PPC: [stubs] Optimize LoadGlobalViaContextStub and StoreGlobalViaContextStub.

src/ppc/macro-assembler-ppc.h

Index: src/ppc/macro-assembler-ppc.h
diff --git a/src/ppc/macro-assembler-ppc.h b/src/ppc/macro-assembler-ppc.h
index e830be9111f2fd8c78ebecc2251149ae5e736edc..09a42ab7a8b0420a3b4df6ac5fb02f06613ea521 100644
--- a/src/ppc/macro-assembler-ppc.h
+++ b/src/ppc/macro-assembler-ppc.h
@@ -213,7 +213,7 @@ class MacroAssembler : public Assembler {
   // |object| is the object being stored into, |value| is the object being
   // stored.  value and scratch registers are clobbered by the operation.
   // The offset is the offset from the start of the object, not the offset from
-  // the tagged HeapObject pointer.  For use with FieldOperand(reg, off).
+  // the tagged HeapObject pointer.  For use with FieldMemOperand(reg, off).
   void RecordWriteField(
       Register object, int offset, Register value, Register scratch,
       LinkRegisterStatus lr_status, SaveFPRegsMode save_fp,
@@ -1549,7 +1549,7 @@ class CodePatcher {
 // -----------------------------------------------------------------------------
 // Static helper functions.
 
-inline MemOperand ContextOperand(Register context, int index) {
+inline MemOperand ContextOperand(Register context, int index = 0) {
   return MemOperand(context, Context::SlotOffset(index));
 }