https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108368
Bug ID: 108368
Summary: [13 Regression] Dead Code Elimination Regression at
-O3 since r13-1759-gdbb093f4f15
Product: gcc
Version: 13.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: yann at ywg dot ch
Target Milestone: ---
Created attachment 54244
--> https://gcc.gnu.org/bugzilla/attachment.cgi?id=54244&action=edit
Case file
cat case.c #1409
int a;
int b;
short c;
static int d = 4;
void foo();
void e(int f) {}
int main() {
unsigned g = -27;
for (; g > 7; ++g) {
e(c && g);
b ? 0 : a;
if (g) {
if (0 >= d)
foo();
} else
d = 0;
}
}
`gcc-f99d7d669eaa2830eb5878df4da67e77ec791522 (trunk) -O3` can not eliminate
`foo` but `gcc-releases/gcc-12.2.0 -O3` can.
`gcc-f99d7d669eaa2830eb5878df4da67e77ec791522 (trunk) -O3 -S -o /dev/stdout
case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
pushq %rbx
.cfi_def_cfa_offset 16
.cfi_offset 3, -16
movl $27, %ebx
.L5:
movl d(%rip), %eax
testl %eax, %eax
jle .L8
.L4:
xorl %eax, %eax
popq %rbx
.cfi_remember_state
.cfi_def_cfa_offset 8
ret
.p2align 4,,10
.p2align 3
.L8:
.cfi_restore_state
xorl %eax, %eax
call foo
subl $1, %ebx
jne .L5
jmp .L4
---------- END OUTPUT ---------
`gcc-releases/gcc-12.2.0 -O3 -S -o /dev/stdout case.c`
--------- OUTPUT ---------
main:
.LFB1:
.cfi_startproc
xorl %eax, %eax
ret
---------- END OUTPUT ---------
Bisects to: r13-1759-gdbb093f4f15
commit dbb093f4f15ea66f2ce5cd2dc1903a6894563356
Author: Andrew MacLeod <[email protected]>
Date: Mon Jul 18 15:04:23 2022 -0400
Resolve complicated join nodes in range_from_dom.
Join nodes which carry outgoing ranges on incoming edges are uncommon,
but can still be resolved by setting the dominator range, and then
calculating incoming edges. Avoid doing so if one of the incoing edges
is not dominated by the same dominator.
* gimple-range-cache.cc (ranger_cache::range_from_dom): Check
for incoming ranges on join nodes and add to worklist.
