https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97529
Bug ID: 97529
Summary: Condition not constant folded
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: jmuizelaar at mozilla dot com
Target Milestone: ---
>From https://github.com/rust-lang/rust/issues/74938
GCC compiles:
#include <stddef.h>
const size_t N = 3;
int foo(size_t len) {
size_t newlen = (len / N) * N;
return newlen <= len;
}
to:
foo:
movabs rdx, -6148914691236517205
mov rax, rdi
mul rdx
mov rax, rdx
and rdx, -2
shr rax
add rdx, rax
xor eax, eax
cmp rdi, rdx
setnb al
ret
N:
.quad 3
clang:
foo: # @foo
mov eax, 1
ret
N:
.quad 3
