[PATCH] D69563: [LV] Strip wrap flags from vectorized reductions

[Ayal Zaks via Phabricator via llvm-commits]

Ayal added inline comments.


================
Comment at: llvm/lib/Transforms/Vectorize/LoopVectorize.cpp:3891
+  Instruction *LoopExitInstr = RdxDesc.getLoopExitInstr();
+  assert(LoopExitInstr != nullptr && "null loop exit instruction");
+  SmallVector<Instruction *, 8> Worklist;
----------------
dantrushin wrote:
> Ayal wrote:
> > There's no need to deal with LoopExitInstr in this implementation; it's probably clearer to start from the Phi as in the original version.
> I'm passing `RecurrenceDescriptor` to this function
> (so I can easily check reduction type here).
> I only can get loop exit instruction from it, not Phi. 
> Here I need *any* reduction instruction to start with, and I don't see much difference between `Phi` and `LoopExitInstr`. 
> 
> Do you want me to pass in Phi instead and check reduction type at call site? 
OK, right. Can pass both RdxDesc and Phi, but using LoopExitInstr is also fine.

It is tempting though to then try and save redundant Loop->contains() calls, perhaps by restricting them only to users of LoopExitInstr, as in:

```
if ((Cur != LoopExitInstr || OrigLoop->contains(UI->getParent())) && Visited.insert(UI).second)
```
?


Repository:
  rG LLVM Github Monorepo

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  https://reviews.llvm.org/D69563/new/

https://reviews.llvm.org/D69563