src/compiler/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 "compiler/glsl_types.h"
  36 #include "util/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_pointer_hash_table_create(NULL);
  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
  49    /* Free assignment list */
  50    exec_node *n;
  51    while ((n = ivre->assign_list.pop_head()) != NULL) {
  52       struct assignment_entry *assignment_entry =
  53          exec_node_data(struct assignment_entry, n, link);
  54       free(assignment_entry);
  55    }
  56
  57    delete ivre;
  58 }
  59
  60 ir_variable_refcount_visitor::~ir_variable_refcount_visitor()
  61 {
  62    ralloc_free(this->mem_ctx);
  63    _mesa_hash_table_destroy(this->ht, free_entry);
  64 }
  65
  66 // constructor
  67 ir_variable_refcount_entry::ir_variable_refcount_entry(ir_variable *var)
  68 {
  69    this->var = var;
  70    assigned_count = 0;
  71    declaration = false;
  72    referenced_count = 0;
  73 }
  74
  75
  76 ir_variable_refcount_entry *
  77 ir_variable_refcount_visitor::get_variable_entry(ir_variable *var)
  78 {
  79    assert(var);
  80
  81    struct hash_entry *e = _mesa_hash_table_search(this->ht, var);
  82    if (e)
  83       return (ir_variable_refcount_entry *)e->data;
  84
  85    ir_variable_refcount_entry *entry = new ir_variable_refcount_entry(var);
  86    assert(entry->referenced_count == 0);
  87    _mesa_hash_table_insert(this->ht, var, entry);
  88
  89    return entry;
  90 }
  91
  92
  93 ir_visitor_status
  94 ir_variable_refcount_visitor::visit(ir_variable *ir)
  95 {
  96    ir_variable_refcount_entry *entry = this->get_variable_entry(ir);
  97    if (entry)
  98       entry->declaration = true;
  99
 100    return visit_continue;
 101 }
 102
 103
 104 ir_visitor_status
 105 ir_variable_refcount_visitor::visit(ir_dereference_variable *ir)
 106 {
 107    ir_variable *const var = ir->variable_referenced();
 108    ir_variable_refcount_entry *entry = this->get_variable_entry(var);
 109
 110    if (entry)
 111       entry->referenced_count++;
 112
 113    return visit_continue;
 114 }
 115
 116
 117 ir_visitor_status
 118 ir_variable_refcount_visitor::visit_enter(ir_function_signature *ir)
 119 {
 120    /* We don't want to descend into the function parameters and
 121     * dead-code eliminate them, so just accept the body here.
 122     */
 123    visit_list_elements(this, &ir->body);
 124    return visit_continue_with_parent;
 125 }
 126
 127
 128 ir_visitor_status
 129 ir_variable_refcount_visitor::visit_leave(ir_assignment *ir)
 130 {
 131    ir_variable_refcount_entry *entry;
 132    entry = this->get_variable_entry(ir->lhs->variable_referenced());
 133    if (entry) {
 134       entry->assigned_count++;
 135
 136       /* Build a list for dead code optimisation. Don't add assignment if it
 137        * was declared out of scope (outside the instruction stream). Also don't
 138        * bother adding any more to the list if there are more references than
 139        * assignments as this means the variable is used and won't be optimised
 140        * out.
 141        */
 142       assert(entry->referenced_count >= entry->assigned_count);
 143       if (entry->referenced_count == entry->assigned_count) {
 144          struct assignment_entry *assignment_entry =
 145             (struct assignment_entry *)calloc(1, sizeof(*assignment_entry));
 146          assignment_entry->assign = ir;
 147          entry->assign_list.push_head(&assignment_entry->link);
 148       }
 149    }
 150
 151    return visit_continue;
 152 }