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be3c532bf4
- Make __fto64 function more readable - Call worker function directly for __rt_sdiv/udiv - Adapt __rt_sdiv64/udiv64 asm shims accordingly - Add header files to CMake source list CORE-17607 CORE-17614 CORE-17703 CORE-17604 Addendum tof2bc1f0e,e448094eand54406bf4.
136 lines
3.5 KiB
C
136 lines
3.5 KiB
C
/*
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* PROJECT: ReactOS CRT library
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* LICENSE: MIT (https://spdx.org/licenses/MIT)
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* PURPOSE: Implementation of __rt_div_worker
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* COPYRIGHT: Copyright 2015 Timo Kreuzer <timo.kreuzer@reactos.org>
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* Copyright 2021 Roman Masanin <36927roma@gmail.com>
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*/
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/*
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* See also:
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* http://research.microsoft.com/pubs/70645/tr-2008-141.pdf
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* https://web.archive.org/web/20100110044008/http://research.microsoft.com/en-us/um/redmond/projects/invisible/src/crt/md/arm/_div10.s.htm
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* https://github.com/bawoodruff/BeagleBoard/blob/2731e3174af6daefe4a287a6be82e5ff9c46c99a/OS/BootLoader/Runtime/_udiv.c
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* https://github.com/bawoodruff/BeagleBoard/blob/2731e3174af6daefe4a287a6be82e5ff9c46c99a/OS/BootLoader/Runtime/arm/_udivsi3.s
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* https://github.com/bawoodruff/BeagleBoard/blob/2731e3174af6daefe4a287a6be82e5ff9c46c99a/OS/BootLoader/Runtime/arm/divide.s
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* https://github.com/qemu/edk2/blob/e3c7db50cac9125607df49d5873991df6df11eae/ArmPkg/Library/CompilerIntrinsicsLib/Arm/uldiv.asm
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* https://github.com/jmonesti/qemu-4.1.1/blob/55fb6a81039a62174c2763759324c43a67d752a1/roms/ipxe/src/arch/arm32/libgcc/lldivmod.S
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*/
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#ifdef _USE_64_BITS_
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typedef unsigned long long UINT3264;
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typedef long long INT3264;
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typedef struct
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{
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unsigned long long quotient; /* to be returned in R0,R1 */
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unsigned long long modulus; /* to be returned in R2,R3 */
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} RETURN_TYPE;
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#define _CountLeadingZeros _CountLeadingZeros64
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#else
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typedef unsigned int UINT3264;
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typedef int INT3264;
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typedef unsigned long long RETURN_TYPE; /* to be returned in R0,R1 */
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#endif
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__forceinline
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void
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__brkdiv0(void)
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{
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__emit(0xDEF9);
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}
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typedef union _ARM_DIVRESULT
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{
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RETURN_TYPE raw_data;
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struct
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{
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UINT3264 quotient;
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UINT3264 modulus;
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} data;
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} ARM_DIVRESULT;
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RETURN_TYPE
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__rt_div_worker(
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UINT3264 divisor,
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UINT3264 dividend)
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{
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ARM_DIVRESULT result;
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UINT3264 shift;
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UINT3264 mask;
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UINT3264 quotient;
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#ifdef _SIGNED_DIV_
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int dividend_sign = 0;
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int divisor_sign = 0;
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#endif // _SIGNED_DIV_
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if (divisor == 0)
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{
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/* Raise divide by zero error */
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__brkdiv0();
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}
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#ifdef _SIGNED_DIV_
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if ((INT3264)dividend < 0)
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{
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dividend_sign = 1;
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dividend = -(INT3264)dividend;
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}
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if ((INT3264)divisor < 0)
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{
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divisor_sign = 1;
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divisor = -(INT3264)divisor;
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}
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#endif // _SIGNED_DIV_
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if (divisor > dividend)
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{
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result.data.quotient = 0;
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#ifdef _SIGNED_DIV_
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if (dividend_sign)
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dividend = -(INT3264)dividend;
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#endif // _SIGNED_DIV_
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result.data.modulus = dividend;
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return result.raw_data;
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}
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/* Get the difference in count of leading zeros between dividend and divisor */
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shift = _CountLeadingZeros(divisor);
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shift -= _CountLeadingZeros(dividend);
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/* Shift the divisor to the left, so that it's highest bit is the same
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as the highest bit of the dividend */
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divisor <<= shift;
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mask = (UINT3264)1 << shift;
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quotient = 0;
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do
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{
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if (dividend >= divisor)
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{
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quotient |= mask;
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dividend -= divisor;
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}
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divisor >>= 1;
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mask >>= 1;
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}
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while (mask);
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#ifdef _SIGNED_DIV_
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if (dividend_sign ^ divisor_sign)
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{
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quotient = -(INT3264)quotient;
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}
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if (dividend_sign)
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{
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dividend = -(INT3264)dividend;
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}
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#endif // _SIGNED_DIV_
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result.data.quotient = quotient;
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result.data.modulus = dividend;
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return result.raw_data;
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}
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