[flang-commits] [flang] [flang][OpenMP] Allow common blocks in nested directives (PR #88430)

[Leandro Lupori via flang-commits]

https://github.com/luporl updated https://github.com/llvm/llvm-project/pull/88430

>From d4630a369953a28e12fb66be2b70158b290d2477 Mon Sep 17 00:00:00 2001
From: Leandro Lupori <leandro.lupori at linaro.org>
Date: Thu, 11 Apr 2024 16:33:39 -0300
Subject: [PATCH 1/2] [flang][OpenMP] Allow common blocks in nested directives

COMMON block names must be declared in the same scoping unit in
which the OpenMP directive or clause appears. However, given that
common blocks and threadprivate directives can't be nested inside
other directives, such as parallel, and based on the behavior of
other compilers, it seems that OpenMP block constructs should not
be considered as scoping units.

This patch implements this behavior by also looking for common
block names in the scoping unit of the outermost directive.
---
 flang/lib/Semantics/resolve-directives.cpp | 17 +++++++++++++----
 flang/test/Semantics/OpenMP/resolve03.f90  | 16 ++++++++++++++++
 2 files changed, 29 insertions(+), 4 deletions(-)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 27af192f606be9..ac1c988e174275 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -2096,10 +2096,19 @@ Symbol *OmpAttributeVisitor::ResolveOmpCommonBlockName(
     name->symbol = cur;
     return cur;
   }
-  // Then check parent scope
-  if (auto *prev{GetContext().scope.parent().FindCommonBlock(name->source)}) {
-    name->symbol = prev;
-    return prev;
+  // Then check parent scope, skipping OpenMP scopes and making sure
+  // that the top directive started its own scope.
+  DirContext &topDirContext = dirContext_.front();
+  Scope &topDirScope = topDirContext.scope;
+  assert(!topDirContext.directiveSource.empty());
+  assert(!topDirScope.sourceRange().empty());
+  if (!topDirScope.IsTopLevel() &&
+      topDirContext.directiveSource.begin() ==
+          topDirScope.sourceRange().begin()) {
+    if (auto *prev{topDirScope.parent().FindCommonBlock(name->source)}) {
+      name->symbol = prev;
+      return prev;
+    }
   }
   return nullptr;
 }
diff --git a/flang/test/Semantics/OpenMP/resolve03.f90 b/flang/test/Semantics/OpenMP/resolve03.f90
index b9306c4fe9cb4d..1228f070e0595f 100644
--- a/flang/test/Semantics/OpenMP/resolve03.f90
+++ b/flang/test/Semantics/OpenMP/resolve03.f90
@@ -8,6 +8,9 @@
 
   common /c/ a, b
   integer a(3), b
+  common /tc/ xy
+  integer xz
+  !$omp threadprivate(/tc/)
 
   A = 1
   B = 2
@@ -19,4 +22,17 @@
     !$omp end parallel
   end block
   print *, a, b
+
+  ! Common block names may be used inside nested OpenMP directives.
+  !$omp parallel
+    !$omp parallel copyin(/tc/)
+      xz = xz + 10
+    !$omp end parallel
+  !$omp end parallel
+
+  !$omp parallel
+    !$omp single
+      xz = 18
+    !$omp end single copyprivate(/tc/)
+  !$omp end parallel
 end

>From 7581f9650dc9270cae645fb3d9a4461fa4c02d63 Mon Sep 17 00:00:00 2001
From: Leandro Lupori <leandro.lupori at linaro.org>
Date: Wed, 17 Apr 2024 14:04:25 -0300
Subject: [PATCH 2/2] Search for common blocks in the current scoping unit

---
 flang/lib/Semantics/resolve-directives.cpp | 22 ++++------------------
 flang/test/Semantics/OpenMP/resolve03.f90  | 17 +++++++++++++----
 2 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index ac1c988e174275..f1eec8a15b85e7 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -2091,24 +2091,10 @@ Symbol *OmpAttributeVisitor::ResolveOmpCommonBlockName(
   if (!name) {
     return nullptr;
   }
-  // First check if the Common Block is declared in the current scope
-  if (auto *cur{GetContext().scope.FindCommonBlock(name->source)}) {
-    name->symbol = cur;
-    return cur;
-  }
-  // Then check parent scope, skipping OpenMP scopes and making sure
-  // that the top directive started its own scope.
-  DirContext &topDirContext = dirContext_.front();
-  Scope &topDirScope = topDirContext.scope;
-  assert(!topDirContext.directiveSource.empty());
-  assert(!topDirScope.sourceRange().empty());
-  if (!topDirScope.IsTopLevel() &&
-      topDirContext.directiveSource.begin() ==
-          topDirScope.sourceRange().begin()) {
-    if (auto *prev{topDirScope.parent().FindCommonBlock(name->source)}) {
-      name->symbol = prev;
-      return prev;
-    }
+  if (auto *cb{GetProgramUnitOrBlockConstructContaining(GetContext().scope)
+                   .FindCommonBlock(name->source)}) {
+    name->symbol = cb;
+    return cb;
   }
   return nullptr;
 }
diff --git a/flang/test/Semantics/OpenMP/resolve03.f90 b/flang/test/Semantics/OpenMP/resolve03.f90
index 1228f070e0595f..ebc66ca12ebf44 100644
--- a/flang/test/Semantics/OpenMP/resolve03.f90
+++ b/flang/test/Semantics/OpenMP/resolve03.f90
@@ -8,8 +8,8 @@
 
   common /c/ a, b
   integer a(3), b
-  common /tc/ xy
-  integer xz
+  common /tc/ x
+  integer x
   !$omp threadprivate(/tc/)
 
   A = 1
@@ -23,16 +23,25 @@
   end block
   print *, a, b
 
+  !$omp parallel
+    block
+      !$omp single
+        x = 18
+      !ERROR: COMMON block must be declared in the same scoping unit in which the OpenMP directive or clause appears
+      !$omp end single copyprivate(/tc/)
+    end block
+  !$omp end parallel
+
   ! Common block names may be used inside nested OpenMP directives.
   !$omp parallel
     !$omp parallel copyin(/tc/)
-      xz = xz + 10
+      x = x + 10
     !$omp end parallel
   !$omp end parallel
 
   !$omp parallel
     !$omp single
-      xz = 18
+      x = 18
     !$omp end single copyprivate(/tc/)
   !$omp end parallel
 end