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_hash_table_create(NULL, _mesa_hash_pointer,
117 _mesa_key_pointer_equal);
118 this->limiting_terminator = NULL;
119 }
120
~loop_variable_state()121 ~loop_variable_state()
122 {
123 _mesa_hash_table_destroy(this->var_hash, NULL);
124 }
125
126 DECLARE_RALLOC_CXX_OPERATORS(loop_variable_state)
127 };
128
129
130 class loop_variable : public exec_node {
131 public:
132 /** The variable in question. */
133 ir_variable *var;
134
135 /** Is the variable read in the loop before it is written? */
136 bool read_before_write;
137
138 /** Are all variables in the RHS of the assignment loop constants? */
139 bool rhs_clean;
140
141 /**
142 * Is there an assignment to the variable that is conditional, or inside a
143 * nested loop?
144 */
145 bool conditional_or_nested_assignment;
146
147 /** Reference to the first assignment to the variable in the loop body. */
148 ir_assignment *first_assignment;
149
150 /** Number of assignments to the variable in the loop body. */
151 unsigned num_assignments;
152
153 /**
154 * Increment value for a loop induction variable
155 *
156 * If this is a loop induction variable, the amount by which the variable
157 * is incremented on each iteration through the loop.
158 *
159 * If this is not a loop induction variable, NULL.
160 */
161 ir_rvalue *increment;
162
163
is_induction_var()164 inline bool is_induction_var() const
165 {
166 /* Induction variables always have a non-null increment, and vice
167 * versa.
168 */
169 return this->increment != NULL;
170 }
171
172
is_loop_constant()173 inline bool is_loop_constant() const
174 {
175 const bool is_const = (this->num_assignments == 0)
176 || (((this->num_assignments == 1)
177 && !this->conditional_or_nested_assignment
178 && !this->read_before_write
179 && this->rhs_clean) || this->var->data.read_only);
180
181 /* If the RHS of *the* assignment is clean, then there must be exactly
182 * one assignment of the variable.
183 */
184 assert((this->rhs_clean && (this->num_assignments == 1))
185 || !this->rhs_clean);
186
187 return is_const;
188 }
189
190 void record_reference(bool in_assignee,
191 bool in_conditional_code_or_nested_loop,
192 ir_assignment *current_assignment);
193 };
194
195
196 class loop_terminator : public exec_node {
197 public:
loop_terminator()198 loop_terminator()
199 : ir(NULL), iterations(-1)
200 {
201 }
202
203 /**
204 * Statement which terminates the loop.
205 */
206 ir_if *ir;
207
208 /**
209 * The number of iterations after which the terminator is known to
210 * terminate the loop (if that is a fixed value). Otherwise -1.
211 */
212 int iterations;
213
214 /* Does the if continue from the then branch or the else branch */
215 bool continue_from_then;
216 };
217
218
219 class loop_state {
220 public:
221 ~loop_state();
222
223 /**
224 * Get the loop variable state data for a particular loop
225 */
226 loop_variable_state *get(const ir_loop *);
227
228 loop_variable_state *insert(ir_loop *ir);
229
230 bool loop_found;
231
232 private:
233 loop_state();
234
235 /**
236 * Hash table containing all loops that have been analyzed.
237 */
238 hash_table *ht;
239
240 void *mem_ctx;
241
242 friend loop_state *analyze_loop_variables(exec_list *instructions);
243 };
244
245 #endif /* LOOP_ANALYSIS_H */
246