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authormarha <marha@users.sourceforge.net>2010-11-29 22:05:53 +0000
committermarha <marha@users.sourceforge.net>2010-11-29 22:05:53 +0000
commitfed109d6a33c0871291d1bb2f3f6b7a3d1a3e9d7 (patch)
treefa1ba494685a71e28a096990a8707680c7cb378b /mesalib/src/glsl/loop_analysis.h
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parent6fda93be42ace9eeab0e82ceebb6798961c9105c (diff)
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+/* -*- c++ -*- */
+/*
+ * Copyright © 2010 Intel Corporation
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+ * DEALINGS IN THE SOFTWARE.
+ */
+
+#pragma once
+#ifndef LOOP_ANALYSIS_H
+#define LOOP_ANALYSIS_H
+
+#include "ir.h"
+#include "program/hash_table.h"
+
+/**
+ * Analyze and classify all variables used in all loops in the instruction list
+ */
+extern class loop_state *
+analyze_loop_variables(exec_list *instructions);
+
+
+/**
+ * Fill in loop control fields
+ *
+ * Based on analysis of loop variables, this function tries to remove sequences
+ * in the loop of the form
+ *
+ * (if (expression bool ...) (break))
+ *
+ * and fill in the \c ir_loop::from, \c ir_loop::to, and \c ir_loop::counter
+ * fields of the \c ir_loop.
+ *
+ * In this process, some conditional break-statements may be eliminated
+ * altogether. For example, if it is provable that one loop exit condition will
+ * always be satisfied before another, the unnecessary exit condition will be
+ * removed.
+ */
+extern bool
+set_loop_controls(exec_list *instructions, loop_state *ls);
+
+
+extern bool
+unroll_loops(exec_list *instructions, loop_state *ls, unsigned max_iterations);
+
+
+/**
+ * Tracking for all variables used in a loop
+ */
+class loop_variable_state : public exec_node {
+public:
+ class loop_variable *get(const ir_variable *);
+ class loop_variable *insert(ir_variable *);
+ class loop_terminator *insert(ir_if *);
+
+
+ /**
+ * Loop whose variable state is being tracked by this structure
+ */
+ ir_loop *loop;
+
+ /**
+ * Variables that have not yet been classified
+ */
+ exec_list variables;
+
+ /**
+ * Variables whose values are constant within the body of the loop
+ *
+ * This list contains \c loop_variable objects.
+ */
+ exec_list constants;
+
+ /**
+ * Induction variables for this loop
+ *
+ * This list contains \c loop_variable objects.
+ */
+ exec_list induction_variables;
+
+ /**
+ * Simple if-statements that lead to the termination of the loop
+ *
+ * This list contains \c loop_terminator objects.
+ *
+ * \sa is_loop_terminator
+ */
+ exec_list terminators;
+
+ /**
+ * Hash table containing all variables accessed in this loop
+ */
+ hash_table *var_hash;
+
+ /**
+ * Maximum number of loop iterations.
+ *
+ * If this value is negative, then the loop may be infinite. This actually
+ * means that analysis was unable to determine an upper bound on the number
+ * of loop iterations.
+ */
+ int max_iterations;
+
+ /**
+ * Number of ir_loop_jump instructions that operate on this loop
+ */
+ unsigned num_loop_jumps;
+
+ loop_variable_state()
+ {
+ this->max_iterations = -1;
+ this->num_loop_jumps = 0;
+ this->var_hash = hash_table_ctor(0, hash_table_pointer_hash,
+ hash_table_pointer_compare);
+ }
+
+ ~loop_variable_state()
+ {
+ hash_table_dtor(this->var_hash);
+ }
+};
+
+
+class loop_variable : public exec_node {
+public:
+ /** The variable in question. */
+ ir_variable *var;
+
+ /** Is the variable read in the loop before it is written? */
+ bool read_before_write;
+
+ /** Are all variables in the RHS of the assignment loop constants? */
+ bool rhs_clean;
+
+ /** Is there an assignment to the variable that is conditional? */
+ bool conditional_assignment;
+
+ /** Reference to the first assignment to the variable in the loop body. */
+ ir_assignment *first_assignment;
+
+ /** Number of assignments to the variable in the loop body. */
+ unsigned num_assignments;
+
+ /**
+ * Increment values for loop induction variables
+ *
+ * Loop induction variables have a single increment of the form
+ * \c b * \c biv + \c c, where \c b and \c c are loop constants and \c i
+ * is a basic loop induction variable.
+ *
+ * If \c iv_scale is \c NULL, 1 is used. If \c biv is the same as \c var,
+ * then \c var is a basic loop induction variable.
+ */
+ /*@{*/
+ ir_rvalue *iv_scale;
+ ir_variable *biv;
+ ir_rvalue *increment;
+ /*@}*/
+
+
+ inline bool is_loop_constant() const
+ {
+ const bool is_const = (this->num_assignments == 0)
+ || ((this->num_assignments == 1)
+ && !this->conditional_assignment
+ && !this->read_before_write
+ && this->rhs_clean);
+
+ /* If the RHS of *the* assignment is clean, then there must be exactly
+ * one assignment of the variable.
+ */
+ assert((this->rhs_clean && (this->num_assignments == 1))
+ || !this->rhs_clean);
+
+ /* Variables that are marked read-only *MUST* be loop constant.
+ */
+ assert(!this->var->read_only || (this->var->read_only && is_const));
+
+ return is_const;
+ }
+};
+
+
+class loop_terminator : public exec_node {
+public:
+ ir_if *ir;
+};
+
+
+class loop_state {
+public:
+ ~loop_state();
+
+ /**
+ * Get the loop variable state data for a particular loop
+ */
+ loop_variable_state *get(const ir_loop *);
+
+ loop_variable_state *insert(ir_loop *ir);
+
+private:
+ loop_state();
+
+ /**
+ * Hash table containing all loops that have been analyzed.
+ */
+ hash_table *ht;
+
+ void *mem_ctx;
+
+ friend class loop_analysis;
+};
+
+#endif /* LOOP_ANALYSIS_H */