Add direct moves to/from VSR and exploit them for FP/INT conversions

This patch corresponds to review:
http://reviews.llvm.org/D8928

It adds direct move instructions to/from VSX registers to GPR's. These are
exploited for FP <-> INT conversions.

llvm-svn: 234682
diff --git a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
index 71365af..f313b0a 100644
--- a/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
+++ b/llvm/lib/Target/PowerPC/PPCSubtarget.cpp
@@ -97,6 +97,7 @@
   HasICBT = false;
   HasInvariantFunctionDescriptors = false;
   HasPartwordAtomics = false;
+  HasDirectMove = false;
   IsQPXStackUnaligned = false;
   HasHTM = false;
 }