[flang-commits] [flang] [llvm] [FLANG][OpenMP]Add frontend support for ASSUME and ASSUMES (PR #120770)

Mats Petersson via flang-commits flang-commits at lists.llvm.org
Tue Dec 24 03:54:43 PST 2024


https://github.com/Leporacanthicus updated https://github.com/llvm/llvm-project/pull/120770

>From 8bc17fac5b91cfc30f4072d8cf8cdcbfbdc3f945 Mon Sep 17 00:00:00 2001
From: Mats Petersson <mats.petersson at arm.com>
Date: Fri, 20 Dec 2024 16:04:59 +0000
Subject: [PATCH 1/2] [FLANG][OpenMP]Add frontend support for ASSUME and
 ASSUMES

Enough suport to parse correctly formed directives of !$OMP ASSUME
and !$OMP ASSUMES with teh related clauses that go with them:
ABSENT, CONTAINS, NO_OPENPP, NO_OPENMP_ROUTINES, NO_PARALLELISM
and HOLDS.

Tests added for unparsing and dump parse-tree.

Semantics support is very minimal and no specific tests added.

The lowering will hit a TODO, and there are tests in Lower/OpenMP/Todo
to make it clear that this is currently expected behaviour.
---
 .../FlangOmpReport/FlangOmpReportVisitor.cpp  |  4 +
 flang/include/flang/Parser/dump-parse-tree.h  | 12 +++
 flang/include/flang/Parser/parse-tree.h       | 85 ++++++++++++++++++-
 flang/lib/Lower/OpenMP/OpenMP.cpp             | 18 ++++
 flang/lib/Parser/openmp-parsers.cpp           | 38 ++++++++-
 flang/lib/Parser/unparse.cpp                  | 20 ++++-
 flang/lib/Semantics/check-omp-structure.cpp   | 17 ++++
 flang/lib/Semantics/check-omp-structure.h     |  4 +
 flang/test/Lower/OpenMP/Todo/assume.f90       |  6 ++
 flang/test/Lower/OpenMP/Todo/assumes.f90      |  9 ++
 flang/test/Parser/OpenMP/assumption.f90       | 66 ++++++++++++++
 llvm/include/llvm/Frontend/OpenMP/OMP.td      | 19 +++++
 12 files changed, 295 insertions(+), 3 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/Todo/assume.f90
 create mode 100644 flang/test/Lower/OpenMP/Todo/assumes.f90
 create mode 100644 flang/test/Parser/OpenMP/assumption.f90

diff --git a/flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp b/flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp
index 665b92be008986..498cd2d7e33b24 100644
--- a/flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp
+++ b/flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp
@@ -129,6 +129,10 @@ std::string OpenMPCounterVisitor::getName(const OpenMPConstruct &c) {
             const CharBlock &source{std::get<0>(c.t).source};
             return normalize_construct_name(source.ToString());
           },
+          [&](const OpenMPAssumeConstruct &c) -> std::string {
+            const CharBlock &source{std::get<0>(c.t).source};
+            return normalize_construct_name(source.ToString());
+          },
           [&](const OpenMPAllocatorsConstruct &c) -> std::string {
             const CharBlock &source{std::get<0>(c.t).source};
             return normalize_construct_name(source.ToString());
diff --git a/flang/include/flang/Parser/dump-parse-tree.h b/flang/include/flang/Parser/dump-parse-tree.h
index 940caaeea9c3b7..4c88b9583c25f9 100644
--- a/flang/include/flang/Parser/dump-parse-tree.h
+++ b/flang/include/flang/Parser/dump-parse-tree.h
@@ -483,6 +483,7 @@ class ParseTreeDumper {
   NODE_ENUM(OmpMapTypeModifier, Value)
   NODE(parser, OmpIteratorSpecifier)
   NODE(parser, OmpIterator)
+  NODE(parser, OmpAbsentClause)
   NODE(parser, OmpAffinityClause)
   NODE(OmpAffinityClause, Modifier)
   NODE(parser, OmpAlignment)
@@ -516,6 +517,7 @@ class ParseTreeDumper {
 #include "llvm/Frontend/OpenMP/OMP.inc"
   NODE(parser, OmpClauseList)
   NODE(parser, OmpCriticalDirective)
+  NODE(parser, OmpContainsClause)
   NODE(parser, OmpDeclareTargetSpecifier)
   NODE(parser, OmpDeclareTargetWithClause)
   NODE(parser, OmpDeclareTargetWithList)
@@ -555,6 +557,8 @@ class ParseTreeDumper {
   NODE(parser, OmpExpectation)
   NODE_ENUM(OmpExpectation, Value)
   NODE(parser, OmpDirectiveNameModifier)
+  NODE(parser, OmpDirectiveNameEntry)
+  NODE(parser, OmpHoldsClause)
   NODE(parser, OmpIfClause)
   NODE(OmpIfClause, Modifier)
   NODE(parser, OmpLastprivateClause)
@@ -578,6 +582,9 @@ class ParseTreeDumper {
   }
   NODE(parser, OmpObject)
   NODE(parser, OmpObjectList)
+  NODE(parser, OmpNoOpenMPClause)
+  NODE(parser, OmpNoOpenMPRoutinesClause)
+  NODE(parser, OmpNoParallelismClause)
   NODE(parser, OmpOrderClause)
   NODE(OmpOrderClause, Modifier)
   NODE_ENUM(OmpOrderClause, Ordering)
@@ -643,6 +650,11 @@ class ParseTreeDumper {
   NODE(parser, OpenACCStandaloneDeclarativeConstruct)
   NODE(parser, OpenACCStandaloneConstruct)
   NODE(parser, OpenACCWaitConstruct)
+  NODE(parser, OpenMPAssumeConstruct)
+  NODE(parser, OpenMPAssumesConstruct)
+  NODE(parser, OpenMPAssumesPartConstruct)
+  NODE(parser, OmpAssumesDirective)
+  NODE(parser, OmpEndAssumesDirective)
   NODE(parser, OpenMPAtomicConstruct)
   NODE(parser, OpenMPBlockConstruct)
   NODE(parser, OpenMPCancelConstruct)
diff --git a/flang/include/flang/Parser/parse-tree.h b/flang/include/flang/Parser/parse-tree.h
index 1d97126d17dbc4..a89938036d9c3f 100644
--- a/flang/include/flang/Parser/parse-tree.h
+++ b/flang/include/flang/Parser/parse-tree.h
@@ -3740,6 +3740,19 @@ struct OmpVariableCategory {
 
