[PATCH] D22547: [LSV] Don't move stores across may-load instrs, and loosen restrictions on moving loads.

[Justin Lebar via llvm-commits]

jlebar created this revision.
jlebar added a reviewer: asbirlea.
jlebar added subscribers: arsenm, llvm-commits.
Herald added subscribers: mzolotukhin, jholewinski.

Previously we wouldn't move loads/stores across instructions that had
side-effects, where that was defined as may-write may-throw.  But this
is both overly- and underly-restrictive:

 - Stores can't safely be moved across instructions that may load.
 - Loads can be moved across may-throw instructions; it's only may-write
   instructions that must be a barrier.

This patch also adds a DEBUG check that all instructions in our chain
are either loads or stores.

https://reviews.llvm.org/D22547

Files:
  lib/Transforms/Vectorize/LoadStoreVectorizer.cpp
  test/Transforms/LoadStoreVectorizer/NVPTX/merge-across-side-effects.ll

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