https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81556
Bug ID: 81556
Summary: Wrong code at -O2
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: babokin at gmail dot com
Target Milestone: ---
gcc trunk, rev250545, x86_64.
This one seems to be different from previously reported bugs. Minimum opt level
to trigger bug is -O2, switching slsr doesn't help (-fno-tree-slsr).
> cat f.cpp
#include <stdio.h>
unsigned long int var_0 = 13272098465497875865UL;
unsigned long int var_1 = 15341539099603541390UL;
unsigned long int var_2 = 2;
unsigned long int var_3 = 17471558040813171499UL;
unsigned long int var_4 = 1;
unsigned long int var_5 = 0;
unsigned long int var_6 = 0;
void foo() {
bool a = var_2 > 1;
var_5 = var_4 % ((var_2 > 1) << 9);
var_6 = a & (var_3 & (a & var_0 & var_1));
}
int main() {
foo();
printf("0x%llx, 0x%llx\n", var_5, var_6);
return 0;
}
> g++ -O0 f.cpp -o out; ./out
0x1, 0x0
> g++ -O2 f.cpp -o out; ./out
0x1, 0x9020100000000108
