1//===------------ udivmodhi4.S - uint16 div & mod -------------------------===//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// As described at
10// https://gcc.gnu.org/wiki/avr-gcc#Exceptions_to_the_Calling_Convention, the
11// prototype is `struct {uint16, uint16}  __udivmodhi4(uint16, uint16)`.
12// The uint16 quotient is returned via R23:R22, and the uint16 remainder is
13// returned via R25:R24, while R21/R26/R27 are clobbered.
14//
15//===----------------------------------------------------------------------===//
16
17	.text
18	.align 2
19
20	.globl __udivmodhi4
21	.type  __udivmodhi4, @function
22
23__udivmodhi4:
24	sub     r26, r26
25	sub     r27, r27           ; Initialize the remainder to zero.
26	ldi     r21, 17            ; Only loop 16 rounds for uint16.
27
28__udivmodhi4_loop:
29	adc     r24, r24
30	adc     r25, r25
31	dec     r21
32	breq    __udivmodhi4_end
33	adc     r26, r26
34	adc     r27, r27
35	cp      r26, r22
36	cpc     r27, r23           ; Compare with the divisor.
37	brcs    __udivmodhi4_loop
38	sub     r26, r22
39	sbc     r27, r23           ; Subtract the divisor.
40	rjmp    __udivmodhi4_loop
41
42__udivmodhi4_end:
43	com     r24
44	com     r25
45	mov     r22, r24
46	mov     r23, r25           ; The quotient is returned in R23:R22.
47	mov     r24, r26
48	mov     r25, r27           ; The remainder is returned in in R25:R24.
49	ret
50