 // --- Clauses
 
+struct OmpDirectiveNameEntry {
+  WRAPPER_CLASS_BOILERPLATE(OmpDirectiveNameEntry, llvm::omp::Directive);
+};
+using OmpDirectiveList = std::list<OmpDirectiveNameEntry>;
+
+// Ref: [5.2:214]
+//
+// absent-clause ->
+//   ABSENT(directive-name[, directive-name])
+struct OmpAbsentClause {
+  WRAPPER_CLASS_BOILERPLATE(OmpAbsentClause, OmpDirectiveList);
+};
+
 // Ref: [5.0:135-140], [5.1:161-166], [5.2:264-265]
 //
 // affinity-clause ->
@@ -3808,6 +3821,14 @@ struct OmpBindClause {
   WRAPPER_CLASS_BOILERPLATE(OmpBindClause, Binding);
 };
 
+// Ref: [5.2:214]
+//
+// contains-clause ->
+//   CONTAINS(directive-name[, directive-name])
+struct OmpContainsClause {
+  WRAPPER_CLASS_BOILERPLATE(OmpContainsClause, OmpDirectiveList);
+};
+
 // Ref: [4.5:46-50], [5.0:74-78], [5.1:92-96], [5.2:109]
 //
 // default-clause ->
@@ -3971,6 +3992,15 @@ struct OmpGrainsizeClause {
   std::tuple<MODIFIERS(), ScalarIntExpr> t;
 };
 
+// Ref: [5.2: 214]
+//
+// holds-clause ->
+//   HOLDS(expr[, expr])
+struct OmpHoldsClause {
+  using ExprList = std::list<common::Indirection<Expr>>;
+  WRAPPER_CLASS_BOILERPLATE(OmpHoldsClause, ExprList);
+};
+
 // Ref: [5.2:72-73], in 4.5-5.1 it's scattered over individual directives
 // that allow the IF clause.
 //
@@ -4042,6 +4072,21 @@ struct OmpMessageClause {
   WRAPPER_CLASS_BOILERPLATE(OmpMessageClause, Expr);
 };
 
+// Ref: [5.2: 214]
+//
+// no_openmp_clause -> NO_OPENMP
+EMPTY_CLASS(OmpNoOpenMPClause);
+
+// Ref: [5.2: 214]
+//
+// no_openmp_routines_clause -> NO_OPENMP_ROUTINES
+EMPTY_CLASS(OmpNoOpenMPRoutinesClause);
+
+// Ref: [5.2: 214]
+//
+// no_parallelism_clause -> NO_PARALELISM
+EMPTY_CLASS(OmpNoParallelismClause);
+
 // Ref: [4.5:87-91], [5.0:140-146], [5.1:166-171], [5.2:270]
 //
 // num-tasks-clause ->
@@ -4174,6 +4219,44 @@ struct OmpClauseList {
 
 // --- Directives and constructs
 
+// Ref: [5.2: 213-216]
+//
+// assume-construct ->
+//   ASSUME absent-clause | contains-clause | holds-clause | no-openmp-clause |
+//          no-openmp-routines-clause | no-parallelism-clause
+struct OpenMPAssumeConstruct {
+  TUPLE_CLASS_BOILERPLATE(OpenMPAssumeConstruct);
+  std::tuple<Verbatim, OmpClauseList> t;
+  CharBlock source;
+};
+
+struct OmpAssumesDirective {
+  TUPLE_CLASS_BOILERPLATE(OmpAssumesDirective);
+  std::tuple<Verbatim, OmpClauseList> t;
+  CharBlock source;
+};
+
+struct OmpEndAssumesDirective {
+  TUPLE_CLASS_BOILERPLATE(OmpEndAssumesDirective);
+  std::tuple<Verbatim> t;
+  CharBlock source;
+};
+
+//    structured-block
+// ...
+struct OpenMPAssumesPartConstruct {
+  WRAPPER_CLASS_BOILERPLATE(OpenMPAssumesPartConstruct, Block);
+  CharBlock source;
+};
+
+struct OpenMPAssumesConstruct {
+  TUPLE_CLASS_BOILERPLATE(OpenMPAssumesConstruct);
+  std::tuple<OmpAssumesDirective, OpenMPAssumesPartConstruct,
+      OmpEndAssumesDirective>
+      t;
+  CharBlock source;
+};
+
 // 2.7.2 SECTIONS
 // 2.11.2 PARALLEL SECTIONS
 struct OmpSectionsDirective {
@@ -4580,7 +4663,7 @@ struct OpenMPConstruct {
       OpenMPSectionConstruct, OpenMPLoopConstruct, OpenMPBlockConstruct,
       OpenMPAtomicConstruct, OpenMPDeclarativeAllocate, OpenMPErrorConstruct,
       OpenMPExecutableAllocate, OpenMPAllocatorsConstruct,
-      OpenMPCriticalConstruct>
+      OpenMPAssumeConstruct, OpenMPAssumesConstruct, OpenMPCriticalConstruct>
       u;
 };
 
diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index c61ab67d95a957..cc3cd95f69d77e 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -2893,6 +2893,24 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
                  queue.begin());
 }
 
+static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
+                   semantics::SemanticsContext &semaCtx,
+                   lower::pft::Evaluation &eval,
+                   const parser::OpenMPAssumeConstruct &assumeConstruct) {
+  const auto &verbatim = std::get<parser::Verbatim>(assumeConstruct.t);
+  mlir::Location clauseLocation = converter.genLocation(verbatim.source);
+  TODO(clauseLocation, "OpenMP ASSUME construct");
+}
+
+static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
+                   semantics::SemanticsContext &semaCtx,
+                   lower::pft::Evaluation &eval,
+                   const parser::OpenMPAssumesConstruct &assumesConstruct) {
+  mlir::Location clauseLocation =
+      converter.genLocation(assumesConstruct.source);
+  TODO(clauseLocation, "OpenMP ASSUMES construct");
+}
+
 static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
                    semantics::SemanticsContext &semaCtx,
                    lower::pft::Evaluation &eval,
diff --git a/flang/lib/Parser/openmp-parsers.cpp b/flang/lib/Parser/openmp-parsers.cpp
index 67385c03f66c80..a9b995bbf5e2bb 100644
--- a/flang/lib/Parser/openmp-parsers.cpp
+++ b/flang/lib/Parser/openmp-parsers.cpp
@@ -577,7 +577,14 @@ TYPE_PARSER(construct<OmpSeverityClause>(
 
