mirror of
https://github.com/openhwgroup/cvw
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134 lines
5.2 KiB
C
134 lines
5.2 KiB
C
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/*============================================================================
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This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
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Package, Release 3e, by John R. Hauser.
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Copyright 2011, 2012, 2013, 2014, 2017 The Regents of the University of
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California. All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice,
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this list of conditions, and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice,
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this list of conditions, and the following disclaimer in the documentation
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and/or other materials provided with the distribution.
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3. Neither the name of the University nor the names of its contributors may
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be used to endorse or promote products derived from this software without
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specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
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EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
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DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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=============================================================================*/
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#include <stdbool.h>
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#include <stdint.h>
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#include "platform.h"
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#include "internals.h"
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#include "specialize.h"
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#include "softfloat.h"
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float64_t f64_sqrt( float64_t a )
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{
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union ui64_f64 uA;
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uint_fast64_t uiA;
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bool signA;
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int_fast16_t expA;
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uint_fast64_t sigA, uiZ;
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struct exp16_sig64 normExpSig;
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int_fast16_t expZ;
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uint32_t sig32A, recipSqrt32, sig32Z;
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uint_fast64_t rem;
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uint32_t q;
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uint_fast64_t sigZ, shiftedSigZ;
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union ui64_f64 uZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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uA.f = a;
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uiA = uA.ui;
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signA = signF64UI( uiA );
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expA = expF64UI( uiA );
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sigA = fracF64UI( uiA );
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( expA == 0x7FF ) {
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if ( sigA ) {
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uiZ = softfloat_propagateNaNF64UI( uiA, 0 );
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goto uiZ;
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}
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if ( ! signA ) return a;
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goto invalid;
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( signA ) {
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if ( ! (expA | sigA) ) return a;
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goto invalid;
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( ! expA ) {
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if ( ! sigA ) return a;
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normExpSig = softfloat_normSubnormalF64Sig( sigA );
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expA = normExpSig.exp;
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sigA = normExpSig.sig;
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}
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/*------------------------------------------------------------------------
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| (`sig32Z' is guaranteed to be a lower bound on the square root of
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| `sig32A', which makes `sig32Z' also a lower bound on the square root of
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| `sigA'.)
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*------------------------------------------------------------------------*/
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expZ = ((expA - 0x3FF)>>1) + 0x3FE;
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expA &= 1;
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sigA |= UINT64_C( 0x0010000000000000 );
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sig32A = sigA>>21;
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recipSqrt32 = softfloat_approxRecipSqrt32_1( expA, sig32A );
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sig32Z = ((uint_fast64_t) sig32A * recipSqrt32)>>32;
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if ( expA ) {
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sigA <<= 8;
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sig32Z >>= 1;
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} else {
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sigA <<= 9;
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}
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rem = sigA - (uint_fast64_t) sig32Z * sig32Z;
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q = ((uint32_t) (rem>>2) * (uint_fast64_t) recipSqrt32)>>32;
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sigZ = ((uint_fast64_t) sig32Z<<32 | 1<<5) + ((uint_fast64_t) q<<3);
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( (sigZ & 0x1FF) < 0x22 ) {
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sigZ &= ~(uint_fast64_t) 0x3F;
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shiftedSigZ = sigZ>>6;
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rem = (sigA<<52) - shiftedSigZ * shiftedSigZ;
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if ( rem & UINT64_C( 0x8000000000000000 ) ) {
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--sigZ;
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} else {
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if ( rem ) sigZ |= 1;
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}
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}
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return softfloat_roundPackToF64( 0, expZ, sigZ );
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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invalid:
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softfloat_raiseFlags( softfloat_flag_invalid );
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uiZ = defaultNaNF64UI;
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uiZ:
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uZ.ui = uiZ;
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return uZ.f;
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}
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