https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95248
Bug ID: 95248
Summary: GCC produces incorrect code with -O3 for loops
Product: gcc
Version: 10.0
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: ---
GCC produces incorrect code with -O3 for loops
Error:
>$ gcc -O0 driver.cpp func.cpp && ./a.out
1
>$ gcc -O3 driver.cpp func.cpp && ./a.out
0
Reproducer:
>$ cat driver.cpp
#include <stdio.h>
int var_2 = -2013646301;
int var_3 = -1126567434;
unsigned int var_12 = 1;
unsigned int var_19;
unsigned int arr_25 [24] [21] [15] [17] [15] ;
void test();
int main() {
test();
printf("%u\n", var_19);
}
>$ cat func.cpp
extern int var_2;
extern int var_3;
extern unsigned int var_12;
extern unsigned int var_19;
extern unsigned int arr_25 [24] [21] [15] [17] [15] ;
void test() {
for (int a = 0; a < 3; a = 42)
for (int b = 0; b < 20; b++)
for (int c = 0; c < 4; c = 4)
for (int d = 0; d < 6; d += 4)
for (int e = 0; e < 4; e += 2) {
arr_25[a][b][c][d][e] = var_2 || var_3;
var_19 = var_12;
}
}
GCC version:
gcc version 11.0.0 (ed63c387aa0bc1846082524455a6ff1fcec40f9d)
