[Interpreter] Add support for parameter variables.

src/objects-inl.h

Index: src/objects-inl.h
diff --git a/src/objects-inl.h b/src/objects-inl.h
index f1309ece199a5d5d2556506cf96d7bddb03cb135..d335ec4439a9c5f752737553d3b4b78ec81f0164 100644
--- a/src/objects-inl.h
+++ b/src/objects-inl.h
@@ -4052,6 +4052,18 @@ int BytecodeArray::frame_size() const {
 }
 
 
+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;
 }