The following fixes bogus folding (introducing signed overflow)
for the X +- C1 CMP Y +- C2 to X CMP Y +- C2 +- C1 transform
where we let through a sign-change of the remaining constant operand.
Fixed as follows, bootstrap and regtest running on
x86_64-unknown-linux-gnu.
Richard.
2014-05-28 Richard Biener <rguent...@suse.de>
PR middle-end/61045
* fold-const.c (fold_comparison): When folding
X +- C1 CMP Y +- C2 to X CMP Y +- C2 +- C1 also ensure
the sign of the remaining constant operand stays the same.
* gcc.dg/pr61045.c: New testcase.
Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c (revision 211011)
+++ gcc/fold-const.c (working copy)
@@ -9239,7 +9239,7 @@ fold_comparison (location_t loc, enum tr
/* Transform comparisons of the form X +- C1 CMP Y +- C2 to
X CMP Y +- C2 +- C1 for signed X, Y. This is valid if
the resulting offset is smaller in absolute value than the
- original one. */
+ original one and has the same sign. */
if (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (arg0))
&& (TREE_CODE (arg0) == PLUS_EXPR || TREE_CODE (arg0) == MINUS_EXPR)
&& (TREE_CODE (TREE_OPERAND (arg0, 1)) == INTEGER_CST
@@ -9258,32 +9258,35 @@ fold_comparison (location_t loc, enum tr
"a comparison");
/* Put the constant on the side where it doesn't overflow and is
- of lower absolute value than before. */
+ of lower absolute value and of same sign than before. */
cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1)
? MINUS_EXPR : PLUS_EXPR,
const2, const1);
if (!TREE_OVERFLOW (cst)
- && tree_int_cst_compare (const2, cst) == tree_int_cst_sgn (const2))
+ && tree_int_cst_compare (const2, cst) == tree_int_cst_sgn (const2)
+ && tree_int_cst_sgn (cst) == tree_int_cst_sgn (const2))
{
fold_overflow_warning (warnmsg, WARN_STRICT_OVERFLOW_COMPARISON);
return fold_build2_loc (loc, code, type,
- variable1,
- fold_build2_loc (loc,
- TREE_CODE (arg1), TREE_TYPE (arg1),
- variable2, cst));
+ variable1,
+ fold_build2_loc (loc, TREE_CODE (arg1),
+ TREE_TYPE (arg1),
+ variable2, cst));
}
cst = int_const_binop (TREE_CODE (arg0) == TREE_CODE (arg1)
? MINUS_EXPR : PLUS_EXPR,
const1, const2);
if (!TREE_OVERFLOW (cst)
- && tree_int_cst_compare (const1, cst) == tree_int_cst_sgn (const1))
+ && tree_int_cst_compare (const1, cst) == tree_int_cst_sgn (const1)
+ && tree_int_cst_sgn (cst) == tree_int_cst_sgn (const1))
{
fold_overflow_warning (warnmsg, WARN_STRICT_OVERFLOW_COMPARISON);
return fold_build2_loc (loc, code, type,
- fold_build2_loc (loc, TREE_CODE (arg0), TREE_TYPE
(arg0),
- variable1, cst),
- variable2);
+ fold_build2_loc (loc, TREE_CODE (arg0),
+ TREE_TYPE (arg0),
+ variable1, cst),
+ variable2);
}
}
Index: gcc/testsuite/gcc.dg/pr61045.c
===================================================================
--- gcc/testsuite/gcc.dg/pr61045.c (revision 0)
+++ gcc/testsuite/gcc.dg/pr61045.c (working copy)
@@ -0,0 +1,12 @@
+/* { dg-do run } */
+/* { dg-options "-fstrict-overflow" } */
+
+int main ()
+{
+ int a = 0;
+ int b = __INT_MAX__;
+ int t = (a - 2) > (b - 1);
+ if (t != 0)
+ __builtin_abort();
+ return 0;
+}
