ASM output removing labels used by cbz and cbnz instructions on aarch64

[GrayJack]

I noticed that the output of cargo asm on aarch64 removes the labels used on the branching instructions cbz and cbnz.

I made a simple strchr example:

#[no_mangle]
pub unsafe extern "C" fn strchr(mut str: *const c_char, ch: c_int) -> *mut c_char {
    let ch = ch as c_char;
    loop {
        if *str == 0 {
            break ptr::null_mut();
        }

        if *str == ch {
            break str as *mut c_char;
        }

        str = str.add(1);
    }
}

Output:

	.globl	_strchr
	.p2align	2
_strchr:
Lfunc_begin439:
	.cfi_startproc
	ldrb w9, [x0]
	cbz w9, LBB439_4
	and w8, w1, #0xff
	cmp w9, w8
	b.eq LBB439_5
	ldrb w9, [x0, #1]!
	cbnz w9, LBB439_2
	mov x0, #0
LBB439_5:
	ret

Expected result should be:

	.globl	_strchr
	.p2align	2
_strchr:
	ldrb	w9, [x0]
	cbz	w9, LBB439_4
	and	w8, w1, #0xff
LBB439_2:
	cmp	w9, w8
	b.eq	LBB439_5
	ldrb	w9, [x0, #1]!
	cbnz	w9, LBB439_2
LBB439_4:
	mov	x0, #0
LBB439_5:
	ret

I tested this on aarch64 macOS and Linux and this happens to these instruction on both.

[pacak]

Is this actual or expected output? And what should the other output should be?

[GrayJack]

Sorry, I forgot to include that.

The expected result would be:

	.globl	_strchr
	.p2align	2
_strchr:
	ldrb	w9, [x0]
	cbz	w9, LBB439_4
	and	w8, w1, #0xff
LBB439_2:
	cmp	w9, w8
	b.eq	LBB439_5
	ldrb	w9, [x0, #1]!
	cbnz	w9, LBB439_2
LBB439_4:
	mov	x0, #0
LBB439_5:
	ret

[pacak]

Will take a look. Can you include the .s file from target folder? You should be able to find exact name if you pass one or more -v flags - this way I should be able to test if it worked without having to mess with cross-compilation.

[GrayJack]

Sure! Here it is:

tests-02b2c38f374f3d00.s.zip

[pacak]

0.2.41 is out, this issue should be fixed.