115 lines
5.7 KiB
C
115 lines
5.7 KiB
C
/* -------------------------------------------------------------- */
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/* (C)Copyright 2006,2007, */
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/* International Business Machines Corporation, */
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/* Sony Computer Entertainment, Incorporated, */
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/* Toshiba Corporation, */
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/* */
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/* All Rights Reserved. */
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/* */
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/* Redistribution and use in source and binary forms, with or */
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/* without modification, are permitted provided that the */
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/* following conditions are met: */
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/* */
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/* - Redistributions of source code must retain the above copyright*/
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/* notice, this list of conditions and the following disclaimer. */
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/* */
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/* - Redistributions in binary form must reproduce the above */
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/* copyright notice, this list of conditions and the following */
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/* disclaimer in the documentation and/or other materials */
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/* provided with the distribution. */
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/* */
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/* - Neither the name of IBM Corporation nor the names of its */
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/* contributors may be used to endorse or promote products */
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/* derived from this software without specific prior written */
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/* permission. */
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/* Redistributions of source code must retain the above copyright */
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/* notice, this list of conditions and the following disclaimer. */
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/* */
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/* Redistributions in binary form must reproduce the above */
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/* copyright notice, this list of conditions and the following */
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/* disclaimer in the documentation and/or other materials */
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/* provided with the distribution. */
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/* */
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/* Neither the name of IBM Corporation nor the names of its */
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/* contributors may be used to endorse or promote products */
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/* derived from this software without specific prior written */
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/* permission. */
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/* */
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/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */
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/* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */
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/* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */
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/* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */
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/* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */
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/* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */
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/* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */
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/* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */
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/* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */
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/* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */
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/* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */
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/* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */
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/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
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/* -------------------------------------------------------------- */
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/* PROLOG END TAG zYx */
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#ifdef __SPU__
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#ifndef _RECIPD2_H_
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#define _RECIPD2_H_ 1
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#include <spu_intrinsics.h>
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/*
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* FUNCTION
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* vector double _recipd2(vector double value)
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*
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* DESCRIPTION
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* The _recipd2 function inverts "value" and returns the result.
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* Computation is performed using the single precision reciprocal
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* estimate and interpolate instructions to produce a 12 accurate
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* estimate.
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*
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* One (1) iteration of a Newton-Raphson is performed to improve
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* accuracy to single precision floating point. Two additional double
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* precision iterations are needed to achieve a full double
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* preicision result.
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*
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* The Newton-Raphson iteration is of the form:
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* X[i+1] = X[i] * (2.0 - b*X[i])
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* where b is the input value to be inverted
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*
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*/
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static __inline vector double _recipd2(vector double value_d)
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{
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vector unsigned long long zero = (vector unsigned long long) { 0x0000000000000000ULL, 0x0000000000000000ULL };
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vector unsigned long long expmask = (vector unsigned long long) { 0x7FF0000000000000ULL, 0x7FF0000000000000ULL };
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vector unsigned long long signmask = (vector unsigned long long) { 0x8000000000000000ULL, 0x8000000000000000ULL };
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vector float x0;
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vector float value;
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vector float two = spu_splats(2.0f);
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vector double two_d = spu_splats(2.0);
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vector double x1, x2, x3;
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vector double bias;
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/* Bias the divisor to correct for double precision floating
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* point exponents that are out of single precision range.
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*/
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bias = spu_xor(spu_and(value_d, (vector double)expmask), (vector double)expmask);
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value = spu_roundtf(spu_mul(value_d, bias));
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x0 = spu_re(value);
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x1 = spu_extend(spu_mul(x0, spu_nmsub(value, x0, two)));
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x1 = spu_mul(x1, bias);
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x2 = spu_mul(x1, spu_nmsub(value_d, x1, two_d));
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x3 = spu_mul(x2, spu_nmsub(value_d, x2, two_d));
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/* Handle input = +/- infinity or +/-0. */
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vec_double2 xabs = spu_andc(value_d, (vec_double2)signmask);
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vec_ullong2 zeroinf = spu_or(spu_cmpeq(xabs, (vec_double2)expmask),
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spu_cmpeq(xabs, (vec_double2)zero));
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x3 = spu_sel(x3, spu_xor(value_d, (vector double)expmask), zeroinf);
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return (x3);
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}
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#endif /* _RECIPD2_H_ */
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#endif /* __SPU__ */
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