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https://github.com/RGBCube/serenity
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12072dbac5
It removes empty `BasicBlock`s with an unconditional jump continuation and then removes unreferenced blocks from the graph.
85 lines
2.3 KiB
C++
85 lines
2.3 KiB
C++
/*
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* Copyright (c) 2023, Dan Klishch <danilklishch@gmail.com>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include "Compiler/Passes/CFGSimplificationPass.h"
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#include "AST/AST.h"
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#include "Function.h"
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namespace JSSpecCompiler {
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void CFGSimplificationPass::process_function()
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{
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auto& graph = *m_function->m_cfg;
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m_replacement.clear();
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m_replacement.resize(graph.blocks_count());
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m_state.clear();
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m_state.resize(graph.blocks_count());
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for (auto const& block : graph.blocks) {
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m_replacement[block->m_index] = block;
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if (block->m_expressions.size() == 0)
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if (auto jump = as<ControlFlowJump>(block->m_continuation); jump)
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m_replacement[block->m_index] = jump->m_block;
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}
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for (size_t i = 0; i < graph.blocks_count(); ++i)
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if (m_state[i] == State::NotUsed)
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VERIFY(compute_replacement_block(i));
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// Fixing references
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graph.start_block = m_replacement[graph.start_block->m_index];
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for (auto const& block : graph.blocks) {
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for (auto* next_block : block->m_continuation->references())
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*next_block = m_replacement[(*next_block)->m_index];
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}
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// Removing unused nodes
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m_state.span().fill(State::NotUsed);
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compute_referenced_blocks(graph.start_block);
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size_t j = 0;
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for (size_t i = 0; i < graph.blocks_count(); ++i) {
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if (m_state[graph.blocks[i]->m_index] == State::Used) {
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graph.blocks[j] = graph.blocks[i];
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graph.blocks[j]->m_index = j;
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++j;
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}
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}
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graph.blocks.shrink(j);
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}
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bool CFGSimplificationPass::compute_replacement_block(size_t i)
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{
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if (m_state[i] == State::CurrentlyInside)
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return false;
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VERIFY(m_state[i] == State::NotUsed);
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m_state[i] = State::CurrentlyInside;
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size_t j = m_replacement[i]->m_index;
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if (i == j)
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return true;
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if (m_state[j] == State::NotUsed)
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if (!compute_replacement_block(j))
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return false;
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m_replacement[i] = m_replacement[j];
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m_state[i] = State::Used;
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return true;
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}
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void CFGSimplificationPass::compute_referenced_blocks(BasicBlockRef block)
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{
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if (m_state[block->m_index] == State::Used)
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return;
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m_state[block->m_index] = State::Used;
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for (auto* next : block->m_continuation->references())
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compute_referenced_blocks(*next);
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}
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}
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