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 "c99_math.h"
  28
  29 #include <limits.h>
  30 #include <stdint.h>
  31
  32 #if defined(__SSE__) || defined(_MSC_VER)
  33 /* MSVC always has SSE nowadays */
  34 #include <xmmintrin.h>
  35 #include <emmintrin.h>
  36 #endif
  37
  38 #ifdef __SSE4_1__
  39 #include <smmintrin.h>
  40 #endif
  41
  42 /* The C standard library has functions round()/rint()/nearbyint() that round
  43  * their arguments according to the rounding mode set in the floating-point
  44  * control register. While there are trunc()/ceil()/floor() functions that do
  45  * a specific operation without modifying the rounding mode, there is no
  46  * roundeven() in any version of C.
  47  *
  48  * Technical Specification 18661 (ISO/IEC TS 18661-1:2014) adds roundeven(),
  49  * but it's unfortunately not implemented by glibc.
  50  *
  51  * This implementation differs in that it does not raise the inexact exception.
  52  *
  53  * We use rint() to implement these functions, with the assumption that the
  54  * floating-point rounding mode has not been changed from the default Round
  55  * to Nearest.
  56  */
  57
  58 /**
  59  * \brief Rounds \c x to the nearest integer, with ties to the even integer.
  60  */
  61 static inline float
  62 _mesa_roundevenf(float x)
  63 {
  64 #ifdef __SSE4_1__
  65    float ret;
  66    __m128 m = _mm_load_ss(&x);
  67    m = _mm_round_ss(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
  68    _mm_store_ss(&ret, m);
  69    return ret;
  70 #else
  71    return rintf(x);
  72 #endif
  73 }
  74
  75 /**
  76  * \brief Rounds \c x to the nearest integer, with ties to the even integer.
  77  */
  78 static inline double
  79 _mesa_roundeven(double x)
  80 {
  81 #ifdef __SSE4_1__
  82    double ret;
  83    __m128d m = _mm_load_sd(&x);
  84    m = _mm_round_sd(m, m, _MM_FROUND_CUR_DIRECTION | _MM_FROUND_NO_EXC);
  85    _mm_store_sd(&ret, m);
  86    return ret;
  87 #else
  88    return rint(x);
  89 #endif
  90 }
  91
  92 /**
  93  * \brief Rounds \c x to the nearest integer, with ties to the even integer,
  94  * and returns the value as a long int.
  95  */
  96 static inline long
  97 _mesa_lroundevenf(float x)
  98 {
  99 #if defined(__SSE__) || defined(_MSC_VER)
 100 #if LONG_MAX == INT64_MAX
 101    return _mm_cvtss_si64(_mm_load_ss(&x));
 102 #elif LONG_MAX == INT32_MAX
 103    return _mm_cvtss_si32(_mm_load_ss(&x));
 104 #else
 105 #error "Unsupported long size"
 106 #endif
 107 #else
 108    return lrintf(x);
 109 #endif
 110 }
 111
 112 /**
 113  * \brief Rounds \c x to the nearest integer, with ties to the even integer,
 114  * and returns the value as a long int.
 115  */
 116 static inline long
 117 _mesa_lroundeven(double x)
 118 {
 119 #if defined(__SSE__) || defined(_MSC_VER)
 120 #if LONG_MAX == INT64_MAX
 121    return _mm_cvtsd_si64(_mm_load_sd(&x));
 122 #elif LONG_MAX == INT32_MAX
 123    return _mm_cvtsd_si32(_mm_load_sd(&x));
 124 #else
 125 #error "Unsupported long size"
 126 #endif
 127 #else
 128    return lrint(x);
 129 #endif
 130 }
 131
 132 #endif