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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 opt_redundant_jumps.cpp
* Remove certain types of redundant jumps
*/
#include "ir.h"
namespace {
class redundant_jumps_visitor : public ir_hierarchical_visitor {
public:
redundant_jumps_visitor()
{
this->progress = false;
}
virtual ir_visitor_status visit_leave(ir_if *);
virtual ir_visitor_status visit_leave(ir_loop *);
virtual ir_visitor_status visit_enter(ir_assignment *);
bool progress;
};
} /* unnamed namespace */
/* We only care about the top level instructions, so don't descend
* into expressions.
*/
ir_visitor_status
redundant_jumps_visitor::visit_enter(ir_assignment *ir)
{
return visit_continue_with_parent;
}
ir_visitor_status
redundant_jumps_visitor::visit_leave(ir_if *ir)
{
/* If the last instruction in both branches is a 'break' or a 'continue',
* pull it out of the branches and insert it after the if-statment. Note
* that both must be the same type (either 'break' or 'continue').
*/
ir_instruction *const last_then =
(ir_instruction *) ir->then_instructions.get_tail();
ir_instruction *const last_else =
(ir_instruction *) ir->else_instructions.get_tail();
if ((last_then == NULL) || (last_else == NULL))
return visit_continue;
if ((last_then->ir_type != ir_type_loop_jump)
|| (last_else->ir_type != ir_type_loop_jump))
return visit_continue;
ir_loop_jump *const then_jump = (ir_loop_jump *) last_then;
ir_loop_jump *const else_jump = (ir_loop_jump *) last_else;
if (then_jump->mode != else_jump->mode)
return visit_continue;
then_jump->remove();
else_jump->remove();
this->progress = true;
ir->insert_after(then_jump);
/* If both branchs of the if-statement are now empty, remove the
* if-statement.
*/
if (ir->then_instructions.is_empty() && ir->else_instructions.is_empty())
ir->remove();
return visit_continue;
}
ir_visitor_status
redundant_jumps_visitor::visit_leave(ir_loop *ir)
{
/* If the last instruction of a loop body is a 'continue', remove it.
*/
ir_instruction *const last =
(ir_instruction *) ir->body_instructions.get_tail();
if (last && (last->ir_type == ir_type_loop_jump)
&& (((ir_loop_jump *) last)->mode == ir_loop_jump::jump_continue)) {
last->remove();
this->progress = true;
}
return visit_continue;
}
bool
optimize_redundant_jumps(exec_list *instructions)
{
redundant_jumps_visitor v;
v.run(instructions);
return v.progress;
}
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