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/*
* 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 ir_if_return.cpp
*
* If a function includes an if statement that returns from both
* branches, then make the branches write the return val to a temp and
* return the temp after the if statement.
*
* This allows inlinining in the common case of short functions that
* return one of two values based on a condition. This helps on
* hardware with no branching support, and may even be a useful
* transform on hardware supporting control flow by masked returns
* with normal returns.
*/
#include "ir.h"
class ir_if_return_visitor : public ir_hierarchical_visitor {
public:
ir_if_return_visitor()
{
this->progress = false;
}
ir_visitor_status visit_enter(ir_if *);
bool progress;
};
bool
do_if_return(exec_list *instructions)
{
ir_if_return_visitor v;
do {
v.progress = false;
visit_list_elements(&v, instructions);
} while (v.progress);
return v.progress;
}
/**
* Removes any instructions after a (unconditional) return, since they will
* never be executed.
*/
static void
truncate_after_instruction(ir_instruction *ir)
{
while (!ir->get_next()->is_tail_sentinel())
((ir_instruction *)ir->get_next())->remove();
}
/**
* Returns an ir_instruction of the first ir_return in the exec_list, or NULL.
*/
static ir_return *
find_return_in_block(exec_list *instructions)
{
foreach_iter(exec_list_iterator, iter, *instructions) {
ir_instruction *ir = (ir_instruction *)iter.get();
if (ir->ir_type == ir_type_return)
return (ir_return *)ir;
}
return NULL;
}
ir_visitor_status
ir_if_return_visitor::visit_enter(ir_if *ir)
{
ir_return *then_return = NULL;
ir_return *else_return = NULL;
then_return = find_return_in_block(&ir->then_instructions);
else_return = find_return_in_block(&ir->else_instructions);
if (!then_return || !else_return)
return visit_continue;
/* Trim off any trailing instructions after the return statements
* on both sides.
*/
truncate_after_instruction(then_return);
truncate_after_instruction(else_return);
this->progress = true;
if (!then_return->value) {
then_return->remove();
else_return->remove();
ir->insert_after(new(ir) ir_return(NULL));
} else {
ir_assignment *assign;
ir_variable *new_var = new(ir) ir_variable(then_return->value->type,
"if_return_tmp",
ir_var_temporary);
ir->insert_before(new_var);
assign = new(ir) ir_assignment(new(ir) ir_dereference_variable(new_var),
then_return->value, NULL);
then_return->replace_with(assign);
assign = new(ir) ir_assignment(new(ir) ir_dereference_variable(new_var),
else_return->value, NULL);
else_return->replace_with(assign);
ir_dereference_variable *deref = new(ir) ir_dereference_variable(new_var);
ir->insert_after(new(ir) ir_return(deref));
}
return visit_continue;
}
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