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142 lines
5.5 KiB
C
142 lines
5.5 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 3c, by John R. Hauser.
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Copyright 2011, 2012, 2013, 2014, 2015, 2016 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
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softfloat_subMagsF64( uint_fast64_t uiA, uint_fast64_t uiB, bool signZ )
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{
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int_fast16_t expA;
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uint_fast64_t sigA;
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int_fast16_t expB;
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uint_fast64_t sigB;
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int_fast16_t expDiff;
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uint_fast64_t uiZ;
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int_fast64_t sigDiff;
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int_fast8_t shiftDist;
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int_fast16_t expZ;
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uint_fast64_t sigZ;
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union ui64_f64 uZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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expA = expF64UI( uiA );
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sigA = fracF64UI( uiA );
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expB = expF64UI( uiB );
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sigB = fracF64UI( uiB );
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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expDiff = expA - expB;
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if ( ! expDiff ) {
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/*--------------------------------------------------------------------
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*--------------------------------------------------------------------*/
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if ( expA == 0x7FF ) {
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if ( sigA | sigB ) goto propagateNaN;
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softfloat_raiseFlags( softfloat_flag_invalid );
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uiZ = defaultNaNF64UI;
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goto uiZ;
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}
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sigDiff = sigA - sigB;
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if ( ! sigDiff ) {
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uiZ =
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packToF64UI(
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(softfloat_roundingMode == softfloat_round_min), 0, 0 );
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goto uiZ;
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}
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if ( expA ) --expA;
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if ( sigDiff < 0 ) {
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signZ = ! signZ;
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sigDiff = -sigDiff;
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}
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shiftDist = softfloat_countLeadingZeros64( sigDiff ) - 11;
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expZ = expA - shiftDist;
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if ( expZ < 0 ) {
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shiftDist = expA;
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expZ = 0;
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}
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uiZ = packToF64UI( signZ, expZ, sigDiff<<shiftDist );
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goto uiZ;
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} else {
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/*--------------------------------------------------------------------
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*--------------------------------------------------------------------*/
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sigA <<= 10;
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sigB <<= 10;
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if ( expDiff < 0 ) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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signZ = ! signZ;
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if ( expB == 0x7FF ) {
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if ( sigB ) goto propagateNaN;
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uiZ = packToF64UI( signZ, 0x7FF, 0 );
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goto uiZ;
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}
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sigA += expA ? UINT64_C( 0x4000000000000000 ) : sigA;
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sigA = softfloat_shiftRightJam64( sigA, -expDiff );
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sigB |= UINT64_C( 0x4000000000000000 );
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expZ = expB;
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sigZ = sigB - sigA;
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} else {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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if ( expA == 0x7FF ) {
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if ( sigA ) goto propagateNaN;
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uiZ = uiA;
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goto uiZ;
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}
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sigB += expB ? UINT64_C( 0x4000000000000000 ) : sigB;
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sigB = softfloat_shiftRightJam64( sigB, expDiff );
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sigA |= UINT64_C( 0x4000000000000000 );
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expZ = expA;
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sigZ = sigA - sigB;
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}
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return softfloat_normRoundPackToF64( signZ, expZ - 1, sigZ );
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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propagateNaN:
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uiZ = softfloat_propagateNaNF64UI( uiA, uiB );
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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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