Eyck Jentzsch
dcaf5467e8
(http://www.jhauser.us/arithmetic/SoftFloat.html) with RISCV specialization and cmake build
257 lines
10 KiB
C
257 lines
10 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, 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 "softfloat.h"
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extFloat80_t
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softfloat_roundPackToExtF80(
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bool sign,
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int_fast32_t exp,
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uint_fast64_t sig,
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uint_fast64_t sigExtra,
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uint_fast8_t roundingPrecision
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)
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{
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uint_fast8_t roundingMode;
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bool roundNearEven;
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uint_fast64_t roundIncrement, roundMask, roundBits;
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bool isTiny, doIncrement;
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struct uint64_extra sig64Extra;
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union { struct extFloat80M s; extFloat80_t f; } uZ;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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roundingMode = softfloat_roundingMode;
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roundNearEven = (roundingMode == softfloat_round_near_even);
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if ( roundingPrecision == 80 ) goto precision80;
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if ( roundingPrecision == 64 ) {
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roundIncrement = UINT64_C( 0x0000000000000400 );
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roundMask = UINT64_C( 0x00000000000007FF );
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} else if ( roundingPrecision == 32 ) {
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roundIncrement = UINT64_C( 0x0000008000000000 );
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roundMask = UINT64_C( 0x000000FFFFFFFFFF );
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} else {
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goto precision80;
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}
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sig |= (sigExtra != 0);
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if ( ! roundNearEven && (roundingMode != softfloat_round_near_maxMag) ) {
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roundIncrement =
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(roundingMode
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== (sign ? softfloat_round_min : softfloat_round_max))
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? roundMask
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: 0;
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}
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roundBits = sig & roundMask;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( 0x7FFD <= (uint32_t) (exp - 1) ) {
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if ( exp <= 0 ) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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isTiny =
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(softfloat_detectTininess
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== softfloat_tininess_beforeRounding)
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|| (exp < 0)
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|| (sig <= (uint64_t) (sig + roundIncrement));
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sig = softfloat_shiftRightJam64( sig, 1 - exp );
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roundBits = sig & roundMask;
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if ( roundBits ) {
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if ( isTiny ) softfloat_raiseFlags( softfloat_flag_underflow );
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softfloat_exceptionFlags |= softfloat_flag_inexact;
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#ifdef SOFTFLOAT_ROUND_ODD
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if ( roundingMode == softfloat_round_odd ) {
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sig |= roundMask + 1;
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}
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#endif
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}
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sig += roundIncrement;
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exp = ((sig & UINT64_C( 0x8000000000000000 )) != 0);
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roundIncrement = roundMask + 1;
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if ( roundNearEven && (roundBits<<1 == roundIncrement) ) {
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roundMask |= roundIncrement;
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}
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sig &= ~roundMask;
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goto packReturn;
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}
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if (
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(0x7FFE < exp)
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|| ((exp == 0x7FFE) && ((uint64_t) (sig + roundIncrement) < sig))
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) {
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goto overflow;
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}
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( roundBits ) {
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softfloat_exceptionFlags |= softfloat_flag_inexact;
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#ifdef SOFTFLOAT_ROUND_ODD
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if ( roundingMode == softfloat_round_odd ) {
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sig = (sig & ~roundMask) | (roundMask + 1);
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goto packReturn;
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}
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#endif
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}
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sig = (uint64_t) (sig + roundIncrement);
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if ( sig < roundIncrement ) {
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++exp;
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sig = UINT64_C( 0x8000000000000000 );
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}
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roundIncrement = roundMask + 1;
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if ( roundNearEven && (roundBits<<1 == roundIncrement) ) {
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roundMask |= roundIncrement;
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}
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sig &= ~roundMask;
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goto packReturn;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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precision80:
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doIncrement = (UINT64_C( 0x8000000000000000 ) <= sigExtra);
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if ( ! roundNearEven && (roundingMode != softfloat_round_near_maxMag) ) {
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doIncrement =
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(roundingMode
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== (sign ? softfloat_round_min : softfloat_round_max))
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&& sigExtra;
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( 0x7FFD <= (uint32_t) (exp - 1) ) {
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if ( exp <= 0 ) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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isTiny =
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(softfloat_detectTininess
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== softfloat_tininess_beforeRounding)
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|| (exp < 0)
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|| ! doIncrement
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|| (sig < UINT64_C( 0xFFFFFFFFFFFFFFFF ));
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sig64Extra =
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softfloat_shiftRightJam64Extra( sig, sigExtra, 1 - exp );
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exp = 0;
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sig = sig64Extra.v;
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sigExtra = sig64Extra.extra;
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if ( sigExtra ) {
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if ( isTiny ) softfloat_raiseFlags( softfloat_flag_underflow );
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softfloat_exceptionFlags |= softfloat_flag_inexact;
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#ifdef SOFTFLOAT_ROUND_ODD
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if ( roundingMode == softfloat_round_odd ) {
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sig |= 1;
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goto packReturn;
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}
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#endif
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}
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doIncrement = (UINT64_C( 0x8000000000000000 ) <= sigExtra);
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if (
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! roundNearEven
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&& (roundingMode != softfloat_round_near_maxMag)
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) {
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doIncrement =
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(roundingMode
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== (sign ? softfloat_round_min : softfloat_round_max))
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&& sigExtra;
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}
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if ( doIncrement ) {
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++sig;
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sig &=
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~(uint_fast64_t)
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(! (sigExtra & UINT64_C( 0x7FFFFFFFFFFFFFFF ))
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& roundNearEven);
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exp = ((sig & UINT64_C( 0x8000000000000000 )) != 0);
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}
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goto packReturn;
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}
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if (
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(0x7FFE < exp)
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|| ((exp == 0x7FFE) && (sig == UINT64_C( 0xFFFFFFFFFFFFFFFF ))
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&& doIncrement)
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) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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roundMask = 0;
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overflow:
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softfloat_raiseFlags(
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softfloat_flag_overflow | softfloat_flag_inexact );
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if (
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roundNearEven
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|| (roundingMode == softfloat_round_near_maxMag)
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|| (roundingMode
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== (sign ? softfloat_round_min : softfloat_round_max))
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) {
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exp = 0x7FFF;
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sig = UINT64_C( 0x8000000000000000 );
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} else {
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exp = 0x7FFE;
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sig = ~roundMask;
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}
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goto packReturn;
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}
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if ( sigExtra ) {
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softfloat_exceptionFlags |= softfloat_flag_inexact;
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#ifdef SOFTFLOAT_ROUND_ODD
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if ( roundingMode == softfloat_round_odd ) {
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sig |= 1;
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goto packReturn;
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}
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#endif
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}
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if ( doIncrement ) {
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++sig;
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if ( ! sig ) {
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++exp;
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sig = UINT64_C( 0x8000000000000000 );
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} else {
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sig &=
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~(uint_fast64_t)
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(! (sigExtra & UINT64_C( 0x7FFFFFFFFFFFFFFF ))
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& roundNearEven);
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}
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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packReturn:
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uZ.s.signExp = packToExtF80UI64( sign, exp );
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uZ.s.signif = sig;
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return uZ.f;
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}
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