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| 2 | /*============================================================================
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| 3 |
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| 4 | This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
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| 5 | Package, Release 3e, by John R. Hauser.
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| 6 |
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| 7 | Copyright 2011, 2012, 2013, 2014, 2015, 2016 The Regents of the University of
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| 8 | California. All rights reserved.
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| 9 |
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| 10 | Redistribution and use in source and binary forms, with or without
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| 11 | modification, are permitted provided that the following conditions are met:
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| 12 |
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| 13 | 1. Redistributions of source code must retain the above copyright notice,
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| 14 | this list of conditions, and the following disclaimer.
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| 15 |
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| 16 | 2. Redistributions in binary form must reproduce the above copyright notice,
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| 17 | this list of conditions, and the following disclaimer in the documentation
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| 18 | and/or other materials provided with the distribution.
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| 19 |
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| 20 | 3. Neither the name of the University nor the names of its contributors may
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| 21 | be used to endorse or promote products derived from this software without
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| 22 | specific prior written permission.
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| 23 |
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| 24 | THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
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| 25 | EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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| 26 | WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE
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| 27 | DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY
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| 28 | DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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| 29 | (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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| 30 | LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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| 31 | ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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| 32 | (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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| 33 | SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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| 34 |
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| 35 | =============================================================================*/
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| 36 |
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| 37 | #include <stdint.h>
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| 38 | #include "platform.h"
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| 39 |
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| 40 | #ifndef softfloat_approxRecipSqrt32_1
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| 41 |
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| 42 | extern const uint16_t softfloat_approxRecipSqrt_1k0s[];
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| 43 | extern const uint16_t softfloat_approxRecipSqrt_1k1s[];
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| 44 |
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| 45 | uint32_t softfloat_approxRecipSqrt32_1( unsigned int oddExpA, uint32_t a )
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| 46 | {
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| 47 | int index;
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| 48 | uint16_t eps, r0;
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| 49 | uint_fast32_t ESqrR0;
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| 50 | uint32_t sigma0;
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| 51 | uint_fast32_t r;
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| 52 | uint32_t sqrSigma0;
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| 53 |
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| 54 | index = (a>>27 & 0xE) + oddExpA;
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| 55 | eps = (uint16_t) (a>>12);
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| 56 | r0 = softfloat_approxRecipSqrt_1k0s[index]
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| 57 | - ((softfloat_approxRecipSqrt_1k1s[index] * (uint_fast32_t) eps)
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| 58 | >>20);
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| 59 | ESqrR0 = (uint_fast32_t) r0 * r0;
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| 60 | if ( ! oddExpA ) ESqrR0 <<= 1;
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| 61 | sigma0 = ~(uint_fast32_t) (((uint32_t) ESqrR0 * (uint_fast64_t) a)>>23);
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| 62 | r = ((uint_fast32_t) r0<<16) + ((r0 * (uint_fast64_t) sigma0)>>25);
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| 63 | sqrSigma0 = ((uint_fast64_t) sigma0 * sigma0)>>32;
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| 64 | r += ((uint32_t) ((r>>1) + (r>>3) - ((uint_fast32_t) r0<<14))
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| 65 | * (uint_fast64_t) sqrSigma0)
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| 66 | >>48;
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| 67 | if ( ! (r & 0x80000000) ) r = 0x80000000;
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| 68 | return r;
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| 69 |
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| 70 | }
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| 71 |
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| 72 | #endif
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| 73 |
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