The DEBUG() macro is too generic so it might clash with other projects.
This is going to be deprecated and replaced by LLVM_DEBUG() as soon as https://reviews.llvm.org/D43624 is submitted.
This is the command I used to do the replacement and formatting:
git grep -l 'DEBUG' | xargs sed -i 's/\bDEBUG\s\?(/LLVM_DEBUG(/g'
git diff -U0 master | ../clang/tools/clang-format/clang-format-diff.py -i -p1 -style LLVM