/*
* 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.
*/
/**
* \file opt_copy_propagation.cpp
*
* Moves usage of recently-copied variables to the previous copy of
* the variable.
*
* This should reduce the number of MOV instructions in the generated
* programs unless copy propagation is also done on the LIR, and may
* help anyway by triggering other optimizations that live in the HIR.
*/
#include "ir.h"
#include "ir_visitor.h"
#include "ir_basic_block.h"
#include "ir_optimization.h"
#include "glsl_types.h"
namespace {
class acp_entry : public exec_node
{
public:
acp_entry(ir_variable *lhs, ir_variable *rhs)
{
assert(lhs);
assert(rhs);
this->lhs = lhs;
this->rhs = rhs;
}
ir_variable *lhs;
ir_variable *rhs;
};
class kill_entry : public exec_node
{
public:
kill_entry(ir_variable *var)
{
assert(var);
this->var = var;
}
ir_variable *var;
};
class ir_copy_propagation_visitor : public ir_hierarchical_visitor {
public:
ir_copy_propagation_visitor()
{
progress = false;
mem_ctx = ralloc_context(0);
this->acp = new(mem_ctx) exec_list;
this->kills = new(mem_ctx) exec_list;
}
~ir_copy_propagation_visitor()
{
ralloc_free(mem_ctx);
}
virtual ir_visitor_status visit(class ir_dereference_variable *);
virtual ir_visitor_status visit_enter(class ir_loop *);
virtual ir_visitor_status visit_enter(class ir_function_signature *);
virtual ir_visitor_status visit_enter(class ir_function *);
virtual ir_visitor_status visit_leave(class ir_assignment *);
virtual ir_visitor_status visit_enter(class ir_call *);
virtual ir_visitor_status visit_enter(class ir_if *);
void add_copy(ir_assignment *ir);
void kill(ir_variable *ir);
void handle_if_block(exec_list *instructions);
/** List of acp_entry: The available copies to propagate */
exec_list *acp;
/**
* List of kill_entry: The variables whose values were killed in this
* block.
*/
exec_list *kills;
bool progress;
bool killed_all;
void *mem_ctx;
};
} /* unnamed namespace */
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function_signature *ir)
{
/* Treat entry into a function signature as a completely separate
* block. Any instructions at global scope will be shuffled into
* main() at link time, so they're irrelevant to us.
*/
exec_list *orig_acp = this->acp;
exec_list *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
this->acp = new(mem_ctx) exec_list;
this->kills = new(mem_ctx) exec_list;
this->killed_all = false;
visit_list_elements(this, &ir->body);
this->kills = orig_kills;
this->acp = orig_acp;
this->killed_all = orig_killed_all;
return visit_continue_with_parent;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_leave(ir_assignment *ir)
{
kill(ir->lhs->variable_referenced());
add_copy(ir);
return visit_continue;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_function *ir)
{
(void) ir;
return visit_continue;
}
/**
* Replaces dereferences of ACP RHS variables with ACP LHS variables.
*
* This is where the actual copy propagation occurs. Note that the
* rewriting of ir_dereference means that the ir_dereference instance
* must not be shared by multiple IR operations!
*/
ir_visitor_status
ir_copy_propagation_visitor::visit(ir_dereference_variable *ir)
{
if (this->in_assignee)
return visit_continue;
ir_variable *var = ir->var;
foreach_iter(exec_list_iterator, iter, *this->acp) {
acp_entry *entry = (acp_entry *)iter.get();
if (var == entry->lhs) {
ir->var = entry->rhs;
this->progress = true;
break;
}
}
return visit_continue;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_call *ir)
{
/* Do copy propagation on call parameters, but skip any out params */
exec_list_iterator sig_param_iter = ir->callee->parameters.iterator();
foreach_iter(exec_list_iterator, iter, ir->actual_parameters) {
ir_variable *sig_param = (ir_variable *)sig_param_iter.get();
ir_instruction *ir = (ir_instruction *)iter.get();
if (sig_param->mode != ir_var_function_out
&& sig_param->mode != ir_var_function_inout) {
ir->accept(this);
}
sig_param_iter.next();
}
/* Since we're unlinked, we don't (necessarily) know the side effects of
* this call. So kill all copies.
