src/glsl/ir_constant_folding.cpp

   1 /*
   2  * Copyright © 2010 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 ir_constant_folding.cpp
  26  * Replace constant-valued expressions with references to constant values.
  27  */
  28
  29 #include "ir.h"
  30 #include "ir_visitor.h"
  31 #include "ir_optimization.h"
  32 #include "glsl_types.h"
  33
  34 /**
  35  * Visitor class for replacing expressions with ir_constant values.
  36  */
  37
  38 class ir_constant_folding_visitor : public ir_visitor {
  39 public:
  40    ir_constant_folding_visitor()
  41    {
  42       this->progress = false;
  43    }
  44
  45    virtual ~ir_constant_folding_visitor()
  46    {
  47       /* empty */
  48    }
  49
  50    /**
  51     * \name Visit methods
  52     *
  53     * As typical for the visitor pattern, there must be one \c visit method for
  54     * each concrete subclass of \c ir_instruction.  Virtual base classes within
  55     * the hierarchy should not have \c visit methods.
  56     */
  57    /*@{*/
  58    virtual void visit(ir_variable *);
  59    virtual void visit(ir_function_signature *);
  60    virtual void visit(ir_function *);
  61    virtual void visit(ir_expression *);
  62    virtual void visit(ir_texture *);
  63    virtual void visit(ir_swizzle *);
  64    virtual void visit(ir_dereference_variable *);
  65    virtual void visit(ir_dereference_array *);
  66    virtual void visit(ir_dereference_record *);
  67    virtual void visit(ir_assignment *);
  68    virtual void visit(ir_constant *);
  69    virtual void visit(ir_call *);
  70    virtual void visit(ir_return *);
  71    virtual void visit(ir_discard *);
  72    virtual void visit(ir_if *);
  73    virtual void visit(ir_loop *);
  74    virtual void visit(ir_loop_jump *);
  75    /*@}*/
  76
  77    void fold_constant(ir_rvalue **rvalue);
  78
  79    bool progress;
  80 };
  81
  82 void
  83 ir_constant_folding_visitor::fold_constant(ir_rvalue **rvalue)
  84 {
  85    if ((*rvalue)->ir_type == ir_type_constant)
  86       return;
  87
  88    ir_constant *constant = (*rvalue)->constant_expression_value();
  89    if (constant) {
  90       *rvalue = constant;
  91       this->progress = true;
  92    } else {
  93       (*rvalue)->accept(this);
  94    }
  95 }
  96
  97 void
  98 ir_constant_folding_visitor::visit(ir_variable *ir)
  99 {
 100    (void) ir;
 101 }
 102
 103
 104 void
 105 ir_constant_folding_visitor::visit(ir_function_signature *ir)
 106 {
 107    visit_exec_list(&ir->body, this);
 108 }
 109
 110
 111 void
 112 ir_constant_folding_visitor::visit(ir_function *ir)
 113 {
 114    foreach_iter(exec_list_iterator, iter, *ir) {
 115       ir_function_signature *const sig = (ir_function_signature *) iter.get();
 116       sig->accept(this);
 117    }
 118 }
 119
 120 void
 121 ir_constant_folding_visitor::visit(ir_expression *ir)
 122 {
 123    unsigned int operand;
 124
 125    for (operand = 0; operand < ir->get_num_operands(); operand++) {
 126       fold_constant(&ir->operands[operand]);
 127    }
 128 }
 129
 130
 131 void
 132 ir_constant_folding_visitor::visit(ir_texture *ir)
 133 {
 134    // FINISHME: Do stuff with texture lookups
 135    (void) ir;
 136 }
 137
 138
 139 void
 140 ir_constant_folding_visitor::visit(ir_swizzle *ir)
 141 {
 142    ir->val->accept(this);
 143 }
 144
 145
 146 void
 147 ir_constant_folding_visitor::visit(ir_dereference_variable *ir)
 148 {
 149    (void) ir;
 150 }
 151
 152
 153 void
 154 ir_constant_folding_visitor::visit(ir_dereference_array *ir)
 155 {
 156    fold_constant(&ir->array_index);
 157    ir->array->accept(this);
 158 }
 159
 160
 161 void
 162 ir_constant_folding_visitor::visit(ir_dereference_record *ir)
 163 {
 164    ir->record->accept(this);
 165 }
 166
 167
 168 void
 169 ir_constant_folding_visitor::visit(ir_assignment *ir)
 170 {
 171    fold_constant(&ir->rhs);
 172
 173    if (ir->condition) {
 174       /* If the condition is constant, either remove the condition or
 175        * remove the never-executed assignment.
 176        */
 177       ir_constant *const_val = ir->condition->constant_expression_value();
 178       if (const_val) {
 179          if (const_val->value.b[0])
 180             ir->condition = NULL;
 181          else
 182             ir->remove();
 183       }
 184       this->progress = true;
 185    }
 186 }
 187
 188
 189 void
 190 ir_constant_folding_visitor::visit(ir_constant *ir)
 191 {
 192    (void) ir;
 193 }
 194
 195
 196 void
 197 ir_constant_folding_visitor::visit(ir_call *ir)
 198 {
 199    (void) ir;
 200 }
 201
 202
 203 void
 204 ir_constant_folding_visitor::visit(ir_return *ir)
 205 {
 206    (void) ir;
 207 }
 208
 209
 210 void
 211 ir_constant_folding_visitor::visit(ir_discard *ir)
 212 {
 213    (void) ir;
 214 }
 215
 216
 217 void
 218 ir_constant_folding_visitor::visit(ir_if *ir)
 219 {
 220    fold_constant(&ir->condition);
 221
 222    visit_exec_list(&ir->then_instructions, this);
 223    visit_exec_list(&ir->else_instructions, this);
 224 }
 225
 226
 227 void
 228 ir_constant_folding_visitor::visit(ir_loop *ir)
 229 {
 230    (void) ir;
 231 }
 232
 233
 234 void
 235 ir_constant_folding_visitor::visit(ir_loop_jump *ir)
 236 {
 237    (void) ir;
 238 }
 239
 240 bool
 241 do_constant_folding(exec_list *instructions)
 242 {
 243    ir_constant_folding_visitor constant_folding;
 244
 245    visit_exec_list(instructions, &constant_folding);
 246
 247    return constant_folding.progress;
 248 }