 TYPE_PARSER(construct<OmpMessageClause>(expr))
 
-TYPE_PARSER(
+TYPE_PARSER(construct<OmpHoldsClause>(many(maybe(","_tok) >> indirect(expr))))
+TYPE_PARSER(construct<OmpAbsentClause>(many(maybe(","_tok) >>
+    construct<OmpDirectiveNameEntry>(OmpDirectiveNameParser{}))))
+TYPE_PARSER(construct<OmpContainsClause>(many(maybe(","_tok) >>
+    construct<OmpDirectiveNameEntry>(OmpDirectiveNameParser{}))))
+
+TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
+                            parenthesized(Parser<OmpAbsentClause>{}))) ||
     "ACQUIRE" >> construct<OmpClause>(construct<OmpClause::Acquire>()) ||
     "ACQ_REL" >> construct<OmpClause>(construct<OmpClause::AcqRel>()) ||
     "AFFINITY" >> construct<OmpClause>(construct<OmpClause::Affinity>(
@@ -597,6 +604,8 @@ TYPE_PARSER(
                   parenthesized(Parser<OmpBindClause>{}))) ||
     "COLLAPSE" >> construct<OmpClause>(construct<OmpClause::Collapse>(
                       parenthesized(scalarIntConstantExpr))) ||
+    "CONTAINS" >> construct<OmpClause>(construct<OmpClause::Contains>(
+                      parenthesized(Parser<OmpContainsClause>{}))) ||
     "COPYIN" >> construct<OmpClause>(construct<OmpClause::Copyin>(
                     parenthesized(Parser<OmpObjectList>{}))) ||
     "COPYPRIVATE" >> construct<OmpClause>(construct<OmpClause::Copyprivate>(
@@ -641,6 +650,8 @@ TYPE_PARSER(
             parenthesized(Parser<OmpObjectList>{}))) ||
     "HINT" >> construct<OmpClause>(
                   construct<OmpClause::Hint>(parenthesized(constantExpr))) ||
+    "HOLDS" >> construct<OmpClause>(construct<OmpClause::Holds>(
+                   parenthesized(Parser<OmpHoldsClause>{}))) ||
     "IF" >> construct<OmpClause>(construct<OmpClause::If>(
                 parenthesized(Parser<OmpIfClause>{}))) ||
     "INBRANCH" >> construct<OmpClause>(construct<OmpClause::Inbranch>()) ||
@@ -665,6 +676,11 @@ TYPE_PARSER(
     "NOTINBRANCH" >>
         construct<OmpClause>(construct<OmpClause::Notinbranch>()) ||
     "NOWAIT" >> construct<OmpClause>(construct<OmpClause::Nowait>()) ||
+    "NO_OPENMP"_id >> construct<OmpClause>(construct<OmpClause::NoOpenmp>()) ||
+    "NO_OPENMP_ROUTINES" >>
+        construct<OmpClause>(construct<OmpClause::NoOpenmpRoutines>()) ||
+    "NO_PARALLELISM" >>
+        construct<OmpClause>(construct<OmpClause::NoParallelism>()) ||
     "NUM_TASKS" >> construct<OmpClause>(construct<OmpClause::NumTasks>(
                        parenthesized(Parser<OmpNumTasksClause>{}))) ||
     "NUM_TEAMS" >> construct<OmpClause>(construct<OmpClause::NumTeams>(
@@ -1085,6 +1101,24 @@ TYPE_PARSER(startOmpLine >>
                 Parser<OpenMPThreadprivate>{})) /
             endOmpLine))
 
+// Assume Construct
+TYPE_PARSER(sourced(construct<OpenMPAssumeConstruct>(
+                        verbatim("ASSUME"_tok), Parser<OmpClauseList>{}) /
+    endOmpLine))
+// Assumes Construct
+TYPE_PARSER(sourced(construct<OmpAssumesDirective>(
+    verbatim("ASSUMES"_tok), Parser<OmpClauseList>{})))
+
+TYPE_PARSER(sourced(construct<OmpEndAssumesDirective>(
+    verbatim(startOmpLine >> "END ASSUMES"_tok))))
+
+TYPE_PARSER(construct<OpenMPAssumesPartConstruct>(block))
+
+TYPE_PARSER(sourced(construct<OpenMPAssumesConstruct>(
+    maybe("BEGIN"_tok) >> Parser<OmpAssumesDirective>{} / endOmpLine,
+    Parser<OpenMPAssumesPartConstruct>{},
+    Parser<OmpEndAssumesDirective>{} / endOmpLine)))
+
 // Block Construct
 TYPE_PARSER(construct<OpenMPBlockConstruct>(
     Parser<OmpBeginBlockDirective>{} / endOmpLine, block,
@@ -1131,6 +1165,8 @@ TYPE_CONTEXT_PARSER("OpenMP construct"_en_US,
                 construct<OpenMPConstruct>(Parser<OpenMPExecutableAllocate>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPAllocatorsConstruct>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPDeclarativeAllocate>{}),
+                construct<OpenMPConstruct>(Parser<OpenMPAssumesConstruct>{}),
+                construct<OpenMPConstruct>(Parser<OpenMPAssumeConstruct>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPCriticalConstruct>{}))))
 
 // END OMP Block directives
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index 0a6af7435b4a22..a3887cd42cd850 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -2077,6 +2077,9 @@ class UnparseVisitor {
   void Unparse(const OmpDirectiveNameModifier &x) {
     Word(llvm::omp::getOpenMPDirectiveName(x.v));
   }
+  void Unparse(const OmpDirectiveNameEntry &x) {
+    Word(llvm::omp::getOpenMPDirectiveName(x.v));
+  }
   void Unparse(const OmpIteratorSpecifier &x) {
     Walk(std::get<TypeDeclarationStmt>(x.t));
     Put(" = ");
@@ -2113,6 +2116,8 @@ class UnparseVisitor {
     Walk(std::get<std::optional<std::list<Modifier>>>(x.t), ": ");
     Walk(std::get<ScalarIntExpr>(x.t));
   }
+  void Unparse(const OmpAbsentClause &x) { Walk("", x.v, ","); }
+  void Unparse(const OmpContainsClause &x) { Walk("", x.v, ","); }
   void Unparse(const OmpAffinityClause &x) {
     using Modifier = OmpAffinityClause::Modifier;
     Walk(std::get<std::optional<std::list<Modifier>>>(x.t), ": ");
@@ -2590,6 +2595,13 @@ class UnparseVisitor {
       Walk(*end);
     }
   }
+  void Unparse(const OpenMPAssumeConstruct &x) {
+    BeginOpenMP();
+    Word("!$OMP ASSUME");
+    Walk(std::get<OmpClauseList>(x.t), ", ");
+    Put("\n");
+    EndOpenMP();
+  }
   void Unparse(const OmpCriticalDirective &x) {
     BeginOpenMP();
     Word("!$OMP CRITICAL");
@@ -2806,7 +2818,9 @@ class UnparseVisitor {
     Put("\n");
     EndOpenMP();
   }
-  void Unparse(const OmpClauseList &x) { Walk(" ", x.v, " "); }
+  void Unparse(const OmpClauseList &x, const char *sep = " ") {
+    Walk(" ", x.v, sep);
+  }
   void Unparse(const OpenMPSimpleStandaloneConstruct &x) {
     BeginOpenMP();
     Word("!$OMP ");
@@ -3065,6 +3079,10 @@ class UnparseVisitor {
     return Walk("", list, comma, suffix);
   }
 
