src/mesa/main/sse_minmax.c

   1 /*
   2  * Copyright © 2014 Timothy Arceri
   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  * Author:
  24  *    Timothy Arceri <t_arceri@yahoo.com.au>
  25  *
  26  */
  27
  28 #include "main/sse_minmax.h"
  29 #include <smmintrin.h>
  30 #include <stdint.h>
  31
  32 void
  33 _mesa_uint_array_min_max(const unsigned *ui_indices, unsigned *min_index,
  34                          unsigned *max_index, const unsigned count)
  35 {
  36    unsigned max_ui = 0;
  37    unsigned min_ui = ~0U;
  38    unsigned i = 0;
  39    unsigned aligned_count = count;
  40
  41    /* handle the first few values without SSE until the pointer is aligned */
  42    while (((uintptr_t)ui_indices & 15) && aligned_count) {
  43       if (*ui_indices > max_ui)
  44          max_ui = *ui_indices;
  45       if (*ui_indices < min_ui)
  46          min_ui = *ui_indices;
  47
  48       aligned_count--;
  49       ui_indices++;
  50    }
  51
  52    /* TODO: The actual threshold for SSE begin useful may be higher than 8.
  53     * Some careful microbenchmarks and measurement are required to
  54     * find the actual tipping point.
  55     */
  56    if (aligned_count >= 8) {
  57       unsigned max_arr[4] __attribute__ ((aligned (16)));
  58       unsigned min_arr[4] __attribute__ ((aligned (16)));
  59       unsigned vec_count;
  60       __m128i max_ui4 = _mm_setzero_si128();
  61       __m128i min_ui4 = _mm_set1_epi32(~0U);
  62       __m128i ui_indices4;
  63       __m128i *ui_indices_ptr;
  64
  65       vec_count = aligned_count & ~0x3;
  66       ui_indices_ptr = (__m128i *)ui_indices;
  67       for (i = 0; i < vec_count / 4; i++) {
  68          ui_indices4 = _mm_load_si128(&ui_indices_ptr[i]);
  69          max_ui4 = _mm_max_epu32(ui_indices4, max_ui4);
  70          min_ui4 = _mm_min_epu32(ui_indices4, min_ui4);
  71       }
  72
  73       _mm_store_si128((__m128i *)max_arr, max_ui4);
  74       _mm_store_si128((__m128i *)min_arr, min_ui4);
  75
  76       for (i = 0; i < 4; i++) {
  77          if (max_arr[i] > max_ui)
  78             max_ui = max_arr[i];
  79          if (min_arr[i] < min_ui)
  80             min_ui = min_arr[i];
  81       }
  82       i = vec_count;
  83    }
  84
  85    for (; i < aligned_count; i++) {
  86       if (ui_indices[i] > max_ui)
  87          max_ui = ui_indices[i];
  88       if (ui_indices[i] < min_ui)
  89          min_ui = ui_indices[i];
  90    }
  91
  92    *min_index = min_ui;
  93    *max_index = max_ui;
  94 }