https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82078
Bug ID: 82078
Summary: wrong code at -O3 in both 32-bit and 64-bit modes on
x86_64-linux-gnu
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: chengniansun at gmail dot com
Target Milestone: ---
$ gcc-trunk -v
Using built-in specs.
COLLECT_GCC=gcc-trunk
COLLECT_LTO_WRAPPER=/usr/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/8.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-source-trunk/configure --enable-languages=c,c++,lto
--prefix=/usr/local/gcc-trunk --disable-bootstrap
Thread model: posix
gcc version 8.0.0 20170901 (experimental) [trunk revision 251580] (GCC)
$ gcc-trunk -O3 small.c ; ./a.out
2
$ gcc-trunk -O0 small.c ; ./a.out
0
$ cat small.c
int printf(const char *, ...);
struct S0 {
signed f4;
signed f9 : 5;
} a[6][5], b = {2}
;
int c, d;
int fn1() {
struct S0 e[5][5];
struct S0 f;
b = f = e[2][5] = a[5][0];
if (d)
;
else
return f.f9;
e[c][45] = a[4][4];
}
int main() {
fn1();
printf("%d\n", b.f4);
return 0;
}
$