*/
acp->make_empty();
this->killed_all = true;
return visit_continue_with_parent;
}
void
ir_copy_propagation_visitor::handle_if_block(exec_list *instructions)
{
exec_list *orig_acp = this->acp;
exec_list *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
this->acp = new(mem_ctx) exec_list;
this->kills = new(mem_ctx) exec_list;
this->killed_all = false;
/* Populate the initial acp with a copy of the original */
foreach_iter(exec_list_iterator, iter, *orig_acp) {
acp_entry *a = (acp_entry *)iter.get();
this->acp->push_tail(new(this->mem_ctx) acp_entry(a->lhs, a->rhs));
}
visit_list_elements(this, instructions);
if (this->killed_all) {
orig_acp->make_empty();
}
exec_list *new_kills = this->kills;
this->kills = orig_kills;
this->acp = orig_acp;
this->killed_all = this->killed_all || orig_killed_all;
foreach_iter(exec_list_iterator, iter, *new_kills) {
kill_entry *k = (kill_entry *)iter.get();
kill(k->var);
}
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_if *ir)
{
ir->condition->accept(this);
handle_if_block(&ir->then_instructions);
handle_if_block(&ir->else_instructions);
/* handle_if_block() already descended into the children. */
return visit_continue_with_parent;
}
ir_visitor_status
ir_copy_propagation_visitor::visit_enter(ir_loop *ir)
{
exec_list *orig_acp = this->acp;
exec_list *orig_kills = this->kills;
bool orig_killed_all = this->killed_all;
/* FINISHME: For now, the initial acp for loops is totally empty.
* We could go through once, then go through again with the acp
* cloned minus the killed entries after the first run through.
*/
this->acp = new(mem_ctx) exec_list;
this->kills = new(mem_ctx) exec_list;
this->killed_all = false;
visit_list_elements(this, &ir->body_instructions);
if (this->killed_all) {
orig_acp->make_empty();
}
exec_list *new_kills = this->kills;
this->kills = orig_kills;
this->acp = orig_acp;
this->killed_all = this->killed_all || orig_killed_all;
foreach_iter(exec_list_iterator, iter, *new_kills) {
kill_entry *k = (kill_entry *)iter.get();
kill(k->var);
}
/* already descended into the children. */
return visit_continue_with_parent;
}
void
ir_copy_propagation_visitor::kill(ir_variable *var)
{
assert(var != NULL);
/* Remove any entries currently in the ACP for this kill. */
foreach_iter(exec_list_iterator, iter, *acp) {
acp_entry *entry = (acp_entry *)iter.get();
if (entry->lhs == var || entry->rhs == var) {
entry->remove();
}
}
/* Add the LHS variable to the list of killed variables in this block.
*/
this->kills->push_tail(new(this->mem_ctx) kill_entry(var));
}
/**
* Adds an entry to the available copy list if it's a plain assignment
* of a variable to a variable.
*/
void
ir_copy_propagation_visitor::add_copy(ir_assignment *ir)
{
acp_entry *entry;
if (ir->condition)
return;
ir_variable *lhs_var = ir->whole_variable_written();
ir_variable *rhs_var = ir->rhs->whole_variable_referenced();
if ((lhs_var != NULL) && (rhs_var != NULL)) {
if (lhs_var == rhs_var) {
/* This is a dumb assignment, but we've conveniently noticed
* it here. Removing it now would mess up the loop iteration
* calling us. Just flag it to not execute, and someone else
* will clean up the mess.
*/
ir->condition = new(ralloc_parent(ir)) ir_constant(false);
this->progress = true;
} else {
entry = new(this->mem_ctx) acp_entry(lhs_var, rhs_var);
this->acp->push_tail(entry);
}
}
}
/**
* Does a copy propagation pass on the code present in the instruction stream.
*/
bool
do_copy_propagation(exec_list *instructions)
{
ir_copy_propagation_visitor v;
visit_list_elements(&v, instructions);
return v.progress;
}