Add monomorphic CompareNilICs and Crankshaft support

src/ast.cc

 // Copyright 2012 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 52 matching lines @@
 bool Expression::IsStringLiteral() {
   return AsLiteral() != NULL && AsLiteral()->handle()->IsString();
 }
 
 
 bool Expression::IsNullLiteral() {
   return AsLiteral() != NULL && AsLiteral()->handle()->IsNull();
 }
 
 
+bool Expression::IsUndefinedLiteral() {
+  return AsLiteral() != NULL && AsLiteral()->handle()->IsUndefined();
+}
+
+
 VariableProxy::VariableProxy(Isolate* isolate, Variable* var)
     : Expression(isolate),
       name_(var->name()),
       var_(NULL),  // Will be set by the call to BindTo.
       is_this_(var->is_this()),
       is_trivial_(false),
       is_lvalue_(false),
       position_(RelocInfo::kNoPosition),
       interface_(var->interface()) {
   BindTo(var);
@@ skipping 262 matching lines @@
 
 
 static bool IsVoidOfLiteral(Expression* expr) {
   UnaryOperation* maybe_unary = expr->AsUnaryOperation();
   return maybe_unary != NULL &&
       maybe_unary->op() == Token::VOID &&
       maybe_unary->expression()->AsLiteral() != NULL;
 }
 
 
-// Check for the pattern: void <literal> equals <expression>
+// Check for the pattern: void <literal> equals <expression> or
+// undefined equals <expression>
 static bool MatchLiteralCompareUndefined(Expression* left,
                                          Token::Value op,
                                          Expression* right,
                                          Expression** expr) {
   if (IsVoidOfLiteral(left) && Token::IsEqualityOp(op)) {
     *expr = right;
     return true;
   }
+  if (left->IsUndefinedLiteral() && Token::IsEqualityOp(op)) {
+    *expr = right;
+    return true;
+  }
   return false;
 }
 
 
 bool CompareOperation::IsLiteralCompareUndefined(Expression** expr) {
   return MatchLiteralCompareUndefined(left_, op_, right_, expr) ||
       MatchLiteralCompareUndefined(right_, op_, left_, expr);
 }
 
 
@@ skipping 740 matching lines @@
     OS::SNPrintF(buffer, "%d", Smi::cast(*handle_)->value());
     str = arr;
   } else {
     str = DoubleToCString(handle_->Number(), buffer);
   }
   return FACTORY->NewStringFromAscii(CStrVector(str));
 }
 
 
 } }  // namespace v8::internal