https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100162
Bug ID: 100162 Summary: missed optimization for dead code elimination at -O3 (vs. -O2) 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: --- [720] % 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/11.0.1/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 11.0.1 20210420 (experimental) [master revision 67378cd63d6:5e36407d599:250f234988b6231669a720c52101d3686d645072] (GCC) [721] % [721] % gcctk -O2 -S -o O2.s small.c [722] % gcctk -O3 -S -o O3.s small.c [723] % [723] % wc O2.s O3.s 52 119 923 O2.s 70 150 1143 O3.s 122 269 2066 total [724] % [724] % grep foo O2.s [725] % grep foo O3.s call foo [726] % [726] % cat small.c extern void foo(void); int printf(const char *, ...); int a, b, c[5][1]; int main() { for (a = 0; a < 5; a++) c[a][b] = 2; if ((b || 0) / c[0][0]) foo(); printf("checksum=0"); return 0; }