https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122366
Bug ID: 122366
Summary: Suboptimal max + negate combination
Product: gcc
Version: 15.0
Status: UNCONFIRMED
Keywords: missed-optimization
Severity: normal
Priority: P3
Component: target
Assignee: unassigned at gcc dot gnu.org
Reporter: ktkachov at gcc dot gnu.org
Target Milestone: ---
Target: aarch64
Small testcase for aarch64:
#include <algorithm>
int
foo (int a, int b)
{
return std::max (-a, b);
}
Generates with -O2:
foo(int, int):
neg w0, w0
cmp w0, w1
csel w0, w0, w1, ge
ret
But Clang manages to generate the shorter:
foo(int, int):
cmn w1, w0
csneg w0, w1, w0, gt
ret
