[Bug rtl-optimization/117393] New: Consider inlining memcmp(a, b, small constant)==0 on -Os

[blubban at gmail dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=117393

            Bug ID: 117393
           Summary: Consider inlining memcmp(a, b, small constant)==0 on
                    -Os
           Product: gcc
           Version: 14.2.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: rtl-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: blubban at gmail dot com
  Target Milestone: ---

int square(char* a, char* b) {
    return !__builtin_memcmp(a, b, 4);
}


-Os


Expected:

square(char*, char*):
        mov     eax, DWORD PTR [rsi]
        cmp     DWORD PTR [rdi], eax
        sete    al
        movzx   eax, al
        ret


Actual:

square(char*, char*):
        push    rax
        mov     edx, 4
        call    memcmp
        pop     rdx
        test    eax, eax
        sete    al
        movzx   eax, al
        ret


It is inlined for sizes 0 and 1, but I'd expect 2, 4, 8 and 16 to be inlined as
well.

https://godbolt.org/z/7WEzWT6se