libclc/generic/lib/math/exp2.cl

   1 /*
   2  * Copyright (c) 2014,2015 Advanced Micro Devices, Inc.
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a copy
   5  * of this software and associated documentation files (the "Software"), to deal
   6  * in the Software without restriction, including without limitation the rights
   7  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
   8  * copies of the Software, and to permit persons to whom the Software is
   9  * furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice shall be included in
  12  * all copies or substantial portions of the Software.
  13  *
  14  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  15  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  16  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  17  * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  18  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  19  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  20  * THE SOFTWARE.
  21  */
  22
  23 #include <clc/clc.h>
  24
  25 #include "math.h"
  26 #include "../clcmacro.h"
  27
  28 _CLC_OVERLOAD _CLC_DEF float exp2(float x) {
  29
  30     // Reduce x
  31     const float ln2HI = 0x1.62e300p-1f;
  32     const float ln2LO = 0x1.2fefa2p-17f;
  33
  34     float t = rint(x);
  35     int p = (int)t;
  36     float tt = x - t;
  37     float hi = tt * ln2HI;
  38     float lo = tt * ln2LO;
  39
  40     // Evaluate poly
  41     t = hi + lo;
  42     tt  = t*t;
  43     float v = mad(tt,
  44                   -mad(tt,
  45                        mad(tt,
  46                            mad(tt,
  47                                mad(tt, 0x1.637698p-25f, -0x1.bbd41cp-20f),
  48                                0x1.1566aap-14f),
  49                            -0x1.6c16c2p-9f),
  50                        0x1.555556p-3f),
  51                   t);
  52
  53     float y = 1.0f - (((-lo) - MATH_DIVIDE(t * v, 2.0f - v)) - hi);
  54
  55     // Scale by 2^p
  56     float r =  as_float(as_int(y) + (p << 23));
  57
  58     const float ulim =  128.0f;
  59     const float llim = -126.0f;
  60
  61     r = x < llim ? 0.0f : r;
  62     r = x < ulim ? r : as_float(0x7f800000);
  63     return isnan(x) ? x : r;
  64 }
  65
  66 _CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, float, exp2, float)
  67
  68 #ifdef cl_khr_fp64
  69
  70 #include "exp_helper.h"
  71
  72 #pragma OPENCL EXTENSION cl_khr_fp64 : enable
  73
  74 _CLC_OVERLOAD _CLC_DEF double exp2(double x) {
  75     const double R_LN2 = 0x1.62e42fefa39efp-1; // ln(2)
  76     const double R_1_BY_64 = 1.0 / 64.0;
  77
  78     int n = convert_int(x * 64.0);
  79     double r = R_LN2 * fma(-R_1_BY_64, (double)n, x);
  80     return __clc_exp_helper(x, -1074.0, 1024.0, r, n);
  81 }
  82
  83
  84 _CLC_UNARY_VECTORIZE(_CLC_OVERLOAD _CLC_DEF, double, exp2, double)
  85
  86 #endif