Bootstrapped and tested on x86_64-unknown-linux-gnu, applied.
Richard.
2015-09-23 Richard Biener <rguent...@suse.de>
PR middle-end/67662
* fold-const.c (fold_binary_loc): Do not reassociate two vars with
undefined overflow unless they will cancel out.
* gcc.dg/ubsan/pr67662.c: New testcase.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 228037)
+++ gcc/fold-const.c (working copy)
@@ -9493,25 +9511,32 @@ fold_binary_loc (location_t loc,
{
tree tmp0 = var0;
tree tmp1 = var1;
+ bool one_neg = false;
if (TREE_CODE (tmp0) == NEGATE_EXPR)
- tmp0 = TREE_OPERAND (tmp0, 0);
+ {
+ tmp0 = TREE_OPERAND (tmp0, 0);
+ one_neg = !one_neg;
+ }
if (CONVERT_EXPR_P (tmp0)
&& INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
&& (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp0, 0)))
<= TYPE_PRECISION (atype)))
tmp0 = TREE_OPERAND (tmp0, 0);
if (TREE_CODE (tmp1) == NEGATE_EXPR)
- tmp1 = TREE_OPERAND (tmp1, 0);
+ {
+ tmp1 = TREE_OPERAND (tmp1, 0);
+ one_neg = !one_neg;
+ }
if (CONVERT_EXPR_P (tmp1)
&& INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
&& (TYPE_PRECISION (TREE_TYPE (TREE_OPERAND (tmp1, 0)))
<= TYPE_PRECISION (atype)))
tmp1 = TREE_OPERAND (tmp1, 0);
/* The only case we can still associate with two variables
- is if they are the same, modulo negation and bit-pattern
- preserving conversions. */
- if (!operand_equal_p (tmp0, tmp1, 0))
+ is if they cancel out. */
+ if (!one_neg
+ || !operand_equal_p (tmp0, tmp1, 0))
ok = false;
}
}
Index: gcc/testsuite/gcc.dg/ubsan/pr67662.c
===================================================================
--- gcc/testsuite/gcc.dg/ubsan/pr67662.c (revision 0)
+++ gcc/testsuite/gcc.dg/ubsan/pr67662.c (working copy)
@@ -0,0 +1,14 @@
+/* { dg-do run } */
+/* { dg-options "-fsanitize=undefined" } */
+
+extern void abort (void);
+
+int
+main (void)
+{
+ int halfmaxval = __INT_MAX__ / 2 + 1;
+ int maxval = halfmaxval - 1 + halfmaxval;
+ if (maxval != __INT_MAX__)
+ abort ();
+ return 0;
+}
