LibJS: Remove redundant Store op

If the property for GetByValue in Generator::load_from_reference is a calculated value this would be stored in an allocated register and returned from the function. Not all callers want this information however, so now only give it out when asked for. Reduced the instruction count for Kraken/ai-astar.js function "neighbours" from 214 to 192.
tbhaxor · Nov 8, 2023 · bb9230b · bb9230b
1 parent 13726fd
commit bb9230b
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Showing 3 changed files with 21 additions and 12 deletions.
diff --git a/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp b/Userland/Libraries/LibJS/Bytecode/ASTCodegen.cpp
@@ -525,7 +525,7 @@ Bytecode::CodeGenerationErrorOr<void> AssignmentExpression::generate_bytecode(By
     VERIFY(m_lhs.has<NonnullRefPtr<Expression const>>());
     auto& lhs = m_lhs.get<NonnullRefPtr<Expression const>>();
 
-    auto reference_registers = TRY(generator.emit_load_from_reference(lhs));
+    auto reference_registers = TRY(generator.emit_load_from_reference(lhs, Bytecode::Generator::CollectRegisters::Yes));
 
     Bytecode::BasicBlock* rhs_block_ptr { nullptr };
     Bytecode::BasicBlock* end_block_ptr { nullptr };
@@ -1057,7 +1057,7 @@ Bytecode::CodeGenerationErrorOr<void> ArrayExpression::generate_bytecode(Bytecod
 Bytecode::CodeGenerationErrorOr<void> MemberExpression::generate_bytecode(Bytecode::Generator& generator) const
 {
     Bytecode::Generator::SourceLocationScope scope(generator, *this);
-    (void)TRY(generator.emit_load_from_reference(*this));
+    (void)TRY(generator.emit_load_from_reference(*this, Bytecode::Generator::CollectRegisters::No));
     return {};
 }
 
@@ -2258,7 +2258,7 @@ Bytecode::CodeGenerationErrorOr<void> TaggedTemplateLiteral::generate_bytecode(B
 Bytecode::CodeGenerationErrorOr<void> UpdateExpression::generate_bytecode(Bytecode::Generator& generator) const
 {
     Bytecode::Generator::SourceLocationScope scope(generator, *this);
-    auto reference_registers = TRY(generator.emit_load_from_reference(*m_argument));
+    auto reference_registers = TRY(generator.emit_load_from_reference(*m_argument, Bytecode::Generator::CollectRegisters::Yes));
 
     Optional<Bytecode::Register> previous_value_for_postfix_reg;
     if (!m_prefixed) {

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.cpp b/Userland/Libraries/LibJS/Bytecode/Generator.cpp
@@ -205,7 +205,7 @@ CodeGenerationErrorOr<Generator::ReferenceRegisters> Generator::emit_super_refer
     };
 }
 
-CodeGenerationErrorOr<Optional<Generator::ReferenceRegisters>> Generator::emit_load_from_reference(JS::ASTNode const& node)
+CodeGenerationErrorOr<Optional<Generator::ReferenceRegisters>> Generator::emit_load_from_reference(JS::ASTNode const& node, CollectRegisters collect_registers)
 {
     if (is<Identifier>(node)) {
         auto& identifier = static_cast<Identifier const&>(node);
@@ -238,15 +238,20 @@ CodeGenerationErrorOr<Optional<Generator::ReferenceRegisters>> Generator::emit_l
                 emit<Bytecode::Op::Store>(object_reg);
 
                 TRY(expression.property().generate_bytecode(*this));
-                auto property_reg = allocate_register();
-                emit<Bytecode::Op::Store>(property_reg);
+                Optional<Register> property_reg {};
+                if (collect_registers == CollectRegisters::Yes) {
+                    property_reg = allocate_register();
+                    emit<Bytecode::Op::Store>(property_reg.value());
+                }
 
                 emit<Bytecode::Op::GetByValue>(object_reg);
-                return ReferenceRegisters {
-                    .base = object_reg,
-                    .referenced_name = property_reg,
-                    .this_value = object_reg,
-                };
+                if (collect_registers == CollectRegisters::Yes)
+                    return ReferenceRegisters {
+                        .base = object_reg,
+                        .referenced_name = property_reg.value(),
+                        .this_value = object_reg,
+                    };
+                return Optional<ReferenceRegisters> {};
             } else if (expression.property().is_identifier()) {
                 auto identifier_table_ref = intern_identifier(verify_cast<Identifier>(expression.property()).string());
                 emit_get_by_id(identifier_table_ref);

diff --git a/Userland/Libraries/LibJS/Bytecode/Generator.h b/Userland/Libraries/LibJS/Bytecode/Generator.h
@@ -98,7 +98,11 @@ class Generator {
         Register this_value;                // [[ThisValue]]
     };
 
-    CodeGenerationErrorOr<Optional<ReferenceRegisters>> emit_load_from_reference(JS::ASTNode const&);
+    enum class CollectRegisters {
+        Yes,
+        No
+    };
+    CodeGenerationErrorOr<Optional<ReferenceRegisters>> emit_load_from_reference(JS::ASTNode const&, CollectRegisters);
     CodeGenerationErrorOr<void> emit_store_to_reference(JS::ASTNode const&);
     CodeGenerationErrorOr<void> emit_store_to_reference(ReferenceRegisters const&);
     CodeGenerationErrorOr<void> emit_delete_reference(JS::ASTNode const&);