Add explicit keywords.

llvm-svn: 48801
diff --git a/llvm/lib/Target/PowerPC/PPCInstrInfo.h b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
index e659129..d74399d 100644
--- a/llvm/lib/Target/PowerPC/PPCInstrInfo.h
+++ b/llvm/lib/Target/PowerPC/PPCInstrInfo.h
@@ -72,7 +72,7 @@
                             const TargetRegisterClass *RC,
                             SmallVectorImpl<MachineInstr*> &NewMIs) const;
 public:
-  PPCInstrInfo(PPCTargetMachine &TM);
+  explicit PPCInstrInfo(PPCTargetMachine &TM);
 
   /// getRegisterInfo - TargetInstrInfo is a superset of MRegister info.  As
   /// such, whenever a client has an instance of instruction info, it should