https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99793
Bug ID: 99793 Summary: missed optimization for dead code elimination at -Os, -O2 and -O3 (vs. -O1) 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: --- [610] % 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 20210326 (experimental) [master revision 9d45e848d02:ca344bbd24f:6081d8994ed1a0aef6b7f5fb34f091faa3580416] (GCC) [611] % [611] % gcctk -O1 -S -o O1.s small.c [612] % gcctk -O3 -S -o O3.s small.c [613] % [613] % wc O1.s O3.s 17 38 365 O1.s 37 78 633 O3.s 54 116 998 total [614] % [614] % grep foo O1.s [615] % grep foo O3.s call foo [616] % [616] % cat small.c extern void foo(void); static int a, *b = &a, c, *d = &c; int main() { int **e = &d; if (!((unsigned)((*e = d) == 0) - (*b = 1))) foo(); return 0; }