https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114545
Bug ID: 114545
Summary: [11/12/13/14 Regression] Missed optimization for CSE
Product: gcc
Version: 14.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: 652023330028 at smail dot nju.edu.cn
Target Milestone: ---
Hello, we noticed that there may be a missed CSE (t+c). Here is the reduced
code:
https://godbolt.org/z/f68qWa89s
int a, b, c;
void func() {
int t=0;
t = -a;
b = -(t + c);
a = t + c;
}
GCC -O3 -fwrapv:
func():
mov edx, DWORD PTR a[rip]
mov eax, DWORD PTR c[rip]
mov ecx, edx
sub ecx, eax
sub eax, edx
mov DWORD PTR b[rip], ecx
mov DWORD PTR a[rip], eax
ret
Expected code:
GCC-7.5:
func():
mov eax, DWORD PTR c[rip]
sub eax, DWORD PTR a[rip]
mov edx, eax
mov DWORD PTR a[rip], eax
neg edx
mov DWORD PTR b[rip], edx
ret
Thank you very much for your time and effort! We look forward to hearing from
you.
