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

flang/docs/Directives.md

@@ -32,6 +32,22 @@ A list of non-standard directives supported by Flang
     end
   end interface
 ```
+  Note that it's not allowed to pass array actual argument to `ignore_trk(R)`
+  dummy argument that is a scalar with `VALUE` attribute, for example:
+```
+  interface
+    subroutine s(b)
+      !dir$ ignore_tkr(r) b
+      integer, value :: b
+    end
+  end interface
+  integer :: a(5)
+  call s(a)
+```
+  The reason for this limitation is that scalars with `VALUE` attribute can
+  be passed in registers, so it's not clear how lowering should handle this
+  case. (Passing scalar actual argument to `ignore_tkr(R)` dummy argument
+  that is a scalar with `VALUE` attribute is allowed.)
 * `!dir$ assume_aligned desginator:alignment`, where designator is a variable,
   maybe with array indices, and alignment is what the compiler should assume the
   alignment to be. E.g A:64 or B(1,1,1):128. The alignment should be a power of 2,

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(

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