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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 _RECIPF4_H_
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#define _RECIPF4_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 _recipf4(vector float value)
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*
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* DESCRIPTION
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* The _recipf4 function inverts the vector "value" and returns the
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* result.
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*
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*/
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static __inline vector float _recipf4(vector float a)
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{
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/* This function has been designed to provide a
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* full function operation that presisely computes
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* the reciprocal for the entire range of extended
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* single precision input <a>. This includes:
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*
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* 1) Computing the reciprocal to full single precision
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* floating point accuracy.
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* 2) Round the result consistently with the rounding
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* mode of the processor - truncated toward zero.
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* 3) Underflow and overflow results are clamped to
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* Smin and Smax and flagged with the appropriate
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* UNF or OVF exception in the FPSCR.
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* 4) Divide By Zero (DBZ) exception is produced when
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* the input <a> has a zero exponent. A reciprocal
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* of correctly signed Smax is produced.
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* 5) Resulting denorm reciprocal will be coerced to +0.
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* 6) If a non-compliant IEEE result is produced, the
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* a DIFF exception is generated.
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*/
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vector float err, x0, x1;
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vector float mult;
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vector float mant_a;
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vector float one = spu_splats(1.0f);
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vector unsigned int exp, exp_a;
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vector unsigned int exp_mask = (vec_uint4)spu_splats(0x7F800000);
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/* If a has a zero exponent, then set the divide by zero
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* (DBZ) exception flag. The estimate result is discarded.
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*/
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(void)si_frest((qword)(a));
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/* For computing the reciprocal, force the value
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* into the range (1.0 <= 0 < 2.0).
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*/
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mant_a = spu_sel(a, one, exp_mask);
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/* Compute the reciprocal using the reciprocal estimate
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* followed by one iteration of the Newton-Raphson.
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* Due to truncation error, the quotient result may be low
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* by 1 ulp (unit of least position). Conditionally add one
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* if the estimate is too small.
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*/
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x0 = spu_re(mant_a);
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x0 = spu_madd(spu_nmsub(mant_a, x0, one), x0, x0);
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x1 = (vector float)(spu_add((vector unsigned int)(x0), 1));
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err = spu_nmsub(mant_a, x1, one);
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x1 = spu_sel(x0, x1, spu_cmpgt((vector signed int)(err), -1));
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/* Compute the reciprocal's expected exponent. If the exponent
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* is out of range, then force the resulting exponent to 0.
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* (127 with the bias). We correct for the out of range
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* values by computing a multiplier (mult) that will force the
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* result to the correct out of range value and set the
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* correct exception flag (UNF, OVF, or neither). The multiplier
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* is also conditioned to generate correctly signed Smax if the
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* inoput <a> is a denorm or zero.
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*/
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exp_a = spu_and((vector unsigned int)a, exp_mask);
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exp = spu_add(spu_sub(spu_splats((unsigned int)0x7F000000), exp_a), spu_cmpabsgt(mant_a, one));
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/* The default multiplier is 1.0. If an underflow is detected (ie,
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* either the dividend <a> is a denorm/zero, or the computed exponent is
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* less than or equal to a biased 0), force the multiplier to 0.0.
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*/
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mult = spu_and(one, (vector float)spu_cmpgt((vector signed int)(exp), 0));
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/* Force the multiplier to positive Smax (0x7FFFFFFF) and the biased exponent
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* to 127, if the divisor is denorm/zero or the computed biased exponent is
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* greater than 255.
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*/
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mult = spu_or(mult, (vector float)spu_rlmask(spu_cmpeq(exp_a, 0), -1));
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/* Insert the exponent into the result and perform the
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* final multiplication.
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*/
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x1 = spu_sel(x1, (vector float)exp, exp_mask);
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x1 = spu_mul(x1, mult);
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return (x1);
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}
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#endif /* _RECIPF4_H_ */
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#endif /* __SPU__ */
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