src/compiler/nir/nir_lower_clip_cull_distance_arrays.c

   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 #include "nir.h"
  25 #include "nir_builder.h"
  26
  27 /**
  28  * @file
  29  *
  30  * This pass combines clip and cull distance arrays in separate locations and
  31  * colocates them both in VARYING_SLOT_CLIP_DIST0.  It does so by maintaining
  32  * two arrays but making them compact and using location_frac to stack them on
  33  * top of each other.
  34  */
  35
  36 /**
  37  * Get the length of the clip/cull distance array, looking past
  38  * any interface block arrays.
  39  */
  40 static unsigned
  41 get_unwrapped_array_length(nir_shader *nir, nir_variable *var)
  42 {
  43    if (!var)
  44       return 0;
  45
  46    /* Unwrap GS input and TCS input/output interfaces.  We want the
  47     * underlying clip/cull distance array length, not the per-vertex
  48     * array length.
  49     */
  50    const struct glsl_type *type = var->type;
  51    if (nir_is_per_vertex_io(var, nir->info.stage))
  52       type = glsl_get_array_element(type);
  53
  54    assert(glsl_type_is_array(type));
  55
  56    return glsl_get_length(type);
  57 }
  58
  59 static bool
  60 combine_clip_cull(nir_shader *nir,
  61                   nir_variable_mode mode,
  62                   bool store_info)
  63 {
  64    nir_variable *cull = NULL;
  65    nir_variable *clip = NULL;
  66
  67    nir_foreach_variable_with_modes(var, nir, mode) {
  68       if (var->data.location == VARYING_SLOT_CLIP_DIST0)
  69          clip = var;
  70
  71       if (var->data.location == VARYING_SLOT_CULL_DIST0)
  72          cull = var;
  73    }
  74
  75    if (!cull && !clip) {
  76       /* If this is run after optimizations and the variables have been
  77        * eliminated, we should update the shader info, because no other
  78        * place does that.
  79        */
  80       if (store_info) {
  81          nir->info.clip_distance_array_size = 0;
  82          nir->info.cull_distance_array_size = 0;
  83       }
  84       return false;
  85    }
  86
  87    if (!cull && clip) {
  88       /* The GLSL IR lowering pass must have converted these to vectors */
  89       if (!clip->data.compact)
  90          return false;
  91
  92       /* If this pass has already run, don't repeat.  We would think that
  93        * the combined clip/cull distance array was clip-only and mess up.
  94        */
  95       if (clip->data.how_declared == nir_var_hidden)
  96          return false;
  97    }
  98
  99    const unsigned clip_array_size = get_unwrapped_array_length(nir, clip);
 100    const unsigned cull_array_size = get_unwrapped_array_length(nir, cull);
 101
 102    if (store_info) {
 103       nir->info.clip_distance_array_size = clip_array_size;
 104       nir->info.cull_distance_array_size = cull_array_size;
 105    }
 106
 107    if (clip) {
 108       assert(clip->data.compact);
 109       clip->data.how_declared = nir_var_hidden;
 110    }
 111
 112    if (cull) {
 113       assert(cull->data.compact);
 114       cull->data.how_declared = nir_var_hidden;
 115       cull->data.location = VARYING_SLOT_CLIP_DIST0 + clip_array_size / 4;
 116       cull->data.location_frac = clip_array_size % 4;
 117    }
 118
 119    return true;
 120 }
 121
 122 bool
 123 nir_lower_clip_cull_distance_arrays(nir_shader *nir)
 124 {
 125    bool progress = false;
 126
 127    if (nir->info.stage <= MESA_SHADER_GEOMETRY)
 128       progress |= combine_clip_cull(nir, nir_var_shader_out, true);
 129
 130    if (nir->info.stage > MESA_SHADER_VERTEX)
 131       progress |= combine_clip_cull(nir, nir_var_shader_in, false);
 132
 133    nir_foreach_function(function, nir) {
 134       if (!function->impl)
 135          continue;
 136
 137       if (progress) {
 138          nir_metadata_preserve(function->impl,
 139                                nir_metadata_block_index |
 140                                nir_metadata_dominance |
 141                                nir_metadata_live_ssa_defs |
 142                                nir_metadata_loop_analysis);
 143       } else {
 144          nir_metadata_preserve(function->impl, nir_metadata_all);
 145       }
 146    }
 147
 148    return progress;
 149 }