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 separate clip and cull distance arrays into a
  31  * single array that contains both.  Clip distances come first, then
  32  * cull distances.  It also populates nir_shader_info with the size
  33  * of the original arrays so the driver knows which are which.
  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 /**
  60  * Update the type of the combined array (including interface block nesting).
  61  */
  62 static void
  63 update_type(nir_variable *var, gl_shader_stage stage, unsigned length)
  64 {
  65    const struct glsl_type *type = glsl_array_type(glsl_float_type(), length, 0);
  66
  67    if (nir_is_per_vertex_io(var, stage))
  68       type = glsl_array_type(type, glsl_get_length(var->type), 0);
  69
  70    var->type = type;
  71 }
  72
  73 static void
  74 rewrite_clip_cull_deref(nir_builder *b,
  75                         nir_deref_instr *deref,
  76                         const struct glsl_type *type,
  77                         unsigned tail_offset)
  78 {
  79    deref->type = type;
  80
  81    if (glsl_type_is_array(type)) {
  82       const struct glsl_type *child_type = glsl_get_array_element(type);
  83       nir_foreach_use(src, &deref->dest.ssa) {
  84          rewrite_clip_cull_deref(b, nir_instr_as_deref(src->parent_instr),
  85                                  child_type, tail_offset);
  86       }
  87    } else {
  88       assert(glsl_type_is_scalar(type));
  89
  90       /* This is the end of the line.  Add the tail offset if needed */
  91       if (tail_offset > 0) {
  92          b->cursor = nir_before_instr(&deref->instr);
  93          assert(deref->deref_type == nir_deref_type_array);
  94          nir_ssa_def *index = nir_iadd(b, deref->arr.index.ssa,
  95                                           nir_imm_int(b, tail_offset));
  96          nir_instr_rewrite_src(&deref->instr, &deref->arr.index,
  97                                nir_src_for_ssa(index));
  98       }
  99    }
 100 }
 101
 102 static void
 103 rewrite_references(nir_builder *b,
 104                    nir_instr *instr,
 105                    nir_variable *combined,
 106                    unsigned cull_offset)
 107 {
 108    if (instr->type != nir_instr_type_deref)
 109       return;
 110
 111    nir_deref_instr *deref = nir_instr_as_deref(instr);
 112    if (deref->deref_type != nir_deref_type_var)
 113       return;
 114
 115    if (deref->var->data.mode != combined->data.mode)
 116       return;
 117
 118    const unsigned location = deref->var->data.location;
 119    if (location != VARYING_SLOT_CLIP_DIST0 &&
 120        location != VARYING_SLOT_CULL_DIST0)
 121       return;
 122
 123    deref->var = combined;
 124    if (location == VARYING_SLOT_CULL_DIST0)
 125       rewrite_clip_cull_deref(b, deref, combined->type, cull_offset);
 126    else
 127       rewrite_clip_cull_deref(b, deref, combined->type, 0);
 128 }
 129
 130 static bool
 131 combine_clip_cull(nir_shader *nir,
 132                   struct exec_list *vars,
 133                   bool store_info)
 134 {
 135    nir_variable *cull = NULL;
 136    nir_variable *clip = NULL;
 137    bool progress = false;
 138
 139    nir_foreach_variable(var, vars) {
 140       if (var->data.location == VARYING_SLOT_CLIP_DIST0)
 141          clip = var;
 142
 143       if (var->data.location == VARYING_SLOT_CULL_DIST0)
 144          cull = var;
 145    }
 146
 147    /* if the GLSL lowering pass has already run, don't bother repeating */
 148    if (!cull && clip) {
 149       if (!glsl_type_is_array(clip->type))
 150          return false;
 151    }
 152
 153    const unsigned clip_array_size = get_unwrapped_array_length(nir, clip);
 154    const unsigned cull_array_size = get_unwrapped_array_length(nir, cull);
 155
 156    if (store_info) {
 157       nir->info.clip_distance_array_size = clip_array_size;
 158       nir->info.cull_distance_array_size = cull_array_size;
 159    }
 160
 161    if (clip)
 162       clip->data.compact = true;
 163
 164    if (cull)
 165       cull->data.compact = true;
 166
 167    if (cull_array_size > 0) {
 168       if (clip_array_size == 0) {
 169          /* No clip distances, just change the cull distance location */
 170          cull->data.location = VARYING_SLOT_CLIP_DIST0;
 171       } else {
 172          /* Turn the ClipDistance array into a combined one */
 173          update_type(clip, nir->info.stage, clip_array_size + cull_array_size);
 174
 175          /* Rewrite CullDistance to reference the combined array */
 176          nir_foreach_function(function, nir) {
 177             if (function->impl) {
 178                nir_builder b;
 179                nir_builder_init(&b, function->impl);
 180
 181                nir_foreach_block(block, function->impl) {
 182                   nir_foreach_instr(instr, block) {
 183                      rewrite_references(&b, instr, clip, clip_array_size);
 184                   }
 185                }
 186             }
 187          }
 188
 189          /* Delete the old CullDistance variable */
 190          exec_node_remove(&cull->node);
 191          ralloc_free(cull);
 192       }
 193
 194       nir_foreach_function(function, nir) {
 195          if (function->impl) {
 196             nir_metadata_preserve(function->impl,
 197                                   nir_metadata_block_index |
 198                                   nir_metadata_dominance);
 199          }
 200       }
 201       progress = true;
 202    }
 203
 204    return progress;
 205 }
 206
 207 bool
 208 nir_lower_clip_cull_distance_arrays(nir_shader *nir)
 209 {
 210    bool progress = false;
 211
 212    if (nir->info.stage <= MESA_SHADER_GEOMETRY)
 213       progress |= combine_clip_cull(nir, &nir->outputs, true);
 214
 215    if (nir->info.stage > MESA_SHADER_VERTEX)
 216       progress |= combine_clip_cull(nir, &nir->inputs, false);
 217
 218    return progress;
 219 }