[PATCH] D85332: [SCCP] Do not replace deref'able ptr with un-deref'able one.

[Eli Friedman via Phabricator via llvm-commits]

efriedma added a comment.

LLVM's memory model isn't completely settled with respect to how to determine the "base" of a pointer; see https://bugs.llvm.org/show_bug.cgi?id=34548 etc. But consensus is that the general transform you're describing isn't legal without proving more about the pointer. (e.g. that the two pointers have the same base, or the replaced value isn't used for any memory operations).



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Comment at: llvm/lib/Transforms/Scalar/SCCP.cpp:1357
+          BasicAAResult::DecomposeGEPExpression(C, Dec, DL, nullptr, nullptr);
+          auto *BaseTy = Dec.Base->getType()->getPointerElementType();
+          if (BaseTy->isArrayTy() &&
----------------
I'm not sure I completely follow what this code is doing, but using getPointerElementType() like this is probably wrong.


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  https://reviews.llvm.org/D85332/new/

https://reviews.llvm.org/D85332