[flang-commits] [flang] [Flang][OpenMP] Correct ArrayElements in Reduction Clause (PR #196094)

[Jack Styles via flang-commits]

================
@@ -1592,6 +1592,29 @@ static bool hasDeferredCharacterLength(const Fortran::semantics::Symbol &sym) {
          type->characterTypeSpec().length().isDeferred();
 }
 
+static mlir::Value
+findOverriddenExprValue(const Fortran::lower::ExprToValueMap &map,
+                        const Fortran::lower::SomeExpr &expr) {
+  if (auto match = map.find(&expr); match != map.end())
+    return match->second;
+
+  if (!Fortran::evaluate::IsArrayElement(expr))
+    return {};
+
+  for (auto [key, value] : map) {
+    if (key == llvm::DenseMapInfo<
+                   const Fortran::lower::SomeExpr *>::getEmptyKey() ||
+        key == llvm::DenseMapInfo<
+                   const Fortran::lower::SomeExpr *>::getTombstoneKey())
+      continue;
+    if (Fortran::evaluate::IsArrayElement(*key) &&
+        key->AsFortran() == expr.AsFortran())
----------------
Stylie777 wrote:

I'm not sure this is defensive, rather ensuring that cases where multiple array elements are included in a reduction (say `reduction(+: a(2), a(3))`, the correct element is selected. Otherwise it may end up selecting the wrong array element.

I have however reworked this to use the ArrayRef's for comparison rather than pure string comparison, this is safer and allows for Array Sections too.

https://github.com/llvm/llvm-project/pull/196094