https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100740
Bug ID: 100740 Summary: wrong code at -O1 and above on x86_64-linux-gnu Product: gcc Version: unknown 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: --- This seems to be quite long-latent, impacting GCC 9.1 and later. [636] % gcctk -v Using built-in specs. COLLECT_GCC=gcctk COLLECT_LTO_WRAPPER=/local/suz-local/software/local/gcc-trunk/libexec/gcc/x86_64-pc-linux-gnu/12.0.0/lto-wrapper Target: x86_64-pc-linux-gnu Configured with: ../gcc-trunk/configure --disable-bootstrap --prefix=/local/suz-local/software/local/gcc-trunk --enable-languages=c,c++ --disable-werror --enable-multilib --with-system-zlib Thread model: posix Supported LTO compression algorithms: zlib gcc version 12.0.0 20210524 (experimental) [master revision dc084c487e9:bd7ae6b8ef8:9d38e096c5e3b1c2233b28d0e6ff8ee81517af56] (GCC) [637] % [637] % gcctk -O0 small.c; ./a.out [638] % [638] % gcctk -O1 small.c [639] % ./a.out Aborted [640] % [640] % cat small.c unsigned a, b; int main() { unsigned c = 0; for (a = 0; a < 2; a++) for (b = 0; b < 2; b++) if (++c < a) __builtin_abort (); return 0; }