* Clean up the code a bit

* Clean up the code a bit
* Allow structs with negative offsets.  This enables the em3d benchmark to
  be made typesafe.  In this case, the struct had an array as the first
  element, so a negative index was ok (the expr was -8 + 8x)

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@2271 91177308-0d34-0410-b5e6-96231b3b80d8