tree dbf7ee48d5aa06dc4ba1ca88702e5e667e17a9db
parent a65ff5e0576ace8ffeb1a6dc8784a61cd2498fba
author Nicolas Geoffray <ngeoffray@google.com> 1453200774 +0000
committer Nicolas Geoffray <ngeoffray@google.com> 1453209847 +0000

Disable DCE when there are irreducible loops.

Also ensure an instruction that requires an environment
does have one.

Change-Id: I41a8460e05ef320f872197d3be7847e7ffaa6ee8