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//===------------ udivmodhi4.S - uint16 div & mod -------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// As described at
// https://gcc.gnu.org/wiki/avr-gcc#Exceptions_to_the_Calling_Convention, the
// prototype is `struct {uint16, uint16} __udivmodhi4(uint16, uint16)`.
// The uint16 quotient is returned via R23:R22, and the uint16 remainder is
// returned via R25:R24, while R21/R26/R27 are clobbered.
//
//===----------------------------------------------------------------------===//
.text
.align 2
.globl __udivmodhi4
.type __udivmodhi4, @function
__udivmodhi4:
sub r26, r26
sub r27, r27 ; Initialize the remainder to zero.
ldi r21, 17 ; Only loop 16 rounds for uint16.
__udivmodhi4_loop:
adc r24, r24
adc r25, r25
dec r21
breq __udivmodhi4_end
adc r26, r26
adc r27, r27
cp r26, r22
cpc r27, r23 ; Compare with the divisor.
brcs __udivmodhi4_loop
sub r26, r22
sbc r27, r23 ; Subtract the divisor.
rjmp __udivmodhi4_loop
__udivmodhi4_end:
com r24
com r25
mov r22, r24
mov r23, r25 ; The quotient is returned in R23:R22.
mov r24, r26
mov r25, r27 ; The remainder is returned in in R25:R24.
ret
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