125 lines
3.6 KiB
C++
125 lines
3.6 KiB
C++
/*
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* Copyright © 2010 Intel Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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* DEALINGS IN THE SOFTWARE.
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*/
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/**
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* \file opt_redundant_jumps.cpp
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* Remove certain types of redundant jumps
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*/
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#include "ir.h"
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namespace {
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class redundant_jumps_visitor : public ir_hierarchical_visitor {
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public:
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redundant_jumps_visitor()
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{
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this->progress = false;
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}
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virtual ir_visitor_status visit_leave(ir_if *);
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virtual ir_visitor_status visit_leave(ir_loop *);
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virtual ir_visitor_status visit_enter(ir_assignment *);
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bool progress;
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};
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} /* unnamed namespace */
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/* We only care about the top level instructions, so don't descend
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* into expressions.
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*/
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ir_visitor_status
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redundant_jumps_visitor::visit_enter(ir_assignment *)
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{
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return visit_continue_with_parent;
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}
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ir_visitor_status
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redundant_jumps_visitor::visit_leave(ir_if *ir)
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{
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/* If the last instruction in both branches is a 'break' or a 'continue',
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* pull it out of the branches and insert it after the if-statment. Note
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* that both must be the same type (either 'break' or 'continue').
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*/
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ir_instruction *const last_then =
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(ir_instruction *) ir->then_instructions.get_tail();
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ir_instruction *const last_else =
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(ir_instruction *) ir->else_instructions.get_tail();
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if ((last_then == NULL) || (last_else == NULL))
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return visit_continue;
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if ((last_then->ir_type != ir_type_loop_jump)
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|| (last_else->ir_type != ir_type_loop_jump))
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return visit_continue;
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ir_loop_jump *const then_jump = (ir_loop_jump *) last_then;
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ir_loop_jump *const else_jump = (ir_loop_jump *) last_else;
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if (then_jump->mode != else_jump->mode)
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return visit_continue;
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then_jump->remove();
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else_jump->remove();
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this->progress = true;
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ir->insert_after(then_jump);
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/* If both branchs of the if-statement are now empty, remove the
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* if-statement.
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*/
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if (ir->then_instructions.is_empty() && ir->else_instructions.is_empty())
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ir->remove();
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return visit_continue;
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}
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ir_visitor_status
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redundant_jumps_visitor::visit_leave(ir_loop *ir)
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{
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/* If the last instruction of a loop body is a 'continue', remove it.
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*/
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ir_instruction *const last =
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(ir_instruction *) ir->body_instructions.get_tail();
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if (last && (last->ir_type == ir_type_loop_jump)
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&& (((ir_loop_jump *) last)->mode == ir_loop_jump::jump_continue)) {
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last->remove();
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this->progress = true;
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}
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return visit_continue;
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}
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bool
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optimize_redundant_jumps(exec_list *instructions)
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{
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redundant_jumps_visitor v;
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v.run(instructions);
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return v.progress;
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}
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