From 460c2eaa4ad5dd2b19339d65affa25b00782dcb0 Mon Sep 17 00:00:00 2001
From: Kiran Chandramohan <kiran.chandramohan@arm.com>
Date: Thu, 9 Mar 2023 14:05:08 +0000
Subject: [PATCH] [Flang][OpenMP] Restrict check to worksharing construct
 reductions

The outer context private check for reduction variables was firing
for all constructs. This check is not applicable to non-worksharing
constructs.

OpenMP 5.2: Section 5.5.8
A list item that appears in a reduction clause on a worksharing construct
must be shared in the parallel region to which a correspodning worksharing
region binds.

Reviewed By: peixin

Differential Revision: https://reviews.llvm.org/D144824
---
 flang/lib/Semantics/check-omp-structure.cpp | 10 +++++--
 flang/lib/Semantics/check-omp-structure.h   |  2 +-
 flang/test/Semantics/OpenMP/reduction07.f90 | 46 +++++++----------------------
 3 files changed, 19 insertions(+), 39 deletions(-)

diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index b30ea41..cffdabf 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -1981,7 +1981,13 @@ void OmpStructureChecker::CheckReductionTypeList(
   CheckIntentInPointerAndDefinable(
       ompObjectList, llvm::omp::Clause::OMPC_reduction);
   CheckReductionArraySection(ompObjectList);
-  CheckMultipleAppearanceAcrossContext(ompObjectList);
+  // If this is a worksharing construct then ensure the reduction variable
+  // is not private in the parallel region that it binds to.
+  OmpDirectiveSet workshareSet{llvm::omp::Directive::OMPD_do,
+      llvm::omp::Directive::OMPD_sections, llvm::omp::Directive::OMPD_do_simd};
+  if (workshareSet.test(GetContext().directive)) {
+    CheckSharedBindingInOuterContext(ompObjectList);
+  }
 }
 
 void OmpStructureChecker::CheckIntentInPointerAndDefinable(
@@ -2026,7 +2032,7 @@ void OmpStructureChecker::CheckReductionArraySection(
   }
 }
 
-void OmpStructureChecker::CheckMultipleAppearanceAcrossContext(
+void OmpStructureChecker::CheckSharedBindingInOuterContext(
     const parser::OmpObjectList &redObjectList) {
   //  TODO: Verify the assumption here that the immediately enclosing region is
   //  the parallel region to which the worksharing construct having reduction
diff --git a/flang/lib/Semantics/check-omp-structure.h b/flang/lib/Semantics/check-omp-structure.h
index 2751cdd..992531a 100644
--- a/flang/lib/Semantics/check-omp-structure.h
+++ b/flang/lib/Semantics/check-omp-structure.h
@@ -259,7 +259,7 @@ private:
       const parser::OmpObjectList &, const llvm::omp::Clause);
   void CheckArraySection(const parser::ArrayElement &arrayElement,
       const parser::Name &name, const llvm::omp::Clause clause);
-  void CheckMultipleAppearanceAcrossContext(
+  void CheckSharedBindingInOuterContext(
       const parser::OmpObjectList &ompObjectList);
   const parser::OmpObjectList *GetOmpObjectList(const parser::OmpClause &);
   void CheckPredefinedAllocatorRestriction(const parser::CharBlock &source,
diff --git a/flang/test/Semantics/OpenMP/reduction07.f90 b/flang/test/Semantics/OpenMP/reduction07.f90
index a3b5876..98ed69a 100644
--- a/flang/test/Semantics/OpenMP/reduction07.f90
+++ b/flang/test/Semantics/OpenMP/reduction07.f90
@@ -78,42 +78,6 @@ a = a + 10
 !$omp parallel reduction(*:a)
 !$omp end parallel
 
-
-!$omp parallel reduction(+:a)
-!ERROR: REDUCTION clause is not allowed on the WORKSHARE directive
-!ERROR: REDUCTION variable 'a' is REDUCTION in outer context must be shared in the parallel regions to which any of the worksharing regions arising from the worksharing construct bind.
-!$omp workshare reduction(*:a)
-a = a + 10
-!$omp end workshare
-!$omp end parallel
-
-!$omp parallel reduction(*:a)
-!$omp end parallel
-
-
-!$omp parallel reduction(+:a)
-!ERROR: REDUCTION clause is not allowed on the SINGLE directive
-!ERROR: REDUCTION variable 'a' is REDUCTION in outer context must be shared in the parallel regions to which any of the worksharing regions arising from the worksharing construct bind.
-!$omp single reduction(*:a)
-a = a + 10
-!$omp end single
-!$omp end parallel
-
-!$omp parallel reduction(+:a)
-!$omp end parallel
-
-
-!$omp parallel reduction(+:a)
-!ERROR: REDUCTION clause is not allowed on the SINGLE directive
-!ERROR: REDUCTION variable 'a' is REDUCTION in outer context must be shared in the parallel regions to which any of the worksharing regions arising from the worksharing construct bind.
-!$omp single reduction(iand:a)
-a = a + 10
-!$omp end single
-!$omp end parallel
-
-!$omp parallel reduction(iand:a)
-!$omp end parallel
-
 !$omp parallel reduction(ieor:a)
 !ERROR: REDUCTION variable 'a' is REDUCTION in outer context must be shared in the parallel regions to which any of the worksharing regions arising from the worksharing construct bind.
 !$omp sections reduction(+:a)
@@ -121,7 +85,17 @@ a = ieor(a, 10)
 !$omp end sections
 !$omp end parallel
 
+!$omp parallel private(a)
 !$omp parallel reduction(ieor:a)
 !$omp end parallel
+!$omp end parallel
+
+!$omp task firstprivate(a)
+!$omp parallel do reduction(+:a)
+do i=1,10
+  a=a+j
+end do
+!$omp end parallel do
+!$omp end task
 
 end program omp_reduction
-- 
2.7.4