https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112994
Bug ID: 112994
Summary: [Regression] Missed optimization for redundancy
computation elimination because pattern is broken
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 maybe there is a missed optimization for redundancy
computation elimination.
Different from PR 111718, this missed optimization is a regression and not just
because of one missing pattern, but because of changes that broke patterns that
could have been eliminated:
The pattern /* Simplify (t * 2) / t) -> 2. */ is broken.
https://godbolt.org/z/3er613Krx
int n,m;
void test(int a, int b){
n=a+a;
b=n;
m=(n+b)/(b);
}
GCC (trunk) -O3:
test(int, int):
lea eax, [0+rdi*4]
lea ecx, [rdi+rdi]
cdq
mov DWORD PTR n[rip], ecx
idiv ecx
mov DWORD PTR m[rip], eax
ret
Expected code (GCC 11.4 -O3):
test(int, int):
mov DWORD PTR m[rip], 2
add edi, edi
mov DWORD PTR n[rip], edi
ret
If our targeting is accurate, then this issue was caused by this commit:
https://github.com/gcc-mirror/gcc/commit/d846f225c25
Thank you very much for your time and effort! We look forward to hearing from
you.
