[Guile-commits] GNU Guile branch, master, updated. v2.1.0-110-ge7f6497

[Mark H Weaver]

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- Log -----------------------------------------------------------------
commit e7f64971ed62a6b58f86b5d90a15b24733e36a8d
Author: Mark H Weaver <address@hidden>
Date:   Tue Aug 6 17:03:56 2013 -0400

    RTL VM: Avoid untagging inums in 'logand' and 'logior'.
    
    * libguile/vm-engine.c (logand, logior): Avoid untagging.

commit d2295ba5716b60a5f0b28b1b91fd2ed3cf1192f5
Author: Mark H Weaver <address@hidden>
Date:   Tue Aug 6 17:00:23 2013 -0400

    RTL VM: Avoid signed overflows in 'add1' and 'sub1'.
    
    * libguile/vm-engine.c (INUM_MIN, INUM_MAX): Redefine without making
      assumptions about the representation.
      (INUM_STEP): New macro.
      (add1, sub1): Avoid signed overflows, and use INUM_STEP.

commit 0bd659658ba2a2b6dab9cb75f693818e5ce8241b
Author: Mark H Weaver <address@hidden>
Date:   Tue Aug 6 16:51:41 2013 -0400

    RTL VM: ash: Use SCM_SRS and fix large right shifts in fast path.
    
    * libguile/vm-engine.c (ash): Use SCM_SRS, and handle large right
      shifts properly.

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

Summary of changes:
 libguile/vm-engine.c |   43 ++++++++++++++++++++++++++-----------------
 1 files changed, 26 insertions(+), 17 deletions(-)

diff --git a/libguile/vm-engine.c b/libguile/vm-engine.c
index 1300a1e..613c638 100644
--- a/libguile/vm-engine.c
+++ b/libguile/vm-engine.c
@@ -490,6 +490,7 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
 #undef INIT
 #undef INUM_MAX
 #undef INUM_MIN
+#undef INUM_STEP
 #undef jump_table
 #undef LOCAL_REF
 #undef LOCAL_SET
@@ -754,8 +755,13 @@ VM_NAME (SCM vm, SCM program, SCM *argv, int nargs)
   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 INUM_MAX  \
+  ((scm_t_signed_bits) SCM_UNPACK (SCM_I_MAKINUM (SCM_MOST_POSITIVE_FIXNUM)))
+#define INUM_MIN  \
+  ((scm_t_signed_bits) SCM_UNPACK (SCM_I_MAKINUM (SCM_MOST_NEGATIVE_FIXNUM)))
+#define INUM_STEP                                \
+  ((scm_t_signed_bits) SCM_UNPACK (SCM_INUM1)    \
+   - (scm_t_signed_bits) SCM_UNPACK (SCM_INUM0))
 
 #define BINARY_INTEGER_OP(CFUNC,SFUNC)                                      \
   {                                                             \
@@ -2807,15 +2813,14 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t 
nargs_)
     {
       ARGS1 (x);
 
-      /* Check for overflow.  */
-      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) < INUM_MAX))
+      /* Check for overflow.  We must avoid overflow in the signed
+         addition below, even if X is not an inum.  */
+      if (SCM_LIKELY ((scm_t_signed_bits) SCM_UNPACK (x) <= INUM_MAX - 
INUM_STEP))
         {
           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);
+          /* Add 1 to the integer without untagging.  */
+          result = SCM_PACK ((scm_t_signed_bits) SCM_UNPACK (x) + INUM_STEP);
 
           if (SCM_LIKELY (SCM_I_INUMP (result)))
             RETURN (result);
@@ -2842,15 +2847,14 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t 
nargs_)
     {
       ARGS1 (x);
 
-      /* Check for underflow.  */
-      if (SCM_LIKELY ((scm_t_intptr) SCM_UNPACK (x) > INUM_MIN))
+      /* Check for overflow.  We must avoid overflow in the signed
+         subtraction below, even if X is not an inum.  */
+      if (SCM_LIKELY ((scm_t_signed_bits) SCM_UNPACK (x) >= INUM_MIN + 
INUM_STEP))
         {
           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);
+          /* Substract 1 from the integer without untagging.  */
+          result = SCM_PACK ((scm_t_signed_bits) SCM_UNPACK (x) - INUM_STEP);
 
           if (SCM_LIKELY (SCM_I_INUMP (result)))
             RETURN (result);
@@ -2926,7 +2930,10 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t 
nargs_)
         {
           if (SCM_I_INUM (y) < 0)
             /* Right shift, will be a fixnum. */
-            RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) >> -SCM_I_INUM (y)));
+            RETURN (SCM_I_MAKINUM
+                    (SCM_SRS (SCM_I_INUM (x),
+                              (-SCM_I_INUM (y) <= SCM_I_FIXNUM_BIT-1)
+                              ? -SCM_I_INUM (y) : SCM_I_FIXNUM_BIT-1)));
           else
             /* Left shift. See comments in scm_ash. */
             {
@@ -2956,7 +2963,8 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t 
nargs_)
     {
       ARGS2 (x, y);
       if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
-        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) & SCM_I_INUM (y)));
+        /* Compute bitwise AND without untagging */
+        RETURN (SCM_PACK (SCM_UNPACK (x) & SCM_UNPACK (y)));
       SYNC_IP ();
       RETURN (scm_logand (x, y));
     }
@@ -2969,7 +2977,8 @@ RTL_VM_NAME (SCM vm, SCM program, SCM *argv, size_t 
nargs_)
     {
       ARGS2 (x, y);
       if (SCM_I_INUMP (x) && SCM_I_INUMP (y))
-        RETURN (SCM_I_MAKINUM (SCM_I_INUM (x) | SCM_I_INUM (y)));
+        /* Compute bitwise OR without untagging */
+        RETURN (SCM_PACK (SCM_UNPACK (x) | SCM_UNPACK (y)));
       SYNC_IP ();
       RETURN (scm_logior (x, y));
     }


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