From 5c95bf945c632925efba86dd5dceccdb9da8884c Mon Sep 17 00:00:00 2001
From: Jakub Jelinek <jakub@redhat.com>
Date: Wed, 29 Nov 2023 12:26:50 +0100
Subject: [PATCH] fold-const: Fix up multiple_of_p [PR112733]
We ICE on the following testcase when wi::multiple_of_p is called on
widest_int 1 and -128 with UNSIGNED. I still need to work on the
actual wide-int.cc issue, the latest patch attached to the PR regressed
bitint-{38,39}.c, so will need to debug that, but there is a clear bug
on the fold-const.cc side as well - widest_int is a signed representation
by definition, using UNSIGNED with it certainly doesn't match what was
intended, because -128 as the second operand effectively means unsigned
131072 bit 0xfffff............ffff80 integer, not the signed char -128
that appeared in the source.
In the INTEGER_CST case a few lines above this we already use
case INTEGER_CST:
if (TREE_CODE (bottom) != INTEGER_CST || integer_zerop (bottom))
return false;
return wi::multiple_of_p (wi::to_widest (top), wi::to_widest (bottom),
SIGNED);
so I think using SIGNED with widest_int is best there (compared to the
other choices in the PR).
2023-11-29 Jakub Jelinek <jakub@redhat.com>
PR middle-end/112733
* fold-const.cc (multiple_of_p): Pass SIGNED rather than
UNSIGNED for wi::multiple_of_p on widest_int arguments.
* gcc.dg/pr112733.c: New test.
---
gcc/fold-const.cc | 2 +-
gcc/testsuite/gcc.dg/pr112733.c | 16 ++++++++++++++++
2 files changed, 17 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/gcc.dg/pr112733.c
diff --git a/gcc/fold-const.cc b/gcc/fold-const.cc
index dff09b81f7bc..2692b98ceac2 100644
--- a/gcc/fold-const.cc
+++ b/gcc/fold-const.cc
@@ -14563,7 +14563,7 @@ multiple_of_p (tree type, const_tree top, const_tree bottom, bool nowrap)
&& TREE_CODE (op2) == INTEGER_CST
&& integer_pow2p (bottom)
&& wi::multiple_of_p (wi::to_widest (op2),
- wi::to_widest (bottom), UNSIGNED))
+ wi::to_widest (bottom), SIGNED))
return true;
op1 = gimple_assign_rhs1 (stmt);
diff --git a/gcc/testsuite/gcc.dg/pr112733.c b/gcc/testsuite/gcc.dg/pr112733.c
new file mode 100644
index 000000000000..d6f99f760775
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr112733.c
@@ -0,0 +1,16 @@
+/* PR middle-end/112733 */
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+signed char a, c;
+short b;
+
+void
+foo (void)
+{
+ signed char *e = &a;
+ c = foo != 0;
+ *e &= c;
+ for (; b; --b)
+ *e &= -128;
+}
--
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