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

src/arm/full-codegen-arm.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 3946 matching lines @@
     __ bind(&done);
 
     context()->Plug(r0);
   } 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(r0, if_true);
     __ ldr(r0, FieldMemOperand(r0, HeapObject::kMapOffset));
     __ LoadRoot(ip, Heap::kHeapNumberMapRootIndex);
     __ cmp(r0, ip);
     Split(eq, if_true, if_false, fall_through);
   } else if (check->Equals(isolate()->heap()->string_symbol())) {
@@ skipping 33 matching lines @@
     __ b(lt, if_false);
     __ CompareInstanceType(r0, r1, LAST_NONCALLABLE_SPEC_OBJECT_TYPE);
     __ b(gt, if_false);
     // Check for undetectable objects => false.
     __ ldrb(r1, FieldMemOperand(r0, Map::kBitFieldOffset));
     __ tst(r1, Operand(1 << Map::kIsUndetectable));
     Split(eq, 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) {
+  { AccumulatorValueContext context(this);

[fschneider, 2011/06/21 11:36:08]

This expression should not be visited in a typeof-context. Instead replace the
whole block with just

VisitForAccumulatorValue(expr)

The difference is in a typeof-expression there is no ReferenceError thrown if
the sub-expression is not defined.
Maybe the unit test should be extended to catch that case. 

[Steven, 2011/06/22 10:00:53]

Done.

+    VisitForTypeofValue(expr);
+  }
+  PrepareForBailoutBeforeSplit(TOS_REG, true, if_true, if_false);
+
+  __ CompareRoot(r0, Heap::kUndefinedValueRootIndex);
+  Split(eq, 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;
@@ skipping 247 matching lines @@
   __ mov(r1, Operand(r1, ASR, 1));  // Un-smi-tag value.
   __ add(pc, r1, Operand(masm_->CodeObject()));
 }
 
 
 #undef __
 
 } }  // namespace v8::internal
 
 #endif  // V8_TARGET_ARCH_ARM