[PPC] Implement vmrgew and vmrgow instructions

This patch adds support for the vector merge even word and vector merge odd word
instructions introduced in POWER8.

Phabricator review: http://reviews.llvm.org/D10704

llvm-svn: 240650
diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.h b/llvm/lib/Target/PowerPC/PPCISelLowering.h
index 7fd3f9c..02242b5 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.h
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.h
@@ -382,6 +382,11 @@
     bool isVMRGHShuffleMask(ShuffleVectorSDNode *N, unsigned UnitSize,
                             unsigned ShuffleKind, SelectionDAG &DAG);
 
+    /// isVMRGEOShuffleMask - Return true if this is a shuffle mask suitable for
+    /// a VMRGEW or VMRGOW instruction
+    bool isVMRGEOShuffleMask(ShuffleVectorSDNode *N, bool CheckEven,
+                             unsigned ShuffleKind, SelectionDAG &DAG);
+  
     /// isVSLDOIShuffleMask - If this is a vsldoi shuffle mask, return the
     /// shift amount, otherwise return -1.
     int isVSLDOIShuffleMask(SDNode *N, unsigned ShuffleKind,