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[PATCH] Don't consider TREE_OVERFLOW in folding of comparisons with highest/lowest type's value (PR tree-optimization/37664)
- From: Jakub Jelinek <jakub at redhat dot com>
- To: gcc-patches at gcc dot gnu dot org
- Date: Thu, 16 Oct 2008 09:08:12 +0200
- Subject: [PATCH] Don't consider TREE_OVERFLOW in folding of comparisons with highest/lowest type's value (PR tree-optimization/37664)
- Reply-to: Jakub Jelinek <jakub at redhat dot com>
Hi!
On this testcase, VRP is upset by (unsigned int) x > UINT_MAX (OVF),
for ASSERT_EXPR it clears the TREE_OVERFLOW flag (since PR37327)
and then ICEs because this ASSERT_EXPR's condition folds to boolean_false_node.
Is there any reason why fold prohibits folding of comparisons with
highest or lowest type's value if the value has TREE_OVERFLOW set?
I've tried to construct a testcase where C/C++ would care, but if one
of the arguments has TREE_OVERFLOW set, then the warning/error is reported
already when folding that value, not when folding the comparison.
This passed bootstrap/regtest, so if it matters, it doesn't reproduce
on anything we have in the tree.
Ok for trunk?
2008-10-16 Jakub Jelinek <jakub@redhat.com>
PR tree-optimization/37664
* fold-const.c (fold_binary): When optimizing comparison with
highest or lowest type's value, don't consider TREE_OVERFLOW.
* gcc.c-torture/compile/pr37664.c: New test.
--- gcc/fold-const.c.jj 2008-09-30 16:57:11.000000000 +0200
+++ gcc/fold-const.c 2008-10-16 01:02:42.000000000 +0200
@@ -12447,7 +12447,6 @@ fold_binary (enum tree_code code, tree t
unsigned int width = TYPE_PRECISION (arg1_type);
if (TREE_CODE (arg1) == INTEGER_CST
- && !TREE_OVERFLOW (arg1)
&& width <= 2 * HOST_BITS_PER_WIDE_INT
&& (INTEGRAL_TYPE_P (arg1_type) || POINTER_TYPE_P (arg1_type)))
{
--- gcc/testsuite/gcc.c-torture/compile/pr37664.c.jj 2008-10-15 14:14:23.000000000 +0200
+++ gcc/testsuite/gcc.c-torture/compile/pr37664.c 2008-10-15 14:14:04.000000000 +0200
@@ -0,0 +1,14 @@
+/* PR tree-optimization/37664 */
+
+int v;
+
+int
+foo ()
+{
+ int a = 0x8899A862;
+ int b = 0x8E * a;
+ int c = (b % b);
+ if (v > (4294967295U >> c))
+ return v;
+ return 0;
+}
Jakub