84 lines
2.9 KiB
C
84 lines
2.9 KiB
C
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/*
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(C) Copyright 2001,2006,
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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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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright notice,
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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 names of the copyright holders nor the names of their
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contributors may be used to endorse or promote products derived from this
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software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
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PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER
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OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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#ifndef _LDEXP_H_
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#define _LDEXP_H_ 1
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#include <spu_intrinsics.h>
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#include "headers/vec_literal.h"
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/* ldexp computes x * 2^exp. This function variant computes the result
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* and handles overflow, underflow, and denorms by breaking the problem
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* into:
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* exp = MAX(exp, -2044)
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* exp = MIN(exp, 2046)
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* e1 = exp / 2
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* e2 = exp - e1;
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* x * 2^e1 * 2^e2
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*/
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static __inline double _ldexp(double x, int exp)
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{
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vec_int4 e, e1, e2;
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vec_int4 min = VEC_SPLAT_S32(-2044);
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vec_int4 max = VEC_SPLAT_S32(2046);
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vec_uint4 cmp_min, cmp_max;
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vec_uint4 shift = VEC_LITERAL(vec_uint4, 20, 32, 20, 32);
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vec_double2 f1, f2;
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vec_double2 in, out;
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in = spu_promote(x, 0);
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e = spu_promote(exp, 0);
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/* Clamp the specified exponent to the range -2044 to 2046.
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*/
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cmp_min = spu_cmpgt(e, min);
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cmp_max = spu_cmpgt(e, max);
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e = spu_sel(min, e, cmp_min);
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e = spu_sel(e, max, cmp_max);
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/* Generate the factors f1 = 2^e1 and f2 = 2^e2
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*/
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e1 = spu_rlmaska(e, -1);
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e2 = spu_sub(e, e1);
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f1 = (vec_double2)spu_sl(spu_add(e1, 1023), shift);
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f2 = (vec_double2)spu_sl(spu_add(e2, 1023), shift);
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/* Compute the product x * 2^e1 * 2^e2
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*/
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out = spu_mul(spu_mul(in, f1), f2);
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return (spu_extract(out, 0));
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}
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#endif /* _LDEXP_H_ */
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