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       /* empty */
  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
  80 void
  81 ir_constant_folding_visitor::fold_constant(ir_rvalue **rvalue)
  82 {
  83    if ((*rvalue)->ir_type == ir_type_constant)
  84       return;
  85
  86    ir_constant *constant = (*rvalue)->constant_expression_value();
  87    if (constant) {
  88       *rvalue = constant;
  89    } else {
  90       (*rvalue)->accept(this);
  91    }
  92 }
  93
  94 void
  95 ir_constant_folding_visitor::visit(ir_variable *ir)
  96 {
  97    (void) ir;
  98 }
  99
 100
 101 void
 102 ir_constant_folding_visitor::visit(ir_function_signature *ir)
 103 {
 104    visit_exec_list(&ir->body, this);
 105 }
 106
 107
 108 void
 109 ir_constant_folding_visitor::visit(ir_function *ir)
 110 {
 111    foreach_iter(exec_list_iterator, iter, *ir) {
 112       ir_function_signature *const sig = (ir_function_signature *) iter.get();
 113       sig->accept(this);
 114    }
 115 }
 116
 117 void
 118 ir_constant_folding_visitor::visit(ir_expression *ir)
 119 {
 120    unsigned int operand;
 121
 122    for (operand = 0; operand < ir->get_num_operands(); operand++) {
 123       fold_constant(&ir->operands[operand]);
 124    }
 125 }
 126
 127
 128 void
 129 ir_constant_folding_visitor::visit(ir_texture *ir)
 130 {
 131    // FINISHME: Do stuff with texture lookups
 132    (void) ir;
 133 }
 134
 135
 136 void
 137 ir_constant_folding_visitor::visit(ir_swizzle *ir)
 138 {
 139    ir->val->accept(this);
 140 }
 141
 142
 143 void
 144 ir_constant_folding_visitor::visit(ir_dereference_variable *ir)
 145 {
 146    (void) ir;
 147 }
 148
 149
 150 void
 151 ir_constant_folding_visitor::visit(ir_dereference_array *ir)
 152 {
 153    fold_constant(&ir->array_index);
 154    ir->array->accept(this);
 155 }
 156
 157
 158 void
 159 ir_constant_folding_visitor::visit(ir_dereference_record *ir)
 160 {
 161    ir->record->accept(this);
 162 }
 163
 164
 165 void
 166 ir_constant_folding_visitor::visit(ir_assignment *ir)
 167 {
 168    fold_constant(&ir->rhs);
 169
 170    if (ir->condition) {
 171       /* If the condition is constant, either remove the condition or
 172        * remove the never-executed assignment.
 173        */
 174       ir_constant *const_val = ir->condition->constant_expression_value();
 175       if (const_val) {
 176          if (const_val->value.b[0])
 177             ir->condition = NULL;
 178          else
 179             ir->remove();
 180       }
 181    }
 182 }
 183
 184
 185 void
 186 ir_constant_folding_visitor::visit(ir_constant *ir)
 187 {
 188    (void) ir;
 189 }
 190
 191
 192 void
 193 ir_constant_folding_visitor::visit(ir_call *ir)
 194 {
 195    (void) ir;
 196 }
 197
 198
 199 void
 200 ir_constant_folding_visitor::visit(ir_return *ir)
 201 {
 202    (void) ir;
 203 }
 204
 205
 206 void
 207 ir_constant_folding_visitor::visit(ir_discard *ir)
 208 {
 209    (void) ir;
 210 }
 211
 212
 213 void
 214 ir_constant_folding_visitor::visit(ir_if *ir)
 215 {
 216    fold_constant(&ir->condition);
 217
 218    visit_exec_list(&ir->then_instructions, this);
 219    visit_exec_list(&ir->else_instructions, this);
 220 }
 221
 222
 223 void
 224 ir_constant_folding_visitor::visit(ir_loop *ir)
 225 {
 226    (void) ir;
 227 }
 228
 229
 230 void
 231 ir_constant_folding_visitor::visit(ir_loop_jump *ir)
 232 {
 233    (void) ir;
 234 }
 235
 236 bool
 237 do_constant_folding(exec_list *instructions)
 238 {
 239    ir_constant_folding_visitor constant_folding;
 240
 241    visit_exec_list(instructions, &constant_folding);
 242
 243    /* FINISHME: Return real progress. */
 244    return false;
 245 }