src/glsl/ir_variable_refcount.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_variable_refcount.cpp
  26  *
  27  * Provides a visitor which produces a list of variables referenced,
  28  * how many times they were referenced and assigned, and whether they
  29  * were defined in the scope.
  30  */
  31
  32 #include "ir.h"
  33 #include "ir_visitor.h"
  34 #include "ir_variable_refcount.h"
  35 #include "glsl_types.h"
  36 #include "main/hash_table.h"
  37
  38 ir_variable_refcount_visitor::ir_variable_refcount_visitor()
  39 {
  40    this->mem_ctx = ralloc_context(NULL);
  41    this->ht = _mesa_hash_table_create(NULL, _mesa_key_pointer_equal);
  42 }
  43
  44 static void
  45 free_entry(struct hash_entry *entry)
  46 {
  47    ir_variable_refcount_entry *ivre = (ir_variable_refcount_entry *) entry->data;
  48    delete ivre;
  49 }
  50
  51 ir_variable_refcount_visitor::~ir_variable_refcount_visitor()
  52 {
  53    ralloc_free(this->mem_ctx);
  54    _mesa_hash_table_destroy(this->ht, free_entry);
  55 }
  56
  57 // constructor
  58 ir_variable_refcount_entry::ir_variable_refcount_entry(ir_variable *var)
  59 {
  60    this->var = var;
  61    assign = NULL;
  62    assigned_count = 0;
  63    declaration = false;
  64    referenced_count = 0;
  65 }
  66
  67
  68 ir_variable_refcount_entry *
  69 ir_variable_refcount_visitor::get_variable_entry(ir_variable *var)
  70 {
  71    assert(var);
  72
  73    struct hash_entry *e = _mesa_hash_table_search(this->ht,
  74                                                     _mesa_hash_pointer(var),
  75                                                     var);
  76    if (e)
  77       return (ir_variable_refcount_entry *)e->data;
  78
  79    ir_variable_refcount_entry *entry = new ir_variable_refcount_entry(var);
  80    assert(entry->referenced_count == 0);
  81    _mesa_hash_table_insert(this->ht, _mesa_hash_pointer(var), var, entry);
  82
  83    return entry;
  84 }
  85
  86
  87 ir_visitor_status
  88 ir_variable_refcount_visitor::visit(ir_variable *ir)
  89 {
  90    ir_variable_refcount_entry *entry = this->get_variable_entry(ir);
  91    if (entry)
  92       entry->declaration = true;
  93
  94    return visit_continue;
  95 }
  96
  97
  98 ir_visitor_status
  99 ir_variable_refcount_visitor::visit(ir_dereference_variable *ir)
 100 {
 101    ir_variable *const var = ir->variable_referenced();
 102    ir_variable_refcount_entry *entry = this->get_variable_entry(var);
 103
 104    if (entry)
 105       entry->referenced_count++;
 106
 107    return visit_continue;
 108 }
 109
 110
 111 ir_visitor_status
 112 ir_variable_refcount_visitor::visit_enter(ir_function_signature *ir)
 113 {
 114    /* We don't want to descend into the function parameters and
 115     * dead-code eliminate them, so just accept the body here.
 116     */
 117    visit_list_elements(this, &ir->body);
 118    return visit_continue_with_parent;
 119 }
 120
 121
 122 ir_visitor_status
 123 ir_variable_refcount_visitor::visit_leave(ir_assignment *ir)
 124 {
 125    ir_variable_refcount_entry *entry;
 126    entry = this->get_variable_entry(ir->lhs->variable_referenced());
 127    if (entry) {
 128       entry->assigned_count++;
 129       if (entry->assign == NULL)
 130          entry->assign = ir;
 131    }
 132
 133    return visit_continue;
 134 }
 135
 136
 137 ir_visitor_status
 138 ir_variable_refcount_visitor::visit_leave(ir_loop *ir)
 139 {
 140    /* If the loop has a counter variable, it is implicitly referenced and
 141     * assigned to.  Note that since the LHS of an assignment is counted as a
 142     * reference, we actually have to increment referenced_count by 2 so that
 143     * later code will know that the variable isn't just assigned to.
 144     */
 145    if (ir->counter != NULL) {
 146       ir_variable_refcount_entry *entry =
 147          this->get_variable_entry(ir->counter);
 148       if (entry) {
 149          entry->referenced_count += 2;
 150          entry->assigned_count++;
 151       }
 152    }
 153
 154    return visit_continue;
 155 }