Set NumSignBits to 1 if KnownZero/KnownOne are being zero extended. In theory it

is possible to do better if the high bit is set in either KnownZero/KnownOne, but
in practice NumSignBits is always 1 when we are zero extending because nothing
is known about that register.

llvm-svn: 126465

llvm/lib/CodeGen/SelectionDAG/FunctionLoweringInfo.cpp

@@ -270,6 +270,7 @@ FunctionLoweringInfo::GetLiveOutRegInfo(unsigned Reg, unsigned BitWidth) {
     return NULL;
 
   if (BitWidth > LOI->KnownZero.getBitWidth()) {
+    LOI->NumSignBits = 1;
     LOI->KnownZero = LOI->KnownZero.zextOrTrunc(BitWidth);
     LOI->KnownOne = LOI->KnownOne.zextOrTrunc(BitWidth);
   }