[flang-commits] [flang] [flang][OpenMP] Properly resolve CRITICAL construct names (PR #205904)

[Krzysztof Parzyszek via flang-commits]

https://github.com/kparzysz created https://github.com/llvm/llvm-project/pull/205904

Resolve the names of CRITICAL constructs even if they are reserved names.

Fixes https://github.com/llvm/llvm-project/issues/205855

>From 2727c4cbdc03f0da2527e56870e6b1fc7ef6eadf Mon Sep 17 00:00:00 2001
From: Krzysztof Parzyszek <Krzysztof.Parzyszek at amd.com>
Date: Thu, 25 Jun 2026 13:05:22 -0500
Subject: [PATCH] [flang][OpenMP] Properly resolve CRITICAL construct names

Resolve the names of CRITICAL constructs even if they are reserved names.

Fixes https://github.com/llvm/llvm-project/issues/205855
---
 flang/lib/Semantics/check-omp-structure.cpp   |  7 ++-
 flang/lib/Semantics/resolve-names.cpp         | 52 +++++++++++--------
 .../OpenMP/critical-reserved-name.f90         |  8 +++
 .../Semantics/OpenMP/reserved-locator.f90     |  2 +-
 4 files changed, 46 insertions(+), 23 deletions(-)
 create mode 100644 flang/test/Semantics/OpenMP/critical-reserved-name.f90

diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 061b2bdf775d0..fcd5e884db18d 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -649,7 +649,7 @@ void OmpStructureChecker::Enter(const parser::OmpLocator &x) {
   if (auto *reserved{parser::Unwrap<parser::OmpReservedIdentifier>(x.u)}) {
     std::string name{parser::ToLowerCaseLetters(reserved->v.source.ToString())};
     if (!llvm::is_contained(llvm::omp::getReservedLocatorNames(), name)) {
-      context_.Say(reserved->v.source, "'%s' is not a valid locator"_err_en_US,
+      context_.Say(reserved->v.source, "Invalid use of a reserved name '%s'"_err_en_US,
           parser::ToUpperCaseLetters(name));
     }
   }
@@ -3099,6 +3099,11 @@ void OmpStructureChecker::Enter(const parser::OpenMPCriticalConstruct &x) {
     if (auto *object{parser::Unwrap<parser::OmpObject>(arg.u)}) {
       if (auto *designator{GetDesignatorFromObj(*object)}) {
         return parser::GetDesignatorNameIfDataRef(*designator);
+      } else if (auto *locator{std::get_if<parser::OmpLocator>(&object->u)}) {
+        if (auto *res{
+                std::get_if<parser::OmpReservedIdentifier>(&locator->u)}) {
+          return &res->v;
+        }
       }
     }
     return static_cast<const parser::Name *>(nullptr);
diff --git a/flang/lib/Semantics/resolve-names.cpp b/flang/lib/Semantics/resolve-names.cpp
index 11e24a5e1cccb..8f7d5f0d3f959 100644
--- a/flang/lib/Semantics/resolve-names.cpp
+++ b/flang/lib/Semantics/resolve-names.cpp
@@ -2168,29 +2168,39 @@ void OmpVisitor::ProcessReductionSpecifier(
 }
 
 void OmpVisitor::ResolveCriticalName(const parser::OmpArgument &arg) {
-  auto &globalScope{[&]() -> Scope & {
-    for (Scope *s{&currScope()};; s = &s->parent()) {
-      if (s->IsTopLevel()) {
-        return *s;
-      }
-    }
-    llvm_unreachable("Cannot find global scope");
-  }()};
+  auto *object{parser::Unwrap<parser::OmpObject>(arg.u)};
+  if (!object) {
+    return;
+  }
 
-  if (auto *object{parser::Unwrap<parser::OmpObject>(arg.u)}) {
-    if (auto *desg{parser::omp::GetDesignatorFromObj(*object)}) {
-      if (auto *name{parser::GetDesignatorNameIfDataRef(*desg)}) {
-        if (auto *symbol{FindInScope(globalScope, *name)}) {
-          if (!symbol->test(Symbol::Flag::OmpCriticalLock)) {
-            SayWithDecl(*name, *symbol,
-                "CRITICAL construct name '%s' conflicts with a previous declaration"_warn_en_US,
-                name->ToString());
-          }
-        } else {
-          name->symbol = &MakeSymbol(globalScope, name->source, Attrs{});
-          name->symbol->set(Symbol::Flag::OmpCriticalLock);
-        }
+  const parser::Name *name{common::visit( //
+      common::visitors{//
+          [&](const parser::Designator &x) -> const parser::Name * {
+            return parser::GetDesignatorNameIfDataRef(x);
+          },
+          [&](const parser::OmpLocator &x) -> const parser::Name * {
+            if (auto *res{std::get_if<parser::OmpReservedIdentifier>(&x.u)}) {
+              return &res->v;
+            }
+            return nullptr;
+          },
+          [&](const parser::Name &) -> const parser::Name * { return nullptr; },
+          [&](const parser::OmpObject::Invalid &) -> const parser::Name * {
+            return nullptr;
+          }},
+      object->u)};
+
+  if (name) {
+    if (auto *symbol{FindInScope(context().globalScope(), *name)}) {
+      if (!symbol->test(Symbol::Flag::OmpCriticalLock)) {
+        SayWithDecl(*name, *symbol,
+            "CRITICAL construct name '%s' conflicts with a previous declaration"_warn_en_US,
+            name->ToString());
       }
+    } else {
+      name->symbol =
+          &MakeSymbol(context().globalScope(), name->source, Attrs{});
+      name->symbol->set(Symbol::Flag::OmpCriticalLock);
     }
   }
 }
diff --git a/flang/test/Semantics/OpenMP/critical-reserved-name.f90 b/flang/test/Semantics/OpenMP/critical-reserved-name.f90
new file mode 100644
index 0000000000000..9516f0c07d7b7
--- /dev/null
+++ b/flang/test/Semantics/OpenMP/critical-reserved-name.f90
@@ -0,0 +1,8 @@
+! RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp
+
+subroutine f
+  !ERROR: Invalid use of a reserved name 'OMP_C'
+  !$omp critical(omp_c)
+  !ERROR: Invalid use of a reserved name 'OMP_C'
+  !$omp end critical(omp_c)
+end
diff --git a/flang/test/Semantics/OpenMP/reserved-locator.f90 b/flang/test/Semantics/OpenMP/reserved-locator.f90
index 3fc45ffa0f54c..ae2a6d59f4c74 100644
--- a/flang/test/Semantics/OpenMP/reserved-locator.f90
+++ b/flang/test/Semantics/OpenMP/reserved-locator.f90
@@ -1,6 +1,6 @@
 !RUN: %python %S/../test_errors.py %s %flang_fc1 -fopenmp -fopenmp-version=60
 
 subroutine f
-!ERROR: 'OMP_SOME_MEMORY' is not a valid locator
+!ERROR: Invalid use of a reserved name 'OMP_SOME_MEMORY'
   !$omp target update from(omp_some_memory)
 end