Add isExtractSubreg property.

This patch adds a new property: isExtractSubreg and the related target hooks:
TargetIntrInfo::getExtractSubregInputs and
TargetInstrInfo::getExtractSubregLikeInputs to specify that a target specific
instruction is a (kind of) EXTRACT_SUBREG.

The approach is similar to r215394.

<rdar://problem/12702965>

llvm-svn: 216130
diff --git a/llvm/utils/TableGen/CodeGenInstruction.cpp b/llvm/utils/TableGen/CodeGenInstruction.cpp
index 179858d..20edef5 100644
--- a/llvm/utils/TableGen/CodeGenInstruction.cpp
+++ b/llvm/utils/TableGen/CodeGenInstruction.cpp
@@ -315,6 +315,7 @@
   hasCtrlDep   = R->getValueAsBit("hasCtrlDep");
   isNotDuplicable = R->getValueAsBit("isNotDuplicable");
   isRegSequence = R->getValueAsBit("isRegSequence");
+  isExtractSubreg = R->getValueAsBit("isExtractSubreg");
 
   bool Unset;
   mayLoad      = R->getValueAsBitOrUnset("mayLoad", Unset);