[Interpreter] Adds support for DeleteLookupSlot to Interpreter.

src/interpreter/bytecode-generator.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/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/control-flow-builders.h"
 #include "src/objects.h"
@@ skipping 1763 matching lines @@
         // Deleting local var/let/const, context variables, and arguments
         // does not have any effect.
         if (variable->HasThisName(isolate())) {
           builder()->LoadTrue();
         } else {
           builder()->LoadFalse();
         }
         break;
       }
       case VariableLocation::LOOKUP: {
-        UNIMPLEMENTED();
+        builder()->LoadLiteral(variable->name()).DeleteLookupSlot();

[mythria, 2015/12/22 11:22:55]

I load the name to the accumulator instead of passing it to the bytecode as an
operand to be inline with other variants of Delete operation. We could pass it
as an explicit operand to reduce the size. I think it is not a frequent case, so
may not save much. We would also need an additional bytecode for the wide
variant if we pass name as an operand.

[oth, 2015/12/22 16:00:56]

Yes, this seems reasonable. We should have more data on bytecode frequencies
next quarter to guide these issues.

         break;
       }
       default:
         UNREACHABLE();
     }
   } else {
     // Delete of an unresolvable reference returns true.
     VisitForEffect(expr->expression());
     builder()->LoadTrue();
   }
@@ skipping 412 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8