mirror of
https://github.com/ilyakooo0/urbit.git
synced 2024-12-19 12:51:51 +03:00
137 lines
5.2 KiB
C
137 lines
5.2 KiB
C
|
|
/*============================================================================
|
|
|
|
This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
|
|
Package, Release 3c, 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 <stdbool.h>
|
|
#include <stdint.h>
|
|
#include "platform.h"
|
|
#include "internals.h"
|
|
#include "specialize.h"
|
|
#include "softfloat.h"
|
|
|
|
extern const uint16_t softfloat_approxRecipSqrt_1k0s[];
|
|
extern const uint16_t softfloat_approxRecipSqrt_1k1s[];
|
|
|
|
float16_t f16_sqrt( float16_t a )
|
|
{
|
|
union ui16_f16 uA;
|
|
uint_fast16_t uiA;
|
|
bool signA;
|
|
int_fast8_t expA;
|
|
uint_fast16_t sigA, uiZ;
|
|
struct exp8_sig16 normExpSig;
|
|
int_fast8_t expZ;
|
|
int index;
|
|
uint_fast16_t r0;
|
|
uint_fast32_t ESqrR0;
|
|
uint16_t sigma0;
|
|
uint_fast16_t recipSqrt16, sigZ, shiftedSigZ;
|
|
uint16_t negRem;
|
|
union ui16_f16 uZ;
|
|
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
uA.f = a;
|
|
uiA = uA.ui;
|
|
signA = signF16UI( uiA );
|
|
expA = expF16UI( uiA );
|
|
sigA = fracF16UI( uiA );
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
if ( expA == 0x1F ) {
|
|
if ( sigA ) {
|
|
uiZ = softfloat_propagateNaNF16UI( uiA, 0 );
|
|
goto uiZ;
|
|
}
|
|
if ( ! signA ) return a;
|
|
goto invalid;
|
|
}
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
if ( signA ) {
|
|
if ( ! (expA | sigA) ) return a;
|
|
goto invalid;
|
|
}
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
if ( ! expA ) {
|
|
if ( ! sigA ) return a;
|
|
normExpSig = softfloat_normSubnormalF16Sig( sigA );
|
|
expA = normExpSig.exp;
|
|
sigA = normExpSig.sig;
|
|
}
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
expZ = ((expA - 0xF)>>1) + 0xE;
|
|
expA &= 1;
|
|
sigA |= 0x0400;
|
|
index = (sigA>>6 & 0xE) + expA;
|
|
r0 = softfloat_approxRecipSqrt_1k0s[index]
|
|
- (((uint_fast32_t) softfloat_approxRecipSqrt_1k1s[index]
|
|
* (sigA & 0x7F))
|
|
>>11);
|
|
ESqrR0 = ((uint_fast32_t) r0 * r0)>>1;
|
|
if ( expA ) ESqrR0 >>= 1;
|
|
sigma0 = ~(uint_fast16_t) ((ESqrR0 * sigA)>>16);
|
|
recipSqrt16 = r0 + (((uint_fast32_t) r0 * sigma0)>>25);
|
|
if ( ! (recipSqrt16 & 0x8000) ) recipSqrt16 = 0x8000;
|
|
sigZ = ((uint_fast32_t) (sigA<<5) * recipSqrt16)>>16;
|
|
if ( expA ) sigZ >>= 1;
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
++sigZ;
|
|
if ( ! (sigZ & 7) ) {
|
|
shiftedSigZ = sigZ>>1;
|
|
negRem = shiftedSigZ * shiftedSigZ;
|
|
sigZ &= ~1;
|
|
if ( negRem & 0x8000 ) {
|
|
sigZ |= 1;
|
|
} else {
|
|
if ( negRem ) --sigZ;
|
|
}
|
|
}
|
|
return softfloat_roundPackToF16( 0, expZ, sigZ );
|
|
/*------------------------------------------------------------------------
|
|
*------------------------------------------------------------------------*/
|
|
invalid:
|
|
softfloat_raiseFlags( softfloat_flag_invalid );
|
|
uiZ = defaultNaNF16UI;
|
|
uiZ:
|
|
uZ.ui = uiZ;
|
|
return uZ.f;
|
|
|
|
}
|
|
|