https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100314
Bug ID: 100314 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: --- [592] % 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) [593] % [593] % gcctk -O1 -S -o O1.s small.c [594] % gcctk -O3 -S -o O3.s small.c [595] % [595] % wc O1.s O3.s 21 45 392 O1.s 42 86 686 O3.s 63 131 1078 total [596] % [596] % grep foo O1.s [597] % grep foo O3.s jmp foo [598] % [598] % cat small.c extern void foo(void); static int a, *c, g, **j; int b; static void e() { int k, *l[5] = {&k, &k, &k, &k, &k}; while (g) { j = &l[0]; b++; } } static void d(int m) { int **h[30] = {&c}, ***i[1] = {&h[3]}; if (m) foo(); e(); } int main() { d(a); return 0; }