Move variable local to where ita used. NFCI.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@301646 91177308-0d34-0410-b5e6-96231b3b80d8

Author: RKSimon

lib/Target/X86/X86ISelLowering.cpp

@@ -5429,8 +5429,8 @@ static bool getTargetConstantBitsFromNode(SDValue Op, unsigned EltSizeInBits,
                                 unsigned BitOffset) {
     if (!Cst)
       return false;
-    unsigned CstSizeInBits = Cst->getType()->getPrimitiveSizeInBits();
     if (isa<UndefValue>(Cst)) {
+      unsigned CstSizeInBits = Cst->getType()->getPrimitiveSizeInBits();
       Undefs.setBits(BitOffset, BitOffset + CstSizeInBits);
       return true;
     }