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@tblah tblah commented May 12, 2025

I think this was denied by accident in 68180d8.

Flush of a common block is allowed by the standard on my reading. It is
not allowed by classic-flang but is supported by gfortran and ifx.

This doesn't need any lowering changes. The LLVM translation ignores the
flush argument list because the openmp runtime library doesn't support
flushing specific data.

Depends upon #139522. Ignore the first commit in this PR.

@llvmbot llvmbot added flang Flang issues not falling into any other category flang:fir-hlfir flang:openmp flang:semantics labels May 12, 2025
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llvmbot commented May 12, 2025

@llvm/pr-subscribers-flang-fir-hlfir

@llvm/pr-subscribers-flang-openmp

Author: Tom Eccles (tblah)

Changes

I think this was denied by accident in 68180d8.

Flush of a common block is allowed by the standard on my reading. It is
not allowed by classic-flang but is supported by gfortran and ifx.

This doesn't need any lowering changes. The LLVM translation ignores the
flush argument list because the openmp runtime library doesn't support
flushing specific data.

Depends upon #139522. Ignore the first commit in this PR.


Full diff: https://github.com/llvm/llvm-project/pull/139528.diff

3 Files Affected:

  • (modified) flang/lib/Semantics/check-omp-structure.cpp (-7)
  • (modified) flang/lib/Semantics/resolve-directives.cpp (+13)
  • (added) flang/test/Lower/OpenMP/flush-common.f90 (+13)
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index f17de42ca2466..591f30db36baa 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -2304,13 +2304,6 @@ void OmpStructureChecker::Leave(const parser::OpenMPFlushConstruct &x) {
   auto &flushList{std::get<std::optional<parser::OmpArgumentList>>(x.v.t)};
 
   if (flushList) {
-    for (const parser::OmpArgument &arg : flushList->v) {
-      if (auto *sym{GetArgumentSymbol(arg)}; sym && !IsVariableListItem(*sym)) {
-        context_.Say(arg.source,
-            "FLUSH argument must be a variable list item"_err_en_US);
-      }
-    }
-
     if (FindClause(llvm::omp::Clause::OMPC_acquire) ||
         FindClause(llvm::omp::Clause::OMPC_release) ||
         FindClause(llvm::omp::Clause::OMPC_acq_rel)) {
diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 8b1caca34a6a7..68f8cf9f17620 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -409,6 +409,19 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
   }
   void Post(const parser::OpenMPDepobjConstruct &) { PopContext(); }
 
+  bool Pre(const parser::OpenMPFlushConstruct &x) {
+    PushContext(x.source, llvm::omp::Directive::OMPD_flush);
+    for (auto &arg : x.v.Arguments().v) {
+      if (auto *locator{std::get_if<parser::OmpLocator>(&arg.u)}) {
+        if (auto *object{std::get_if<parser::OmpObject>(&locator->u)}) {
+          ResolveOmpObject(*object, Symbol::Flag::OmpDependObject);
+        }
+      }
+    }
+    return true;
+  }
+  void Post(const parser::OpenMPFlushConstruct &) { PopContext(); }
+
   bool Pre(const parser::OpenMPRequiresConstruct &x) {
     using Flags = WithOmpDeclarative::RequiresFlags;
     using Requires = WithOmpDeclarative::RequiresFlag;
diff --git a/flang/test/Lower/OpenMP/flush-common.f90 b/flang/test/Lower/OpenMP/flush-common.f90
new file mode 100644
index 0000000000000..7656141dcb295
--- /dev/null
+++ b/flang/test/Lower/OpenMP/flush-common.f90
@@ -0,0 +1,13 @@
+! RUN: %flang_fc1 -fopenmp -emit-hlfir -o - %s | FileCheck %s
+
+! Regression test to ensure that the name /c/ in the flush argument list is
+! resolved to the common block symbol and common blocks are allowed in the
+! flush argument list.
+
+! CHECK: %[[GLBL:.*]] = fir.address_of({{.*}}) : !fir.ref<!fir.array<4xi8>>
+  common /c/ x
+  real :: x
+! CHECK: omp.flush(%[[GLBL]] : !fir.ref<!fir.array<4xi8>>)
+  !$omp flush(/c/)
+end
+

@llvmbot
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llvmbot commented May 12, 2025

@llvm/pr-subscribers-flang-semantics

Author: Tom Eccles (tblah)

Changes

I think this was denied by accident in 68180d8.

Flush of a common block is allowed by the standard on my reading. It is
not allowed by classic-flang but is supported by gfortran and ifx.

This doesn't need any lowering changes. The LLVM translation ignores the
flush argument list because the openmp runtime library doesn't support
flushing specific data.

Depends upon #139522. Ignore the first commit in this PR.


