| //===------------ 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 |
