newlib/libm/machine/amdgcn/v64df_log.c

   1 /*
   2  * Copyright 2023 Siemens
   3  *
   4  * The authors hereby grant permission to use, copy, modify, distribute,
   5  * and license this software and its documentation for any purpose, provided
   6  * that existing copyright notices are retained in all copies and that this
   7  * notice is included verbatim in any distributions.  No written agreement,
   8  * license, or royalty fee is required for any of the authorized uses.
   9  * Modifications to this software may be copyrighted by their authors
  10  * and need not follow the licensing terms described here, provided that
  11  * the new terms are clearly indicated on the first page of each file where
  12  * they apply.
  13  */
  14
  15 /*
  16  * Copyright (c) 1994-2009  Red Hat, Inc. All rights reserved.
  17  *
  18  * This copyrighted material is made available to anyone wishing to use,
  19  * modify, copy, or redistribute it subject to the terms and conditions
  20  * of the BSD License.   This program is distributed in the hope that
  21  * it will be useful, but WITHOUT ANY WARRANTY expressed or implied,
  22  * including the implied warranties of MERCHANTABILITY or FITNESS FOR
  23  * A PARTICULAR PURPOSE.  A copy of this license is available at
  24  * http://www.opensource.org/licenses. Any Red Hat trademarks that are
  25  * incorporated in the source code or documentation are not subject to
  26  * the BSD License and may only be used or replicated with the express
  27  * permission of Red Hat, Inc.
  28  */
  29
  30 /******************************************************************
  31  * The following routines are coded directly from the algorithms
  32  * and coefficients given in "Software Manual for the Elementary
  33  * Functions" by William J. Cody, Jr. and William Waite, Prentice
  34  * Hall, 1980.
  35  ******************************************************************/
  36
  37 /* Based on newlib/libm/mathfp/s_logarithm.c in Newlib.  */
  38
  39 #include "amdgcnmach.h"
  40
  41 v64si v64df_finite (v64df);
  42 v64si v64df_isnan (v64df);
  43
  44 static const double a[] = { -0.64124943423745581147e+02,
  45                             0.16383943563021534222e+02,
  46                             -0.78956112887481257267 };
  47 static const double b[] = { -0.76949932108494879777e+03,
  48                             0.31203222091924532844e+03,
  49                             -0.35667977739034646171e+02 };
  50 static const double C1 =  22713.0 / 32768.0;
  51 static const double C2 =  1.428606820309417232e-06;
  52
  53 #if defined (__has_builtin) \
  54         && __has_builtin (__builtin_gcn_frexpv_mant) \
  55         && __has_builtin (__builtin_gcn_frexpv_exp) \
  56
  57 DEF_VD_MATH_FUNC (v64df, log, v64df x)
  58 {
  59   FUNCTION_INIT (v64df);
  60
  61   /* Check for domain/range errors here. */
  62   VECTOR_IF (x == 0.0, cond)
  63     errno = ERANGE;
  64     VECTOR_RETURN (VECTOR_INIT (-z_infinity.d), cond);
  65   VECTOR_ELSEIF (x < 0.0, cond)
  66     errno = EDOM;
  67     VECTOR_RETURN (VECTOR_INIT (z_notanum.d), cond);
  68   VECTOR_ELSEIF (__builtin_convertvector (~v64df_finite (x), v64di), cond)
  69     VECTOR_RETURN (VECTOR_MERGE (VECTOR_INIT (z_notanum.d),
  70                                  VECTOR_INIT (z_infinity.d),
  71                                  v64df_isnan (x)),
  72                    cond);
  73   VECTOR_ENDIF
  74
  75   /* Get the exponent and mantissa where x = f * 2^N. */
  76   v64df f = __builtin_gcn_frexpv_mant (x);
  77   v64si N = __builtin_gcn_frexpv_exp (x);
  78
  79   v64df z = f - 0.5;
  80
  81   VECTOR_IF (f > __SQRT_HALF, cond)
  82     VECTOR_COND_MOVE (z, (z - 0.5) / (f * 0.5 + 0.5), cond);
  83   VECTOR_ELSE (cond)
  84     VECTOR_COND_MOVE (N, N - 1, cond);
  85     VECTOR_COND_MOVE (z, z / (z * 0.5 + 0.5), cond);
  86   VECTOR_ENDIF
  87
  88   v64df w = z * z;
  89
  90   /* Use Newton's method with 4 terms. */
  91   z += z * w * ((a[2] * w + a[1]) * w + a[0]) / (((w + b[2]) * w + b[1]) * w + b[0]);
  92
  93   v64df Nf = __builtin_convertvector (N, v64df);
  94   VECTOR_COND_MOVE (z, (Nf * C2 + z) + Nf * C1, N != 0);
  95
  96   VECTOR_RETURN (z, NO_COND);
  97
  98   FUNCTION_RETURN;
  99 }
 100
 101 DEF_VARIANTS (log, df, df)
 102
 103 DEF_VD_MATH_FUNC (v64df, log1p, v64df x)
 104 {
 105   /* TODO: Implement algorithm with better precision.  */
 106   return v64df_log_aux (1 + x, __mask);
 107 }
 108
 109 DEF_VARIANTS (log1p, df, df)
 110
 111 #endif