[flang] Disallow passing array actual arguments to ignore_tkr(r) scalars with VALUE attribute

[eugeneepshteyn]

Scalars with VALUE attribute are likely passed in registers, so it's now clear what lowering should do with the array actual argument in this case. Fail this case with an error before getting to lowering.

[llvmbot]

@llvm/pr-subscribers-flang-semantics

Author: Eugene Epshteyn (eugeneepshteyn)

Changes

Scalars with VALUE attribute are likely passed in registers, so it's now clear what lowering should do with the array actual argument in this case. Fail this case with an error before getting to lowering.

---

Full diff: https://github.com/llvm/llvm-project/pull/166682.diff

2 Files Affected:

• (modified) flang/lib/Semantics/check-call.cpp (+7-2)
• (added) flang/test/Semantics/val-tkr.f90 (+22)

diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
index 995deaa12dd3b..53a22768855e1 100644
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -548,8 +548,13 @@ static void CheckExplicitDataArg(const characteristics::DummyDataObject &dummy,
     actualLastSymbol = &ResolveAssociations(*actualLastSymbol);
   }
   int actualRank{actualType.Rank()};
-  if (dummy.type.attrs().test(
-          characteristics::TypeAndShape::Attr::AssumedShape)) {
+  if (dummyIsValue && dummyRank == 0 &&
+      dummy.ignoreTKR.test(common::IgnoreTKR::Rank) && actualRank > 0) {
+    messages.Say(
+        "Array actual argument may not be associated with IGNORE_TKR(R) scalar %s with VALUE attribute"_err_en_US,
+        dummyName);
+  } else if (dummy.type.attrs().test(
+                 characteristics::TypeAndShape::Attr::AssumedShape)) {
     // 15.5.2.4(16)
     if (actualIsAssumedRank) {
       messages.Say(
diff --git a/flang/test/Semantics/val-tkr.f90 b/flang/test/Semantics/val-tkr.f90
new file mode 100644
index 0000000000000..bed41f3ed0569
--- /dev/null
+++ b/flang/test/Semantics/val-tkr.f90
@@ -0,0 +1,22 @@
+! RUN: %python %S/test_errors.py %s %flang_fc1
+implicit none
+interface
+  subroutine s(b)
+    !dir$ ignore_tkr(tr) b
+    real, value :: b
+  end
+  subroutine s1(b)
+    !dir$ ignore_tkr(r) b
+    integer, value :: b
+  end
+end interface
+integer :: a(5), a1
+! forbid array to scalar with VALUE and ignore_tkr(r)
+!ERROR: Array actual argument may not be associated with IGNORE_TKR(R) scalar dummy argument 'b=' with VALUE attribute
+call s(a)
+!ERROR: Array actual argument may not be associated with IGNORE_TKR(R) scalar dummy argument 'b=' with VALUE attribute
+call s1(a)
+! allow scalar to scalar with VALUE
+call s(a1)
+call s1(a(1))
+end

[jeanPerier]

Thanks Eugene.

Can you update flang/docs/Directives.md to say a word about the VALUE case to explain when it is allowed and what to expect when allowed?

[eugeneepshteyn]

Can you update flang/docs/Directives.md to say a word about the VALUE case to explain when it is allowed and what to expect when allowed?

Doc updated. Please review.