[flang-commits] [flang] [flang][OpenACC] Relax COMMON block usage restriction in OpenACC directives (PR #162659)

[Eugene Epshteyn via flang-commits]

https://github.com/eugeneepshteyn updated https://github.com/llvm/llvm-project/pull/162659

>From 042d2f66bd632fb5d83df0ca4d5c0a3ede031c1c Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Mon, 6 Oct 2025 05:51:32 -0400
Subject: [PATCH 1/4] [flang] Draft of the work to look up COMMON declarations
 in the modules for ACC directives.

---
 flang/lib/Semantics/resolve-directives.cpp | 18 +++++++-----------
 1 file changed, 7 insertions(+), 11 deletions(-)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 18fc63814d973..eefd19f3ac6a9 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -1695,17 +1695,13 @@ void AccAttributeVisitor::Post(const parser::Name &name) {
 
 Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
     const parser::Name *name) {
-  if (auto *prev{name
-              ? GetContext().scope.parent().FindCommonBlock(name->source)
-              : nullptr}) {
-    name->symbol = prev;
-    return prev;
-  }
-  // Check if the Common Block is declared in the current scope
-  if (auto *commonBlockSymbol{
-          name ? GetContext().scope.FindCommonBlock(name->source) : nullptr}) {
-    name->symbol = commonBlockSymbol;
-    return commonBlockSymbol;
+  if (!name) {
+    return nullptr;
+  }
+  if (auto *cb{GetProgramUnitOrBlockConstructContaining(GetContext().scope)
+              .FindCommonBlock(name->source)}) {
+    name->symbol = cb;
+    return cb;
   }
   return nullptr;
 }

>From 931b300841960e8c33c4c1351fdeb0ec1916f329 Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Thu, 9 Oct 2025 06:30:51 -0400
Subject: [PATCH 2/4] Try to handle use association, but didn't work, because
 no symbol

---
 flang/lib/Semantics/resolve-directives.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index eefd19f3ac6a9..583f69dca6bbf 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -1703,6 +1703,12 @@ Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
     name->symbol = cb;
     return cb;
   }
+  if (auto *cb{GetContext().scope.FindSymbol(name->source)}) {
+    if (auto *sym{&cb->GetUltimate()}; sym && sym->has<CommonBlockDetails>()) {
+      name->symbol = sym;
+      return sym;
+    }
+  }
   return nullptr;
 }
 

>From 86cb8b62c9c546f4e5c909a2500e4e8563bd2839 Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Thu, 9 Oct 2025 09:54:23 -0400
Subject: [PATCH 3/4] Searching for COMMON definition in top level modules

---
 flang/lib/Semantics/resolve-directives.cpp | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 583f69dca6bbf..a7fcc4d46e4a5 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -1698,15 +1698,18 @@ Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
   if (!name) {
     return nullptr;
   }
+  // Check the local and surrounding scopes first
   if (auto *cb{GetProgramUnitOrBlockConstructContaining(GetContext().scope)
               .FindCommonBlock(name->source)}) {
     name->symbol = cb;
     return cb;
   }
-  if (auto *cb{GetContext().scope.FindSymbol(name->source)}) {
-    if (auto *sym{&cb->GetUltimate()}; sym && sym->has<CommonBlockDetails>()) {
-      name->symbol = sym;
-      return sym;
+  // Look for COMMON block in the modules
+  for (const Scope &childScope : context_.globalScope().children()) {
+    if (childScope.kind() == Scope::Kind::Module) {
+      auto *cb{childScope.FindCommonBlock(name->source)};
+      name->symbol = cb;
+      return cb;
     }
   }
   return nullptr;
@@ -1757,8 +1760,8 @@ void AccAttributeVisitor::ResolveAccObject(
               }
             } else {
               context_.Say(name.source,
-                  "COMMON block must be declared in the same scoping unit "
-                  "in which the OpenACC directive or clause appears"_err_en_US);
+                  "Could not find COMMON block '%s' used in OpenACC directive"_err_en_US,
+                  name.ToString());
             }
           },
       },

>From f462bf5d170e4bbd82cd46d963baef9077985982 Mon Sep 17 00:00:00 2001
From: Eugene Epshteyn <eepshteyn at nvidia.com>
Date: Thu, 9 Oct 2025 12:16:44 -0400
Subject: [PATCH 4/4] Guard against null cb

---
 flang/lib/Semantics/resolve-directives.cpp | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index a7fcc4d46e4a5..44cfb75e06164 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -1707,9 +1707,10 @@ Symbol *AccAttributeVisitor::ResolveAccCommonBlockName(
   // Look for COMMON block in the modules
   for (const Scope &childScope : context_.globalScope().children()) {
     if (childScope.kind() == Scope::Kind::Module) {
-      auto *cb{childScope.FindCommonBlock(name->source)};
-      name->symbol = cb;
-      return cb;
+      if (auto *cb{childScope.FindCommonBlock(name->source)}) {
+        name->symbol = cb;
+        return cb;
+      }
     }
   }
   return nullptr;