[PATCH] D109647: [AA] Consider globalmemonly in getModRefInfo()

[Nikita Popov via Phabricator via llvm-commits]

nikic requested changes to this revision.
nikic added inline comments.
This revision now requires changes to proceed.


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Comment at: llvm/lib/Analysis/AliasAnalysis.cpp:283
+        getUnderlyingObject(Loc.Ptr->stripPointerCastsForAliasAnalysis());
+    if (!isa<GlobalValue>(V1)) {
+      return ModRefInfo::NoModRef;
----------------
Just because the underlying object is not a global value, doesn't mean that it can't be based on one -- e.g. imagine a global being passed to a function argument. getUnderlyingObject() will just give you the argument in that case, which may still alias with a global.

At the very least, you need to check for isIdentifiedObject() here. However, even that may be insufficient, as noalias arguments are identified objects, but I don't think you can apply this optimization to them (a noalias argument could point to a global, and a globalmemonly function could access the global through a passed-on noalias argument).


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https://reviews.llvm.org/D109647