[clang] For loop generates call to `memcmp`, call to `memcmp` generates call to `bcmp`

[davidstone]

The following code:

#include <cstring>

constexpr auto size = 16;

struct array {
	int m[size];
};

auto equal(
	array const lhs,
	array const rhs
) -> bool {
#ifdef MANUAL
	for (int n = 0; n != size; ++n) {
		if (lhs.m[n] != rhs.m[n]) {
			return false;
		}
	}
	return true;
#else
	return std::memcmp(lhs.m, rhs.m, size * sizeof(int)) == 0;
#endif
}

Generates this assembly with -O3 -DMANUAL

equal(array, array):
        push    rax
        lea     rdi, [rsp + 16]
        lea     rsi, [rsp + 80]
        mov     edx, 64
        call    memcmp@PLT
        test    eax, eax
        sete    al
        pop     rcx
        ret

but with just -O3 it generates

equal(array, array):
        push    rax
        lea     rdi, [rsp + 16]
        lea     rsi, [rsp + 80]
        mov     edx, 64
        call    bcmp@PLT
        test    eax, eax
        sete    al
        pop     rcx
        ret

See it live: https://godbolt.org/z/xEeGMP153

I would expect both versions to generate the call to bcmp.