[PATCH] D57033: [LCSSA] Handle case with single new PHI faster.

[Florian Hahn via Phabricator via llvm-commits]

fhahn marked 2 inline comments as done.
fhahn added inline comments.


================
Comment at: llvm/lib/Transforms/Utils/LCSSA.cpp:205
+        if (UseToRewrite->get()->hasValueHandle())
+          ValueHandleBase::ValueIsRAUWd(*UseToRewrite, AddedPHIs[0]);
+        UseToRewrite->set(AddedPHIs[0]);
----------------
efriedma wrote:
> Maybe worth mentioning that this can call ValueIsRAUWd multiple times for the same value.  (I don't think it's a problem, but took me a minute to understand what this is doing.)
Yep, I can also move it to avoid calling it multiple times.


================
Comment at: llvm/lib/Transforms/Utils/LCSSA.cpp:226
+      Value *V = AddedPHIs.size() == 1 ? AddedPHIs[0]
+                                       : SSAUpdate.FindValueForBlock(UserBB);
+      DVI->setOperand(0, MetadataAsValue::get(Ctx, ValueAsMetadata::get(V)));
----------------
efriedma wrote:
> I'm not sure I understand why you're changing the logic here for the `AddedPHIs.size() != 1` case.
In the AddedPHIs.size() == 1 case, SSAUpdate won't be used to rewrite the uses, so we can just use the only inserted PHI.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D57033/new/

https://reviews.llvm.org/D57033