https://gcc.gnu.org/bugzilla/show_bug.cgi?id=125739
Bug ID: 125739
Summary: wrong code at -O{2,3} with "-fno-tree-dse
-fno-tree-pre -fno-expensive-optimizations
-fno-tree-sra -flto" on x86_64-linux-gnu
Product: gcc
Version: 16.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: zhendong.su at inf dot ethz.ch
Target Milestone: ---
Compiler Explorer: https://godbolt.org/z/eb8efsa33
Note:
- fails: 16.1 and trunk
- works: 15.2 and earlier
[555] % gcctk -v
Using built-in specs.
COLLECT_GCC=gcctk
COLLECT_LTO_WRAPPER=/local/home/suz/suz-local/software/local/gcc-trunk/bin/../libexec/gcc/x86_64-pc-linux-gnu/17.0.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ../gcc-trunk/configure --disable-bootstrap
--enable-checking=yes --prefix=/local/suz-local/software/local/gcc-trunk
--enable-sanitizers --enable-languages=c,c++ --disable-werror --enable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 17.0.0 20260610 (experimental) (GCC)
[556] %
[556] % gcctk -O3 small.c; ./a.out
[557] %
[557] % gcctk -O3 -fno-tree-dse -fno-tree-pre -fno-expensive-optimizations
-fno-tree-sra -flto small.c
[558] % ./a.out
Aborted
[559] %
[559] % cat small.c
typedef struct {
float a;
float aa;
} d;
int e[256], m, n;
int f(int g, int h) {
for (int i = 0; i < 256; ++i) {
unsigned c = i;
for (int j = 0; j < 8; ++j)
c = c & 1 ? c >> 1 ^ 3988292384 : c >> 1;
e[i] = c;
}
unsigned k = g;
int l = h;
for (int b = 0; b < 4; ++b) {
char ab = l;
l >>= 8;
k = k >> 8 ^ e[(k ^ ab) & 255];
}
return k;
}
int o(char p, char q, char r, short s, char t, short u, short v) {
char w, *ag = &w;
d x;
int y = 1;
long z = 1;
x.a = x.aa = 1.0f;
m = 3 - 1073741824 - 3;
*ag = z = z - 2 * m;
z = -186621953 ^ (z + 4);
if (s)
ac:
if (-16385 == y)
x.aa = *ag = 0;
if (s)
y = y - 8193;
m = 2 - 350224399;
if (w)
goto ad;
goto ae;
ad:
x.a = 0 + x.a;
x.aa = 0 + x.aa;
goto ac;
ae:
n = f(0, x.a);
n = f(n, x.aa);
n = f(n, 1.0f);
n = f(n, 1);
n = f(n, (long)((unsigned long)y << 48) >> 48);
n = f(n, z);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 1.0);
n = f(n, 0);
n = f(n, m);
n = f(n, 1);
n = f(n, p);
n = f(n, q);
n = f(n, r);
n = f(n, s);
n = f(n, (long)((unsigned long)t << 56) >> 56);
n = f(n, u);
n = f(n, v);
n = f(n, 1.0f);
n = f(n, 0);
return n;
}
int main() {
int af = o(7, 2, 4, -1, -17, 16384, 1);
if (103539439 != af)
__builtin_abort();
return 0;
}
