https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81740
Bug ID: 81740
Summary: wrong code at -O3 in both 32-bit and 64-bit modes on
x86_64-linux-gnu
Product: gcc
Version: unknown
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 20170806 (experimental) [trunk revision 250895] (GCC)
$
$ gcc-trunk -O3 small.c ; ./a.out > O3.txt
$ gcc-trunk -O0 small.c ; ./a.out > O0.txt
$ diff O3.txt O0.txt
37c37
< 0
---
> 4
$ cat small.c
extern int printf(const char *, ...);
int a[8][10];
short b;
int c, i, d;
int main() {
a[2][5] = b = 4;
for (; b; b--) {
c = 0;
for (; c <= 6; c++)
a[c + 1][b + 2] = a[c][b + 1];
}
for (; i < 8; i++) {
d = 0;
for (; d < 10; d++)
printf("%d\n", a[i][d]);
}
return 0;
}
$
