[Guile-commits] 03/06: VM does not initialize stack frames

[Andy Wingo]

wingo pushed a commit to branch master
in repository guile.

commit f07fadc72e148d13bb4b42a3d9ecde6ab7a2296c
Author: Andy Wingo <address@hidden>
Date:   Thu Jun 6 17:39:53 2019 +0200

    VM does not initialize stack frames
    
    * libguile/jit.c (compile_alloc_frame): Stop initializing locals.
      (compile_bind_rest): Use emit_alloc_frame.
    * libguile/vm-engine.c (assert_nargs_ee_locals, allocate_frame): Don't
      initialize locals.
      (bind_rest): Don't initialize locals, and assert that the locals count
      has a minimum.
---
 libguile/jit.c       | 34 ++--------------------------------
 libguile/vm-engine.c | 27 ++++++++-------------------
 2 files changed, 10 insertions(+), 51 deletions(-)

diff --git a/libguile/jit.c b/libguile/jit.c
index 6e92730..ed95ba5 100644
--- a/libguile/jit.c
+++ b/libguile/jit.c
@@ -1851,38 +1851,8 @@ compile_assert_nargs_le (scm_jit_state *j, uint32_t 
nlocals)
 static void
 compile_alloc_frame (scm_jit_state *j, uint32_t nlocals)
 {
-  jit_gpr_t t = T0, saved_frame_size = T1_PRESERVED;
-
-  if (j->frame_size_min != j->frame_size_max)
-    jit_subr (j->jit, saved_frame_size, FP, SP);
-
   /* This will clear the regalloc, so no need to track clobbers.  */
-  emit_alloc_frame (j, t, nlocals);
-
-  if (j->frame_size_min == j->frame_size_max)
-    {
-      int32_t slots = nlocals - j->frame_size_min;
-
-      if (slots > 0)
-        {
-          jit_movi (j->jit, t, SCM_UNPACK (SCM_UNDEFINED));
-          while (slots-- > 0)
-            emit_sp_set_scm (j, slots, t);
-        }
-    }
-  else
-    {
-      jit_gpr_t walk = saved_frame_size;
-
-      jit_subr (j->jit, walk, FP, saved_frame_size);
-      jit_reloc_t k = jit_bler (j->jit, walk, SP);
-      jit_movi (j->jit, t, SCM_UNPACK (SCM_UNDEFINED));
-      void *head = jit_address (j->jit);
-      jit_subi (j->jit, walk, walk, sizeof (union scm_vm_stack_element));
-      jit_str (j->jit, walk, t);
-      jit_patch_there (j->jit, jit_bner (j->jit, walk, SP), head);
-      jit_patch_here (j->jit, k);
-    }
+  emit_alloc_frame (j, T0, nlocals);
 
   j->frame_size_min = j->frame_size_max = nlocals;
 }
@@ -2007,7 +1977,7 @@ compile_bind_rest (scm_jit_state *j, uint32_t dst)
   
   cons = emit_branch_if_frame_locals_count_greater_than (j, t, dst);
 
-  compile_alloc_frame (j, dst + 1);
+  emit_alloc_frame (j, t, dst + 1);
   emit_movi (j, t, SCM_UNPACK (SCM_EOL));
   emit_sp_set_scm (j, 0, t);
   k = jit_jmp (j->jit);
diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index a2e4be5..5596dab 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -649,8 +649,6 @@ VM_NAME (scm_thread *thread)
       VM_ASSERT (FRAME_LOCALS_COUNT () == expected,
                  CALL_INTRINSIC (error_wrong_num_args, (thread)));
       ALLOC_FRAME (expected + nlocals);
-      while (nlocals--)
-        SP_SET (nlocals, SCM_UNDEFINED);
 
       NEXT (1);
     }
@@ -773,53 +771,44 @@ VM_NAME (scm_thread *thread)
   VM_DEFINE_OP (17, bind_rest, "bind-rest", DOP1 (X8_F24))
     {
       uint32_t dst, nargs;
-      SCM rest = SCM_EOL;
 
       UNPACK_24 (op, dst);
       nargs = FRAME_LOCALS_COUNT ();
 
       if (nargs <= dst)
         {
+          VM_ASSERT (nargs == dst, abort ());
           ALLOC_FRAME (dst + 1);
-          while (nargs < dst)
-            FP_SET (nargs++, SCM_UNDEFINED);
+          SP_SET (0, SCM_EOL);
         }
       else
         {
           SYNC_IP ();
-          rest = CALL_INTRINSIC (cons_rest, (thread, dst));
+          SCM rest = CALL_INTRINSIC (cons_rest, (thread, dst));
           RESET_FRAME (dst + 1);
+          SP_SET (0, rest);
         }
 
-      FP_SET (dst, rest);
-
       NEXT (1);
     }
 
   /* alloc-frame nlocals:24
    *
    * Ensure that there is space on the stack for NLOCALS local variables.
-   * setting any new stack slots to SCM_UNDEFINED.
    */
   VM_DEFINE_OP (18, alloc_frame, "alloc-frame", OP1 (X8_C24))
     {
-      uint32_t nlocals, nargs;
+      uint32_t nlocals;
       UNPACK_24 (op, nlocals);
-
-      nargs = FRAME_LOCALS_COUNT ();
       ALLOC_FRAME (nlocals);
-      while (nlocals-- > nargs)
-        FP_SET (nlocals, SCM_UNDEFINED);
-
       NEXT (1);
     }
 
   /* reset-frame nlocals:24
    *
-   * Like alloc-frame, but doesn't check that the stack is big enough,
-   * and doesn't reset stack slots to SCM_UNDEFINED.  Used to reset the
-   * frame size to something less than the size that was previously set
-   * via alloc-frame.
+   * Like alloc-frame, but doesn't check that the stack is big enough.
+   * Used to reset the frame size to something less than the size that
+   * was previously set via alloc-frame.
    */
   VM_DEFINE_OP (19, reset_frame, "reset-frame", OP1 (X8_C24))
     {