[PATCH] D76010: [ValueTracking] Let isGuaranteedNotToBeUndefOrPoison look into more constants/instructions

[Juneyoung Lee via Phabricator via llvm-commits]

aqjune marked 4 inline comments as done.
aqjune added inline comments.


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:4548
+  // Call stripPointerCastsSameRepresentation to take addrspacecast out of
+  // consideration.
+  auto *StrippedV = V->stripPointerCastsSameRepresentation();
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jdoerfert wrote:
> This is not 100% the idea behind `stripPointerCastsSameRepresentation`:
> `stripPointerCastsSameRepresentation` says the bit-representation stays the same, not that there are no addrspacecasts stripped. If we assume an addressspacecast that is known not to modify the bit-representation will also not modify the poison/undef state, which I think is reasonable, we can do tihs.
Yes, I think in that case undef/poison should be preserved. LangRef says that addrspacecast can be no-op, I believe this function is dealing with the case. 
Updated comment


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Comment at: llvm/lib/Analysis/ValueTracking.cpp:4553
+    // gep inbounds null, 0 is also null.
     return true;
 
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jdoerfert wrote:
> misplaced comment
Added more text to the comment, my underlying idea was that null was also allowed in this case as well.


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https://reviews.llvm.org/D76010