[PATCH] D55120: [MemCpyOpt] memset->memcpy forwarding with undef tail

[Nikita Popov via Phabricator via llvm-commits]

nikic updated this revision to Diff 178076.
nikic edited the summary of this revision.
nikic added a comment.
This revision is now accepted and ready to land.

Fix memory dependence query. We need to query at the location of the memset, but with the size of the memcpy. Otherwise we miss possible writes in the region between the end of the memset and the end of the memcpy. Ideally we'd only query for locations in that region, but as there is no easy way to do so we just use the whole memcpy source region.

Add additional tests which have writes prior to the memset, either in the memset region (legal to optimize, but we currently don't), as well as after the memset region, or overlapping both (not legal to optimize).


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D55120/new/

https://reviews.llvm.org/D55120

Files:
  lib/Transforms/Scalar/MemCpyOptimizer.cpp
  test/Transforms/MemCpyOpt/memset-memcpy-oversized.ll

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