src/util/rounding.h

   1 /*
   2  * Copyright © 2015 Intel Corporation
   3  *
   4  * Permission is hereby granted, free of charge, to any person obtaining a
   5  * copy of this software and associated documentation files (the "Software"),
   6  * to deal in the Software without restriction, including without limitation
   7  * the rights to use, copy, modify, merge, publish, distribute, sublicense,
   8  * and/or sell copies of the Software, and to permit persons to whom the
   9  * Software is furnished to do so, subject to the following conditions:
  10  *
  11  * The above copyright notice and this permission notice (including the next
  12  * paragraph) shall be included in all copies or substantial portions of the
  13  * Software.
  14  *
  15  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  16  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  17  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
  18  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  19  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  20  * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  21  * IN THE SOFTWARE.
  22  */
  23
  24 #ifndef _ROUNDING_H
  25 #define _ROUNDING_H
  26
  27 #include <math.h>
  28
  29 #ifdef __SSE4_1__
  30 #include <smmintrin.h>
  31 #endif
  32
  33 /* The C standard library has functions round()/rint()/nearbyint() that round
  34  * their arguments according to the rounding mode set in the floating-point
  35  * control register. While there are trunc()/ceil()/floor() functions that do
  36  * a specific operation without modifying the rounding mode, there is no
  37  * roundeven() in any version of C.
  38  *
  39  * Technical Specification 18661 (ISO/IEC TS 18661-1:2014) adds roundeven(),
  40  * but it's unfortunately not implemented by glibc.
  41  *
  42  * This implementation differs in that it does not raise the inexact exception.
  43  *
  44  * We use rint() to implement these functions, with the assumption that the
  45  * floating-point rounding mode has not been changed from the default Round
  46  * to Nearest.
  47  */
  48
  49 /**
  50  * \brief Rounds \c x to the nearest integer, with ties to the even integer.
  51  */
  52 static inline float
  53 _mesa_roundevenf(float x)
  54 {
  55 #ifdef __SSE4_1__
  56    float ret;
  57    __m128 m = _mm_load_ss(&x);
  58    m = _mm_round_ss(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
  59    _mm_store_ss(&ret, m);
  60    return ret;
  61 #else
  62    return rintf(x);
  63 #endif
  64 }
  65
  66 /**
  67  * \brief Rounds \c x to the nearest integer, with ties to the even integer.
  68  */
  69 static inline double
  70 _mesa_roundeven(double x)
  71 {
  72 #ifdef __SSE4_1__
  73    double ret;
  74    __m128d m = _mm_load_sd(&x);
  75    m = _mm_round_sd(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
  76    _mm_store_sd(&ret, m);
  77    return ret;
  78 #else
  79    return rint(x);
  80 #endif
  81 }
  82
  83 /**
  84  * \brief Rounds \c x to the nearest integer, with ties to the even integer,
  85  * and returns the value as a long int.
  86  */
  87 static inline long
  88 _mesa_lroundevenf(float x)
  89 {
  90    return lrintf(x);
  91 }
  92
  93 /**
  94  * \brief Rounds \c x to the nearest integer, with ties to the even integer,
  95  * and returns the value as a long int.
  96  */
  97 static inline long
  98 _mesa_lroundeven(double x)
  99 {
 100    return lrint(x);
 101 }
 102
 103 #endif