https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100080
Bug ID: 100080 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: --- [604] % 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 20210414 (experimental) [master revision 006783f4b16:29da9c11552:0589be0c59767cf4cbb0ef0e7d918cf6aa3d606c] (GCC) [605] % [605] % gcctk -O2 -S -o O2.s small.c [606] % gcctk -O3 -S -o O3.s small.c [607] % [607] % wc O2.s O3.s 68 147 999 O2.s 95 202 1373 O3.s 163 349 2372 total [608] % [608] % grep foo O2.s [609] % grep foo O3.s call foo [610] % [610] % cat small.c extern void foo(void); int a, b, d, f; static unsigned c; void e(int g, int *k) { int h, *i = &b, *j = &b; *i = g; c = &b == i; d = c >= (*j = b | *k) && b & (*i == 0); h = a ? 0 : d; if (h) foo(); } int main() { while (f) { int l; e(1, &l); } return 0; }