[Power9] Implement new vsx instructions: load, store instructions for vector and scalar

We follow the comments mentioned in http://reviews.llvm.org/D16842#344378 to
implement this new patch.

This patch implements the following vsx instructions:

Vector load/store:
lxv lxvx lxvb16x lxvl lxvll lxvh8x lxvwsx
stxv stxvb16x stxvh8x stxvl stxvll stxvx
Scalar load/store:
lxsd lxssp lxsibzx lxsihzx
stxsd stxssp stxsibx stxsihx
21 instructions

Phabricator: http://reviews.llvm.org/D16919
llvm-svn: 262906
diff --git a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
index a0b15d5..032112c 100644
--- a/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
+++ b/llvm/lib/Target/PowerPC/AsmParser/PPCAsmParser.cpp
@@ -492,6 +492,9 @@
   bool isS16ImmX4() const { return Kind == Expression ||
                                    (Kind == Immediate && isInt<16>(getImm()) &&
                                     (getImm() & 3) == 0); }
+  bool isS16ImmX16() const { return Kind == Expression ||
+                                    (Kind == Immediate && isInt<16>(getImm()) &&
+                                     (getImm() & 15) == 0); }
   bool isS17Imm() const {
     switch (Kind) {
       case Expression: