[all-commits] [llvm/llvm-project] bccc9a: Don't vectorize PHIs in catchswitch blocks

[Bill Schmidt via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bccc9aa81c1c1d212acd3314895731ec4de30e35
      https://github.com/llvm/llvm-project/commit/bccc9aa81c1c1d212acd3314895731ec4de30e35
  Author: William Schmidt <william.schmidt at intel.com>
  Date:   2022-07-19 (Tue, 19 Jul 2022)

  Changed paths:
    M llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp
    A llvm/test/Transforms/SLPVectorizer/X86/catchswitch.ll

  Log Message:
  -----------
  Don't vectorize PHIs in catchswitch blocks

We currently assert in vectorizeTree(TreeEntry*) when processing a PHI
bundle in a block containing a catchswitch.  We attempt to set the
IRBuilder insertion point following the catchswitch, which is invalid.
This is done so that ShuffleBuilder.finalize() knows where to insert
a shuffle if one is needed.

To avoid this occurring, watch out for catchswitch blocks during
buildTree_rec() processing, and avoid adding PHIs in such blocks to
the vectorizable tree.  It is unlikely that constraining vectorization
over an exception path will cause a noticeable performance loss, so
this seems preferable to trying to anticipate when a shuffle will and
will not be required.