+  void Walk(const OmpClauseList &x, const char *sep = " ") {
+    return Walk(" ", x.v, sep);
+  }
+
   // Traverse a std::tuple<>, with an optional separator.
   template <std::size_t J = 0, typename T>
   void WalkTupleElements(const T &tuple, const char *separator) {
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 414753305a6e37..775b6bcfb76fdc 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -1185,6 +1185,23 @@ void OmpStructureChecker::CheckMasterNesting(
   }
 }
 
+void OmpStructureChecker::Enter(const parser::OpenMPAssumeConstruct &x) {
+  const auto &dir{std::get<parser::Verbatim>(x.t)};
+  PushContextAndClauseSets(dir.source, llvm::omp::Directive::OMPD_assume);
+}
+
+void OmpStructureChecker::Leave(const parser::OpenMPAssumeConstruct &) {
+  dirContext_.pop_back();
+}
+
+void OmpStructureChecker::Enter(const parser::OpenMPAssumesConstruct &x) {
+  PushContextAndClauseSets(x.source, llvm::omp::Directive::OMPD_assumes);
+}
+
+void OmpStructureChecker::Leave(const parser::OpenMPAssumesConstruct &) {
+  dirContext_.pop_back();
+}
+
 void OmpStructureChecker::Leave(const parser::OpenMPBlockConstruct &) {
   if (GetDirectiveNest(TargetBlockOnlyTeams)) {
     ExitDirectiveNest(TargetBlockOnlyTeams);
diff --git a/flang/lib/Semantics/check-omp-structure.h b/flang/lib/Semantics/check-omp-structure.h
index 346a7bed9138f0..ffd36e9cd3324c 100644
--- a/flang/lib/Semantics/check-omp-structure.h
+++ b/flang/lib/Semantics/check-omp-structure.h
@@ -78,6 +78,10 @@ class OmpStructureChecker
   void Enter(const parser::OmpEndLoopDirective &);
   void Leave(const parser::OmpEndLoopDirective &);
 
+  void Enter(const parser::OpenMPAssumeConstruct &);
+  void Leave(const parser::OpenMPAssumeConstruct &);
+  void Enter(const parser::OpenMPAssumesConstruct &);
+  void Leave(const parser::OpenMPAssumesConstruct &);
   void Enter(const parser::OpenMPBlockConstruct &);
   void Leave(const parser::OpenMPBlockConstruct &);
   void Leave(const parser::OmpBeginBlockDirective &);
diff --git a/flang/test/Lower/OpenMP/Todo/assume.f90 b/flang/test/Lower/OpenMP/Todo/assume.f90
new file mode 100644
index 00000000000000..6942c7774663ed
--- /dev/null
+++ b/flang/test/Lower/OpenMP/Todo/assume.f90
@@ -0,0 +1,6 @@
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: OpenMP ASSUME construct
+program p
+  !$omp assume no_openmp
+end program p
diff --git a/flang/test/Lower/OpenMP/Todo/assumes.f90 b/flang/test/Lower/OpenMP/Todo/assumes.f90
new file mode 100644
index 00000000000000..73ad1526e83cc4
--- /dev/null
+++ b/flang/test/Lower/OpenMP/Todo/assumes.f90
@@ -0,0 +1,9 @@
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: OpenMP ASSUMES construct
+program p
+  integer r
+  !$omp assumes no_openmp
+  print *,r
+  !$omp end assumes
+end program p
diff --git a/flang/test/Parser/OpenMP/assumption.f90 b/flang/test/Parser/OpenMP/assumption.f90
new file mode 100644
index 00000000000000..74c10126a76c61
--- /dev/null
+++ b/flang/test/Parser/OpenMP/assumption.f90
@@ -0,0 +1,66 @@
+! RUN: %flang_fc1  -fopenmp-version=51 -fopenmp -fdebug-unparse-no-sema %s 2>&1 | FileCheck %s
+!!! RUN: %flang_fc1  -fopenmp-version=51 -fopenmp -fdebug-dump-parse-tree-no-sema %s 2>&1 | FileCheck %s --check-prefix="PARSE-TREE"
+
+subroutine sub1
+  integer :: r
+!CHECK: !$OMP ASSUME NO_OPENMP
+!PARSE-TREE:   ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumeConstruct
+!PARSE-TREE:   Verbatim
+!PARSE-TREE:   OmpClauseList -> OmpClause -> NoOpenmp
+  !$omp assume no_openmp
+!CHECK: !$OMP ASSUME NO_PARALLELISM
+!PARSE-TREE:   ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumeConstruct
+!PARSE-TREE:   Verbatim
+!PARSE-TREE:   OmpClauseList -> OmpClause -> NoParallelism
+  !$omp assume no_parallelism
+!CHECK: !$OMP ASSUME NO_OPENMP_ROUTINES
+!PARSE-TREE:   ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumeConstruct
+!PARSE-TREE:   Verbatim
+!PARSE-TREE:   OmpClauseList -> OmpClause -> NoOpenmpRoutines  
+  !$omp assume no_openmp_routines
+!CHECK: !$OMP ASSUME ABSENT(ALLOCATE), CONTAINS(WORKSHARE,TASK)
+!PARSE-TREE:   ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumeConstruct
+!PARSE-TREE:   Verbatim
+!PARSE-TREE:   OmpClauseList -> OmpClause -> Absent -> OmpAbsentClause -> OmpDirectiveNameEntry -> llvm::omp::Directive = allocate
+!PARSE-TREE:   OmpClause -> Contains -> OmpContainsClause -> OmpDirectiveNameEntry -> llvm::omp::Directive = workshare
+!PARSE-TREE:   OmpDirectiveNameEntry -> llvm::omp::Directive = task
+ !$omp assume absent(allocate), contains(workshare, task)
+!CHECK: !$OMP ASSUME HOLDS(1==1)
+  !$omp assume holds(1.eq.1)
+  print *, r
+end subroutine sub1
+
+subroutine sub2
+  integer :: r
+!CHECK !$OMP ASSUMES NO_OPENMP
+!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumesConstruct
+!PARSE-TREE: OmpAssumesDirective
+!PARSE-TREE: Verbatim
+!PARSE-TREE: OmpClauseList -> OmpClause -> NoOpenmp
+!PARSE-TREE: OpenMPAssumesPartConstruct -> Block
+!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> AssignmentStmt
+!PARSE-TREE: Expr -> Add
+!PARSE-TREE: OmpEndAssumesDirective
+  !$omp assumes no_openmp
+  r = r + 1
+!CHECK !$OMP END ASSUMES
+  !$omp end assumes
+end subroutine sub2
+
+subroutine sub3
+  integer :: r
+!CHECK !$OMP ASSUMES NO_OPENMP
+!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumesConstruct
+!PARSE-TREE: OmpAssumesDirective
+!PARSE-TREE: Verbatim
+!PARSE-TREE: OmpClauseList -> OmpClause -> NoOpenmp
+!PARSE-TREE: OpenMPAssumesPartConstruct -> Block
+!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> AssignmentStmt
+!PARSE-TREE: Expr -> Add
+!PARSE-TREE: OmpEndAssumesDirective
+  !$omp begin assumes no_openmp
+  r = r + 1
+!CHECK !$OMP END ASSUMES
+  !$omp end assumes
+end subroutine sub3
+  
diff --git a/llvm/include/llvm/Frontend/OpenMP/OMP.td b/llvm/include/llvm/Frontend/OpenMP/OMP.td
index e36eb77cefe7e3..01d073d5db09ab 100644
--- a/llvm/include/llvm/Frontend/OpenMP/OMP.td
+++ b/llvm/include/llvm/Frontend/OpenMP/OMP.td
@@ -34,6 +34,7 @@ def OpenMP : DirectiveLanguage {
 
