[Interpreter] Add support for parameter variables.

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 4034 matching lines @@
   DCHECK(IsAligned(frame_size, static_cast<unsigned>(kPointerSize)));
   WRITE_INT_FIELD(this, kFrameSizeOffset, frame_size);
 }
 
 
 int BytecodeArray::frame_size() const {
   return READ_INT_FIELD(this, kFrameSizeOffset);
 }
 
 
+void BytecodeArray::set_parameter_count(int number_of_parameters) {
+  DCHECK_GE(number_of_parameters, 0);
+  WRITE_INT_FIELD(this, kParameterSizeOffset,
+                  (number_of_parameters << kPointerSizeLog2));
+}
+
+
+int BytecodeArray::parameter_count() const {
+  return READ_INT_FIELD(this, kParameterSizeOffset) >> kPointerSizeLog2;

[Michael Starzinger, 2015/08/26 13:44:36]

Can we leave a short one-liner comment here that the "count" is stored as a
"size" so that generated code can use it directly?

Also is this "trick" really worth it? Don't most of the architectures should
have instructions with the appropriate scalling factors? Not an expert on this,
so I don't mind either way.

[rmcilroy, 2015/08/27 09:54:39]

Done.
I don't think they are always available AFAIKT. E.g., on Arm you can scale and
immediate add or scale the offset for an ldr, but you can't scale a reg+reg add
or the result of an ldr which is what would be needed here.

+}
+
+
 Address BytecodeArray::GetFirstBytecodeAddress() {
   return reinterpret_cast<Address>(this) - kHeapObjectTag + kHeaderSize;
 }
 
 
 int BytecodeArray::BytecodeArraySize() { return SizeFor(this->length()); }
 
 
 ACCESSORS(FixedTypedArrayBase, base_pointer, Object, kBasePointerOffset)
 
@@ skipping 3787 matching lines @@
 #undef READ_INT64_FIELD
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_