https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90017
Bug ID: 90017
Summary: gcc generates wrong debug information at -O3
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: debug
Assignee: unassigned at gcc dot gnu.org
Reporter: qrzhang at gatech dot edu
Target Milestone: ---
It seems to be a recent regression, starting at r269302.
It only affects "-O3" and trunk.
The correct value is "l=0". With -O3, it generates l=8.
$ gcc-trunk -v
gcc version 9.0.1 20190408 (experimental) [trunk revision 270202] (GCC)
#correct output#
$ gcc-trunk -g abc.c
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x4004a5: file abc.c, line 15.
Breakpoint 1, main () at abc.c:15
15 optimize_me_not();
$1 = 0
#wrong output#
$ gcc-trunk -g abc.c -O3
$ gdb -x cmds -batch a.out
Breakpoint 1 at 0x400470: file abc.c, line 15.
Breakpoint 1, main () at abc.c:15
15 optimize_me_not();
$1 = 8
$ cat abc.c
__attribute__((noipa)) optimize_me_not(){
__asm__ volatile ("" : : : "memory");
}
int a, b;
int c[][2] = {{2}, {5}, 2};
int main() {
{
int l;
for (; b <= 1; b++) {
l = 0;
for (; l <= 8; l++) {
a ^= c[b + 1][b];
if (a)
optimize_me_not();
}
}
}
}
$ cat cmds
b 15
r
p l
k
q