 def OMPC_Absent : Clause<"absent"> {
   let clangClass = "OMPAbsentClause";
+  let flangClass = "OmpAbsentClause";
 }
 def OMPC_Acquire : Clause<"acquire"> {
   let clangClass = "OMPAcquireClause";
@@ -106,6 +107,7 @@ def OMPC_CancellationConstructType : Clause<"cancellation_construct_type"> {
 }
 def OMPC_Contains : Clause<"contains"> {
   let clangClass = "OMPContainsClause";
+  let flangClass = "OmpContainsClause";
 }
 def OMPC_Capture : Clause<"capture"> {
   let clangClass = "OMPCaptureClause";
@@ -224,6 +226,7 @@ def OMPC_Hint : Clause<"hint"> {
 }
 def OMPC_Holds : Clause<"holds"> {
   let clangClass = "OMPHoldsClause";
+  let flangClass = "OmpHoldsClause";
 }
 def OMPC_If : Clause<"if"> {
   let clangClass = "OMPIfClause";
@@ -552,6 +555,14 @@ def OMP_Allocators : Directive<"allocators"> {
 def OMP_Assumes : Directive<"assumes"> {
   let association = AS_None;
   let category = CA_Informational;
+  let allowedOnceClauses = [
+    VersionedClause<OMPC_Absent, 51>,
+    VersionedClause<OMPC_Contains, 51>,
+    VersionedClause<OMPC_Holds, 51>,
+    VersionedClause<OMPC_NoOpenMP, 51>,
+    VersionedClause<OMPC_NoOpenMPRoutines, 51>,
+    VersionedClause<OMPC_NoParallelism, 51>,
+  ];
 }
 def OMP_EndAssumes : Directive<"end assumes"> {
   let association = AS_Delimited;
@@ -597,6 +608,14 @@ def OMP_Barrier : Directive<"barrier"> {
 def OMP_BeginAssumes : Directive<"begin assumes"> {
   let association = AS_Delimited;
   let category = CA_Informational;
+  let allowedOnceClauses = [
+    VersionedClause<OMPC_Absent, 51>,
+    VersionedClause<OMPC_Contains, 51>,
+    VersionedClause<OMPC_Holds, 51>,
+    VersionedClause<OMPC_NoOpenMP, 51>,
+    VersionedClause<OMPC_NoOpenMPRoutines, 51>,
+    VersionedClause<OMPC_NoParallelism, 51>,
+  ];
 }
 def OMP_BeginDeclareTarget : Directive<"begin declare target"> {
   let allowedClauses = [

>From 3e63e24fe38daf32fd9b94fb4ef9f65e7bddd536 Mon Sep 17 00:00:00 2001
From: Mats Petersson <mats.petersson at arm.com>
Date: Tue, 24 Dec 2024 11:51:20 +0000
Subject: [PATCH 2/2] Review comments

---
 flang/include/flang/Parser/dump-parse-tree.h  |  4 +-
 flang/include/flang/Parser/parse-tree.h       | 40 +++++++------
 flang/lib/Lower/OpenMP/OpenMP.cpp             | 19 ++++--
 flang/lib/Parser/openmp-parsers.cpp           | 59 +++++++++++--------
 flang/lib/Parser/unparse.cpp                  | 25 +++++++-
 flang/lib/Semantics/check-omp-structure.cpp   |  8 +++
 flang/lib/Semantics/check-omp-structure.h     |  2 +
 flang/test/Lower/OpenMP/Todo/assumes.f90      |  5 +-
 .../test/Lower/OpenMP/Todo/begin-assumes.f90  |  9 +++
 flang/test/Parser/OpenMP/assumption.f90       | 35 ++++-------
 10 files changed, 125 insertions(+), 81 deletions(-)
 create mode 100644 flang/test/Lower/OpenMP/Todo/begin-assumes.f90

