[flang-commits] [flang] [flang] Disallow passing array actual arguments to ignore_tkr(r) scalars with VALUE attribute (PR #166682)

[Eugene Epshteyn via flang-commits]

https://github.com/eugeneepshteyn updated https://github.com/llvm/llvm-project/pull/166682

>From def02de9c48f6600d72a22010a33792610d6ab8c Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Wed, 5 Nov 2025 20:01:49 -0500
Subject: [PATCH 1/3] [flang] Disallow passing array actual arguments to
 ignore_tkr(r) scalars with VALUE attribute

---
 flang/lib/Semantics/check-call.cpp |  7 ++++++-
 flang/test/Semantics/val-tkr.f90   | 22 ++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)
 create mode 100644 flang/test/Semantics/val-tkr.f90

diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
index 995deaa12dd3b..054286af790ab 100644
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -548,7 +548,12 @@ static void CheckExplicitDataArg(const characteristics::DummyDataObject &dummy,
     actualLastSymbol = &ResolveAssociations(*actualLastSymbol);
   }
   int actualRank{actualType.Rank()};
-  if (dummy.type.attrs().test(
+  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) {
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

>From e7bf466d123bdee28dcd60d90a2da0b5d3d34c7d Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Wed, 5 Nov 2025 20:04:01 -0500
Subject: [PATCH 2/3] clang-format

---
 flang/lib/Semantics/check-call.cpp | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/flang/lib/Semantics/check-call.cpp b/flang/lib/Semantics/check-call.cpp
index 054286af790ab..53a22768855e1 100644
--- a/flang/lib/Semantics/check-call.cpp
+++ b/flang/lib/Semantics/check-call.cpp
@@ -551,10 +551,10 @@ static void CheckExplicitDataArg(const characteristics::DummyDataObject &dummy,
   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);
+        "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)) {
+                 characteristics::TypeAndShape::Attr::AssumedShape)) {
     // 15.5.2.4(16)
     if (actualIsAssumedRank) {
       messages.Say(

>From 9c0282de0210f52c2e2ce28d14a1110f01782685 Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Thu, 6 Nov 2025 13:15:53 -0500
Subject: [PATCH 3/3] Updated directives docs with the new limitation

---
 flang/docs/Directives.md | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/flang/docs/Directives.md b/flang/docs/Directives.md
index 2f16a8d579f8b..902f1530a2672 100644
--- a/flang/docs/Directives.md
+++ b/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,