107 lines
4.9 KiB
C
107 lines
4.9 KiB
C
/*============================================================================
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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 "internals.h"
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#include "primitives.h"
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#include "softfloat.h"
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float16_t
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softfloat_roundPackToF16(bool sign, int16_t exp, uint16_t sig, struct softfloat_status_t *status)
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{
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uint8_t roundingMode;
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bool roundNearEven;
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uint8_t roundIncrement, roundBits;
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bool isTiny;
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uint16_t uiZ;
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uint16_t sigRef;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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roundingMode = softfloat_getRoundingMode(status);
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roundNearEven = (roundingMode == softfloat_round_near_even);
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roundIncrement = 0x8;
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if (! roundNearEven && (roundingMode != softfloat_round_near_maxMag)) {
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roundIncrement =
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(roundingMode == (sign ? softfloat_round_min : softfloat_round_max)) ? 0xF : 0;
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}
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roundBits = sig & 0xF;
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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if (0x1D <= (unsigned int) exp) {
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if (exp < 0) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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isTiny = (exp < -1) || (sig + roundIncrement < 0x8000);
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sig = softfloat_shiftRightJam32(sig, -exp);
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exp = 0;
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roundBits = sig & 0xF;
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if (isTiny) {
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if (! softfloat_isMaskedException(status, softfloat_flag_underflow) || roundBits) {
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softfloat_raiseFlags(status, softfloat_flag_underflow);
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}
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if (softfloat_flushUnderflowToZero(status)) {
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softfloat_raiseFlags(status, softfloat_flag_underflow | softfloat_flag_inexact);
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return packToF16UI(sign, 0, 0);
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}
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}
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} else if ((0x1D < exp) || (0x8000 <= sig + roundIncrement)) {
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/*----------------------------------------------------------------
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*----------------------------------------------------------------*/
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softfloat_raiseFlags(status, softfloat_flag_overflow);
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if (roundBits || softfloat_isMaskedException(status, softfloat_flag_overflow)) {
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softfloat_raiseFlags(status, softfloat_flag_inexact);
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if (roundIncrement != 0) softfloat_setRoundingUp(status);
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}
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uiZ = packToF16UI(sign, 0x1F, 0) - ! roundIncrement;
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return uiZ;
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}
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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sigRef = sig;
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sig = (sig + roundIncrement)>>4;
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sig &= ~(uint16_t) (! (roundBits ^ 8) & roundNearEven);
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if (! sig) exp = 0;
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if (roundBits) {
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softfloat_raiseFlags(status, softfloat_flag_inexact);
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if ((sig << 4) > sigRef) softfloat_setRoundingUp(status);
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}
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/*------------------------------------------------------------------------
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*------------------------------------------------------------------------*/
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return packToF16UI(sign, exp, sig);
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}
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