https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99835
Bug ID: 99835 Summary: missed optimization for dead code elimination at -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: --- [558] % 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 20210330 (experimental) [master revision 8aac913adfc:ff4ebc2f17c:65374af219f9c5c594951a07e766fe70c1136a1f] (GCC) [559] % [559] % gcctk -O1 -S -o O1.s small.c [560] % gcctk -O3 -S -o O3.s small.c [561] % [561] % wc O1.s O3.s 23 45 420 O1.s 35 66 615 O3.s 58 111 1035 total [562] % [562] % grep foo O1.s [563] % grep foo O3.s jmp foo [564] % [564] % cat small.c extern void foo(void); static int a, d; void b(); static int c() { foo(); b(); } void b() { while (d) { if (!a) break; c(); } } int main() { b(); return 0; }