s_approxRecip32_1.c

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/*============================================================================

This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic
Package, Release 3c, by John R. Hauser.

Copyright 2011, 2012, 2013, 2014, 2015, 2016 The Regents of the University of
California.  All rights reserved.

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    be used to endorse or promote products derived from this software without
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THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY
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=============================================================================*/

#include <stdint.h>
#include "platform.h"

#ifndef softfloat_approxRecip32_1

extern const uint16_t softfloat_approxRecip_1k0s[16];
extern const uint16_t softfloat_approxRecip_1k1s[16];

uint32_t softfloat_approxRecip32_1( uint32_t a )
{
    int index;
    uint16_t eps, r0;
    uint32_t sigma0;
    uint_fast32_t r;
    uint32_t sqrSigma0;

    index = a>>27 & 0xF;
    eps = (uint16_t) (a>>11);
    r0 = softfloat_approxRecip_1k0s[index]
             - ((softfloat_approxRecip_1k1s[index] * (uint_fast32_t) eps)>>20);
    sigma0 = ~(uint_fast32_t) ((r0 * (uint_fast64_t) a)>>7);
    r = ((uint_fast32_t) r0<<16) + ((r0 * (uint_fast64_t) sigma0)>>24);
    sqrSigma0 = ((uint_fast64_t) sigma0 * sigma0)>>32;
    r += ((uint32_t) r * (uint_fast64_t) sqrSigma0)>>48;
    return r;

}

#endif