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169 lines
7.3 KiB
C
169 lines
7.3 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 _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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* a) X[i+1] = X[i] * (2.0 - b*X[i])
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* or
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* b) X[i+1] = X[i] + X[i]*(1.0 - X[i]*b)
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* where b is the input value to be inverted
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*
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* The later (b) form improves the accuracy to 99.95% correctly rounded.
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*/
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static __inline vector double _recipd2(vector double value_in)
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{
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vec_float4 x0;
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vec_float4 value;
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vec_float4 one = spu_splats(1.0f);
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vec_double2 one_d = spu_splats(1.0);
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vec_double2 x1, x2, x3;
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vec_double2 scale;
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vec_double2 exp, value_d;
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vec_ullong2 expmask = spu_splats(0x7FF0000000000000ULL);
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vec_ullong2 is0inf;
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#ifdef __SPU_EDP__
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vec_ullong2 isdenorm;
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vec_ullong2 expmask_minus1 = spu_splats(0x7FE0000000000000ULL);
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/* Determine special input values. For example, if the input is a denorm, infinity or 0 */
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isdenorm = spu_testsv(value_in, (SPU_SV_POS_DENORM | SPU_SV_NEG_DENORM));
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is0inf = spu_testsv(value_in, (SPU_SV_NEG_ZERO | SPU_SV_POS_ZERO |
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SPU_SV_NEG_INFINITY | SPU_SV_POS_INFINITY));
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/* Scale 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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exp = spu_and(value_in, (vec_double2)expmask);
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scale = spu_xor(exp, (vec_double2)spu_sel(expmask, expmask_minus1, isdenorm));
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value_d = spu_mul(value_in, scale);
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value = spu_roundtf(value_d);
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/* Perform reciprocal with 1 single precision and 2 double precision
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* Newton-Raphson iterations.
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*/
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x0 = spu_re(value);
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x1 = spu_extend(spu_madd(spu_nmsub(value, x0, one), x0, x0));
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x2 = spu_madd(spu_nmsub(value_d, x1, one_d), x1, x1);
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x3 = spu_madd(spu_nmsub(value_d, x2, one_d), x2, x2);
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x3 = spu_sel(spu_mul(x3, scale), spu_xor(value_in, (vector double)expmask), is0inf);
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#else /* !__SPU_EDP__ */
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vec_uint4 isinf, iszero, isdenorm0;
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vec_double2 value_abs;
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vec_double2 sign = spu_splats(-0.0);
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vec_double2 denorm_scale = (vec_double2)spu_splats(0x4330000000000000ULL);
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vec_double2 exp_53 = (vec_double2)spu_splats(0x0350000000000000ULL);
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vec_uchar16 splat_hi = (vec_uchar16){0,1,2,3, 0,1,2,3, 8,9,10,11, 8,9,10,11};
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vec_uchar16 swap = (vec_uchar16){4,5,6,7, 0,1,2,3, 12,13,14,15, 8,9,10,11};
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value_abs = spu_andc(value_in, sign);
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exp = spu_and(value_in, (vec_double2)expmask);
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/* Determine if the input is a special value. These include:
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* denorm - then we must coerce it to a normal value.
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* zero - then we must return an infinity
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* infinity - then we must return a zero.
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*/
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isdenorm0 = spu_cmpeq(spu_shuffle((vec_uint4)exp, (vec_uint4)exp, splat_hi), 0);
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isinf = spu_cmpeq((vec_uint4)value_abs, (vec_uint4)expmask);
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iszero = spu_cmpeq((vec_uint4)value_abs, 0);
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isinf = spu_and(isinf, spu_shuffle(isinf, isinf, swap));
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iszero = spu_and(iszero, spu_shuffle(iszero, iszero, swap));
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is0inf = (vec_ullong2)spu_or(isinf, iszero);
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/* If the inputs is a denorm, we must first convert it to a normal number since
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* arithmetic operations on denormals produces 0 on Cell/B.E.
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*/
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value_d = spu_sub(spu_or(value_abs, exp_53), exp_53);
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value_d = spu_sel(value_abs, value_d, (vec_ullong2)isdenorm0);
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/* Scale 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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scale = spu_xor(spu_and(value_d, (vec_double2)expmask), (vec_double2)expmask);
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value_d = spu_mul(value_d, scale);
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value = spu_roundtf(value_d);
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/* Perform reciprocal with 1 single precision and 2 double precision
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* Newton-Raphson iterations. The bias is removed after the single
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* precision iteration.
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*/
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x0 = spu_re(value);
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x1 = spu_extend(spu_madd(spu_nmsub(value, x0, one), x0, x0));
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x2 = spu_madd(spu_nmsub(value_d, x1, one_d), x1, x1);
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x3 = spu_madd(spu_nmsub(value_d, x2, one_d), x2, x2);
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x3 = spu_mul(x3, spu_sel(scale, value_in, (vec_ullong2)sign));
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x3 = spu_sel(x3, spu_mul(x3, denorm_scale), (vec_ullong2)isdenorm0);
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x3 = spu_sel(x3, spu_xor(value_in, (vector double)expmask), is0inf);
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#endif /* __SPU_EDP__ */
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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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