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 */
34extern class loop_state *
35analyze_loop_variables(exec_list *instructions);
36
37static inline bool
38is_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
45extern bool
46unroll_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 */
53class loop_variable_state : public exec_node {
54public:
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
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
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
129class loop_variable : public exec_node {
130public:
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
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
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
195class loop_terminator : public exec_node {
196public:
197   loop_terminator()
198      : ir(NULL), iterations(-1)
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
218class loop_state {
219public:
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
231private:
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