[PATCH] D76923: [NFC] Improve performances of Value::getSingleUndroppableUse

[Tyker via Phabricator via llvm-commits]

Tyker updated this revision to Diff 253334.
Tyker added a comment.

In D76923#1946433 <https://reviews.llvm.org/D76923#1946433>, @nikic wrote:

> I do wonder whether there's a middle ground here: Rather than adding a tag to `Use`, we could use a bit of subclass data on `CallInst` to indicate whether the call is droppable. That would reduce `User->isDroppable()` to a compare and mask check, and we could at least inline it.


from profiling i saw that most of the cost of getSingleUndroppableUse comes from Use::getUser (+0.16%) and not from User::isDroppable (+0.05%). so i don't think this would make the difference we want.

with this revision i moved the tag to the Prev pointer because it is accessed much less than Val and it already has a tag so i just added a bit to the tag.
maybe this revision has less overhead.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D76923/new/

https://reviews.llvm.org/D76923

Files:
  llvm/include/llvm/IR/Use.h
  llvm/include/llvm/IR/User.h
  llvm/include/llvm/IR/Value.h
  llvm/lib/IR/Instructions.cpp
  llvm/lib/IR/Use.cpp
  llvm/lib/IR/User.cpp
  llvm/lib/IR/Value.cpp
  llvm/lib/Transforms/IPO/Attributor.cpp

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