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
  78 void
  79 ir_constant_folding_visitor::visit(ir_variable *ir)
  80 {
  81    (void) ir;
  82 }
  83
  84
  85 void
  86 ir_constant_folding_visitor::visit(ir_function_signature *ir)
  87 {
  88    visit_exec_list(&ir->body, this);
  89 }
  90
  91
  92 void
  93 ir_constant_folding_visitor::visit(ir_function *ir)
  94 {
  95    foreach_iter(exec_list_iterator, iter, *ir) {
  96       ir_function_signature *const sig = (ir_function_signature *) iter.get();
  97       sig->accept(this);
  98    }
  99 }
 100
 101 void
 102 ir_constant_folding_visitor::visit(ir_expression *ir)
 103 {
 104    ir_constant *op[2];
 105    unsigned int operand;
 106
 107    for (operand = 0; operand < ir->get_num_operands(); operand++) {
 108       op[operand] = ir->operands[operand]->constant_expression_value();
 109       if (op[operand]) {
 110          ir->operands[operand] = op[operand];
 111       } else {
 112          ir->operands[operand]->accept(this);
 113       }
 114    }
 115 }
 116
 117
 118 void
 119 ir_constant_folding_visitor::visit(ir_texture *ir)
 120 {
 121    // FINISHME: Do stuff with texture lookups
 122    (void) ir;
 123 }
 124
 125
 126 void
 127 ir_constant_folding_visitor::visit(ir_swizzle *ir)
 128 {
 129    ir->val->accept(this);
 130 }
 131
 132
 133 void
 134 ir_constant_folding_visitor::visit(ir_dereference_variable *ir)
 135 {
 136    (void) ir;
 137 }
 138
 139
 140 void
 141 ir_constant_folding_visitor::visit(ir_dereference_array *ir)
 142 {
 143    ir_constant *const_val =
 144       ir->array_index->constant_expression_value();
 145
 146    if (const_val)
 147       ir->array_index = const_val;
 148    else
 149       ir->array_index->accept(this);
 150
 151    ir->array->accept(this);
 152 }
 153
 154
 155 void
 156 ir_constant_folding_visitor::visit(ir_dereference_record *ir)
 157 {
 158    ir->record->accept(this);
 159 }
 160
 161
 162 void
 163 ir_constant_folding_visitor::visit(ir_assignment *ir)
 164 {
 165    ir_constant *const_val = ir->rhs->constant_expression_value();
 166    if (const_val)
 167       ir->rhs = const_val;
 168    else
 169       ir->rhs->accept(this);
 170
 171    if (ir->condition) {
 172       /* If the condition is constant, either remove the condition or
 173        * remove the never-executed assignment.
 174        */
 175       const_val = ir->condition->constant_expression_value();
 176       if (const_val) {
 177          if (const_val->value.b[0])
 178             ir->condition = NULL;
 179          else
 180             ir->remove();
 181       }
 182    }
 183 }
 184
 185
 186 void
 187 ir_constant_folding_visitor::visit(ir_constant *ir)
 188 {
 189    (void) ir;
 190 }
 191
 192
 193 void
 194 ir_constant_folding_visitor::visit(ir_call *ir)
 195 {
 196    (void) ir;
 197 }
 198
 199
 200 void
 201 ir_constant_folding_visitor::visit(ir_return *ir)
 202 {
 203    (void) ir;
 204 }
 205
 206
 207 void
 208 ir_constant_folding_visitor::visit(ir_discard *ir)
 209 {
 210    (void) ir;
 211 }
 212
 213
 214 void
 215 ir_constant_folding_visitor::visit(ir_if *ir)
 216 {
 217    ir_constant *const_val = ir->condition->constant_expression_value();
 218    if (const_val)
 219       ir->condition = const_val;
 220    else
 221       ir->condition->accept(this);
 222
 223    visit_exec_list(&ir->then_instructions, this);
 224    visit_exec_list(&ir->else_instructions, this);
 225 }
 226
 227
 228 void
 229 ir_constant_folding_visitor::visit(ir_loop *ir)
 230 {
 231    (void) ir;
 232 }
 233
 234
 235 void
 236 ir_constant_folding_visitor::visit(ir_loop_jump *ir)
 237 {
 238    (void) ir;
 239 }
 240
 241 bool
 242 do_constant_folding(exec_list *instructions)
 243 {
 244    ir_constant_folding_visitor constant_folding;
 245
 246    visit_exec_list(instructions, &constant_folding);
 247
 248    /* FINISHME: Return real progress. */
 249    return false;
 250 }