https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100315
Bug ID: 100315 Summary: missed optimization for dead code elimination at -O3, -O2 (vs. -O1, -Os) 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: --- [583] % 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/12.0.0/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 12.0.0 20210428 (experimental) [master revision 852dd866e2f:9b04e5b2651:b81e2d5e76a6bcc71f45b122e8b5538ddb7ebf4c] (GCC) [584] % [584] % gcctk -O1 -S -o O1.s small.c [585] % gcctk -O3 -S -o O3.s small.c [586] % [586] % wc O1.s O3.s 14 30 303 O1.s 18 39 364 O3.s 32 69 667 total [587] % [587] % grep foo O1.s [588] % grep foo O3.s call foo [589] % [589] % cat small.c extern void foo(void); static int a; static void b(int c) { if (c) { foo(); while (1) ; } } void d() { int e = 0; while (1) { b(a); e++; } }