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Diffstat (limited to 'newlib/libm/machine/spu/headers/log2f4.h')
| -rw-r--r-- | newlib/libm/machine/spu/headers/log2f4.h | 136 |
1 files changed, 136 insertions, 0 deletions
diff --git a/newlib/libm/machine/spu/headers/log2f4.h b/newlib/libm/machine/spu/headers/log2f4.h new file mode 100644 index 000000000..b19ec24bb --- /dev/null +++ b/newlib/libm/machine/spu/headers/log2f4.h @@ -0,0 +1,136 @@ +/* -------------------------------------------------------------- */ +/* (C)Copyright 2006,2007, */ +/* 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. */ +/* 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 _LOG2F4_H_ +#define _LOG2F4_H_ 1 + +#include <spu_intrinsics.h> + +/* + * FUNCTION + * vector float _log2f4(vector float x) + * + * DESCRIPTION + * The _log2f4 function computes log (base 2) on a vector if inputs + * values x. The _log2f4 function is approximated as a polynomial of + * order 8 (C. Hastings, Jr, 1955). + * + * __8__ + * \ + * \ + * log2f(1+x) = / Ci*x^i + * /____ + * i=1 + * + * for x in the range 0.0 to 1.0 + * + * C1 = 1.4426898816672 + * C2 = -0.72116591947498 + * C3 = 0.47868480909345 + * C4 = -0.34730547155299 + * C5 = 0.24187369696082 + * C6 = -0.13753123777116 + * C7 = 0.052064690894143 + * C8 = -0.0093104962134977 + * + * This function assumes that x is a non-zero positive value. + * + */ +static __inline vector float _log2f4(vector float x) +{ + vector signed int exponent; + vector float result; + vector float x2, x4; + vector float hi, lo; + + /* Extract the exponent from the input X. + */ + exponent = (vector signed int)spu_and(spu_rlmask((vector unsigned int)(x), -23), 0xFF); + exponent = spu_add(exponent, -127); + + /* Compute the remainder after removing the exponent. + */ + x = (vector float)spu_sub((vector signed int)(x), spu_sl(exponent, 23)); + + /* Calculate the log2 of the remainder using the polynomial + * approximation. + */ + x = spu_sub(x, spu_splats(1.0f)); + + /* 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). + */ + x2 = spu_mul(x, x); + x4 = spu_mul(x2, x2); + + hi = spu_madd(x, spu_splats(-0.0093104962134977f), spu_splats(0.052064690894143f)); + hi = spu_madd(x, hi, spu_splats(-0.13753123777116f)); + hi = spu_madd(x, hi, spu_splats( 0.24187369696082f)); + hi = spu_madd(x, hi, spu_splats(-0.34730547155299f)); + lo = spu_madd(x, spu_splats(0.47868480909345f), spu_splats(-0.72116591947498f)); + lo = spu_madd(x, lo, spu_splats(1.4426898816672f)); + lo = spu_mul(x, lo); + result = spu_madd(x4, hi, lo); + + /* Add the exponent back into the result. + */ + result = spu_add(result, spu_convtf(exponent, 0)); + + return (result); +} + +#endif /* _LOG2F4_H_ */ +#endif /* __SPU__ */ |