diff --git a/flang/include/flang/Parser/dump-parse-tree.h b/flang/include/flang/Parser/dump-parse-tree.h
index 4c88b9583c25f9..9bf087290464ee 100644
--- a/flang/include/flang/Parser/dump-parse-tree.h
+++ b/flang/include/flang/Parser/dump-parse-tree.h
@@ -557,7 +557,6 @@ class ParseTreeDumper {
   NODE(parser, OmpExpectation)
   NODE_ENUM(OmpExpectation, Value)
   NODE(parser, OmpDirectiveNameModifier)
-  NODE(parser, OmpDirectiveNameEntry)
   NODE(parser, OmpHoldsClause)
   NODE(parser, OmpIfClause)
   NODE(OmpIfClause, Modifier)
@@ -653,7 +652,8 @@ class ParseTreeDumper {
   NODE(parser, OpenMPAssumeConstruct)
   NODE(parser, OpenMPAssumesConstruct)
   NODE(parser, OpenMPAssumesPartConstruct)
-  NODE(parser, OmpAssumesDirective)
+  NODE(parser, OmpBeginAssumesDirective)
+  NODE(parser, OpenMPBeginAssumesConstruct)
   NODE(parser, OmpEndAssumesDirective)
   NODE(parser, OpenMPAtomicConstruct)
   NODE(parser, OpenMPBlockConstruct)
diff --git a/flang/include/flang/Parser/parse-tree.h b/flang/include/flang/Parser/parse-tree.h
index a89938036d9c3f..8446c71fe06f5e 100644
--- a/flang/include/flang/Parser/parse-tree.h
+++ b/flang/include/flang/Parser/parse-tree.h
@@ -3740,10 +3740,7 @@ struct OmpVariableCategory {
 
 // --- Clauses
 
-struct OmpDirectiveNameEntry {
-  WRAPPER_CLASS_BOILERPLATE(OmpDirectiveNameEntry, llvm::omp::Directive);
-};
-using OmpDirectiveList = std::list<OmpDirectiveNameEntry>;
+using OmpDirectiveList = std::list<llvm::omp::Directive>;
 
 // Ref: [5.2:214]
 //
@@ -3995,10 +3992,9 @@ struct OmpGrainsizeClause {
 // Ref: [5.2: 214]
 //
 // holds-clause ->
-//   HOLDS(expr[, expr])
+//   HOLDS(expr)
 struct OmpHoldsClause {
-  using ExprList = std::list<common::Indirection<Expr>>;
-  WRAPPER_CLASS_BOILERPLATE(OmpHoldsClause, ExprList);
+  WRAPPER_CLASS_BOILERPLATE(OmpHoldsClause, common::Indirection<Expr>);
 };
 
 // Ref: [5.2:72-73], in 4.5-5.1 it's scattered over individual directives
@@ -4230,15 +4226,20 @@ struct OpenMPAssumeConstruct {
   CharBlock source;
 };
 
-struct OmpAssumesDirective {
-  TUPLE_CLASS_BOILERPLATE(OmpAssumesDirective);
+struct OpenMPAssumesConstruct {
+  TUPLE_CLASS_BOILERPLATE(OpenMPAssumesConstruct);
+  std::tuple<Verbatim, OmpClauseList> t;
+  CharBlock source;
+};
+
+struct OmpBeginAssumesDirective {
+  TUPLE_CLASS_BOILERPLATE(OmpBeginAssumesDirective);
   std::tuple<Verbatim, OmpClauseList> t;
   CharBlock source;
 };
 
 struct OmpEndAssumesDirective {
-  TUPLE_CLASS_BOILERPLATE(OmpEndAssumesDirective);
-  std::tuple<Verbatim> t;
+  WRAPPER_CLASS_BOILERPLATE(OmpEndAssumesDirective, Verbatim);
   CharBlock source;
 };
 
@@ -4249,9 +4250,9 @@ struct OpenMPAssumesPartConstruct {
   CharBlock source;
 };
 
-struct OpenMPAssumesConstruct {
-  TUPLE_CLASS_BOILERPLATE(OpenMPAssumesConstruct);
-  std::tuple<OmpAssumesDirective, OpenMPAssumesPartConstruct,
+struct OpenMPBeginAssumesConstruct {
+  TUPLE_CLASS_BOILERPLATE(OpenMPBeginAssumesConstruct);
+  std::tuple<OmpBeginAssumesDirective, OpenMPAssumesPartConstruct,
       OmpEndAssumesDirective>
       t;
   CharBlock source;
@@ -4390,10 +4391,10 @@ struct OpenMPDeclarativeAllocate {
 struct OpenMPDeclarativeConstruct {
   UNION_CLASS_BOILERPLATE(OpenMPDeclarativeConstruct);
   CharBlock source;
-  std::variant<OpenMPDeclarativeAllocate, OpenMPDeclareMapperConstruct,
-      OpenMPDeclareReductionConstruct, OpenMPDeclareSimdConstruct,
-      OpenMPDeclareTargetConstruct, OpenMPThreadprivate,
-      OpenMPRequiresConstruct>
+  std::variant<OpenMPDeclarativeAllocate, OpenMPAssumesConstruct,
+      OpenMPDeclareMapperConstruct, OpenMPDeclareReductionConstruct,
+      OpenMPDeclareSimdConstruct, OpenMPDeclareTargetConstruct,
+      OpenMPThreadprivate, OpenMPRequiresConstruct>
       u;
 };
 
@@ -4663,7 +4664,8 @@ struct OpenMPConstruct {
       OpenMPSectionConstruct, OpenMPLoopConstruct, OpenMPBlockConstruct,
       OpenMPAtomicConstruct, OpenMPDeclarativeAllocate, OpenMPErrorConstruct,
       OpenMPExecutableAllocate, OpenMPAllocatorsConstruct,
-      OpenMPAssumeConstruct, OpenMPAssumesConstruct, OpenMPCriticalConstruct>
+      OpenMPAssumeConstruct, OpenMPBeginAssumesConstruct,
+      OpenMPCriticalConstruct>
       u;
 };
 
diff --git a/flang/lib/Lower/OpenMP/OpenMP.cpp b/flang/lib/Lower/OpenMP/OpenMP.cpp
index cc3cd95f69d77e..2af896bac5d196 100644
--- a/flang/lib/Lower/OpenMP/OpenMP.cpp
+++ b/flang/lib/Lower/OpenMP/OpenMP.cpp
@@ -2601,6 +2601,13 @@ genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   TODO(converter.getCurrentLocation(), "OpenMPDeclarativeAllocate");
 }
 
+static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
+                   semantics::SemanticsContext &semaCtx,
+                   lower::pft::Evaluation &eval,
+                   const parser::OpenMPAssumesConstruct &assumesConstruct) {
+  TODO(converter.getCurrentLocation(), "OpenMP ASSUMES declaration");
+}
+
 static void genOMP(
     lower::AbstractConverter &converter, lower::SymMap &symTable,
     semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
@@ -2902,13 +2909,13 @@ static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
   TODO(clauseLocation, "OpenMP ASSUME construct");
 }
 
