188 lines
7.1 KiB
C
188 lines
7.1 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, 2015, 2016, 2017 The Regents of the
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University of 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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float16_t softfloat_subMagsF16( uint_fast16_t uiA, uint_fast16_t uiB )
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{
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int_fast8_t expA;
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uint_fast16_t sigA;
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int_fast8_t expB;
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uint_fast16_t sigB;
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int_fast8_t expDiff;
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uint_fast16_t uiZ;
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int_fast16_t sigDiff;
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bool signZ;
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int_fast8_t shiftDist, expZ;
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uint_fast16_t sigZ, sigX, sigY;
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uint_fast32_t sig32Z;
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int_fast8_t roundingMode;
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union ui16_f16 uZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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expA = expF16UI( uiA );
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sigA = fracF16UI( uiA );
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expB = expF16UI( uiB );
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sigB = fracF16UI( 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 == 0x1F ) {
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if ( sigA | sigB ) goto propagateNaN;
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softfloat_raiseFlags( softfloat_flag_invalid );
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uiZ = defaultNaNF16UI;
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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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packToF16UI(
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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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signZ = signF16UI( uiA );
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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_countLeadingZeros16( sigDiff ) - 5;
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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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sigZ = sigDiff<<shiftDist;
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goto pack;
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} else {
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/*--------------------------------------------------------------------
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*--------------------------------------------------------------------*/
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signZ = signF16UI( uiA );
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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 == 0x1F ) {
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if ( sigB ) goto propagateNaN;
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uiZ = packToF16UI( signZ, 0x1F, 0 );
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goto uiZ;
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}
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if ( expDiff <= -13 ) {
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uiZ = packToF16UI( signZ, expB, sigB );
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if ( expA | sigA ) goto subEpsilon;
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goto uiZ;
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}
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expZ = expA + 19;
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sigX = sigB | 0x0400;
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sigY = sigA + (expA ? 0x0400 : sigA);
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expDiff = -expDiff;
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} else {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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uiZ = uiA;
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if ( expA == 0x1F ) {
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if ( sigA ) goto propagateNaN;
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goto uiZ;
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}
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if ( 13 <= expDiff ) {
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if ( expB | sigB ) goto subEpsilon;
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goto uiZ;
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}
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expZ = expB + 19;
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sigX = sigA | 0x0400;
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sigY = sigB + (expB ? 0x0400 : sigB);
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}
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sig32Z = ((uint_fast32_t) sigX<<expDiff) - sigY;
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shiftDist = softfloat_countLeadingZeros32( sig32Z ) - 1;
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sig32Z <<= shiftDist;
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expZ -= shiftDist;
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sigZ = sig32Z>>16;
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if ( sig32Z & 0xFFFF ) {
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sigZ |= 1;
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} else {
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if ( ! (sigZ & 0xF) && ((unsigned int) expZ < 0x1E) ) {
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sigZ >>= 4;
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goto pack;
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}
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}
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return softfloat_roundPackToF16( signZ, expZ, sigZ );
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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propagateNaN:
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uiZ = softfloat_propagateNaNF16UI( uiA, uiB );
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goto uiZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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subEpsilon:
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roundingMode = softfloat_roundingMode;
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if ( roundingMode != softfloat_round_near_even ) {
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if (
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(roundingMode == softfloat_round_minMag)
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|| (roundingMode
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== (signF16UI( uiZ ) ? softfloat_round_max
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: softfloat_round_min))
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) {
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--uiZ;
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}
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#ifdef SOFTFLOAT_ROUND_ODD
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else if ( roundingMode == softfloat_round_odd ) {
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uiZ = (uiZ - 1) | 1;
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}
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#endif
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}
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softfloat_exceptionFlags |= softfloat_flag_inexact;
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goto uiZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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pack:
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uiZ = packToF16UI( signZ, expZ, sigZ );
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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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