From c9ae0ce54c2ce67e0116baf4e81600a0e66103c3 Mon Sep 17 00:00:00 2001
From: agozillon <Andrew.Gozillon@amd.com>
Date: Fri, 10 Oct 2025 23:23:22 -0500
Subject: [PATCH] [Flang][OpenMP] Increase detection capability for requires
 usm (and others)

Currently, the compiler only picks up some cases where requires is designated
such as in the main program. However, it'll gloss over cases such as when it
is specified by a user in a module, that's then used elsewhere.

This patch attempts to amend that by searching the varying scopes in the
current program module more comprehensively.
---
 flang/lib/Lower/Bridge.cpp               | 27 ++++++++++++++----------
 flang/test/Lower/OpenMP/requires-usm.f90 | 22 +++++++++++++++++++
 2 files changed, 38 insertions(+), 11 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/requires-usm.f90

diff --git a/flang/lib/Lower/Bridge.cpp b/flang/lib/Lower/Bridge.cpp
index 68adf346fe8c0..358b57d76d32e 100644
--- a/flang/lib/Lower/Bridge.cpp
+++ b/flang/lib/Lower/Bridge.cpp
@@ -415,7 +415,8 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     // - Define module variables and OpenMP/OpenACC declarative constructs so
     //   they are available before lowering any function that may use them.
     bool hasMainProgram = false;
-    const Fortran::semantics::Symbol *globalOmpRequiresSymbol = nullptr;
+    llvm::SmallVector<const Fortran::semantics::Symbol *>
+        globalOmpRequiresSymbols;
     createBuilderOutsideOfFuncOpAndDo([&]() {
       for (Fortran::lower::pft::Program::Units &u : pft.getUnits()) {
         Fortran::common::visit(
@@ -424,8 +425,7 @@ class FirConverter : public Fortran::lower::AbstractConverter {
                   if (f.isMainProgram())
                     hasMainProgram = true;
                   declareFunction(f);
-                  if (!globalOmpRequiresSymbol)
-                    globalOmpRequiresSymbol = f.getScope().symbol();
+                  globalOmpRequiresSymbols.push_back(f.getScope().symbol());
                 },
                 [&](Fortran::lower::pft::ModuleLikeUnit &m) {
                   lowerModuleDeclScope(m);
@@ -433,12 +433,15 @@ class FirConverter : public Fortran::lower::AbstractConverter {
                        m.containedUnitList)
                     if (auto *f =
                             std::get_if<Fortran::lower::pft::FunctionLikeUnit>(
-                                &unit))
+                                &unit)) {
                       declareFunction(*f);
+                      globalOmpRequiresSymbols.push_back(
+                          f->getScope().symbol());
+                    }
+                  globalOmpRequiresSymbols.push_back(m.getScope().symbol());
                 },
                 [&](Fortran::lower::pft::BlockDataUnit &b) {
-                  if (!globalOmpRequiresSymbol)
-                    globalOmpRequiresSymbol = b.symTab.symbol();
+                  globalOmpRequiresSymbols.push_back(b.symTab.symbol());
                 },
                 [&](Fortran::lower::pft::CompilerDirectiveUnit &d) {},
                 [&](Fortran::lower::pft::OpenACCDirectiveUnit &d) {},
@@ -481,7 +484,7 @@ class FirConverter : public Fortran::lower::AbstractConverter {
                                   Fortran::common::LanguageFeature::Coarray));
       });
 
-    finalizeOpenMPLowering(globalOmpRequiresSymbol);
+    finalizeOpenMPLowering(globalOmpRequiresSymbols);
   }
 
   /// Declare a function.
@@ -6681,7 +6684,8 @@ class FirConverter : public Fortran::lower::AbstractConverter {
   /// Performing OpenMP lowering actions that were deferred to the end of
   /// lowering.
   void finalizeOpenMPLowering(
-      const Fortran::semantics::Symbol *globalOmpRequiresSymbol) {
+      llvm::SmallVectorImpl<const Fortran::semantics::Symbol *>
+          &globalOmpRequiresSymbol) {
     if (!ompDeferredDeclareTarget.empty()) {
       bool deferredDeviceFuncFound =
           Fortran::lower::markOpenMPDeferredDeclareTargetFunctions(
@@ -6690,9 +6694,10 @@ class FirConverter : public Fortran::lower::AbstractConverter {
     }
 
     // Set the module attribute related to OpenMP requires directives
-    if (ompDeviceCodeFound)
-      Fortran::lower::genOpenMPRequires(getModuleOp().getOperation(),
-                                        globalOmpRequiresSymbol);
+    if (ompDeviceCodeFound) {
+      for (auto sym : globalOmpRequiresSymbol)
+        Fortran::lower::genOpenMPRequires(getModuleOp().getOperation(), sym);
+    }
   }
 
   /// Record fir.dummy_scope operation for this function.
diff --git a/flang/test/Lower/OpenMP/requires-usm.f90 b/flang/test/Lower/OpenMP/requires-usm.f90
new file mode 100644
index 0000000000000..600e8387d6ad4
--- /dev/null
+++ b/flang/test/Lower/OpenMP/requires-usm.f90
@@ -0,0 +1,22 @@
+! RUN: %flang_fc1 -emit-hlfir -fopenmp %s -o - | FileCheck %s
+! RUN: %flang_fc1 -emit-hlfir -fopenmp -fopenmp-is-target-device %s -o - | FileCheck %s
+! RUN: bbc -fopenmp -emit-hlfir %s -o - | FileCheck %s
+! RUN: bbc -fopenmp -fopenmp-is-target-device -emit-hlfir %s -o - | FileCheck %s
+
+! Verify that we pick up USM and apply it correctly when it is specified
+! outside of the program.
+
+!CHECK:      module attributes {
+!CHECK-SAME: omp.requires = #omp<clause_requires unified_shared_memory>
+module declare_mod
+    implicit none
+!$omp requires unified_shared_memory
+ contains
+end module
+
+program main
+ use declare_mod
+ implicit none
+!$omp target
+!$omp end target
+end program