SDCC generates wrong code for simple function:

unsigned int is_equal_10(unsigned char a)
{
	return a == 10;
}

Here is produced code:

;tests.c:14: unsigned int is_equal_10(unsigned char a)
;	---------------------------------
; Function is_equal_10
; ---------------------------------
_is_equal_10::
;tests.c:16: return a == 10;
	ld	hl, #2+0
	add	hl, sp
	ld	a, (hl)
	sub	a, #0x0a
	jr	NZ, 00103$
	ld	a, #0x01
	.db	#0x20
00103$:
	xor	a, a
00104$:
	ld	l, a
	ld	h, #0x00
;tests.c:19: }
	ret
;tests.c:21: unsigned int is_greater_10_unsigned_u8(unsigned char a)

Since "xor a, a" the fall-thru with the ".db #0x20" is 20 AF which is "JR nz, <backwards>".

Strangely, the equivalent C function:

unsigned int is_equal_10(unsigned char a)
{
	if (a == 10) return 1;
	return 0;
}

compiles fine.