[PATCH] D115437: [GVN] Try to use an equivalent PHI after constructing one for load set

[Philip Reames via Phabricator via llvm-commits]

reames requested changes to this revision.
reames added inline comments.
This revision now requires changes to proceed.


================
Comment at: llvm/lib/Transforms/Scalar/GVN.cpp:897
   // Perform PHI construction.
-  return SSAUpdate.GetValueInMiddleOfBlock(Load->getParent());
+  auto *V = SSAUpdate.GetValueInMiddleOfBlock(Load->getParent());
+
----------------
Doing this specifically for PRE/FRE is definitely the wrong place.  Particularly, doing so by hacking up the implementation this way.

I think you should look at extending EliminateDuplicatePHINodes, or adding something new which matches recurrences at about the same call point.  That is, let the phi-cycle be created, but then erase it again on the next iteration.  


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D115437/new/

https://reviews.llvm.org/D115437