This is a follow-up patch for r185524. Being assert enabled does not mean
that DEBUG() is enabled, so we need to check the existence of DEBUG() itself.
llvm-svn: 185619
Found that having a method to check the strucutre of the followon graph makes
it easy to debug file readers. The method checks if there's no wrong edge in
followOnNexts and followOnRoots. It is called only when debuggging is enabled
for LayoutPass.
Reviewers: shankarke
CC: llvm-commits
Differential Revision: http://llvm-reviews.chandlerc.com/D922
llvm-svn: 183553
Rui Ueyama