117 lines
5.1 KiB
C
117 lines
5.1 KiB
C
/* -------------------------------------------------------------- */
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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 _SQRTF4_H_
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#define _SQRTF4_H_ 1
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#include <spu_intrinsics.h>
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/*
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* FUNCTION
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* vector float _sqrtf4(vector float in)
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*
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* DESCRIPTION
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* The _sqrtf4 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 float _sqrtf4(vector float in)
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{
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vec_uint4 exp, valid;
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vec_uint4 mask = spu_splats((unsigned int)0xFF000000);
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vec_uint4 half = spu_splats((unsigned int)0x00800000);
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vec_float4 one = spu_splats(1.0f);
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vec_float4 three = spu_splats(3.0f);
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vec_float4 x, y0, y1, y1_n1, y1_p1, y1_p2, y1_p3;
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vec_float4 mant, err, err_p1, err_p2, err_p3;
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vec_float4 out;
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/* Compute the mantissa of the result seperately from
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* the exponent to assure complete accuracy over the allowable
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* input range. The mantissa is computed for inputs in the
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* range [0.5, 2.0).
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*/
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x = spu_sel(in, one, mask);
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y0 = spu_rsqrte(x);
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/* Perform one iteration of the Newton-Raphsom method in single precision
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* arithmetic.
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*/
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y1 = spu_mul(spu_nmsub(x, spu_mul(y0, y0), three),
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spu_mul(y0, (vec_float4)(spu_sub((vec_uint4)(x), half))));
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/* Correct the result for possible error. The range of error is -3 to +1.
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* Identify the extent of the error and correct for it.
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*/
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y1_p3 = (vec_float4)spu_add((vec_uint4)(y1), 3);
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y1_p2 = (vec_float4)spu_add((vec_uint4)(y1), 2);
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y1_p1 = (vec_float4)spu_add((vec_uint4)(y1), 1);
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y1_n1 = (vec_float4)spu_add((vec_uint4)(y1), -1);
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err = spu_nmsub(y1, y1, x);
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err_p1 = spu_nmsub(y1_p1, y1_p1, x);
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err_p2 = spu_nmsub(y1_p2, y1_p2, x);
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err_p3 = spu_nmsub(y1_p3, y1_p3, x);
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mant = spu_sel(y1_n1, y1, spu_cmpgt((vec_int4)(err), -1));
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mant = spu_sel(mant, y1_p1, spu_cmpgt((vec_int4)(err_p1), -1));
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mant = spu_sel(mant, y1_p2, spu_cmpgt((vec_int4)(err_p2), -1));
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mant = spu_sel(mant, y1_p3, spu_cmpgt((vec_int4)(err_p3), -1));
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/* Compute the expected exponent. If the exponent is zero or the input is
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* negative, then set the result to zero.
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*/
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exp = spu_rlmask(spu_add((vec_uint4)(in), (vec_uint4)(one)), -1);
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valid = spu_cmpgt(spu_and((vec_int4)(in), (vec_int4)(mask)), 0);
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/* Merge the computed exponent and mantissa.
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*/
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out = spu_and(spu_sel(mant, (vec_float4)(exp), spu_splats(0xFF800000)), (vec_float4)(valid));
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return (out);
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}
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#endif /* _SQRTF4_H_ */
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#endif /* __SPU__ */
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