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117 lines
2.5 KiB
C
117 lines
2.5 KiB
C
/*
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* COPYRIGHT: BSD - See COPYING.ARM in the top level directory
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* PROJECT: ReactOS CRT library
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* FILE: lib/sdk/crt/math/arm/__rt_div_worker.h
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* PURPOSE: Implementation of __rt_udiv
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* PROGRAMMER: Timo Kreuzer
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* REFERENCE: http://research.microsoft.com/pubs/70645/tr-2008-141.pdf
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* http://research.microsoft.com/en-us/um/redmond/projects/invisible/src/crt/md/arm/_div10.s.htm
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* http://research.microsoft.com/en-us/um/redmond/projects/invisible/src/crt/md/arm/_udiv.c.htm
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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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#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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#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 struct _ARM_DIVRESULT
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{
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UINT3264 quotient; /* to be returned in R0 */
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UINT3264 modulus; /* to be returned in R1 */
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} ARM_DIVRESULT;
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#ifndef _USE_64_BITS_
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__forceinline
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#endif
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void
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__rt_div_worker(
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ARM_DIVRESULT *result,
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UINT3264 divisor,
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UINT3264 dividend)
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{
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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;
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int divisor_sign;
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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->quotient = 0;
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result->modulus = divisor;
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return;
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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->quotient = quotient;
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result->modulus = dividend;
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return;
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}
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