[flang-commits] [flang] [flang] add tbaa tags to global variables (PR #68727)

[Tom Eccles via flang-commits]

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@@ -406,7 +406,7 @@ AliasAnalysis::Source AliasAnalysis::getSource(mlir::Value v) {
         attributes.set(Attribute::Pointer);
     }
 
-  if (type == SourceKind::Global)
+  if (type == SourceKind::Global || type == SourceKind::Direct)
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tblah wrote:

So, if I understand correctly, it *is* safe for me to proceed treating these `Direct` source kinds as globals (I already handle pointer/target elsewhere)?

The information I am encoding in TBAA is roughly "if it is a pointer, target, or if I don't know what it is then assume it could alias with any other data access". I think this covers both the reflective and non-reflective cases:
1. `rhsSrc.isTargetOrPointer()` -> rhs may alias with any data access and so it would alias with lhsSrc no matter what lhsSrc is
2. `lhsSrc.isTargetOrPointer()` -> lhs will alias with rhs, no matter what rhs is.

This is less precise than `fir::AliasAnalysis::alias` but it shouldn't produce incorrect results.

https://github.com/llvm/llvm-project/pull/68727