[flang-commits] [clang] [flang] [flang] Add support for -finit-local-zero (PR #159788)

[via flang-commits]

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@@ -1317,6 +1381,50 @@ static void instantiateLocal(Fortran::lower::AbstractConverter &converter,
       Fortran::lower::genUnpackArray(*converterPtr, loc, *varDef, *sym);
     });
   }
+
+  /// These options do not initialize:
+  ///   1) Any variable already initialized
+  ///   2) objects with the POINTER attribute
+  ///   3) allocatable arrays
+  ///   4) variables that appear in an EQUIVALENCE statement
+
+  auto isEligibleForImplicitAssignment = [&var, &converter]() -> bool {
+    if (!var.hasSymbol())
+      return false;
+
+    const Fortran::semantics::Symbol &sym = var.getSymbol();
+    if (!sym.GetType())
+      return false;
+    if (const auto *details =
+            sym.detailsIf<Fortran::semantics::ObjectEntityDetails>()) {
+      if (details->init())
+        return false;
+    }
+
+    if (sym.attrs().test(Fortran::semantics::Attr::POINTER))
+      return false;
+
+    if (sym.Rank() > 0 &&
+        sym.attrs().test(Fortran::semantics::Attr::ALLOCATABLE))
+      return false;
+
+    if (Fortran::lower::pft::getDependentVariableList(sym).size() > 1)
+      return false;
+
+    if (auto ty = converter.genType(sym)) {
+      auto charTy =
+          mlir::dyn_cast<fir::CharacterType>(hlfir::getFortranElementType(ty));
+      if (charTy && !charTy.hasConstantLen())
+        return false;
+    }
----------------
jeanPerier wrote:

My concern was only with allocatables scalar character with deferred length (that I now think should be rejected). The following should still be zero initialized:

```
subroutine char_init(n)
   character(n) :: x
   call bar(x)
end subroutine
```

https://github.com/llvm/llvm-project/pull/159788