[flang-commits] [flang] [flang] AliasAnalysis: More formally define and distinguish between data and non-data (PR #91020)

[Renaud Kauffmann via flang-commits]

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@@ -97,29 +117,20 @@ AliasResult AliasAnalysis::alias(Value lhs, Value rhs) {
 
   // Indirect case currently not handled. Conservatively assume
   // it aliases with everything
-  if (lhsSrc.kind > SourceKind::Direct || rhsSrc.kind > SourceKind::Direct) {
+  if (lhsSrc.kind >= SourceKind::Indirect ||
+      rhsSrc.kind >= SourceKind::Indirect) {
     return AliasResult::MayAlias;
   }
 
-  // SourceKind::Direct is set for the addresses wrapped in a global boxes.
-  // ie: fir.global @_QMpointersEp : !fir.box<!fir.ptr<f32>>
-  // Though nothing is known about them, they would only alias with targets or
-  // pointers
-  bool directSourceToNonTargetOrPointer = false;
-  if (lhsSrc.u != rhsSrc.u || lhsSrc.kind != rhsSrc.kind) {
-    if ((lhsSrc.kind == SourceKind::Direct && !rhsSrc.isTargetOrPointer()) ||
-        (rhsSrc.kind == SourceKind::Direct && !lhsSrc.isTargetOrPointer()))
-      directSourceToNonTargetOrPointer = true;
-  }
-
-  if (lhsSrc.kind == SourceKind::Direct ||
-      rhsSrc.kind == SourceKind::Direct) {
-    if (!directSourceToNonTargetOrPointer)
-      return AliasResult::MayAlias;
+  // If we have reached the same source but comparing box reference against
+  // data we are not comparing apples-to-apples. The 2 cannot alias.
+  if ((lhsSrc.origin.u == rhsSrc.origin.u) &&
+      lhsSrc.isData() != rhsSrc.isData()) {
----------------
Renaud-K wrote:

We have `isRecordWithPointerComponent` which is a pretty big hammer. It does not distinguish between data and non-data, so %x and %2 will alias. Also in this case, there are indirect loads. The source of %5 is %3 and we do not get passed this load because it is not a source.  I will add the test. There is room for improvement. For instance `isRecordWithPointerComponent` even says that x and y alias.

https://github.com/llvm/llvm-project/pull/91020