[PATCH] D61669: [ValueTracking] Look through ptrmask intrinsics during getUnderlyingObject.

[Florian Hahn via Phabricator via llvm-commits]

fhahn marked an inline comment as done.
fhahn added inline comments.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:3702
+         Call->getIntrinsicID() == Intrinsic::ptrmask;
 }
 
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jdoerfert wrote:
> aqjune wrote:
> > I found that `getArgumentAliasingToReturnedPointer` (which calls this function) is used at `isKnownNonZero` with the following pattern:
> > 
> > ```
> > if (const auto *RP = getArgumentAliasingToReturnedPointer(Call))
> >   return isKnownNonZero(RP, Depth, Q);
> > ```
> > 
> > which seems to assume that the non-zeroness of the result of a function call is equivalent to the non-zeroness of the first argument. `isKnownNonZero` should be fixed, or maybe we can add a boolean flag to `isIntrinsicReturningPointerAliasingArgumentWithoutCapturing` that allows callers to determine its purpose?
> `Value::stripPointerCasts()` is sometimes used with the same assumption but there is it also not given (due to address space casts). In D61607 I try to introduce a version that "keeps the bit pattern the same" to fix uses that put the result in to `isKnownNonZero`-like functions.
> 
> That said, I guess you can introduce an 
> `isIntrinsicReturningPointerArgumentWithoutCapturing`
> to fix this issue?
Sorry for the long delay! I've added a MustPreserveNullness argument in D64150, to distinguish those 2 cases.


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  https://reviews.llvm.org/D61669/new/

https://reviews.llvm.org/D61669