https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100051
Bug ID: 100051 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: --- [719] % 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 20210412 (experimental) [master revision 46c47420a5f:66634f1d5eb:8f17d44ad986e0ae7e81c81179463000ee9d7f43] (GCC) [720] % [720] % gcctk -O1 -S -o O1.s small.c [721] % gcctk -O3 -S -o O3.s small.c [722] % [722] % wc O1.s O3.s 56 121 784 O1.s 68 148 996 O3.s 124 269 1780 total [723] % [723] % grep foo O1.s [724] % grep foo O3.s call foo [725] % [725] % cat small.c extern void foo(void); int a, c, *f, **d = &f; char b; static void e() { if ((2 ^ b) == 0) foo(); } int main() { if (a) { b = 0; int *g = &c; *g = 0; f = *d; *d = f; e(); } return 0; }