From 1dc60b028f37366ec01b809a101224ada7dc82aa Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Mon, 25 Oct 2021 15:16:22 +0200
Subject: [PATCH] LibJS: Add BytecodeGenerator helpers for reference get/put

This allows code sharing between all AST nodes that want to get and/or
put through a reference.
---
 .../Libraries/LibJS/Bytecode/Generator.cpp    | 61 +++++++++++++++++++
 Userland/Libraries/LibJS/Bytecode/Generator.h |  3 +
 2 files changed, 64 insertions(+)

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.cpp b/Userland/Libraries/LibJS/Bytecode/Generator.cpp
index f6dfc923cc..21ee3822c8 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.cpp
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.cpp
@@ -93,4 +93,65 @@ void Generator::end_breakable_scope()
 {
     m_breakable_scopes.take_last();
 }
+
+void Generator::emit_load_from_reference(JS::ASTNode const& node)
+{
+    if (is<Identifier>(node)) {
+        auto& identifier = static_cast<Identifier const&>(node);
+        emit<Bytecode::Op::GetVariable>(intern_identifier(identifier.string()));
+        return;
+    }
+    if (is<MemberExpression>(node)) {
+        auto& expression = static_cast<MemberExpression const&>(node);
+        expression.object().generate_bytecode(*this);
+
+        auto object_reg = allocate_register();
+        emit<Bytecode::Op::Store>(object_reg);
+
+        if (expression.is_computed()) {
+            expression.property().generate_bytecode(*this);
+            emit<Bytecode::Op::GetByValue>(object_reg);
+        } else {
+            auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
+            emit<Bytecode::Op::GetById>(identifier_table_ref);
+        }
+        return;
+    }
+    VERIFY_NOT_REACHED();
+}
+
+void Generator::emit_store_to_reference(JS::ASTNode const& node)
+{
+    if (is<Identifier>(node)) {
+        auto& identifier = static_cast<Identifier const&>(node);
+        emit<Bytecode::Op::SetVariable>(intern_identifier(identifier.string()));
+        return;
+    }
+    if (is<MemberExpression>(node)) {
+        // NOTE: The value is in the accumulator, so we have to store that away first.
+        auto value_reg = allocate_register();
+        emit<Bytecode::Op::Store>(value_reg);
+
+        auto& expression = static_cast<MemberExpression const&>(node);
+        expression.object().generate_bytecode(*this);
+
+        auto object_reg = allocate_register();
+        emit<Bytecode::Op::Store>(object_reg);
+
+        if (expression.is_computed()) {
+            expression.property().generate_bytecode(*this);
+            auto property_reg = allocate_register();
+            emit<Bytecode::Op::Store>(property_reg);
+            emit<Bytecode::Op::Load>(value_reg);
+            emit<Bytecode::Op::PutByValue>(object_reg, property_reg);
+        } else {
+            emit<Bytecode::Op::Load>(value_reg);
+            auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
+            emit<Bytecode::Op::PutById>(object_reg, identifier_table_ref);
+        }
+        return;
+    }
+    VERIFY_NOT_REACHED();
+}
+
 }
diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.h b/Userland/Libraries/LibJS/Bytecode/Generator.h
index 48140c9998..669f05a327 100644
--- a/Userland/Libraries/LibJS/Bytecode/Generator.h
+++ b/Userland/Libraries/LibJS/Bytecode/Generator.h
@@ -70,6 +70,9 @@ public:
         return *static_cast<OpType*>(slot);
     }
 
+    void emit_load_from_reference(JS::ASTNode const&);
+    void emit_store_to_reference(JS::ASTNode const&);
+
     void begin_continuable_scope(Label continue_target);
     void end_continuable_scope();
     void begin_breakable_scope(Label breakable_target);