Hi!
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).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2023-11-29 Jakub Jelinek <ja...@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.jj 2023-11-28 08:46:28.345803059 +0100
+++ gcc/fold-const.cc 2023-11-28 17:16:26.872291024 +0100
@@ -14563,7 +14563,7 @@ multiple_of_p (tree type, const_tree top
&& 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);
--- gcc/testsuite/gcc.dg/pr112733.c.jj 2023-11-28 17:19:06.813048090 +0100
+++ gcc/testsuite/gcc.dg/pr112733.c 2023-11-28 17:18:45.331349335 +0100
@@ -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;
+}
Jakub
