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

[Johannes Doerfert via Phabricator via llvm-commits]

jdoerfert added inline comments.


================
Comment at: llvm/lib/Analysis/ValueTracking.cpp:3702
+         Call->getIntrinsicID() == Intrinsic::ptrmask;
 }
 
----------------
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?


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

https://reviews.llvm.org/D61669