-static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
-                   semantics::SemanticsContext &semaCtx,
-                   lower::pft::Evaluation &eval,
-                   const parser::OpenMPAssumesConstruct &assumesConstruct) {
+static void
+genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
+       semantics::SemanticsContext &semaCtx, lower::pft::Evaluation &eval,
+       const parser::OpenMPBeginAssumesConstruct &beginAssumesConstruct) {
   mlir::Location clauseLocation =
-      converter.genLocation(assumesConstruct.source);
-  TODO(clauseLocation, "OpenMP ASSUMES construct");
+      converter.genLocation(beginAssumesConstruct.source);
+  TODO(clauseLocation, "OpenMP BEGIN ASSUMES construct");
 }
 
 static void genOMP(lower::AbstractConverter &converter, lower::SymMap &symTable,
diff --git a/flang/lib/Parser/openmp-parsers.cpp b/flang/lib/Parser/openmp-parsers.cpp
index a9b995bbf5e2bb..40fbddb8e4866a 100644
--- a/flang/lib/Parser/openmp-parsers.cpp
+++ b/flang/lib/Parser/openmp-parsers.cpp
@@ -577,11 +577,11 @@ TYPE_PARSER(construct<OmpSeverityClause>(
 
 TYPE_PARSER(construct<OmpMessageClause>(expr))
 
-TYPE_PARSER(construct<OmpHoldsClause>(many(maybe(","_tok) >> indirect(expr))))
+TYPE_PARSER(construct<OmpHoldsClause>(indirect(expr)))
 TYPE_PARSER(construct<OmpAbsentClause>(many(maybe(","_tok) >>
-    construct<OmpDirectiveNameEntry>(OmpDirectiveNameParser{}))))
+    construct<llvm::omp::Directive>(OmpDirectiveNameParser{}))))
 TYPE_PARSER(construct<OmpContainsClause>(many(maybe(","_tok) >>
-    construct<OmpDirectiveNameEntry>(OmpDirectiveNameParser{}))))
+    construct<llvm::omp::Directive>(OmpDirectiveNameParser{}))))
 
 TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
                             parenthesized(Parser<OmpAbsentClause>{}))) ||
@@ -1082,40 +1082,46 @@ TYPE_PARSER(
         parenthesized(Parser<OmpObjectList>{}), Parser<OmpClauseList>{})) /
     lookAhead(endOmpLine / !statement(allocateStmt)))
 
+// Assumes Construct
+TYPE_PARSER(sourced(construct<OpenMPAssumesConstruct>(
+    verbatim("ASSUMES"_tok), Parser<OmpClauseList>{})))
+
 // Declarative constructs
-TYPE_PARSER(startOmpLine >>
-    withMessage("expected OpenMP construct"_err_en_US,
-        sourced(construct<OpenMPDeclarativeConstruct>(
-                    Parser<OpenMPDeclareReductionConstruct>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPDeclareMapperConstruct>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPDeclareSimdConstruct>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPDeclareTargetConstruct>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPDeclarativeAllocate>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPRequiresConstruct>{}) ||
-            construct<OpenMPDeclarativeConstruct>(
-                Parser<OpenMPThreadprivate>{})) /
-            endOmpLine))
+TYPE_PARSER(
+    startOmpLine >> withMessage("expected OpenMP construct"_err_en_US,
+                        sourced(construct<OpenMPDeclarativeConstruct>(
+                                    Parser<OpenMPAssumesConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPDeclareReductionConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPDeclareMapperConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPDeclareSimdConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPDeclareTargetConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPDeclarativeAllocate>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPRequiresConstruct>{}) ||
+                            construct<OpenMPDeclarativeConstruct>(
+                                Parser<OpenMPThreadprivate>{})) /
+                            endOmpLine))
 
 // Assume Construct
 TYPE_PARSER(sourced(construct<OpenMPAssumeConstruct>(
                         verbatim("ASSUME"_tok), Parser<OmpClauseList>{}) /
     endOmpLine))
-// Assumes Construct
-TYPE_PARSER(sourced(construct<OmpAssumesDirective>(
-    verbatim("ASSUMES"_tok), Parser<OmpClauseList>{})))
+
+TYPE_PARSER(sourced(construct<OmpBeginAssumesDirective>(
+    "BEGIN"_tok >> verbatim("ASSUMES"_tok), Parser<OmpClauseList>{})))
 
 TYPE_PARSER(sourced(construct<OmpEndAssumesDirective>(
     verbatim(startOmpLine >> "END ASSUMES"_tok))))
 
 TYPE_PARSER(construct<OpenMPAssumesPartConstruct>(block))
 
-TYPE_PARSER(sourced(construct<OpenMPAssumesConstruct>(
-    maybe("BEGIN"_tok) >> Parser<OmpAssumesDirective>{} / endOmpLine,
+TYPE_PARSER(sourced(construct<OpenMPBeginAssumesConstruct>(
+    Parser<OmpBeginAssumesDirective>{} / endOmpLine,
     Parser<OpenMPAssumesPartConstruct>{},
     Parser<OmpEndAssumesDirective>{} / endOmpLine)))
 
@@ -1165,7 +1171,8 @@ TYPE_CONTEXT_PARSER("OpenMP construct"_en_US,
                 construct<OpenMPConstruct>(Parser<OpenMPExecutableAllocate>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPAllocatorsConstruct>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPDeclarativeAllocate>{}),
-                construct<OpenMPConstruct>(Parser<OpenMPAssumesConstruct>{}),
+                construct<OpenMPConstruct>(
+                    Parser<OpenMPBeginAssumesConstruct>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPAssumeConstruct>{}),
                 construct<OpenMPConstruct>(Parser<OpenMPCriticalConstruct>{}))))
 
