(get_condition): Check for overflow when canonicalizing comparison.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@2863 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/loop.c b/gcc/loop.c
index 6ffa6bc..6e093e2 100644 (file)
--- a/gcc/loop.c
+++ b/gcc/loop.c
@@ -6386,34 +6386,43 @@ get_condition (jump, earliest)
   if (GET_MODE_CLASS (GET_MODE (op0)) == MODE_CC)
     return 0;
 
-  /* Canonicalize any ordered comparison with integers involving equality.  */
-  if (GET_CODE (op1) == CONST_INT)
+  /* Canonicalize any ordered comparison with integers involving equality
+     if we can do computations in the relevant mode and we do not
+     overflow.  */
+
+  if (GET_CODE (op1) == CONST_INT
+      && GET_MODE (op0) != VOIDmode
+      && GET_MODE_BITSIZE (GET_MODE (op0)) <= HOST_BITS_PER_WIDE_INT)
     {
       HOST_WIDE_INT const_val = INTVAL (op1);
       unsigned HOST_WIDE_INT uconst_val = const_val;
+      unsigned HOST_WIDE_INT max_val
+       = (unsigned HOST_WIDE_INT) GET_MODE_MASK (GET_MODE (op0));
 
       switch (code)
-      {
-      case LE:
-       code = LT;
-       op1 = GEN_INT (const_val + 1);
-       break;
+       {
+       case LE:
+         if (const_val != max_val >> 1)
+           code = LT,  op1 = GEN_INT (const_val + 1);
+         break;
 
-      case GE:
-       code = GT;
-       op1 = GEN_INT (const_val - 1);
-       break;
+       case GE:
+         if (const_val
+             != (((HOST_WIDE_INT) 1
+                  << (GET_MODE_BITSIZE (GET_MODE (op0)) - 1))))
+           code = GT, op1 = GEN_INT (const_val - 1);
+         break;
 
-      case LEU:
-       code = LTU;
-       op1 = GEN_INT (uconst_val + 1);
-       break;
+       case LEU:
+         if (uconst_val != max_val)
+           code = LTU, op1 = GEN_INT (uconst_val + 1);
+         break;
 
-      case GEU:
-       code = GTU;
-       op1 = GEN_INT (uconst_val - 1);
-       break;
-      }
+       case GEU:
+         if (uconst_val != 0)
+           code = GTU, op1 = GEN_INT (uconst_val - 1);
+         break;
+       }
     }
 
   /* If this was floating-point and we reversed anything other than an