src/compiler/glsl/lower_vertex_id.cpp

   1 /*
   2  * Copyright © 2014 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
  21  * DEALINGS IN THE SOFTWARE.
  22  */
  23
  24 /**
  25  * \file lower_vertex_id.cpp
  26  *
  27  * There exists hardware, such as i965, that does not implement the OpenGL
  28  * semantic for gl_VertexID.  Instead, that hardware does not include the
  29  * value of basevertex in the gl_VertexID value.  To implement the OpenGL
  30  * semantic, we'll have to convert gl_Vertex_ID to
  31  * gl_VertexIDMESA+gl_BaseVertexMESA.
  32  */
  33
  34 #include "glsl_symbol_table.h"
  35 #include "ir_hierarchical_visitor.h"
  36 #include "ir.h"
  37 #include "ir_builder.h"
  38 #include "linker.h"
  39 #include "program/prog_statevars.h"
  40 #include "builtin_functions.h"
  41 #include "main/mtypes.h"
  42
  43 namespace {
  44
  45 class lower_vertex_id_visitor : public ir_hierarchical_visitor {
  46 public:
  47    explicit lower_vertex_id_visitor(ir_function_signature *main_sig,
  48                                     exec_list *ir_list)
  49       : progress(false), VertexID(NULL), gl_VertexID(NULL),
  50         gl_BaseVertex(NULL), main_sig(main_sig), ir_list(ir_list)
  51    {
  52       foreach_in_list(ir_instruction, ir, ir_list) {
  53          ir_variable *const var = ir->as_variable();
  54
  55          if (var != NULL && var->data.mode == ir_var_system_value &&
  56              var->data.location == SYSTEM_VALUE_BASE_VERTEX) {
  57             gl_BaseVertex = var;
  58             break;
  59          }
  60       }
  61    }
  62
  63    virtual ir_visitor_status visit(ir_dereference_variable *);
  64
  65    bool progress;
  66
  67 private:
  68    ir_variable *VertexID;
  69    ir_variable *gl_VertexID;
  70    ir_variable *gl_BaseVertex;
  71
  72    ir_function_signature *main_sig;
  73    exec_list *ir_list;
  74 };
  75
  76 } /* anonymous namespace */
  77
  78 ir_visitor_status
  79 lower_vertex_id_visitor::visit(ir_dereference_variable *ir)
  80 {
  81    if (ir->var->data.mode != ir_var_system_value ||
  82        ir->var->data.location != SYSTEM_VALUE_VERTEX_ID)
  83       return visit_continue;
  84
  85    if (VertexID == NULL) {
  86       const glsl_type *const int_t = glsl_type::int_type;
  87       void *const mem_ctx = ralloc_parent(ir);
  88
  89       VertexID = new(mem_ctx) ir_variable(int_t, "__VertexID",
  90                                           ir_var_temporary);
  91       ir_list->push_head(VertexID);
  92
  93       gl_VertexID = new(mem_ctx) ir_variable(int_t, "gl_VertexIDMESA",
  94                                              ir_var_system_value);
  95       gl_VertexID->data.how_declared = ir_var_declared_implicitly;
  96       gl_VertexID->data.read_only = true;
  97       gl_VertexID->data.location = SYSTEM_VALUE_VERTEX_ID_ZERO_BASE;
  98       gl_VertexID->data.explicit_location = true;
  99       gl_VertexID->data.explicit_index = 0;
 100       ir_list->push_head(gl_VertexID);
 101
 102       if (gl_BaseVertex == NULL) {
 103          gl_BaseVertex = new(mem_ctx) ir_variable(int_t, "gl_BaseVertex",
 104                                                   ir_var_system_value);
 105          gl_BaseVertex->data.how_declared = ir_var_hidden;
 106          gl_BaseVertex->data.read_only = true;
 107          gl_BaseVertex->data.location = SYSTEM_VALUE_BASE_VERTEX;
 108          gl_BaseVertex->data.explicit_location = true;
 109          gl_BaseVertex->data.explicit_index = 0;
 110          ir_list->push_head(gl_BaseVertex);
 111       }
 112
 113       ir_instruction *const inst =
 114          ir_builder::assign(VertexID,
 115                             ir_builder::add(gl_VertexID, gl_BaseVertex));
 116
 117       main_sig->body.push_head(inst);
 118    }
 119
 120    ir->var = VertexID;
 121    progress = true;
 122
 123    return visit_continue;
 124 }
 125
 126 bool
 127 lower_vertex_id(gl_linked_shader *shader)
 128 {
 129    /* gl_VertexID only exists in the vertex shader.
 130     */
 131    if (shader->Stage != MESA_SHADER_VERTEX)
 132       return false;
 133
 134    ir_function_signature *const main_sig =
 135       _mesa_get_main_function_signature(shader->symbols);
 136    if (main_sig == NULL) {
 137       assert(main_sig != NULL);
 138       return false;
 139    }
 140
 141    lower_vertex_id_visitor v(main_sig, shader->ir);
 142
 143    v.run(shader->ir);
 144
 145    return v.progress;
 146 }