Better codegen for '<expression> === void <literal>'.

src/x64/full-codegen-x64.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 3889 matching lines @@
     __ bind(&done);
 
     context()->Plug(rax);
   } else {
     // This expression cannot throw a reference error at the top level.
     VisitInCurrentContext(expr);
   }
 }
 
 
-bool FullCodeGenerator::TryLiteralCompare(Token::Value op,
-                                          Expression* left,
-                                          Expression* right,
-                                          Label* if_true,
-                                          Label* if_false,
-                                          Label* fall_through) {
-  if (op != Token::EQ && op != Token::EQ_STRICT) return false;
-
-  // Check for the pattern: typeof <expression> == <string literal>.
-  Literal* right_literal = right->AsLiteral();
-  if (right_literal == NULL) return false;
-  Handle<Object> right_literal_value = right_literal->handle();
-  if (!right_literal_value->IsString()) return false;
-  UnaryOperation* left_unary = left->AsUnaryOperation();
-  if (left_unary == NULL || left_unary->op() != Token::TYPEOF) return false;
-  Handle<String> check = Handle<String>::cast(right_literal_value);
-
+void FullCodeGenerator::EmitLiteralCompareTypeof(Expression* expr,
+                                                 Handle<String> check,
+                                                 Label* if_true,
+                                                 Label* if_false,
+                                                 Label* fall_through) {
   { AccumulatorValueContext context(this);
-    VisitForTypeofValue(left_unary->expression());
+    VisitForTypeofValue(expr);
   }
   PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
 
   if (check->Equals(isolate()->heap()->number_symbol())) {
     __ JumpIfSmi(rax, if_true);
     __ movq(rax, FieldOperand(rax, HeapObject::kMapOffset));
     __ CompareRoot(rax, Heap::kHeapNumberMapRootIndex);
     Split(equal, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->string_symbol())) {
     __ JumpIfSmi(rax, if_false);
@@ skipping 30 matching lines @@
     __ j(below, if_false);
     __ CmpInstanceType(rdx, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ j(above, if_false);
     // Check for undetectable objects => false.
     __ testb(FieldOperand(rdx, Map::kBitFieldOffset),
              Immediate(1 << Map::kIsUndetectable));
     Split(zero, if_true, if_false, fall_through);
   } else {
     if (if_false != fall_through) __ jmp(if_false);
   }
-
-  return true;
 }
 
 
+void FullCodeGenerator::EmitLiteralCompareUndefined(Expression* expr,
+                                                    Label* if_true,
+                                                    Label* if_false,
+                                                    Label* fall_through) {
+  VisitForAccumulatorValue(expr);
+  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
+
+  __ CompareRoot(rax, Heap::kUndefinedValueRootIndex);
+  Split(equal, if_true, if_false, fall_through);
+}
+
+
 void FullCodeGenerator::VisitCompareOperation(CompareOperation* expr) {
   Comment cmnt(masm_, "[ CompareOperation");
   SetSourcePosition(expr->position());
 
   // Always perform the comparison for its control flow.  Pack the result
   // into the expression's context after the comparison is performed.
   Label materialize_true, materialize_false;
   Label* if_true = NULL;
   Label* if_false = NULL;
   Label* fall_through = NULL;
   context()->PrepareTest(&materialize_true, &materialize_false,
                          &if_true, &if_false, &fall_through);
 
   // First we try a fast inlined version of the compare when one of
   // the operands is a literal.
-  Token::Value op = expr->op();
-  Expression* left = expr->left();
-  Expression* right = expr->right();
-  if (TryLiteralCompare(op, left, right, if_true, if_false, fall_through)) {
+  if (TryLiteralCompare(expr, if_true, if_false, fall_through)) {
     context()->Plug(if_true, if_false);
     return;
   }
 
+  Token::Value op = expr->op();
   VisitForStackValue(expr->left());
   switch (op) {
     case Token::IN:
       VisitForStackValue(expr->right());
       __ InvokeBuiltin(Builtins::IN, CALL_FUNCTION);
       PrepareForBailoutBeforeSplit(TOS_REG, false, NULL, NULL);
       __ CompareRoot(rax, Heap::kTrueValueRootIndex);
       Split(equal, if_true, if_false, fall_through);
       break;
 
@@ skipping 217 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_X64