https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95396
Bug ID: 95396
Summary: GCC produces incorrect code with -O3 for loops
Product: gcc
Version: 11.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: vsevolod.livinskij at frtk dot ru
Target Milestone: ---
Error:
>$ g++ -O0 small.cpp && ./a.out
42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 42 0 0 0
>$ g++ -O3 small.cpp && ./a.out
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 42 0 0 0
Reproducer:
>$ cat small.cpp
#include <stdio.h>
unsigned short arr_26 [20];
signed char arr_25 [2000];
unsigned char b;
int c(int d, int f) { return d > f ? d : f; }
void test() {
for (char e = c(b, 241) + 15; e < 17; e += 1)
arr_26[e] = 42;
}
int main() {
test();
for (size_t i_0 = 0; i_0 < 20; ++i_0)
printf("%d ", arr_26 [i_0]);
printf("\n");
}
GCC version:
11.0.0 (1852a26b925970f64f8d31518ba732fe9c3ade23)
