[PATCH] D15230: [BranchFolding] Merge MMOs during tail merge

[Junmo Park via llvm-commits]

flyingforyou created this revision.
flyingforyou added reviewers: gberry, mcrosier.
flyingforyou added subscribers: rafael, llvm-commits.

Recommit r254694, it was reverted in r254700 to investigate a bot failure.

If we remove the MMOs from Load/Store instructions,
they are treated as volatile. This makes other optimization passes unhappy.
eg. Load/Store Optimization

So, it looks better to merge, not remove.
But if the product of two MMOs count is higher than threshold,
we just remove them for preventing any pathological cases from
causing compile time blowups or overflow.

http://reviews.llvm.org/D15230

Files:
  lib/CodeGen/BranchFolding.cpp

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