mirror of
https://github.com/RGBCube/serenity
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97 lines
2.8 KiB
C++
97 lines
2.8 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 <AK/TypeCasts.h>
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#include "AST/AST.h"
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#include "Compiler/Passes/IfBranchMergingPass.h"
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namespace JSSpecCompiler {
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RecursionDecision IfBranchMergingPass::on_entry(Tree tree)
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{
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if (auto list = as<TreeList>(tree); list) {
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Vector<Tree> result;
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Vector<Tree> unmerged_branches;
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auto merge_if_needed = [&] {
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if (!unmerged_branches.is_empty()) {
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result.append(merge_branches(unmerged_branches));
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unmerged_branches.clear();
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}
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};
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for (auto const& node : list->m_trees) {
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if (is<IfBranch>(node.ptr())) {
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merge_if_needed();
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unmerged_branches.append(node);
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} else if (is<ElseIfBranch>(node.ptr())) {
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unmerged_branches.append(node);
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} else {
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merge_if_needed();
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result.append(node);
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}
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}
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merge_if_needed();
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list->m_trees = move(result);
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}
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return RecursionDecision::Recurse;
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}
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Tree IfBranchMergingPass::merge_branches(Vector<Tree> const& unmerged_branches)
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{
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static const Tree error = make_ref_counted<ErrorNode>("Cannot make sense of if-elseif-else chain"sv);
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VERIFY(unmerged_branches.size() >= 1);
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Vector<Tree> conditions;
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Vector<Tree> branches;
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NullableTree else_branch;
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if (auto if_branch = as<IfBranch>(unmerged_branches[0]); if_branch) {
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conditions.append(if_branch->m_condition);
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branches.append(if_branch->m_branch);
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} else {
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return error;
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}
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for (size_t i = 1; i < unmerged_branches.size(); ++i) {
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auto branch = as<ElseIfBranch>(unmerged_branches[i]);
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if (!branch)
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return error;
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if (!branch->m_condition) {
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// There might be situation like:
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// 1. If <condition>, then
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// ...
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// 2. Else,
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// a. If <condition>, then
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// ...
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// 3. Else,
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// ...
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auto substep_list = as<TreeList>(branch->m_branch);
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if (substep_list && substep_list->m_trees.size() == 1) {
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if (auto nested_if = as<IfBranch>(substep_list->m_trees[0]); nested_if)
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branch = make_ref_counted<ElseIfBranch>(nested_if->m_condition, nested_if->m_branch);
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}
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}
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if (branch->m_condition) {
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conditions.append(branch->m_condition.release_nonnull());
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branches.append(branch->m_branch);
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} else {
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if (i + 1 != unmerged_branches.size())
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return error;
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else_branch = branch->m_branch;
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}
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}
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return make_ref_counted<IfElseIfChain>(move(conditions), move(branches), else_branch);
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}
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}
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