Add the PPC popcntw instruction

The popcntw instruction is available whenever the popcntd instruction is
available, and performs a separate popcnt on the lower and upper 32-bits.
Ignoring the high-order count, this can be used for the 32-bit input case
(saving on the explicit zero extension otherwise required to use popcntd).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178470 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/PowerPC/PPCISelLowering.cpp b/lib/Target/PowerPC/PPCISelLowering.cpp
index a0e8e13..89b42af 100644
--- a/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -190,7 +190,7 @@
   setOperationAction(ISD::CTLZ_ZERO_UNDEF, MVT::i64, Expand);
 
   if (Subtarget->hasPOPCNTD()) {
-    setOperationAction(ISD::CTPOP, MVT::i32  , Promote);
+    setOperationAction(ISD::CTPOP, MVT::i32  , Legal);
     setOperationAction(ISD::CTPOP, MVT::i64  , Legal);
   } else {
     setOperationAction(ISD::CTPOP, MVT::i32  , Expand);