VM_DEFINE_OP (120, bv_s8_set, "bv-s8-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (s8, s8, int8, SCM_T_INT8_MIN, SCM_T_INT8_MAX, 1);
+
+  VM_DEFINE_OP (121, bv_u16_set, "bv-u16-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (u16, u16_native, uint16, 0, SCM_T_UINT16_MAX, 2);
+
+  VM_DEFINE_OP (122, bv_s16_set, "bv-s16-set!", OP1 (U8_U8_U8_U8))
+    BV_FIXABLE_INT_SET (s16, s16_native, int16, SCM_T_INT16_MIN, 
SCM_T_INT16_MAX, 2);
+
+  VM_DEFINE_OP (123, bv_u32_set, "bv-u32-set!", OP1 (U8_U8_U8_U8))
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_SET (u32, u32_native, uint32, 0, SCM_T_UINT32_MAX, 4);
+#else
+    BV_INT_SET (u32, uint32, 4);
+#endif
+
+  VM_DEFINE_OP (124, bv_s32_set, "bv-s32-set!", OP1 (U8_U8_U8_U8))
+#if SIZEOF_VOID_P > 4
+    BV_FIXABLE_INT_SET (s32, s32_native, int32, SCM_T_INT32_MIN, 
SCM_T_INT32_MAX, 4);
+#else
+    BV_INT_SET (s32, int32, 4);
+#endif
+
+  VM_DEFINE_OP (125, bv_u64_set, "bv-u64-set!", OP1 (U8_U8_U8_U8))
+    BV_INT_SET (u64, uint64, 8);
+
+  VM_DEFINE_OP (126, bv_s64_set, "bv-s64-set!", OP1 (U8_U8_U8_U8))
+    BV_INT_SET (s64, int64, 8);
+
+  VM_DEFINE_OP (127, bv_f32_set, "bv-f32-set!", OP1 (U8_U8_U8_U8))
+    BV_FLOAT_SET (f32, ieee_single, float, 4);
+
+  VM_DEFINE_OP (128, bv_f64_set, "bv-f64-set!", OP1 (U8_U8_U8_U8))
+    BV_FLOAT_SET (f64, ieee_double, double, 8);
+
+  END_DISPATCH_SWITCH;
+
+ vm_error_bad_instruction:
+  vm_error_bad_instruction (op);
+
+  abort (); /* never reached */
+}
+
+
+#undef ABORT_CONTINUATION_HOOK
+#undef ALIGNED_P
+#undef APPLY_HOOK
+#undef ARGS1
+#undef ARGS2
+#undef BEGIN_DISPATCH_SWITCH
+#undef BINARY_INTEGER_OP
+#undef BR_ARITHMETIC
+#undef BR_BINARY
+#undef BR_NARGS
+#undef BR_UNARY
+#undef BV_FIXABLE_INT_REF
+#undef BV_FIXABLE_INT_SET
+#undef BV_FLOAT_REF
+#undef BV_FLOAT_SET
+#undef BV_INT_REF
+#undef BV_INT_SET
+#undef CACHE_REGISTER
+#undef CHECK_OVERFLOW
+#undef END_DISPATCH_SWITCH
+#undef FREE_VARIABLE_REF
+#undef INIT
+#undef INUM_MAX
+#undef INUM_MIN
+#undef LOCAL_REF
+#undef LOCAL_SET
+#undef NEXT
+#undef NEXT_HOOK
+#undef NEXT_JUMP
+#undef POP_CONTINUATION_HOOK
+#undef PUSH_CONTINUATION_HOOK
+#undef RESTORE_CONTINUATION_HOOK
+#undef RETURN
+#undef RETURN_ONE_VALUE
+#undef RETURN_VALUE_LIST
+#undef RUN_HOOK
+#undef RUN_HOOK0
+#undef SYNC_ALL
+#undef SYNC_BEFORE_GC
+#undef SYNC_IP
+#undef SYNC_REGISTER
+#undef VARIABLE_BOUNDP
+#undef VARIABLE_REF
+#undef VARIABLE_SET
+#undef VM_CHECK_FREE_VARIABLE
+#undef VM_CHECK_OBJECT
+#undef VM_CHECK_UNDERFLOW
+#undef VM_DEFINE_OP
+#undef VM_INSTRUCTION_TO_LABEL
+#undef VM_USE_HOOKS
+#undef VM_VALIDATE_BYTEVECTOR
+#undef VM_VALIDATE_PAIR
+#undef VM_VALIDATE_STRUCT
+
+/*
+(defun renumber-ops ()
+  "start from top of buffer and renumber 'VM_DEFINE_FOO (\n' sequences"
+  (interactive "")
+  (save-excursion
+    (let ((counter -1)) (goto-char (point-min))
+      (while (re-search-forward "^ *VM_DEFINE_[^ ]+ (\\([^,]+\\)," (point-max) 
t)
+        (replace-match
+         (number-to-string (setq counter (1+ counter)))
+          t t nil 1)))))
+(renumber-ops)
+*/
 /*
   Local Variables:
   c-file-style: "gnu"
diff --git a/libguile/vm.c b/libguile/vm.c
index cbef0d9..f431912 100644
--- a/libguile/vm.c
+++ b/libguile/vm.c
@@ -594,6 +594,30 @@ vm_error_bad_wide_string_length (size_t len)
 
