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 #pragma once 26 #ifndef LOOP_ANALYSIS_H 27 #define LOOP_ANALYSIS_H 28 29 #include "ir.h" 30 #include "program/hash_table.h" 31 32 /** 33 * Analyze and classify all variables used in all loops in the instruction list 34 */ 35 extern class loop_state * 36 analyze_loop_variables(exec_list *instructions); 37 38 39 /** 40 * Fill in loop control fields 41 * 42 * Based on analysis of loop variables, this function tries to remove sequences 43 * in the loop of the form 44 * 45 * (if (expression bool ...) (break)) 46 * 47 * and fill in the \c ir_loop::from, \c ir_loop::to, and \c ir_loop::counter 48 * fields of the \c ir_loop. 49 * 50 * In this process, some conditional break-statements may be eliminated 51 * altogether. For example, if it is provable that one loop exit condition will 52 * always be satisfied before another, the unnecessary exit condition will be 53 * removed. 54 */ 55 extern bool 56 set_loop_controls(exec_list *instructions, loop_state *ls); 57 58 59 extern bool 60 unroll_loops(exec_list *instructions, loop_state *ls, unsigned max_iterations); 61 62 63 /** 64 * Tracking for all variables used in a loop 65 */ 66 class loop_variable_state : public exec_node { 67 public: 68 class loop_variable *get(const ir_variable *); 69 class loop_variable *insert(ir_variable *); 70 class loop_terminator *insert(ir_if *); 71 72 73 /** 74 * Loop whose variable state is being tracked by this structure 75 */ 76 ir_loop *loop; 77 78 /** 79 * Variables that have not yet been classified 80 */ 81 exec_list variables; 82 83 /** 84 * Variables whose values are constant within the body of the loop 85 * 86 * This list contains \c loop_variable objects. 87 */ 88 exec_list constants; 89 90 /** 91 * Induction variables for this loop 92 * 93 * This list contains \c loop_variable objects. 94 */ 95 exec_list induction_variables; 96 97 /** 98 * Simple if-statements that lead to the termination of the loop 99 * 100 * This list contains \c loop_terminator objects. 101 * 102 * \sa is_loop_terminator 103 */ 104 exec_list terminators; 105 106 /** 107 * Hash table containing all variables accessed in this loop 108 */ 109 hash_table *var_hash; 110 111 /** 112 * Maximum number of loop iterations. 113 * 114 * If this value is negative, then the loop may be infinite. This actually 115 * means that analysis was unable to determine an upper bound on the number 116 * of loop iterations. 117 */ 118 int max_iterations; 119 120 /** 121 * Number of ir_loop_jump instructions that operate on this loop 122 */ 123 unsigned num_loop_jumps; 124 125 /** 126 * Whether this loop contains any function calls. 127 */ 128 bool contains_calls; 129 130 loop_variable_state() 131 { 132 this->max_iterations = -1; 133 this->num_loop_jumps = 0; 134 this->contains_calls = false; 135 this->var_hash = hash_table_ctor(0, hash_table_pointer_hash, 136 hash_table_pointer_compare); 137 } 138 139 ~loop_variable_state() 140 { 141 hash_table_dtor(this->var_hash); 142 } 143 144 static void* operator new(size_t size, void *ctx) 145 { 146 void *lvs = ralloc_size(ctx, size); 147 assert(lvs != NULL); 148 149 ralloc_set_destructor(lvs, (void (*)(void*)) destructor); 150 151 return lvs; 152 } 153 154 private: 155 static void 156 destructor(loop_variable_state *lvs) 157 { 158 lvs->~loop_variable_state(); 159 } 160 }; 161 162 163 class loop_variable : public exec_node { 164 public: 165 /** The variable in question. */ 166 ir_variable *var; 167 168 /** Is the variable read in the loop before it is written? */ 169 bool read_before_write; 170 171 /** Are all variables in the RHS of the assignment loop constants? */ 172 bool rhs_clean; 173 174 /** Is there an assignment to the variable that is conditional? */ 175 bool conditional_assignment; 176 177 /** Reference to the first assignment to the variable in the loop body. */ 178 ir_assignment *first_assignment; 179 180 /** Number of assignments to the variable in the loop body. */ 181 unsigned num_assignments; 182 183 /** 184 * Increment values for loop induction variables 185 * 186 * Loop induction variables have a single increment of the form 187 * \c b * \c biv + \c c, where \c b and \c c are loop constants and \c i 188 * is a basic loop induction variable. 189 * 190 * If \c iv_scale is \c NULL, 1 is used. If \c biv is the same as \c var, 191 * then \c var is a basic loop induction variable. 192 */ 193 /*@{*/ 194 ir_rvalue *iv_scale; 195 ir_variable *biv; 196 ir_rvalue *increment; 197 /*@}*/ 198 199 200 inline bool is_loop_constant() const 201 { 202 const bool is_const = (this->num_assignments == 0) 203 || ((this->num_assignments == 1) 204 && !this->conditional_assignment 205 && !this->read_before_write 206 && this->rhs_clean); 207 208 /* If the RHS of *the* assignment is clean, then there must be exactly 209 * one assignment of the variable. 210 */ 211 assert((this->rhs_clean && (this->num_assignments == 1)) 212 || !this->rhs_clean); 213 214 /* Variables that are marked read-only *MUST* be loop constant. 215 */ 216 assert(!this->var->read_only || (this->var->read_only && is_const)); 217 218 return is_const; 219 } 220 }; 221 222 223 class loop_terminator : public exec_node { 224 public: 225 ir_if *ir; 226 }; 227 228 229 class loop_state { 230 public: 231 ~loop_state(); 232 233 /** 234 * Get the loop variable state data for a particular loop 235 */ 236 loop_variable_state *get(const ir_loop *); 237 238 loop_variable_state *insert(ir_loop *ir); 239 240 bool loop_found; 241 242 private: 243 loop_state(); 244 245 /** 246 * Hash table containing all loops that have been analyzed. 247 */ 248 hash_table *ht; 249 250 void *mem_ctx; 251 252 friend class loop_analysis; 253 }; 254 255 #endif /* LOOP_ANALYSIS_H */ 256
