[PATCH] D110256: [SelectionDAG] Replace error prone index check in BaseIndexOffset::computeAliasing

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/CodeGen/SelectionDAG/SelectionDAGAddressAnalysis.cpp:156
+      auto *GV1 = cast<GlobalAddressSDNode>(BasePtr1.getBase())->getGlobal();
+      // It doesn't make sense to access one global value using another globals
+      // values address, so we can assume that there is no aliasing in case of
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bjope wrote:
> I'm not 100% sure about this. https://llvm.org/docs/LangRef.html#global-variables says that "code could assume that the globals are densely packed in their section and try to iterate over them as an array", so does that mean that for example a global variable `@foo` can be accessed using a global variable `@bar` as base ptr and with `(@bar - @foo)` as offset?
Accessing an object using a pointer that is based on a different object is undefined behavior under our [pointer aliasing rules](https://llvm.org/docs/LangRef.html#pointer-aliasing-rules).


Repository:
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CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D110256/new/

https://reviews.llvm.org/D110256