https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87123
Bug ID: 87123
Summary: incorrect optimization involving INT_MIN and
conditional operator
Product: gcc
Version: 7.3.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: andy.koppe at analog dot com
Target Milestone: ---
Reproduced using gcc 5.4.0 on Ubuntu 16.04, gcc 7.3.0 on Cygwin64, and also a
gcc 7.2.1 for ARM:
$ cat test.c
#include <stdio.h>
int x = 0x80000000;
int main(void)
{
unsigned y = (unsigned)(x < 0 ? -x : x) >> 8;
if (y == 0x800000)
printf("Test passed\n");
else
printf("Test failed: y = %#x, expected 0x800000\n", y);
}
$ gcc -O2 test.c
$ ./a.out
Test failed: y = 0x800000, expected 0x800000
Looking at the generated assembly, the "Test passed" path has been optimized
out. The test passes below -O2, or if "(x < 0 ? -x : x)" is replaced with just
"-x".
