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
  42 namespace {
  43
  44 class lower_vertex_id_visitor : public ir_hierarchical_visitor {
  45 public:
  46    explicit lower_vertex_id_visitor(ir_function_signature *main_sig,
  47                                     exec_list *ir_list)
  48       : progress(false), VertexID(NULL), gl_VertexID(NULL),
  49         gl_BaseVertex(NULL), main_sig(main_sig), ir_list(ir_list)
  50    {
  51       foreach_in_list(ir_instruction, ir, ir_list) {
  52          ir_variable *const var = ir->as_variable();
  53
  54          if (var != NULL && var->data.mode == ir_var_system_value &&
  55              var->data.location == SYSTEM_VALUE_BASE_VERTEX) {
  56             gl_BaseVertex = var;
  57             break;
  58          }
  59       }
  60    }
  61
  62    virtual ir_visitor_status visit(ir_dereference_variable *);
  63
  64    bool progress;
  65
  66 private:
  67    ir_variable *VertexID;
  68    ir_variable *gl_VertexID;
  69    ir_variable *gl_BaseVertex;
  70
  71    ir_function_signature *main_sig;
  72    exec_list *ir_list;
  73 };
  74
  75 } /* anonymous namespace */
  76
  77 ir_visitor_status
  78 lower_vertex_id_visitor::visit(ir_dereference_variable *ir)
  79 {
  80    if (ir->var->data.mode != ir_var_system_value ||
  81        ir->var->data.location != SYSTEM_VALUE_VERTEX_ID)
  82       return visit_continue;
  83
  84    if (VertexID == NULL) {
  85       const glsl_type *const int_t = glsl_type::int_type;
  86       void *const mem_ctx = ralloc_parent(ir);
  87
  88       VertexID = new(mem_ctx) ir_variable(int_t, "__VertexID",
  89                                           ir_var_temporary);
  90       ir_list->push_head(VertexID);
  91
  92       gl_VertexID = new(mem_ctx) ir_variable(int_t, "gl_VertexIDMESA",
  93                                              ir_var_system_value);
  94       gl_VertexID->data.how_declared = ir_var_declared_implicitly;
  95       gl_VertexID->data.read_only = true;
  96       gl_VertexID->data.location = SYSTEM_VALUE_VERTEX_ID_ZERO_BASE;
  97       gl_VertexID->data.explicit_location = true;
  98       gl_VertexID->data.explicit_index = 0;
  99       ir_list->push_head(gl_VertexID);
 100
 101       if (gl_BaseVertex == NULL) {
 102          gl_BaseVertex = new(mem_ctx) ir_variable(int_t, "gl_BaseVertex",
 103                                                   ir_var_system_value);
 104          gl_BaseVertex->data.how_declared = ir_var_hidden;
 105          gl_BaseVertex->data.read_only = true;
 106          gl_BaseVertex->data.location = SYSTEM_VALUE_BASE_VERTEX;
 107          gl_BaseVertex->data.explicit_location = true;
 108          gl_BaseVertex->data.explicit_index = 0;
 109          ir_list->push_head(gl_BaseVertex);
 110       }
 111
 112       ir_instruction *const inst =
 113          ir_builder::assign(VertexID,
 114                             ir_builder::add(gl_VertexID, gl_BaseVertex));
 115
 116       main_sig->body.push_head(inst);
 117    }
 118
 119    ir->var = VertexID;
 120    progress = true;
 121
 122    return visit_continue;
 123 }
 124
 125 bool
 126 lower_vertex_id(gl_linked_shader *shader)
 127 {
 128    /* gl_VertexID only exists in the vertex shader.
 129     */
 130    if (shader->Stage != MESA_SHADER_VERTEX)
 131       return false;
 132
 133    ir_function_signature *const main_sig =
 134       _mesa_get_main_function_signature(shader->symbols);
 135    if (main_sig == NULL) {
 136       assert(main_sig != NULL);
 137       return false;
 138    }
 139
 140    lower_vertex_id_visitor v(main_sig, shader->ir);
 141
 142    v.run(shader->ir);
 143
 144    return v.progress;
 145 }