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Diffstat (limited to 'softfloat/f16_sqrt.c')
| -rw-r--r-- | softfloat/f16_sqrt.c | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/softfloat/f16_sqrt.c b/softfloat/f16_sqrt.c new file mode 100644 index 0000000..7ff2923 --- /dev/null +++ b/softfloat/f16_sqrt.c @@ -0,0 +1,136 @@ + +/*============================================================================ + +This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic +Package, Release 3d, by John R. Hauser. + +Copyright 2011, 2012, 2013, 2014, 2015, 2016 The Regents of the University of +California. All rights reserved. + +Redistribution and use in source and binary forms, with or without +modification, are permitted provided that the following conditions are met: + + 1. Redistributions of source code must retain the above copyright notice, + this list of conditions, and the following disclaimer. + + 2. Redistributions in binary form must reproduce the above copyright notice, + this list of conditions, and the following disclaimer in the documentation + and/or other materials provided with the distribution. + + 3. Neither the name of the University nor the names of its contributors may + be used to endorse or promote products derived from this software without + specific prior written permission. + +THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS "AS IS", AND ANY +EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED +WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ARE +DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE FOR ANY +DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES +(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; +LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND +ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT +(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS +SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. + +=============================================================================*/ + +#include <stdbool.h> +#include <stdint.h> +#include "platform.h" +#include "internals.h" +#include "specialize.h" +#include "softfloat.h" + +extern const uint16_t softfloat_approxRecipSqrt_1k0s[]; +extern const uint16_t softfloat_approxRecipSqrt_1k1s[]; + +float16_t f16_sqrt( float16_t a ) +{ + union ui16_f16 uA; + uint_fast16_t uiA; + bool signA; + int_fast8_t expA; + uint_fast16_t sigA, uiZ; + struct exp8_sig16 normExpSig; + int_fast8_t expZ; + int index; + uint_fast16_t r0; + uint_fast32_t ESqrR0; + uint16_t sigma0; + uint_fast16_t recipSqrt16, sigZ, shiftedSigZ; + uint16_t negRem; + union ui16_f16 uZ; + + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + uA.f = a; + uiA = uA.ui; + signA = signF16UI( uiA ); + expA = expF16UI( uiA ); + sigA = fracF16UI( uiA ); + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + if ( expA == 0x1F ) { + if ( sigA ) { + uiZ = softfloat_propagateNaNF16UI( uiA, 0 ); + goto uiZ; + } + if ( ! signA ) return a; + goto invalid; + } + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + if ( signA ) { + if ( ! (expA | sigA) ) return a; + goto invalid; + } + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + if ( ! expA ) { + if ( ! sigA ) return a; + normExpSig = softfloat_normSubnormalF16Sig( sigA ); + expA = normExpSig.exp; + sigA = normExpSig.sig; + } + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + expZ = ((expA - 0xF)>>1) + 0xE; + expA &= 1; + sigA |= 0x0400; + index = (sigA>>6 & 0xE) + expA; + r0 = softfloat_approxRecipSqrt_1k0s[index] + - (((uint_fast32_t) softfloat_approxRecipSqrt_1k1s[index] + * (sigA & 0x7F)) + >>11); + ESqrR0 = ((uint_fast32_t) r0 * r0)>>1; + if ( expA ) ESqrR0 >>= 1; + sigma0 = ~(uint_fast16_t) ((ESqrR0 * sigA)>>16); + recipSqrt16 = r0 + (((uint_fast32_t) r0 * sigma0)>>25); + if ( ! (recipSqrt16 & 0x8000) ) recipSqrt16 = 0x8000; + sigZ = ((uint_fast32_t) (sigA<<5) * recipSqrt16)>>16; + if ( expA ) sigZ >>= 1; + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + ++sigZ; + if ( ! (sigZ & 7) ) { + shiftedSigZ = sigZ>>1; + negRem = shiftedSigZ * shiftedSigZ; + sigZ &= ~1; + if ( negRem & 0x8000 ) { + sigZ |= 1; + } else { + if ( negRem ) --sigZ; + } + } + return softfloat_roundPackToF16( 0, expZ, sigZ ); + /*------------------------------------------------------------------------ + *------------------------------------------------------------------------*/ + invalid: + softfloat_raiseFlags( softfloat_flag_invalid ); + uiZ = defaultNaNF16UI; + uiZ: + uZ.ui = uiZ; + return uZ.f; + +} + |