[all-commits] [llvm/llvm-project] 5225cd: [LoopUnroll] Allow loops with multiple exiting blo...

[whitneywhtsang via All-commits]

  Branch: refs/heads/master
  Home:   https://github.com/llvm/llvm-project
  Commit: 5225cd43e8ff86a43e5ee627c818e82b764065a6
      https://github.com/llvm/llvm-project/commit/5225cd43e8ff86a43e5ee627c818e82b764065a6
  Author: Whitney Tsang <whitneyt at ca.ibm.com>
  Date:   2020-06-14 (Sun, 14 Jun 2020)

  Changed paths:
    M llvm/lib/Transforms/Utils/LoopUnroll.cpp
    M llvm/test/Transforms/LoopUnroll/nonlatchcondbr.ll

  Log Message:
  -----------
  [LoopUnroll] Allow loops with multiple exiting blocks where loop latch
is not necessary one of them.

Summary: Currently LoopUnrollPass already allow loops with multiple
exiting blocks, but it is only allowed when the loop latch is one of the
exiting blocks.
When the loop latch is not an exiting block, then only single exiting
block is supported.
When possible, the single loop latch or the single exiting block
terminator is optimized to an unconditional branch in the unrolled loop.

This patch allows loops with multiple exiting blocks even if the loop
latch is not one of them. However, the optimization of exiting block
terminator to unconditional branch is not done when there exists more
than one exiting block.
Reviewer: dmgreen, Meinersbur, etiotto, fhahn, efriedma, bmahjour
Reviewed By: efriedma
Subscribers: hiraditya, zzheng, llvm-commits
Tag: LLVM
Differential Revision: https://reviews.llvm.org/D81053