Use documented isl function

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@175011 91177308-0d34-0410-b5e6-96231b3b80d8
clang-format a file

git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@175012 91177308-0d34-0410-b5e6-96231b3b80d8