From 56c468474de77cd7b6954a74190f9603d393d02a Mon Sep 17 00:00:00 2001
From: Peter Klausler <pklausler@nvidia.com>
Date: Fri, 31 Jan 2025 10:54:48 -0800
Subject: [PATCH] [flang] Suppress USEs of non-USE'able names in module files
 (#124980)

When harvesting and formatting symbols USE'd from other modules, don't
emit USE statements to module files for names unless they come from the
topmost scope of the module. There was a check to prevent names from
derived type scopes from escaping in this way, but it must be made more
general to prevent other cases like dummy arguments in interfaces.

Fixes https://github.com/llvm/llvm-project/issues/124716.
---
 flang/lib/Semantics/mod-file.cpp   |  6 +++--
 flang/test/Semantics/bug124716.f90 | 36 ++++++++++++++++++++++++++++++
 2 files changed, 40 insertions(+), 2 deletions(-)
 create mode 100644 flang/test/Semantics/bug124716.f90

diff --git a/flang/lib/Semantics/mod-file.cpp b/flang/lib/Semantics/mod-file.cpp
index b45f1c060da2..bef934beaacf 100644
--- a/flang/lib/Semantics/mod-file.cpp
+++ b/flang/lib/Semantics/mod-file.cpp
@@ -306,8 +306,10 @@ void ModFileWriter::PrepareRenamings(const Scope &scope) {
   // to their names in this scope, creating those new names when needed.
   auto &renamings{context_.moduleFileOutputRenamings()};
   for (SymbolRef s : symbolsNeeded) {
-    if (s->owner().kind() == Scope::Kind::DerivedType) {
-      continue; // component or binding: ok
+    if (s->owner().kind() != Scope::Kind::Module) {
+      // Not a USE'able name from a module's top scope;
+      // component, binding, dummy argument, &c.
+      continue;
     }
     const Scope *sMod{FindModuleContaining(s->owner())};
     if (!sMod || sMod == &scope) {
diff --git a/flang/test/Semantics/bug124716.f90 b/flang/test/Semantics/bug124716.f90
new file mode 100644
index 000000000000..c1487a235721
--- /dev/null
+++ b/flang/test/Semantics/bug124716.f90
@@ -0,0 +1,36 @@
+! RUN: %python %S/test_modfile.py %s %flang_fc1
+MODULE m1
+  INTERFACE
+    MODULE SUBROUTINE sub1(N, ARR)
+      INTEGER, INTENT(IN) :: N
+      INTEGER, DIMENSION(N) :: ARR
+    END SUBROUTINE
+  END INTERFACE
+END MODULE
+SUBMODULE (m1) m1sub
+ CONTAINS
+  MODULE SUBROUTINE sub1(N, ARR)
+    INTEGER, INTENT(IN) :: N
+    INTEGER, DIMENSION(N) :: ARR
+    PRINT *, "sub1", N, ARR
+  END SUBROUTINE
+END SUBMODULE
+
+!Expect: m1.mod
+!module m1
+!interface
+!module subroutine sub1(n,arr)
+!integer(4),intent(in)::n
+!integer(4)::arr(1_8:int(n,kind=8))
+!end
+!end interface
+!end
+
+!Expect: m1-m1sub.mod
+!submodule(m1) m1sub
+!contains
+!module subroutine sub1(n,arr)
+!integer(4),intent(in)::n
+!integer(4)::arr(1_8:int(n,kind=8))
+!end
+!end