src/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
  41 namespace {
  42
  43 class lower_vertex_id_visitor : public ir_hierarchical_visitor {
  44 public:
  45    explicit lower_vertex_id_visitor(ir_function_signature *main_sig,
  46                                     exec_list *ir_list)
  47       : progress(false), VertexID(NULL), gl_VertexID(NULL),
  48         gl_BaseVertex(NULL), main_sig(main_sig), ir_list(ir_list)
  49    {
  50       foreach_in_list(ir_instruction, ir, ir_list) {
  51          ir_variable *const var = ir->as_variable();
  52
  53          if (var != NULL && var->data.mode == ir_var_system_value &&
  54              var->data.location == SYSTEM_VALUE_BASE_VERTEX) {
  55             gl_BaseVertex = var;
  56             break;
  57          }
  58       }
  59    }
  60
  61    virtual ir_visitor_status visit(ir_dereference_variable *);
  62
  63    bool progress;
  64
  65 private:
  66    ir_variable *VertexID;
  67    ir_variable *gl_VertexID;
  68    ir_variable *gl_BaseVertex;
  69
  70    ir_function_signature *main_sig;
  71    exec_list *ir_list;
  72 };
  73
  74 } /* anonymous namespace */
  75
  76 ir_visitor_status
  77 lower_vertex_id_visitor::visit(ir_dereference_variable *ir)
  78 {
  79    if (ir->var->data.mode != ir_var_system_value ||
  80        ir->var->data.location != SYSTEM_VALUE_VERTEX_ID)
  81       return visit_continue;
  82
  83    if (VertexID == NULL) {
  84       const glsl_type *const int_t = glsl_type::int_type;
  85       void *const mem_ctx = ralloc_parent(ir);
  86
  87       VertexID = new(mem_ctx) ir_variable(int_t, "__VertexID",
  88                                           ir_var_temporary);
  89       ir_list->push_head(VertexID);
  90
  91       gl_VertexID = new(mem_ctx) ir_variable(int_t, "gl_VertexIDMESA",
  92                                              ir_var_system_value);
  93       gl_VertexID->data.how_declared = ir_var_declared_implicitly;
  94       gl_VertexID->data.read_only = true;
  95       gl_VertexID->data.location = SYSTEM_VALUE_VERTEX_ID_ZERO_BASE;
  96       gl_VertexID->data.explicit_location = true;
  97       gl_VertexID->data.explicit_index = 0;
  98       ir_list->push_head(gl_VertexID);
  99
 100       if (gl_BaseVertex == NULL) {
 101          gl_BaseVertex = new(mem_ctx) ir_variable(int_t, "gl_BaseVertex",
 102                                                   ir_var_system_value);
 103          gl_BaseVertex->data.how_declared = ir_var_declared_implicitly;
 104          gl_BaseVertex->data.read_only = true;
 105          gl_BaseVertex->data.location = SYSTEM_VALUE_BASE_VERTEX;
 106          gl_BaseVertex->data.explicit_location = true;
 107          gl_BaseVertex->data.explicit_index = 0;
 108          ir_list->push_head(gl_BaseVertex);
 109       }
 110
 111       ir_instruction *const inst =
 112          ir_builder::assign(VertexID,
 113                             ir_builder::add(gl_VertexID, gl_BaseVertex));
 114
 115       main_sig->body.push_head(inst);
 116    }
 117
 118    ir->var = VertexID;
 119    progress = true;
 120
 121    return visit_continue;
 122 }
 123
 124 bool
 125 lower_vertex_id(gl_shader *shader)
 126 {
 127    /* gl_VertexID only exists in the vertex shader.
 128     */
 129    if (shader->Stage != MESA_SHADER_VERTEX)
 130       return false;
 131
 132    ir_function_signature *const main_sig =
 133       link_get_main_function_signature(shader);
 134    if (main_sig == NULL) {
 135       assert(main_sig != NULL);
 136       return false;
 137    }
 138
 139    lower_vertex_id_visitor v(main_sig, shader->ir);
 140
 141    v.run(shader->ir);
 142
 143    return v.progress;
 144 }