[PATCH] [LoopDist/LoopVer] Move LoopVersioning to a new module, NFC

[hfinkel at anl.gov]

================
Comment at: include/llvm/Transforms/Utils/LoopVersioning.h:44
@@ +43,3 @@
+  /// \brief Performs the CFG manipulation part of versioning the loop including
+  /// the DominatorTree and LoopInfo updates.
+  void versionLoop(Pass *P);
----------------
anemet wrote:
> hfinkel wrote:
> > From this interface, I find it very unclear how you get out the new versioned loop after the CFG mutation is complete.
> The loop that was used to construct the class will be the "versioned" loop i.e. the loop that will get control if all the memchecks pass.
> 
> This is the loop that typically, the client transform will be interested in modifying.  E.g. this is what LoopDistribute does.
> 
> This is sort of implicit because the versioning is optional.  I think this is a typical algorithm:
> 
>   for each loop L:
>     analyze L
>     if versioning is necessary version L
>     transform L
> 
> The versioning itself is an optional step and you don't change the loop underlying the transformation if versioning was necessary.
> 
> Both loops (versioned, unversioned) are attributes of the class, so we can add APIs to query them as we need them.
> 
> Let me know if you'd be OK just commenting the above or you're requesting an actual API change.
> 
> Thanks very much for the review!
> 
> Adam
In that case, I think the current API is okay, but needs comments.

================
Comment at: include/llvm/Transforms/Utils/LoopVersioning.h:49
@@ +48,3 @@
+  /// loop-defined values used outside of the loop.
+  void addPHINodes(const SmallVectorImpl<Instruction *> &DefsUsedOutside);
+
----------------
This function too needs comments on when/how it should be used.

http://reviews.llvm.org/D10577

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