mirror of
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107 lines
3.2 KiB
C++
107 lines
3.2 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_if_simplification.cpp
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*
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* Moves constant branches of if statements out to the surrounding
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* instruction stream.
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*/
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#include "ir.h"
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namespace {
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class ir_if_simplification_visitor : public ir_hierarchical_visitor {
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public:
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ir_if_simplification_visitor()
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{
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this->made_progress = false;
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}
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ir_visitor_status visit_leave(ir_if *);
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ir_visitor_status visit_enter(ir_assignment *);
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bool made_progress;
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};
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} /* unnamed namespace */
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/* We only care about the top level "if" instructions, so don't
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* descend into expressions.
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*/
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ir_visitor_status
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ir_if_simplification_visitor::visit_enter(ir_assignment *ir)
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{
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(void) ir;
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return visit_continue_with_parent;
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}
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bool
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do_if_simplification(exec_list *instructions)
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{
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ir_if_simplification_visitor v;
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v.run(instructions);
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return v.made_progress;
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}
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ir_visitor_status
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ir_if_simplification_visitor::visit_leave(ir_if *ir)
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{
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/* If the if statement has nothing on either side, remove it. */
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if (ir->then_instructions.is_empty() &&
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ir->else_instructions.is_empty()) {
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ir->remove();
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this->made_progress = true;
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return visit_continue;
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}
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/* FINISHME: Ideally there would be a way to note that the condition results
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* FINISHME: in a constant before processing both of the other subtrees.
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* FINISHME: This can probably be done with some flags, but it would take
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* FINISHME: some work to get right.
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*/
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ir_constant *condition_constant = ir->condition->constant_expression_value();
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if (condition_constant) {
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/* Move the contents of the one branch of the conditional
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* that matters out.
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*/
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if (condition_constant->value.b[0]) {
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foreach_iter(exec_list_iterator, then_iter, ir->then_instructions) {
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ir_instruction *then_ir = (ir_instruction *)then_iter.get();
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ir->insert_before(then_ir);
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}
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} else {
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foreach_iter(exec_list_iterator, else_iter, ir->else_instructions) {
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ir_instruction *else_ir = (ir_instruction *)else_iter.get();
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ir->insert_before(else_ir);
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}
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}
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ir->remove();
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this->made_progress = true;
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}
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return visit_continue;
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}
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