7529cdb3f6
The upcoming vectormath that will used to speed up the SPU version of Extras/BulletMultiThreaded depends on this.
139 lines
5.2 KiB
C
139 lines
5.2 KiB
C
/* exp2f4
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Copyright (C) 2006, 2007 Sony Computer Entertainment Inc.
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All rights reserved.
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Redistribution and use in source and binary forms,
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with or without modification, are permitted provided that the
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following conditions are met:
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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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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of the Sony Computer Entertainment Inc nor the names
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of its contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE.
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*/
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#include <simdmath.h>
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#include <altivec.h>
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#include <math.h>
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#include "common-types.h"
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/*
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* FUNCTION
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* vec_float4 _exp2_v(vec_float4 x)
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*
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* DESCRIPTION
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* _exp2_v computes 2 raised to the input vector x. Computation is
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* performed by observing the 2^(a+b) = 2^a * 2^b.
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* We decompose x into a and b (above) by letting.
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* a = ceil(x), b = x - a;
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*
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* 2^a is easilty computed by placing a into the exponent
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* or a floating point number whose mantissa is all zeros.
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*
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* 2^b is computed using the following polynomial approximation.
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* (C. Hastings, Jr, 1955).
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*
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* __7__
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* \
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* \
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* 2^(-x) = / Ci*x^i
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* /____
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* i=1
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*
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* for x in the range 0.0 to 1.0
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*
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* C0 = 1.0
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* C1 = -0.9999999995
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* C2 = 0.4999999206
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* C3 = -0.1666653019
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* C4 = 0.0416573475
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* C5 = -0.0083013598
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* C6 = 0.0013298820
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* C7 = -0.0001413161
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*
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* This function does not handle out of range conditions. It
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* assumes that x is in the range (-128.0, 127.0]. Values outside
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* this range will produce undefined results.
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*/
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#define _EXP2F_H_LN2 0.69314718055995f /* ln(2) */
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vector float
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exp2f4 (vector float x)
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{
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vec_int4 ix;
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vec_uint4 overflow;
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vec_uint4 underflow;
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vec_float4 frac, frac2, frac4;
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vec_float4 exp_int, exp_frac;
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vec_float4 result;
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vec_float4 hi, lo;
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vec_float4 zeros = vec_splatsf4(0.0f);
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vec_float4 bias;
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/* Break in the input x into two parts ceil(x), x - ceil(x).
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*/
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#if 1
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bias = (vec_float4)(vec_sra((vec_int4)x, vec_splatsu4(31) ));
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bias = (vec_float4)(vec_andc(vec_splatsu4(0x3F7FFFFF), (vec_uint4)bias));
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ix = vec_cts(vec_add(x, bias), 0);
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#else
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bias = vec_sel(vec_floor(x), vec_ceil(x), vec_cmpgt(x, vec_splatsf4(0.0f)));
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ix = vec_cts(bias, 0);
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#endif
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frac = vec_sub(vec_ctf(ix, 0), x);
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frac = vec_madd(frac, vec_splatsf4(_EXP2F_H_LN2), zeros);
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// !!! HRD Changing weird un-understandable and incorrect overflow handling code
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//overflow = vec_sel((vec_uint4)(0x7FFFFFFF), (vec_uint4)x, (vec_uint4)(0x80000000) );
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overflow = (vec_uint4)vec_cmpgt(x, (vec_float4)(vec_splatsi4(0x4300FFFF))); // !!! Biggest possible exponent to fit in range.
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underflow = (vec_uint4)vec_cmpgt(vec_splatsf4(-126.0f), x);
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//exp_int = (vec_float4)(vec_sl(vec_add(ix, (vec_int4)(127)), (vec_uint4)(23))); // !!! HRD <- changing this to correct for
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// !!! overflow (x >= 127.999999f)
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exp_int = (vec_float4)(vec_sl(vec_add(ix, vec_splatsi4(126)), vec_splatsu4(23))); // !!! HRD <- add with saturation
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/* Instruction counts can be reduced if the polynomial was
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* computed entirely from nested (dependent) fma's. However,
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* to reduce the number of pipeline stalls, the polygon is evaluated
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* in two halves (hi amd lo).
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*/
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frac2 = vec_madd(frac, frac, zeros);
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frac4 = vec_madd(frac2, frac2, zeros);
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hi = vec_madd(frac, vec_splatsf4(-0.0001413161), vec_splatsf4(0.0013298820));
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hi = vec_madd(frac, hi, vec_splatsf4(-0.0083013598));
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hi = vec_madd(frac, hi, vec_splatsf4(0.0416573475));
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lo = vec_madd(frac, vec_splatsf4(-0.1666653019), vec_splatsf4(0.4999999206));
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lo = vec_madd(frac, lo, vec_splatsf4(-0.9999999995));
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lo = vec_madd(frac, lo, vec_splatsf4(1.0));
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exp_frac = vec_madd(frac4, hi, lo);
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//ix = vec_add(ix, vec_sr((vec_int4)(exp_frac), (vec_uint4)(23) ));
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result = vec_madd(exp_frac, exp_int, zeros);
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result = vec_madd(exp_frac, exp_int, result); // !!! HRD
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/* Handle overflow */
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result = vec_sel(result, vec_splatsf4(HUGE_VALF), overflow);
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result = vec_sel(result, zeros, underflow);
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//result = vec_sel(result, (vec_float4)(overflow), vec_cmpgt((vec_uint4)(ix), (vec_uint4)(255)));
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return (result);
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}
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