Fix PR36032, PR35432

Summary:

The change fix an assert fail at ScalarEvolutionExpander.cpp:
  assert(ExitCount != SE.getCouldNotCompute() && "Invalid loop count");

Reviewers: sbaranga

Differential Revision: http://reviews.llvm.org/D42604

From: Evgeny Stupachenko <evstupac@gmail.com>
                         <evgeny.v.stupachenko@intel.com>
llvm-svn: 326154