LibJS: Emit GetById instead of GetByValue when key is string literal

Basically convert o["foo"] into o.foo when emitting bytecode. These are
effectively the same thing, and the latter format opts into using an
inline cache for the property lookups.

Libraries/LibJS/Bytecode/ASTCodegen.cpp

@@ -1349,7 +1349,7 @@ static Bytecode::CodeGenerationErrorOr<void> generate_object_binding_pattern_byt
                 excluded_property_names.append(excluded_name);
             }
 
-            generator.emit<Bytecode::Op::GetByValue>(value, object, property_name);
+            generator.emit_get_by_value(value, object, property_name);
         }
 
         if (initializer) {
@@ -1683,7 +1683,7 @@ static Bytecode::CodeGenerationErrorOr<BaseAndValue> get_base_and_value_from_mem
         if (computed_property.has_value()) {
             // 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
             // FIXME: This does ToPropertyKey out of order, which is observable by Symbol.toPrimitive!
-            generator.emit<Bytecode::Op::GetByValueWithThis>(value, super_base, *computed_property, this_value);
+            generator.emit_get_by_value_with_this(value, super_base, *computed_property, this_value);
         } else {
             // 3. Let propertyKey be StringValue of IdentifierName.
             auto identifier_table_ref = generator.intern_identifier(as<Identifier>(member_expression.property()).string());
@@ -1697,7 +1697,7 @@ static Bytecode::CodeGenerationErrorOr<BaseAndValue> get_base_and_value_from_mem
     auto value = generator.allocate_register();
     if (member_expression.is_computed()) {
         auto property = TRY(member_expression.property().generate_bytecode(generator)).value();
-        generator.emit<Bytecode::Op::GetByValue>(value, base, property);
+        generator.emit_get_by_value(value, base, property);
     } else if (is<PrivateIdentifier>(member_expression.property())) {
         generator.emit<Bytecode::Op::GetPrivateById>(
             value,
@@ -3482,7 +3482,7 @@ static Bytecode::CodeGenerationErrorOr<void> generate_optional_chain(Bytecode::G
             [&](OptionalChain::ComputedReference const& ref) -> Bytecode::CodeGenerationErrorOr<void> {
                 generator.emit_mov(current_base, current_value);
                 auto property = TRY(ref.expression->generate_bytecode(generator)).value();
-                generator.emit<Bytecode::Op::GetByValue>(current_value, current_value, property);
+                generator.emit_get_by_value(current_value, current_value, property);
                 return {};
             },
             [&](OptionalChain::MemberReference const& ref) -> Bytecode::CodeGenerationErrorOr<void> {

Libraries/LibJS/Bytecode/Generator.cpp

@@ -687,7 +687,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
         if (super_reference.referenced_name.has_value()) {
             // 5. Let propertyKey be ? ToPropertyKey(propertyNameValue).
             // FIXME: This does ToPropertyKey out of order, which is observable by Symbol.toPrimitive!
-            emit<Bytecode::Op::GetByValueWithThis>(dst, *super_reference.base, *super_reference.referenced_name, *super_reference.this_value);
+            emit_get_by_value_with_this(dst, *super_reference.base, *super_reference.referenced_name, *super_reference.this_value);
         } else {
             // 3. Let propertyKey be StringValue of IdentifierName.
             auto identifier_table_ref = intern_identifier(as<Identifier>(expression.property()).string());
@@ -706,7 +706,7 @@ CodeGenerationErrorOr<Generator::ReferenceOperands> Generator::emit_load_from_re
         auto saved_property = allocate_register();
         emit<Bytecode::Op::Mov>(saved_property, property);
         auto dst = preferred_dst.has_value() ? preferred_dst.value() : allocate_register();
-        emit<Bytecode::Op::GetByValue>(dst, base, property, move(base_identifier));
+        emit_get_by_value(dst, base, property, move(base_identifier));
         return ReferenceOperands {
             .base = base,
             .referenced_name = saved_property,
@@ -1122,6 +1122,30 @@ void Generator::emit_get_by_id_with_this(ScopedOperand dst, ScopedOperand base,
     emit<Op::GetByIdWithThis>(dst, base, id, this_value, m_next_property_lookup_cache++);
 }
 
+void Generator::emit_get_by_value(ScopedOperand dst, ScopedOperand base, ScopedOperand property, Optional<IdentifierTableIndex> base_identifier)
+{
+    if (property.operand().is_constant() && get_constant(property).is_string()) {
+        auto property_key = MUST(get_constant(property).to_property_key(vm()));
+        if (property_key.is_string()) {
+            emit_get_by_id(dst, base, intern_identifier(property_key.as_string()), base_identifier);
+            return;
+        }
+    }
+    emit<Op::GetByValue>(dst, base, property, base_identifier);
+}
+
+void Generator::emit_get_by_value_with_this(ScopedOperand dst, ScopedOperand base, ScopedOperand property, ScopedOperand this_value)
+{
+    if (property.operand().is_constant() && get_constant(property).is_string()) {
+        auto property_key = MUST(get_constant(property).to_property_key(vm()));
+        if (property_key.is_string()) {
+            emit_get_by_id_with_this(dst, base, intern_identifier(property_key.as_string()), this_value);
+            return;
+        }
+    }
+    emit<Op::GetByValueWithThis>(dst, base, property, this_value);
+}
+
 void Generator::emit_iterator_value(ScopedOperand dst, ScopedOperand result)
 {
     emit_get_by_id(dst, result, intern_identifier("value"_fly_string));

Libraries/LibJS/Bytecode/Generator.h

@@ -324,6 +324,9 @@ public:
 
     void emit_get_by_id_with_this(ScopedOperand dst, ScopedOperand base, IdentifierTableIndex, ScopedOperand this_value);
 
+    void emit_get_by_value(ScopedOperand dst, ScopedOperand base, ScopedOperand property, Optional<IdentifierTableIndex> base_identifier = {});
+    void emit_get_by_value_with_this(ScopedOperand dst, ScopedOperand base, ScopedOperand property, ScopedOperand this_value);
+
     void emit_iterator_value(ScopedOperand dst, ScopedOperand result);
     void emit_iterator_complete(ScopedOperand dst, ScopedOperand result);