Require non-NULL register masks.

It doesn't seem worthwhile to give meaning to a NULL register mask
pointer. It complicates all the code using register mask operands.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@149646 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/MachineLICM.cpp b/lib/CodeGen/MachineLICM.cpp
index 49a109e..9b058c3 100644
--- a/lib/CodeGen/MachineLICM.cpp
+++ b/lib/CodeGen/MachineLICM.cpp
@@ -417,10 +417,7 @@
     // We can't hoist an instruction defining a physreg that is clobbered in
     // the loop.
     if (MO.isRegMask()) {
-      if (const uint32_t *Mask = MO.getRegMask())
-        PhysRegClobbers.setBitsNotInMask(Mask);
-      else
-        PhysRegClobbers.set();
+      PhysRegClobbers.setBitsNotInMask(MO.getRegMask());
       continue;
     }