[PATCH] D23191: [BranchFolding] Restrict tail merging loop blocks after machine block placement

[Wei Mi via Phabricator via llvm-commits]

wmi added a comment.

I am running into a problem about the testcase tail-merge-after-mbp.ll. I am working on a patch related with register allocation and it somehow triggers the tail merge before block placement, and breaks the checks in the test. The tail merge triggered is doing in exactly the same way as the test describes.

It seems the patch aims to work on tail merge after bb placement, and it is ok to do the tail merge if only it happens before bb placement. However, the test will fail even if the tail merge happens before bb placement.

I guess we need to add -disable-branch-fold in the test to disable the first pass of tail merge, and only check the result of tail merge called by bb placement?


Repository:
  rL LLVM

https://reviews.llvm.org/D23191