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jeremybenn |
/* -------------------------------------------------------------- */
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/* (C)Copyright 2001,2008, */
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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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/* */
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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 _SQRTD2_H_
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#define _SQRTD2_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 _sqrtd2(vector double in)
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*
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* DESCRIPTION
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* The _sqrtd2 function computes the square root of the vector input "in"
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* and returns the result.
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*
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*/
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static __inline vector double _sqrtd2(vector double in)
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{
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vec_int4 bias_exp;
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vec_uint4 exp;
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vec_float4 fx, fg, fy, fd, fe, fy2, fhalf;
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vec_ullong2 nochange, denorm;
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vec_ullong2 mask = spu_splats(0x7FE0000000000000ULL);
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vec_double2 dx, de, dd, dy, dg, dy2, dhalf;
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vec_double2 neg;
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vec_double2 one = spu_splats(1.0);
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vec_double2 two_pow_52 = (vec_double2)spu_splats(0x4330000000000000ULL);
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/* If the input is a denorm, then multiply it by 2^52 so that the input is no
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* longer denormal.
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*/
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exp = (vec_uint4)spu_and((vec_ullong2)in, spu_splats(0xFFF0000000000000ULL));
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denorm = (vec_ullong2)spu_cmpeq(exp,0);
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in = spu_mul(in, spu_sel(one, two_pow_52, denorm));
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fhalf = spu_splats(0.5f);
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dhalf = spu_splats(0.5);
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/* Coerce the input, in, into the argument reduced space [0.5, 2.0).
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*/
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dx = spu_sel(in, dhalf, mask);
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/* Compute an initial single precision guess for the square root (fg)
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* and half reciprocal (fy2).
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*/
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fx = spu_roundtf(dx);
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fy2 = spu_rsqrte(fx);
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fy = spu_mul(fy2, fhalf);
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fg = spu_mul(fy2, fx); /* 12-bit approximation to sqrt(cx) */
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/* Perform one single precision Newton-Raphson iteration to improve
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* accuracy to about 22 bits.
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*/
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fe = spu_nmsub(fy, fg, fhalf);
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fd = spu_nmsub(fg, fg, fx);
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fy = spu_madd(fy2, fe, fy);
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fg = spu_madd(fy, fd, fg); /* 22-bit approximation */
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dy = spu_extend(fy);
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dg = spu_extend(fg);
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/* Perform two double precision Newton-Raphson iteration to improve
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* accuracy to about 44 and 88 bits repectively.
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*/
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dy2 = spu_add(dy, dy);
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de = spu_nmsub(dy, dg, dhalf);
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dd = spu_nmsub(dg, dg, dx);
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dy = spu_madd(dy2, de, dy);
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dg = spu_madd(dy, dd, dg); /* 44 bit approximation */
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dd = spu_nmsub(dg, dg, dx);
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dg = spu_madd(dy, dd, dg); /* full double precision approximation */
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/* Compute the expected exponent assuming that it is not a special value.
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* See special value handling below.
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*/
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bias_exp = spu_rlmaska(spu_sub((vec_int4)spu_and((vec_ullong2)in, mask),
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(vec_int4)spu_splats(0x3FE0000000000000ULL)),
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-1);
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/* Adjust the exponent bias if the input was denormalized */
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bias_exp = spu_sub(bias_exp, (vec_int4)spu_and(spu_splats(0x01A0000000000000ULL), denorm));
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dg = (vec_double2)spu_add((vec_int4)dg, bias_exp);
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/* Handle special inputs. These include:
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*
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* input output
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* ========= =========
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* -0 -0
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* 0 0
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* +infinity +infinity
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* NaN NaN
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* <0 NaN
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*/
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exp = spu_shuffle(exp, exp, ((vec_uchar16) { 0,1,2,3,0,1,2,3, 8,9,10,11,8,9,10,11 }));
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neg = (vec_double2)spu_rlmaska((vec_int4)exp, -31);
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nochange = spu_or((vec_ullong2)spu_cmpeq(exp, 0x7FF00000),
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spu_cmpeq(in, spu_splats(0.0)));
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dg = spu_sel(spu_or(dg, neg), in, nochange);
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return (dg);
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}
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#endif /* _SQRTD2_H_ */
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#endif /* __SPU__ */
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