 static SCM boot_continuation;
 
+static SCM rtl_boot_continuation;
+static SCM rtl_apply;
+static SCM rtl_values;
+
+static const scm_t_uint32 rtl_boot_continuation_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_halt_values, 0), /* empty stack frame in r0-r2, 
results from r3 */
+  SCM_PACK_RTL_24 (scm_rtl_op_halt, 0) /* result in r0 */
+};
+
+static scm_t_uint32* rtl_boot_multiple_value_continuation_code =
+  (scm_t_uint32 *) rtl_boot_continuation_code;
+
+static scm_t_uint32* rtl_boot_single_value_continuation_code =
+  (scm_t_uint32 *) rtl_boot_continuation_code + 1;
+
+static const scm_t_uint32 rtl_apply_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_apply, 0) /* proc in r0, args from r1, nargs set 
*/
+};
+
+static const scm_t_uint32 rtl_values_code[] = {
+  SCM_PACK_RTL_24 (scm_rtl_op_values, 0) /* vals from r0 */
+};
+
+
 
 /*
  * VM
@@ -637,18 +661,22 @@ initialize_default_stack_size (void)
 }
 
 #define VM_NAME   vm_regular_engine
+#define RTL_VM_NAME   rtl_vm_regular_engine
 #define FUNC_NAME "vm-regular-engine"
 #define VM_ENGINE SCM_VM_REGULAR_ENGINE
 #include "vm-engine.c"
 #undef VM_NAME
+#undef RTL_VM_NAME
 #undef FUNC_NAME
 #undef VM_ENGINE
 
 #define VM_NAME          vm_debug_engine
+#define RTL_VM_NAME   rtl_vm_debug_engine
 #define FUNC_NAME "vm-debug-engine"
 #define VM_ENGINE SCM_VM_DEBUG_ENGINE
 #include "vm-engine.c"
 #undef VM_NAME
+#undef RTL_VM_NAME
 #undef FUNC_NAME
 #undef VM_ENGINE
 
@@ -1110,6 +1138,10 @@ scm_init_vm (void)
 #ifndef SCM_MAGIC_SNARFER
 #include "libguile/vm.x"
 #endif
+
+  rtl_boot_continuation = scm_i_make_rtl_program (rtl_boot_continuation_code);
+  rtl_apply = scm_i_make_rtl_program (rtl_apply_code);
+  rtl_values = scm_i_make_rtl_program (rtl_values_code);
 }
 
 /*
diff --git a/module/system/vm/instruction.scm b/module/system/vm/instruction.scm
index 287e472..81c6ab5 100644
--- a/module/system/vm/instruction.scm
+++ b/module/system/vm/instruction.scm
@@ -1,6 +1,6 @@
 ;;; Guile VM instructions
 
-;; Copyright (C) 2001, 2010 Free Software Foundation, Inc.
+;; Copyright (C) 2001, 2010, 2012 Free Software Foundation, Inc.
 
 ;;; This library is free software; you can redistribute it and/or
 ;;; modify it under the terms of the GNU Lesser General Public
@@ -19,7 +19,8 @@
 ;;; Code:
 
 (define-module (system vm instruction)
-  #:export (instruction-list
+  #:export (rtl-instruction-list
+            instruction-list
            instruction? instruction-length
            instruction-pops instruction-pushes
            instruction->opcode opcode->instruction))
diff --git a/module/system/vm/program.scm b/module/system/vm/program.scm
index 1d01001..1875093 100644
--- a/module/system/vm/program.scm
+++ b/module/system/vm/program.scm
@@ -26,6 +26,7 @@
   #:use-module (srfi srfi-1)
   #:use-module (srfi srfi-26)
   #:export (make-program
+            make-rtl-program
 
             make-binding binding:name binding:boxed? binding:index
             binding:start binding:end
@@ -43,6 +44,7 @@
 
             program-meta
             program-objcode program? program-objects
+            rtl-program? rtl-program-code
             program-module program-base
             program-free-variables
             program-num-free-variables


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