[PowerPC] Add global named register support

Support for the intrinsics that read from and write to global named registers
is added for r1, r2 and r13 (depending on the subtarget).

llvm-svn: 208509
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index f05f5dd..98bdf26 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -398,6 +398,8 @@
 
     SDValue PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const override;
 
+    unsigned getRegisterByName(const char* RegName, EVT VT) const override;
+
     void computeMaskedBitsForTargetNode(const SDValue Op,
                                         APInt &KnownZero,
                                         APInt &KnownOne,