Full diff: https://github.com/llvm/llvm-project/pull/139528.diff

3 Files Affected:

  • (modified) flang/lib/Semantics/check-omp-structure.cpp (-7)
  • (modified) flang/lib/Semantics/resolve-directives.cpp (+13)
  • (added) flang/test/Lower/OpenMP/flush-common.f90 (+13)
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index f17de42ca2466..591f30db36baa 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -2304,13 +2304,6 @@ void OmpStructureChecker::Leave(const parser::OpenMPFlushConstruct &x) {
   auto &flushList{std::get<std::optional<parser::OmpArgumentList>>(x.v.t)};
 
   if (flushList) {
-    for (const parser::OmpArgument &arg : flushList->v) {
-      if (auto *sym{GetArgumentSymbol(arg)}; sym && !IsVariableListItem(*sym)) {
-        context_.Say(arg.source,
-            "FLUSH argument must be a variable list item"_err_en_US);
-      }
-    }
-
     if (FindClause(llvm::omp::Clause::OMPC_acquire) ||
         FindClause(llvm::omp::Clause::OMPC_release) ||
         FindClause(llvm::omp::Clause::OMPC_acq_rel)) {
diff --git a/flang/lib/Semantics/resolve-directives.cpp b/flang/lib/Semantics/resolve-directives.cpp
index 8b1caca34a6a7..68f8cf9f17620 100644
--- a/flang/lib/Semantics/resolve-directives.cpp
+++ b/flang/lib/Semantics/resolve-directives.cpp
@@ -409,6 +409,19 @@ class OmpAttributeVisitor : DirectiveAttributeVisitor<llvm::omp::Directive> {
   }
   void Post(const parser::OpenMPDepobjConstruct &) { PopContext(); }
 
+  bool Pre(const parser::OpenMPFlushConstruct &x) {
+    PushContext(x.source, llvm::omp::Directive::OMPD_flush);
+    for (auto &arg : x.v.Arguments().v) {
+      if (auto *locator{std::get_if<parser::OmpLocator>(&arg.u)}) {
+        if (auto *object{std::get_if<parser::OmpObject>(&locator->u)}) {
+          ResolveOmpObject(*object, Symbol::Flag::OmpDependObject);
+        }
+      }
+    }
+    return true;
+  }
+  void Post(const parser::OpenMPFlushConstruct &) { PopContext(); }
+
   bool Pre(const parser::OpenMPRequiresConstruct &x) {
     using Flags = WithOmpDeclarative::RequiresFlags;
     using Requires = WithOmpDeclarative::RequiresFlag;
diff --git a/flang/test/Lower/OpenMP/flush-common.f90 b/flang/test/Lower/OpenMP/flush-common.f90
new file mode 100644
index 0000000000000..7656141dcb295
--- /dev/null
+++ b/flang/test/Lower/OpenMP/flush-common.f90
@@ -0,0 +1,13 @@
+! RUN: %flang_fc1 -fopenmp -emit-hlfir -o - %s | FileCheck %s
+
+! Regression test to ensure that the name /c/ in the flush argument list is
+! resolved to the common block symbol and common blocks are allowed in the
+! flush argument list.
+
+! CHECK: %[[GLBL:.*]] = fir.address_of({{.*}}) : !fir.ref<!fir.array<4xi8>>
+  common /c/ x
+  real :: x
+! CHECK: omp.flush(%[[GLBL]] : !fir.ref<!fir.array<4xi8>>)
+  !$omp flush(/c/)
+end
+

@kiranktp
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Thanks for the patch Tom. LGTM

I think this was denied by accident in 68180d8.

Flush of a common block is allowed by the standard on my reading. It is
not allowed by classic-flang but is supported by gfortran and ifx.

This doesn't need any lowering changes. The LLVM translation ignores the
flush argument list because the openmp runtime library doesn't support
flushing specific data.

Depends upon llvm#139522. Ignore the first commit in this PR.
@tblah tblah force-pushed the ecclescake/flush-common2 branch from 890a8a0 to 3e6d5c3 Compare May 13, 2025 09:55

if (flushList) {
for (const parser::OmpArgument &arg : flushList->v) {
if (auto *sym{GetArgumentSymbol(arg)}; sym && !IsVariableListItem(*sym)) {
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@kparzysz is this an issue with the function IsVariableListItem?

A variable list item is one of the following:
2 • a variable that is not coindexed and that is not a substring;
3 • an array section that is not coindexed and that does not contain an element that is a substring;
4 • a named constant;
5 • an associate name that may appear in a variable definition context; or
6 • a common block name (enclosed in slashes).

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I wonder whether the following is the correct fix here.

 bool OmpStructureChecker::IsVariableListItem(const Symbol &sym) {
-  return evaluate::IsVariable(sym) || sym.attrs().test(Attr::POINTER);
+  return evaluate::IsVariable(sym) || sym.attrs().test(Attr::POINTER) ||
+      sym.detailsIf<semantics::CommonBlockDetails>();
 }

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My worry was whether that would affect many other constructs. Especially through this use:

void OmpStructureChecker::Enter(const parser::OmpClause &x)

Even if it is wrong that those constructs currently do not accept common blocks, it is unlikely that they will all generate correct code in this case.

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LG.

@tblah tblah merged commit dc0dcab into llvm:main May 19, 2025
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