From 67e07fa4e2150a8daeb52b9ec10dbf5f0a92cbcf Mon Sep 17 00:00:00 2001
From: Dan Klishch <danilklishch@gmail.com>
Date: Sat, 19 Aug 2023 14:14:57 -0400
Subject: [PATCH] JSSpecCompiler: Introduce ControlFlowOperator nodes

---
 .../CodeGenerators/JSSpecCompiler/AST/AST.h   | 49 +++++++++++++++++++
 .../JSSpecCompiler/AST/ASTPrinting.cpp        | 17 +++++++
 .../CodeGenerators/JSSpecCompiler/Forward.h   |  9 ++++
 3 files changed, 75 insertions(+)

diff --git a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h
index a4111326b6c..2f3eac95ceb 100644
--- a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h
+++ b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/AST.h
@@ -80,6 +80,7 @@ protected:
 // ```.
 class Statement : public Node { };
 class Expression : public Node { };
+class ControlFlowOperator : public Statement { };
 
 class ErrorNode : public Expression {
 public:
@@ -96,6 +97,52 @@ protected:
 
 inline Tree const error_tree = make_ref_counted<ErrorNode>();
 
+class ControlFlowFunctionReturn : public ControlFlowOperator {
+public:
+    ControlFlowFunctionReturn(VariableRef return_value)
+        : m_return_value(move(return_value))
+    {
+    }
+
+    VariableRef m_return_value;
+
+protected:
+    void dump_tree(StringBuilder& builder) override;
+};
+
+class ControlFlowJump : public ControlFlowOperator {
+public:
+    ControlFlowJump(BasicBlockRef block)
+        : m_block(block)
+    {
+    }
+
+    BasicBlockRef m_block;
+
+protected:
+    void dump_tree(StringBuilder& builder) override;
+};
+
+// This should be invalid enough to crash program on use.
+inline NonnullRefPtr<ControlFlowOperator> const invalid_continuation = make_ref_counted<ControlFlowJump>(nullptr);
+
+class ControlFlowBranch : public ControlFlowOperator {
+public:
+    ControlFlowBranch(Tree condition, BasicBlockRef then, BasicBlockRef else_)
+        : m_condition(move(condition))
+        , m_then(then)
+        , m_else(else_)
+    {
+    }
+
+    Tree m_condition;
+    BasicBlockRef m_then;
+    BasicBlockRef m_else;
+
+protected:
+    void dump_tree(StringBuilder& builder) override;
+};
+
 class MathematicalConstant : public Expression {
 public:
     MathematicalConstant(i64 number)
@@ -249,6 +296,8 @@ protected:
     void dump_tree(StringBuilder& builder) override;
 };
 
+// Although assert might seems a good candidate for ControlFlowOperator, we are not interested in
+// tracking control flow after a failed assertion.
 class AssertExpression : public Expression {
 public:
     AssertExpression(Tree condition)
diff --git a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp
index bf324563c6a..fd963a82a62 100644
--- a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp
+++ b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/AST/ASTPrinting.cpp
@@ -34,6 +34,23 @@ void ErrorNode::dump_tree(StringBuilder& builder)
     dump_node(builder, "Error \"{}\"", m_error);
 }
 
+void ControlFlowFunctionReturn::dump_tree(StringBuilder& builder)
+{
+    dump_node(builder, "ControlFlowFunctionReturn");
+    m_return_value->format_tree(builder);
+}
+
+void ControlFlowJump::dump_tree(StringBuilder& builder)
+{
+    dump_node(builder, "ControlFlowJump jump={:p}", m_block);
+}
+
+void ControlFlowBranch::dump_tree(StringBuilder& builder)
+{
+    dump_node(builder, "ControlFlowBranch true={:p} false={:p}", m_then, m_else);
+    m_condition->format_tree(builder);
+}
+
 void MathematicalConstant::dump_tree(StringBuilder& builder)
 {
     dump_node(builder, "MathematicalConstant {}", m_number);
diff --git a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Forward.h b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Forward.h
index b56b6699e18..1d7d582093b 100644
--- a/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Forward.h
+++ b/Meta/Lagom/Tools/CodeGenerators/JSSpecCompiler/Forward.h
@@ -21,7 +21,11 @@ using Tree = NonnullRefPtr<Node>;
 class Statement;
 class Expression;
 class ErrorNode;
+class ControlFlowOperator;
 
+class ControlFlowFunctionReturn;
+class ControlFlowJump;
+class ControlFlowBranch;
 class MathematicalConstant;
 class StringLiteral;
 class BinaryOperation;
@@ -38,9 +42,14 @@ class RecordDirectListInitialization;
 class FunctionCall;
 class SlotName;
 class Variable;
+using VariableRef = NonnullRefPtr<Variable>;
 class FunctionPointer;
 using FunctionPointerRef = NonnullRefPtr<FunctionPointer>;
 
+// Compiler/ControlFlowGraph.h
+class BasicBlock;
+using BasicBlockRef = BasicBlock*;
+
 // Compiler/GenericASTPass.h
 class RecursiveASTVisitor;