| |
| /*============================================================================ |
| |
| This C source file is part of the SoftFloat IEEE Floating-Point Arithmetic |
| Package, Release 3, by John R. Hauser. |
| |
| Copyright 2011, 2012, 2013, 2014 The Regents of the University of California |
| (Regents). All Rights Reserved. Redistribution and use in source and binary |
| forms, with or without modification, are permitted provided that the following |
| conditions are met: |
| |
| Redistributions of source code must retain the above copyright notice, |
| this list of conditions, and the following two paragraphs of disclaimer. |
| Redistributions in binary form must reproduce the above copyright notice, |
| this list of conditions, and the following two paragraphs of disclaimer in the |
| documentation and/or other materials provided with the distribution. Neither |
| the name of the Regents nor the names of its contributors may be used to |
| endorse or promote products derived from this software without specific prior |
| written permission. |
| |
| IN NO EVENT SHALL REGENTS BE LIABLE TO ANY PARTY FOR DIRECT, INDIRECT, |
| SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES, INCLUDING LOST PROFITS, ARISING |
| OUT OF THE USE OF THIS SOFTWARE AND ITS DOCUMENTATION, EVEN IF REGENTS HAS |
| BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| |
| REGENTS SPECIFICALLY DISCLAIMS ANY WARRANTIES, INCLUDING, BUT NOT LIMITED |
| TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR |
| PURPOSE. THE SOFTWARE AND ACCOMPANYING DOCUMENTATION, IF ANY, PROVIDED |
| HEREUNDER IS PROVIDED "AS IS". REGENTS HAS NO OBLIGATION TO PROVIDE |
| MAINTENANCE, SUPPORT, UPDATES, ENHANCEMENTS, OR MODIFICATIONS. |
| |
| =============================================================================*/ |
| |
| #include <stdbool.h> |
| #include <stdint.h> |
| #include "platform.h" |
| #include "internals.h" |
| #include "specialize.h" |
| #include "softfloat.h" |
| |
| float64_t f64_sqrt( float64_t a ) |
| { |
| union ui64_f64 uA; |
| uint_fast64_t uiA; |
| bool signA; |
| int_fast16_t expA; |
| uint_fast64_t sigA, uiZ; |
| struct exp16_sig64 normExpSig; |
| int_fast16_t expZ; |
| uint32_t sig32A, recipSqrt32, sig32Z; |
| uint_fast64_t rem; |
| uint32_t q; |
| uint_fast64_t sigZ, shiftedSigZ; |
| union ui64_f64 uZ; |
| |
| /*------------------------------------------------------------------------ |
| *------------------------------------------------------------------------*/ |
| uA.f = a; |
| uiA = uA.ui; |
| signA = signF64UI( uiA ); |
| expA = expF64UI( uiA ); |
| sigA = fracF64UI( uiA ); |
| /*------------------------------------------------------------------------ |
| *------------------------------------------------------------------------*/ |
| if ( expA == 0x7FF ) { |
| if ( sigA ) { |
| uiZ = softfloat_propagateNaNF64UI( 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_normSubnormalF64Sig( sigA ); |
| expA = normExpSig.exp; |
| sigA = normExpSig.sig; |
| } |
| /*------------------------------------------------------------------------ |
| | (`sig32Z' is guaranteed to be a lower bound on the square root of |
| | `sig32A', which makes `sig32Z' also a lower bound on the square root of |
| | `sigA'.) |
| *------------------------------------------------------------------------*/ |
| expZ = ((expA - 0x3FF)>>1) + 0x3FE; |
| expA &= 1; |
| sigA |= UINT64_C( 0x0010000000000000 ); |
| sig32A = sigA>>21; |
| recipSqrt32 = softfloat_approxRecipSqrt32_1( expA, sig32A ); |
| sig32Z = ((uint_fast64_t) sig32A * recipSqrt32)>>32; |
| if ( expA ) { |
| sigA <<= 8; |
| sig32Z >>= 1; |
| } else { |
| sigA <<= 9; |
| } |
| rem = sigA - (uint_fast64_t) sig32Z * sig32Z; |
| q = ((uint32_t) (rem>>2) * (uint_fast64_t) recipSqrt32)>>32; |
| sigZ = ((uint_fast64_t) sig32Z<<32 | 1<<5) + ((uint_fast64_t) q<<3); |
| /*------------------------------------------------------------------------ |
| *------------------------------------------------------------------------*/ |
| if ( (sigZ & 0x1FF) < 1<<5 ) { |
| sigZ &= ~(uint_fast64_t) 0x3F; |
| shiftedSigZ = sigZ>>6; |
| rem = (sigA<<52) - shiftedSigZ * shiftedSigZ; |
| if ( rem & UINT64_C( 0x8000000000000000 ) ) { |
| --sigZ; |
| } else { |
| if ( rem ) sigZ |= 1; |
| } |
| } |
| return softfloat_roundPackToF64( 0, expZ, sigZ ); |
| /*------------------------------------------------------------------------ |
| *------------------------------------------------------------------------*/ |
| invalid: |
| softfloat_raiseFlags( softfloat_flag_invalid ); |
| uiZ = defaultNaNF64UI; |
| uiZ: |
| uZ.ui = uiZ; |
| return uZ.f; |
| |
| } |
| |