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127 lines
2.6 KiB
C
127 lines
2.6 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.c
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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/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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typedef struct _ARM_UDIVRESULT
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{
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unsigned int quotient; /* to be returned in R0 */
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unsigned int modulus; /* to be returned in R1 */
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} ARM_UDIVRESULT;
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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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__forceinline
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void
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__rt_udiv_internal(
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ARM_UDIVRESULT *result,
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unsigned int divisor,
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unsigned int dividend)
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{
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unsigned int shift;
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unsigned int mask;
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unsigned int quotient;
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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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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 = 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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result->quotient = quotient;
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result->modulus = dividend;
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return;
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}
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ARM_UDIVRESULT
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__rt_udiv(
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unsigned int divisor,
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unsigned int dividend)
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{
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ARM_UDIVRESULT result;
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__rt_udiv_internal(&result, divisor, dividend);
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return result;
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}
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typedef struct _ARM_SDIVRESULT
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{
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int quotient; /* to be returned in R0 */
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int modulus; /* to be returned in R1 */
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} ARM_SDIVRESULT;
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ARM_SDIVRESULT
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__rt_sdiv(
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int divisor,
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int dividend)
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{
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ARM_SDIVRESULT result;
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int divisor_sign, dividend_sign;
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dividend_sign = divisor & 0x80000000;
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if (dividend_sign)
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{
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dividend = -dividend;
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}
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divisor_sign = divisor & 0x80000000;
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if (divisor_sign)
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{
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divisor = -divisor;
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}
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__rt_udiv_internal((ARM_UDIVRESULT*)&result, divisor, dividend);
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if (dividend_sign ^ divisor_sign)
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{
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result.quotient = -result.quotient;
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}
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if (dividend_sign)
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{
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result.modulus = -result.modulus;
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}
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return result;
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}
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