Attempt to fix bot failure on Windows.
Looks like this expression was accidentally using 32-bit arithmetic.

llvm-svn: 297969
diff --git a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
index 6a43f4a..29b0db0 100644
--- a/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/DwarfExpression.cpp
@@ -302,7 +302,7 @@
   assert(SubRegisterSizeInBits && "no subregister was registered");
   if (SubRegisterOffsetInBits > 0)
     addShr(SubRegisterOffsetInBits);
-  uint64_t Mask = (1UL << SubRegisterSizeInBits) - 1;
+  uint64_t Mask = (1ULL << (uint64_t)SubRegisterSizeInBits) - 1ULL;
   addAnd(Mask);
 }