tree 3c10c1b0d830baa84400569bd65d4f7d6a5ace94
parent 01f8d556aa7274336f94afe6581bded378f3b4f4
author Philip Reames <listmail@philipreames.com> 1555953223 +0000
committer Philip Reames <listmail@philipreames.com> 1555953223 +0000

[LPM/BPI] Preserve BPI through trivial loop pass pipeline (e.g. LCSSA, LoopSimplify)

Currently, we do not expose BPI to loop passes at all. In the old pass manager, we appear to have been ignoring the fact that LCSSA and/or LoopSimplify didn't preserve BPI, and making it available to the following loop passes anyways.  In the new one, it's invalidated before running any loop pass if either LCSSA or LoopSimplify actually make changes. If they don't make changes, then BPI is valid and available.  So, we go ahead and teach LCSSA and LoopSimplify how to preserve BPI for consistency between old and new pass managers.

This patch avoids an invalidation between the two requires in the following trivial pass pipeline:
opt -passes="requires<branch-prob>,loop(no-op-loop),requires<branch-prob>"
(when the input file is one which requires either LCSSA or LoopSimplify to canonicalize the loops)

Differential Revision: https://reviews.llvm.org/D60790

llvm-svn: 358901