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
38ir_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
44static void
45free_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
60ir_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
67ir_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
76ir_variable_refcount_entry *
77ir_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
93ir_visitor_status
94ir_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
104ir_visitor_status
105ir_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
117ir_visitor_status
118ir_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
128ir_visitor_status
129ir_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}
153