https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110410
Bug ID: 110410
Summary: [14 Regression] Different results between -O0 and -O2
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jwzeng at nuaa dot edu.cn
Target Milestone: ---
The following code snippet:
#include <stdio.h>
int seed;
void hash(int *seed, int v) { *seed ^= v; }
unsigned int var_6 = 1341494070U;
int var_7 = 0;
unsigned short var_8 = 7472;
int var_13 = 518868156U;
unsigned var_17;
#define min(a, b) ((a) < (b) ? (a) : (b))
void test() {
for (int ii_0 = 0; ii_0 < 20; ++ii_0)
for (int ii_1 = 0; ii_1 < 10; ++ii_1)
var_17 = min(var_6 ? var_8 >> (var_13 - 518868145U) : var_7,
1887837879 || 0);
}
int main() {
test(2062689408U);
hash(&seed, var_17);
printf("%d\n", seed);
return 0;
}
> $ /usr/gcc-trunk/bin/gcc -O0 bug.c; ./a.out
> 1
> $ /usr/gcc-trunk/bin/gcc -O2 bug.c; ./a.out
> 3
When compiled with -O2 or -O3, it prints 3 instead of 1. Earlier GCCs do not
have this bug.
> $ /usr/gcc-trunk/bin/gcc --version
gcc (GCC) 14.0.0 20230619 (experimental) [master r14-1917-gf8e0270272]
Copyright (C) 2023 Free Software Foundation, Inc.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE
