Review: back out LLVM pass changes (issue1951042)


Reviewers: ,

I've spent several days tracking down crashes in our LLVM-generated
code, with little satisfaction. I still don't know if this reveals bugs
in LLVM or that we have subtly misused it, but in any case I think we
need to back out the changes from about a week ago where I radically
altered which optimization passes we were scheduling.

This patch takes us back to a place where we run without crashing,
although MUCH slower than we'd like to be. But now that we are correct,
I'll work again on optimization, this time more slowly and carefully, to
ensure that we identify exactly what changes bring us to dragon

Please review this at

Affected files: