[Fix] Dead statements should not confuse the RTC generation

  This fixes http://llvm.org/bugs/show_bug.cgi?id=21166 .

Differential Revision: http://reviews.llvm.org/D5623


git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@219131 91177308-0d34-0410-b5e6-96231b3b80d8