https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100036
Bug ID: 100036 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: ipa Assignee: unassigned at gcc dot gnu.org Reporter: zhendong.su at inf dot ethz.ch CC: marxin at gcc dot gnu.org Target Milestone: --- [562] % 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 20210411 (experimental) [master revision 1d54b138417:e83b9cf4549:936d500dfc17f58f2507ecd0f7f26e4f197052ee] (GCC) [563] % [563] % gcctk -O1 -S -o O1.s small.c [564] % gcctk -O3 -S -o O3.s small.c [565] % [565] % wc O1.s O3.s 27 58 454 O1.s 38 77 665 O3.s 65 135 1119 total [566] % [566] % grep foo O1.s [567] % grep foo O3.s jmp foo [568] % [568] % cat small.c extern void foo(void); int a, *b; static int c, f; inline int *d() { int g[100] = {0}; if (a) { int h = g[0]; foo(); return b; } } int main() { while (1) { if (!c) return f; d(); } return 0; }