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74 lines
2.9 KiB
C
74 lines
2.9 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 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 <stdint.h>
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#include "platform.h"
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#ifndef softfloat_approxRecipSqrt32_1
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extern const uint16_t softfloat_approxRecipSqrt_1k0s[];
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extern const uint16_t softfloat_approxRecipSqrt_1k1s[];
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uint32_t softfloat_approxRecipSqrt32_1( unsigned int oddExpA, uint32_t a )
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{
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int index;
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uint16_t eps, r0;
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uint_fast32_t ESqrR0;
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uint32_t sigma0;
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uint_fast32_t r;
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uint32_t sqrSigma0;
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index = (a>>27 & 0xE) + oddExpA;
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eps = (uint16_t) (a>>12);
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r0 = softfloat_approxRecipSqrt_1k0s[index]
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- ((softfloat_approxRecipSqrt_1k1s[index] * (uint_fast32_t) eps)
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>>20);
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ESqrR0 = (uint_fast32_t) r0 * r0;
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if ( ! oddExpA ) ESqrR0 <<= 1;
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sigma0 = ~(uint_fast32_t) (((uint32_t) ESqrR0 * (uint_fast64_t) a)>>23);
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r = ((uint_fast32_t) r0<<16) + ((r0 * (uint_fast64_t) sigma0)>>25);
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sqrSigma0 = ((uint_fast64_t) sigma0 * sigma0)>>32;
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r += ((uint32_t) ((r>>1) + (r>>3) - ((uint_fast32_t) r0<<14))
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* (uint_fast64_t) sqrSigma0)
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>>48;
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if ( ! (r & 0x80000000) ) r = 0x80000000;
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return r;
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}
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#endif
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