[PATCH] D71093: [InstCombine] Insert instructions before adding them to worklist

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


================
Comment at: llvm/include/llvm/Transforms/InstCombine/InstCombineWorklist.h:95-96
+      auto *UI = cast<Instruction>(U);
+      // Do not add instructions that haven't been properly inserted yet.
+      if (UI->getParent()) {
+        Add(UI);
----------------
kuhar wrote:
> lebedev.ri wrote:
> > The described behavior sounds like a bug to me.
> > More importantly, it's not related to the printing changes?
> The users that I refer to here are new instructions that are being constructed; InstCombine inserts them in subsequent calls to `Add()`. This happens in a few places and it's not obvious to me make it more straight-forward.
> With the changes to the worklist here, everything works like before and the order of iteration is exactly the same.
> 
> Let me know if you want me to dig up some concrete examples for this behavior here.
I'd appreciate an example for this. I can see how it can happen in principle, but not really why we'd write the code that way in practice.


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  https://reviews.llvm.org/D71093/new/

https://reviews.llvm.org/D71093