/* -*- 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 */