https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103388
Bug ID: 103388
Summary: [12 Regression] missed optimization for dead code
elimination at -O3 (vs. -O2)
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);
void bar(void);
static int b, d, e, *c, *f = &d, *h = &b;
int main() {
int **i = &c;
if (e) {
e = *f;
bar();
if (!(((i && d) + *h >= 1 ^ d & b) <= 4 | d))
foo();
}
}
trunk cannot eliminate the call to foo but 11.2.0 can:
gcc-11.2.0 -O3 -S -o /dev/stdout case.c
main:
.LFB0:
.cfi_startproc
movl e(%rip), %ecx
testl %ecx, %ecx
jne .L8
xorl %eax, %eax
ret
.L8:
pushq %rax
.cfi_def_cfa_offset 16
movl d(%rip), %eax
movl %eax, e(%rip)
call bar
xorl %eax, %eax
popq %rdx
.cfi_def_cfa_offset 8
ret
.cfi_endproc
.LFE0:
gcc-trunk -O3 -S -o /dev/stdout case.c
main:
.LFB0:
.cfi_startproc
movl e(%rip), %esi
testl %esi, %esi
jne .L10
xorl %eax, %eax
ret
.L10:
pushq %rcx
.cfi_def_cfa_offset 16
movl d(%rip), %eax
movl %eax, e(%rip)
call bar
movl d(%rip), %edx
movl b(%rip), %eax
cmpl $1, %edx
movl %eax, %ecx
sbbl $-1, %ecx
testl %ecx, %ecx
setg %cl
andl %edx, %eax
movzbl %cl, %ecx
xorl %ecx, %eax
cmpl $4, %eax
setle %al
movzbl %al, %eax
orl %edx, %eax
je .L11
.L3:
xorl %eax, %eax
popq %rdx
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.L11:
.cfi_restore_state
call foo
jmp .L3
.cfi_endproc
.LFE0:
gcc-trunk -v
Using built-in specs.
Supported LTO compression algorithms: zlib zstd
gcc version 12.0.0 20211123 (experimental) (GCC)
Started with
https://gcc.gnu.org/git/?p=gcc.git;a=commit;h=4b3a325f07acebf47e82de227ce1d5ba62f5bcae
