135 lines
5.4 KiB
C
135 lines
5.4 KiB
C
/* -------------------------------------------------------------- */
|
|
/* (C)Copyright 2001,2008, */
|
|
/* International Business Machines Corporation, */
|
|
/* Sony Computer Entertainment, Incorporated, */
|
|
/* Toshiba Corporation, */
|
|
/* */
|
|
/* 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 disclaimer. */
|
|
/* */
|
|
/* - Redistributions in binary form must reproduce the above */
|
|
/* copyright notice, this list of conditions and the following */
|
|
/* disclaimer in the documentation and/or other materials */
|
|
/* provided with the distribution. */
|
|
/* */
|
|
/* - Neither the name of IBM Corporation nor the names of its */
|
|
/* contributors may be used to endorse or promote products */
|
|
/* derived from this software without specific prior written */
|
|
/* permission. */
|
|
/* */
|
|
/* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND */
|
|
/* CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, */
|
|
/* INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF */
|
|
/* MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE */
|
|
/* DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR */
|
|
/* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, */
|
|
/* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT */
|
|
/* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; */
|
|
/* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) */
|
|
/* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN */
|
|
/* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR */
|
|
/* OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, */
|
|
/* EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */
|
|
/* -------------------------------------------------------------- */
|
|
/* PROLOG END TAG zYx */
|
|
#ifdef __SPU__
|
|
#ifndef _EXP2F4_H_
|
|
#define _EXP2F4_H_ 1
|
|
|
|
|
|
#include <spu_intrinsics.h>
|
|
#include "simdmath.h"
|
|
|
|
/*
|
|
* FUNCTION
|
|
* vector float _exp2f4(vector float x)
|
|
*
|
|
* DESCRIPTION
|
|
* The _exp2f4 function computes 2 raised to the input vector x.
|
|
* Computation is performed by observing the 2^(a+b) = 2^a * 2^b.
|
|
* We decompose x into a and b (above) by letting.
|
|
* a = ceil(x), b = x - a;
|
|
*
|
|
* 2^a is easilty computed by placing a into the exponent
|
|
* or a floating point number whose mantissa is all zeros.
|
|
*
|
|
* 2^b is computed using the following polynomial approximation.
|
|
* (C. Hastings, Jr, 1955).
|
|
*
|
|
* __7__
|
|
* \
|
|
* \
|
|
* 2^(-x) = / Ci*x^i
|
|
* /____
|
|
* i=1
|
|
*
|
|
* for x in the range 0.0 to 1.0
|
|
*
|
|
* C0 = 1.0
|
|
* C1 = -0.9999999995
|
|
* C2 = 0.4999999206
|
|
* C3 = -0.1666653019
|
|
* C4 = 0.0416573475
|
|
* C5 = -0.0083013598
|
|
* C6 = 0.0013298820
|
|
* C7 = -0.0001413161
|
|
*
|
|
*/
|
|
static __inline vector float _exp2f4(vector float x)
|
|
{
|
|
vector signed int ix;
|
|
vector unsigned int overflow, underflow;
|
|
vector float frac, frac2, frac4;
|
|
vector float exp_int, exp_frac;
|
|
vector float result;
|
|
vector float hi, lo;
|
|
|
|
vector float bias;
|
|
/* Break in the input x into two parts ceil(x), x - ceil(x).
|
|
*/
|
|
bias = (vector float)(spu_rlmaska((vector signed int)(x), -31));
|
|
bias = (vector float)(spu_andc(spu_splats((unsigned int)0x3F7FFFFF), (vector unsigned int)bias));
|
|
ix = spu_convts(spu_add(x, bias), 0);
|
|
frac = spu_sub(spu_convtf(ix, 0), x);
|
|
frac = spu_mul(frac, spu_splats((float)SM_LN2));
|
|
|
|
overflow = spu_rlmask(spu_cmpgt(ix, 128), -1);
|
|
underflow = spu_cmpgt(ix, -128);
|
|
|
|
exp_int = (vector float)spu_and((vector unsigned int)spu_sl(spu_add(ix, 127), 23), underflow);
|
|
|
|
/* Instruction counts can be reduced if the polynomial was
|
|
* computed entirely from nested (dependent) fma's. However,
|
|
* to reduce the number of pipeline stalls, the polygon is evaluated
|
|
* in two halves (hi amd lo).
|
|
*/
|
|
frac2 = spu_mul(frac, frac);
|
|
frac4 = spu_mul(frac2, frac2);
|
|
|
|
hi = spu_madd(frac, spu_splats(-0.0001413161f), spu_splats(0.0013298820f));
|
|
hi = spu_madd(frac, hi, spu_splats(-0.0083013598f));
|
|
hi = spu_madd(frac, hi, spu_splats(0.0416573475f));
|
|
lo = spu_madd(frac, spu_splats(-0.1666653019f), spu_splats(0.4999999206f));
|
|
lo = spu_madd(frac, lo, spu_splats(-0.9999999995f));
|
|
lo = spu_madd(frac, lo, spu_splats(1.0f));
|
|
|
|
exp_frac = spu_madd(frac4, hi, lo);
|
|
ix = spu_add(ix, spu_rlmask((vector signed int)(exp_frac), -23));
|
|
result = spu_mul(exp_frac, exp_int);
|
|
|
|
/* Handle overflow */
|
|
result = spu_or(result, (vector float)overflow);
|
|
|
|
return (result);
|
|
|
|
}
|
|
|
|
#endif /* _EXP2F4_H_ */
|
|
#endif /* __SPU__ */
|