74 lines
2.9 KiB
C
74 lines
2.9 KiB
C
|
|
||
|
|
/*============================================================================
|
||
|
|
|
||
|
|
This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
|
||
|
|
Package, Release 3e, by John R. Hauser.
|
||
|
|
|
||
|
|
Copyright 2011, 2012, 2013, 2014, 2015, 2016 The Regents of the University of
|
||
|
|
California. All rights reserved.
|
||
|
|
|
||
|
|
Redistribution and use in source and binary forms, with or without
|
||
|
|
modification, are permitted provided that the following conditions are met:
|
||
|
|
|
||
|
|
1. Redistributions of source code must retain the above copyright notice,
|
||
|
|
this list of conditions, and the following disclaimer.
|
||
|
|
|
||
|
|
2. Redistributions in binary form must reproduce the above copyright notice,
|
||
|
|
this list of conditions, and the following disclaimer in the documentation
|
||
|
|
and/or other materials provided with the distribution.
|
||
|
|
|
||
|
|
3. Neither the name of the University nor the names of its contributors may
|
||
|
|
be used to endorse or promote products derived from this software without
|
||
|
|
specific prior written permission.
|
||
|
|
|
||
|
|
THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
|
||
|
|
EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
||
|
|
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
|
||
|
|
DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
|
||
|
|
DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
|
||
|
|
(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
|
||
|
|
LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
|
||
|
|
ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
||
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
|
||
|
|
SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
||
|
|
|
||
|
|
=============================================================================*/
|
||
|
|
|
||
|
|
#include <stdint.h>
|
||
|
|
#include "platform.h"
|
||
|
|
|
||
|
|
#ifndef softfloat_approxRecipSqrt32_1
|
||
|
|
|
||
|
|
extern const uint16_t softfloat_approxRecipSqrt_1k0s[];
|
||
|
|
extern const uint16_t softfloat_approxRecipSqrt_1k1s[];
|
||
|
|
|
||
|
|
uint32_t softfloat_approxRecipSqrt32_1( unsigned int oddExpA, uint32_t a )
|
||
|
|
{
|
||
|
|
int index;
|
||
|
|
uint16_t eps, r0;
|
||
|
|
uint_fast32_t ESqrR0;
|
||
|
|
uint32_t sigma0;
|
||
|
|
uint_fast32_t r;
|
||
|
|
uint32_t sqrSigma0;
|
||
|
|
|
||
|
|
index = (a>>27 & 0xE) + oddExpA;
|
||
|
|
eps = (uint16_t) (a>>12);
|
||
|
|
r0 = softfloat_approxRecipSqrt_1k0s[index]
|
||
|
|
- ((softfloat_approxRecipSqrt_1k1s[index] * (uint_fast32_t) eps)
|
||
|
|
>>20);
|
||
|
|
ESqrR0 = (uint_fast32_t) r0 * r0;
|
||
|
|
if ( ! oddExpA ) ESqrR0 <<= 1;
|
||
|
|
sigma0 = ~(uint_fast32_t) (((uint32_t) ESqrR0 * (uint_fast64_t) a)>>23);
|
||
|
|
r = ((uint_fast32_t) r0<<16) + ((r0 * (uint_fast64_t) sigma0)>>25);
|
||
|
|
sqrSigma0 = ((uint_fast64_t) sigma0 * sigma0)>>32;
|
||
|
|
r += ((uint32_t) ((r>>1) + (r>>3) - ((uint_fast32_t) r0<<14))
|
||
|
|
* (uint_fast64_t) sqrSigma0)
|
||
|
|
>>48;
|
||
|
|
if ( ! (r & 0x80000000) ) r = 0x80000000;
|
||
|
|
return r;
|
||
|
|
|
||
|
|
}
|
||
|
|
|
||
|
|
#endif
|
||
|
|
|