[Polly CodeGen] Break critical edge from RTC to original loop.
This makes polly generate a CFG which is closer to what we want
in LLVM IR, with a loop preheader for the original loop. This is
just a cleanup, but it exposes some fragile assumptions.
I'm not completely happy with the changes related to expandCodeFor;
RTCBB->getTerminator() is basically a random insertion point which
happens to work due to the way we generate runtime checks. I'm not
sure what the right answer looks like, though.
Differential Revision: https://reviews.llvm.org/D26053
llvm-svn: 285864
11 files changed