https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103257
Bug ID: 103257
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 case.c
void foo(void);
unsigned b, c;
static short a(short e, short f) { return e * f; }
int main() {
if (a(1 ^ ((0, 0) ^ 1 && b) <= b, c))
foo();
c = 0;
}
11.2.0 at -O3 can eliminate the call to foo but trunk at -O3 cannot:
gcc11 case.c -S -O3 -o /dev/stdout
main:
.LFB1:
.cfi_startproc
movl b(%rip), %eax
xorl %edx, %edx
testl %eax, %eax
setne %dl
cmpl %edx, %eax
movl $0, %eax
cmovb c(%rip), %ax
testw %ax, %ax
jne .L11
movl $0, c(%rip)
xorl %eax, %eax
ret
.L11:
pushq %rax
.cfi_def_cfa_offset 16
call foo
xorl %edx, %edx
xorl %eax, %eax
movl %edx, c(%rip)
popq %rcx
.cfi_def_cfa_offset 8
ret
.cfi_endproc
gcc-trunk -v
Target: x86_64-pc-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211115 (experimental) (GCC)
It started with
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=0288527f47cec6698b31ccb3210816415506009e
