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