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 static inline bool
  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
 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
 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
 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
 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:
 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 */