https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102982
Bug ID: 102982 Summary: [12 Regression] Dead Code Elimination Regression at -O3 (trunk vs 11.2.0) Product: gcc Version: 12.0 Status: UNCONFIRMED Severity: normal Priority: P3 Component: tree-optimization Assignee: unassigned at gcc dot gnu.org Reporter: theodort at inf dot ethz.ch Target Milestone: --- cat test.c void foo(void); static short a, b, d; static int c[2][2][2] = {0}; int main() { c[0][0][0] = 0; if (c[1][1][1]) { d = a % b >= 1 ^ 2; foo(); } } 11.2.0 at -O3 can eliminate the call to foo but trunk at -O3 cannot: gcc-11 test.c -O3 -S -o /dev/stdout ... main: .LFB0: .cfi_startproc movl $0, c(%rip) movl c+28(%rip), %eax testl %eax, %eax je .L2 ud2 .p2align 4,,10 .p2align 3 .L2: xorl %eax, %eax ret .cfi_endproc gcc-trunk test.c -O3 -S -o /dev/stdout ... main: .LFB0: .cfi_startproc movl $0, c(%rip) movl c+28(%rip), %ecx testl %ecx, %ecx je .L4 pushq %rax .cfi_def_cfa_offset 16 call foo xorl %eax, %eax popq %rdx .cfi_def_cfa_offset 8 ret .L4: xorl %eax, %eax ret .cfi_endproc gcc-trunk -v Using built-in specs. Target: x86_64-pc-linux-gnu Thread model: posix Supported LTO compression algorithms: zlib zstd gcc version 12.0.0 20211028 (experimental) (GCC) Started with https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=b58dc0b803057c0e6032e0d9bd92cd834f72c75c