[Interpreter] Adds support for const/let variables to interpreter.

src/compiler/bytecode-graph-builder.cc

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/bytecode-graph-builder.h"
 
 #include "src/compiler/bytecode-branch-analysis.h"
 #include "src/compiler/linkage.h"
 #include "src/compiler/operator-properties.h"
 #include "src/interpreter/bytecodes.h"
@@ skipping 1495 matching lines @@
 void BytecodeGraphBuilder::VisitJumpIfUndefinedConstantWide() {
   BuildJumpIfEqual(jsgraph()->UndefinedConstant());
 }
 
 void BytecodeGraphBuilder::VisitStackCheck() {
   FrameStateBeforeAndAfter states(this);
   Node* node = NewNode(javascript()->StackCheck());
   environment()->RecordAfterState(node, &states);
 }
 
+void BytecodeGraphBuilder::VisitJumpIfHole() {
+  BuildJumpIfEqual(jsgraph()->TheHoleConstant());
+}
+
+void BytecodeGraphBuilder::VisitJumpIfNotHole() {
+  Node* accumulator = environment()->LookupAccumulator();
+  Node* condition = NewNode(javascript()->StrictEqual(), accumulator,

[Michael Starzinger, 2016/02/08 11:54:08]

Can we use javascript()->StrictNotEqual() here? Or is there a particular reason
that wouldn't work in this case?

[mythria, 2016/02/08 13:22:33]

StrictNotEqual causes an assert fail here:
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/ic/x64/ic-x...

According to my understanding, parser changes all strictNotEqual to stictEqual
and LogicalNot. So we don't see a strictNotEqual.

[Michael Starzinger, 2016/02/08 13:57:45]

Acknowledged. Ah, yeah, I have seen this before. I am fine with keeping this as
is, maybe I'll follow up on this at some point.

+                            jsgraph()->TheHoleConstant());
+  Node* node =
+      NewNode(common()->Select(MachineRepresentation::kTagged), condition,
+              jsgraph()->FalseConstant(), jsgraph()->TrueConstant());
+  BuildConditionalJump(node);
+}
+
 void BytecodeGraphBuilder::VisitReturn() {
   Node* control =
       NewNode(common()->Return(), environment()->LookupAccumulator());
   MergeControlToLeaveFunction(control);
 }
 
 void BytecodeGraphBuilder::VisitDebugger() {
   FrameStateBeforeAndAfter states(this);
   Node* call =
       NewNode(javascript()->CallRuntime(Runtime::kHandleDebuggerStatement));
@@ skipping 305 matching lines @@
     // Phi does not exist yet, introduce one.
     value = NewPhi(inputs, value, control);
     value->ReplaceInput(inputs - 1, other);
   }
   return value;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8