1 /* -*- c++ -*- */
2 /*
3 * Copyright © 2010 Intel Corporation
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
22 * DEALINGS IN THE SOFTWARE.
23 */
24
25 #ifndef LOOP_ANALYSIS_H
26 #define LOOP_ANALYSIS_H
27
28 #include "ir.h"
29 #include "util/hash_table.h"
30
31 /**
32 * Analyze and classify all variables used in all loops in the instruction list
33 */
34 extern class loop_state *
35 analyze_loop_variables(exec_list *instructions);
36
37 static inline bool
is_break(ir_instruction * ir)38 is_break(ir_instruction *ir)
39 {
40 return ir != NULL && ir->ir_type == ir_type_loop_jump &&
41 ((ir_loop_jump *) ir)->is_break();
42 }
43
44
45 extern bool
46 unroll_loops(exec_list *instructions, loop_state *ls,
47 const struct gl_shader_compiler_options *options);
48
49
50 /**
51 * Tracking for all variables used in a loop
52 */
53 class loop_variable_state : public exec_node {
54 public:
55 class loop_variable *get(const ir_variable *);
56 class loop_variable *insert(ir_variable *);
57 class loop_variable *get_or_insert(ir_variable *, bool in_assignee);
58 class loop_terminator *insert(ir_if *, bool continue_from_then);
59
60
61 /**
62 * Variables that have not yet been classified
63 */
64 exec_list variables;
65
66 /**
67 * Variables whose values are constant within the body of the loop
68 *
69 * This list contains \c loop_variable objects.
70 */
71 exec_list constants;
72
73 /**
74 * Induction variables for this loop
75 *
76 * This list contains \c loop_variable objects.
77 */
78 exec_list induction_variables;
79
80 /**
81 * Simple if-statements that lead to the termination of the loop
82 *
83 * This list contains \c loop_terminator objects.
84 *
85 * \sa is_loop_terminator
86 */
87 exec_list terminators;
88
89 /**
90 * If any of the terminators in \c terminators leads to termination of the
91 * loop after a constant number of iterations, this is the terminator that
92 * leads to termination after the smallest number of iterations. Otherwise
93 * NULL.
94 */
95 loop_terminator *limiting_terminator;
96
97 /**
98 * Hash table containing all variables accessed in this loop
99 */
100 hash_table *var_hash;
101
102 /**
103 * Number of ir_loop_jump instructions that operate on this loop
104 */
105 unsigned num_loop_jumps;
106
107 /**
108 * Whether this loop contains any function calls.
109 */
110 bool contains_calls;
111
loop_variable_state()112 loop_variable_state()
113 {
114 this->num_loop_jumps = 0;
115 this->contains_calls = false;
116 this->var_hash = _mesa_pointer_hash_table_create(NULL);
117 this->limiting_terminator = NULL;
118 }
119
~loop_variable_state()120 ~loop_variable_state()
121 {
122 _mesa_hash_table_destroy(this->var_hash, NULL);
123 }
124
125 DECLARE_RALLOC_CXX_OPERATORS(loop_variable_state)
126 };
127
128
129 class loop_variable : public exec_node {
130 public:
131 /** The variable in question. */
132 ir_variable *var;
133
134 /** Is the variable read in the loop before it is written? */
135 bool read_before_write;
136
137 /** Are all variables in the RHS of the assignment loop constants? */
138 bool rhs_clean;
139
140 /**
141 * Is there an assignment to the variable that is conditional, or inside a
142 * nested loop?
143 */
144 bool conditional_or_nested_assignment;
145
146 /** Reference to the first assignment to the variable in the loop body. */
147 ir_assignment *first_assignment;
148
149 /** Number of assignments to the variable in the loop body. */
150 unsigned num_assignments;
151
152 /**
153 * Increment value for a loop induction variable
154 *
155 * If this is a loop induction variable, the amount by which the variable
156 * is incremented on each iteration through the loop.
157 *
158 * If this is not a loop induction variable, NULL.
159 */
160 ir_rvalue *increment;
161
162
is_induction_var()163 inline bool is_induction_var() const
164 {
165 /* Induction variables always have a non-null increment, and vice
166 * versa.
167 */
168 return this->increment != NULL;
169 }
170
171
is_loop_constant()172 inline bool is_loop_constant() const
173 {
174 const bool is_const = (this->num_assignments == 0)
175 || (((this->num_assignments == 1)
176 && !this->conditional_or_nested_assignment
177 && !this->read_before_write
178 && this->rhs_clean) || this->var->data.read_only);
179
180 /* If the RHS of *the* assignment is clean, then there must be exactly
181 * one assignment of the variable.
182 */
183 assert((this->rhs_clean && (this->num_assignments == 1))
184 || !this->rhs_clean);
185
186 return is_const;
187 }
188
189 void record_reference(bool in_assignee,
190 bool in_conditional_code_or_nested_loop,
191 ir_assignment *current_assignment);
192 };
193
194
195 class loop_terminator : public exec_node {
196 public:
loop_terminator(ir_if * ir,bool continue_from_then)197 loop_terminator(ir_if *ir, bool continue_from_then)
198 : ir(ir), iterations(-1), continue_from_then(continue_from_then)
199 {
200 }
201
202 /**
203 * Statement which terminates the loop.
204 */
205 ir_if *ir;
206
207 /**
208 * The number of iterations after which the terminator is known to
209 * terminate the loop (if that is a fixed value). Otherwise -1.
210 */
211 int iterations;
212
213 /* Does the if continue from the then branch or the else branch */
214 bool continue_from_then;
215 };
216
217
218 class loop_state {
219 public:
220 ~loop_state();
221
222 /**
223 * Get the loop variable state data for a particular loop
224 */
225 loop_variable_state *get(const ir_loop *);
226
227 loop_variable_state *insert(ir_loop *ir);
228
229 bool loop_found;
230
231 private:
232 loop_state();
233
234 /**
235 * Hash table containing all loops that have been analyzed.
236 */
237 hash_table *ht;
238
239 void *mem_ctx;
240
241 friend loop_state *analyze_loop_variables(exec_list *instructions);
242 };
243
244 #endif /* LOOP_ANALYSIS_H */
245