https://gcc.gnu.org/bugzilla/show_bug.cgi?id=114546
Bug ID: 114546
Summary: Missed optimization: ~m || n || m+2 ==> 1
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 the code below can be optimized as stated in the title
(c = b || n || a ==> 1), but gcc -O3 (-fwrapv) missed it.
https://godbolt.org/z/6Kss3shKc
int a, b, c;
void test(int m, int n) {
int t = m ^ 100;
n = n / t;
a = m + 2;
b = ~m;
c = b || n || a;
}
GCC -O3 -fwrapv:
test(int, int):
mov eax, esi
lea ecx, [rdi+2]
mov r8d, edi
xor edi, 100
cdq
not r8d
mov DWORD PTR a[rip], ecx
idiv edi
mov DWORD PTR b[rip], r8d
or ecx, r8d
mov esi, eax
xor eax, eax
or esi, ecx
setne al
mov DWORD PTR c[rip], eax
ret
Expected code (Clang):
test(int, int): # @test(int, int)
lea eax, [rdi + 2]
mov dword ptr [rip + a], eax
not edi
mov dword ptr [rip + b], edi
mov dword ptr [rip + c], 1
ret
Thank you very much for your time and effort! We look forward to hearing from
you.
