[PATCH] [MachineLICM] Sink instructions only if they are unlikely to be executed

[Daniel Jasper]

Turns out the IsCopy check was actually important and papered over the fact that we cannot sink something that is used by a PHI (because we sink to before the first non-PHI instruction later). Sinking something that is used by a PHI probably also doesn't make much sense (or at least needs a separate investigation) as e.g. we might sink along the loop-entry edge.

Also simplified the implementation.


http://reviews.llvm.org/D8451

Files:
  lib/CodeGen/MachineLICM.cpp
  test/CodeGen/X86/sink-cheap-instructions.ll

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