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      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_hidden;
    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_linked_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       _mesa_get_main_function_signature(shader->symbols);
    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 }
    145