src/compiler/glsl/loop_analysis.h

   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
  38 extern bool
  39 unroll_loops(exec_list *instructions, loop_state *ls,
  40              const struct gl_shader_compiler_options *options);
  41
  42
  43 /**
  44  * Tracking for all variables used in a loop
  45  */
  46 class loop_variable_state : public exec_node {
  47 public:
  48    class loop_variable *get(const ir_variable *);
  49    class loop_variable *insert(ir_variable *);
  50    class loop_variable *get_or_insert(ir_variable *, bool in_assignee);
  51    class loop_terminator *insert(ir_if *);
  52
  53
  54    /**
  55     * Variables that have not yet been classified
  56     */
  57    exec_list variables;
  58
  59    /**
  60     * Variables whose values are constant within the body of the loop
  61     *
  62     * This list contains \c loop_variable objects.
  63     */
  64    exec_list constants;
  65
  66    /**
  67     * Induction variables for this loop
  68     *
  69     * This list contains \c loop_variable objects.
  70     */
  71    exec_list induction_variables;
  72
  73    /**
  74     * Simple if-statements that lead to the termination of the loop
  75     *
  76     * This list contains \c loop_terminator objects.
  77     *
  78     * \sa is_loop_terminator
  79     */
  80    exec_list terminators;
  81
  82    /**
  83     * If any of the terminators in \c terminators leads to termination of the
  84     * loop after a constant number of iterations, this is the terminator that
  85     * leads to termination after the smallest number of iterations.  Otherwise
  86     * NULL.
  87     */
  88    loop_terminator *limiting_terminator;
  89
  90    /**
  91     * Hash table containing all variables accessed in this loop
  92     */
  93    hash_table *var_hash;
  94
  95    /**
  96     * Number of ir_loop_jump instructions that operate on this loop
  97     */
  98    unsigned num_loop_jumps;
  99
 100    /**
 101     * Whether this loop contains any function calls.
 102     */
 103    bool contains_calls;
 104
 105    loop_variable_state()
 106    {
 107       this->num_loop_jumps = 0;
 108       this->contains_calls = false;
 109       this->var_hash = _mesa_hash_table_create(NULL, _mesa_hash_pointer,
 110                                                _mesa_key_pointer_equal);
 111       this->limiting_terminator = NULL;
 112    }
 113
 114    ~loop_variable_state()
 115    {
 116       _mesa_hash_table_destroy(this->var_hash, NULL);
 117    }
 118
 119    DECLARE_RALLOC_CXX_OPERATORS(loop_variable_state)
 120 };
 121
 122
 123 class loop_variable : public exec_node {
 124 public:
 125    /** The variable in question. */
 126    ir_variable *var;
 127
 128    /** Is the variable read in the loop before it is written? */
 129    bool read_before_write;
 130
 131    /** Are all variables in the RHS of the assignment loop constants? */
 132    bool rhs_clean;
 133
 134    /**
 135     * Is there an assignment to the variable that is conditional, or inside a
 136     * nested loop?
 137     */
 138    bool conditional_or_nested_assignment;
 139
 140    /** Reference to the first assignment to the variable in the loop body. */
 141    ir_assignment *first_assignment;
 142
 143    /** Number of assignments to the variable in the loop body. */
 144    unsigned num_assignments;
 145
 146    /**
 147     * Increment value for a loop induction variable
 148     *
 149     * If this is a loop induction variable, the amount by which the variable
 150     * is incremented on each iteration through the loop.
 151     *
 152     * If this is not a loop induction variable, NULL.
 153     */
 154    ir_rvalue *increment;
 155
 156
 157    inline bool is_induction_var() const
 158    {
 159       /* Induction variables always have a non-null increment, and vice
 160        * versa.
 161        */
 162       return this->increment != NULL;
 163    }
 164
 165
 166    inline bool is_loop_constant() const
 167    {
 168       const bool is_const = (this->num_assignments == 0)
 169          || (((this->num_assignments == 1)
 170              && !this->conditional_or_nested_assignment
 171              && !this->read_before_write
 172              && this->rhs_clean) || this->var->data.read_only);
 173
 174       /* If the RHS of *the* assignment is clean, then there must be exactly
 175        * one assignment of the variable.
 176        */
 177       assert((this->rhs_clean && (this->num_assignments == 1))
 178              || !this->rhs_clean);
 179
 180       return is_const;
 181    }
 182
 183    void record_reference(bool in_assignee,
 184                          bool in_conditional_code_or_nested_loop,
 185                          ir_assignment *current_assignment);
 186 };
 187
 188
 189 class loop_terminator : public exec_node {
 190 public:
 191    loop_terminator()
 192       : ir(NULL), iterations(-1)
 193    {
 194    }
 195
 196    /**
 197     * Statement which terminates the loop.
 198     */
 199    ir_if *ir;
 200
 201    /**
 202     * The number of iterations after which the terminator is known to
 203     * terminate the loop (if that is a fixed value).  Otherwise -1.
 204     */
 205    int iterations;
 206 };
 207
 208
 209 class loop_state {
 210 public:
 211    ~loop_state();
 212
 213    /**
 214     * Get the loop variable state data for a particular loop
 215     */
 216    loop_variable_state *get(const ir_loop *);
 217
 218    loop_variable_state *insert(ir_loop *ir);
 219
 220    bool loop_found;
 221
 222 private:
 223    loop_state();
 224
 225    /**
 226     * Hash table containing all loops that have been analyzed.
 227     */
 228    hash_table *ht;
 229
 230    void *mem_ctx;
 231
 232    friend loop_state *analyze_loop_variables(exec_list *instructions);
 233 };
 234
 235 #endif /* LOOP_ANALYSIS_H */