diff --git a/flang/lib/Parser/unparse.cpp b/flang/lib/Parser/unparse.cpp
index a3887cd42cd850..42d9de399af7d1 100644
--- a/flang/lib/Parser/unparse.cpp
+++ b/flang/lib/Parser/unparse.cpp
@@ -2074,10 +2074,10 @@ class UnparseVisitor {
                   },
         x.u);
   }
-  void Unparse(const OmpDirectiveNameModifier &x) {
-    Word(llvm::omp::getOpenMPDirectiveName(x.v));
+  void Unparse(const llvm::omp::Directive &x) {
+    Word(llvm::omp::getOpenMPDirectiveName(x));
   }
-  void Unparse(const OmpDirectiveNameEntry &x) {
+  void Unparse(const OmpDirectiveNameModifier &x) {
     Word(llvm::omp::getOpenMPDirectiveName(x.v));
   }
   void Unparse(const OmpIteratorSpecifier &x) {
@@ -2602,6 +2602,18 @@ class UnparseVisitor {
     Put("\n");
     EndOpenMP();
   }
+  void Unparse(const OmpBeginAssumesDirective &x) {
+    BeginOpenMP();
+    Word("!$OMP BEGIN ASSUMES");
+    Walk(std::get<OmpClauseList>(x.t), ", ");
+    Put("\n");
+    EndOpenMP();
+  }
+  void Unparse(const OmpEndAssumesDirective &x) {
+    BeginOpenMP();
+    Word("!$OMP END ASSUMES\n");
+    EndOpenMP();
+  }
   void Unparse(const OmpCriticalDirective &x) {
     BeginOpenMP();
     Word("!$OMP CRITICAL");
@@ -2655,6 +2667,13 @@ class UnparseVisitor {
     Word("!$OMP ");
     return common::visit(
         common::visitors{
+            [&](const OpenMPAssumesConstruct &z) {
+              Word("ASSUMES ");
+              Walk(std::get<OmpClauseList>(z.t));
+              Put("\n");
+              EndOpenMP();
+              return false;
+            },
             [&](const OpenMPDeclarativeAllocate &z) {
               Word("ALLOCATE (");
               Walk(std::get<OmpObjectList>(z.t));
diff --git a/flang/lib/Semantics/check-omp-structure.cpp b/flang/lib/Semantics/check-omp-structure.cpp
index 775b6bcfb76fdc..d6ee862ec2cc4e 100644
--- a/flang/lib/Semantics/check-omp-structure.cpp
+++ b/flang/lib/Semantics/check-omp-structure.cpp
@@ -1202,6 +1202,14 @@ void OmpStructureChecker::Leave(const parser::OpenMPAssumesConstruct &) {
   dirContext_.pop_back();
 }
 
+void OmpStructureChecker::Enter(const parser::OpenMPBeginAssumesConstruct &x) {
+  PushContextAndClauseSets(x.source, llvm::omp::Directive::OMPD_assumes);
+}
+
+void OmpStructureChecker::Leave(const parser::OpenMPBeginAssumesConstruct &) {
+  dirContext_.pop_back();
+}
+
 void OmpStructureChecker::Leave(const parser::OpenMPBlockConstruct &) {
   if (GetDirectiveNest(TargetBlockOnlyTeams)) {
     ExitDirectiveNest(TargetBlockOnlyTeams);
diff --git a/flang/lib/Semantics/check-omp-structure.h b/flang/lib/Semantics/check-omp-structure.h
index ffd36e9cd3324c..87675800d5f5bb 100644
--- a/flang/lib/Semantics/check-omp-structure.h
+++ b/flang/lib/Semantics/check-omp-structure.h
@@ -82,6 +82,8 @@ class OmpStructureChecker
   void Leave(const parser::OpenMPAssumeConstruct &);
   void Enter(const parser::OpenMPAssumesConstruct &);
   void Leave(const parser::OpenMPAssumesConstruct &);
+  void Enter(const parser::OpenMPBeginAssumesConstruct &);
+  void Leave(const parser::OpenMPBeginAssumesConstruct &);
   void Enter(const parser::OpenMPBlockConstruct &);
   void Leave(const parser::OpenMPBlockConstruct &);
   void Leave(const parser::OmpBeginBlockDirective &);
diff --git a/flang/test/Lower/OpenMP/Todo/assumes.f90 b/flang/test/Lower/OpenMP/Todo/assumes.f90
index 73ad1526e83cc4..3ef4bd857612fd 100644
--- a/flang/test/Lower/OpenMP/Todo/assumes.f90
+++ b/flang/test/Lower/OpenMP/Todo/assumes.f90
@@ -1,9 +1,8 @@
 ! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1 | FileCheck %s
 
-! CHECK: not yet implemented: OpenMP ASSUMES construct
+! CHECK: not yet implemented: OpenMP ASSUMES declaration
 program p
+!$omp assumes no_openmp
   integer r
-  !$omp assumes no_openmp
   print *,r
-  !$omp end assumes
 end program p
diff --git a/flang/test/Lower/OpenMP/Todo/begin-assumes.f90 b/flang/test/Lower/OpenMP/Todo/begin-assumes.f90
new file mode 100644
index 00000000000000..5aad8be417a35b
--- /dev/null
+++ b/flang/test/Lower/OpenMP/Todo/begin-assumes.f90
@@ -0,0 +1,9 @@
+! RUN: %not_todo_cmd %flang_fc1 -emit-fir -fopenmp -fopenmp-version=51 -o - %s 2>&1 | FileCheck %s
+
+! CHECK: not yet implemented: OpenMP BEGIN ASSUMES construct
+program p
+  integer r
+!$omp begin assumes no_parallelism
+  print *,r
+!$omp end assumes
+end program p
diff --git a/flang/test/Parser/OpenMP/assumption.f90 b/flang/test/Parser/OpenMP/assumption.f90
index 74c10126a76c61..80c15cbf6c3109 100644
--- a/flang/test/Parser/OpenMP/assumption.f90
+++ b/flang/test/Parser/OpenMP/assumption.f90
@@ -1,6 +1,5 @@
 ! RUN: %flang_fc1  -fopenmp-version=51 -fopenmp -fdebug-unparse-no-sema %s 2>&1 | FileCheck %s
 !!! RUN: %flang_fc1  -fopenmp-version=51 -fopenmp -fdebug-dump-parse-tree-no-sema %s 2>&1 | FileCheck %s --check-prefix="PARSE-TREE"
-
 subroutine sub1
   integer :: r
 !CHECK: !$OMP ASSUME NO_OPENMP
@@ -21,9 +20,9 @@ subroutine sub1
 !CHECK: !$OMP ASSUME ABSENT(ALLOCATE), CONTAINS(WORKSHARE,TASK)
 !PARSE-TREE:   ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumeConstruct
 !PARSE-TREE:   Verbatim
-!PARSE-TREE:   OmpClauseList -> OmpClause -> Absent -> OmpAbsentClause -> OmpDirectiveNameEntry -> llvm::omp::Directive = allocate
-!PARSE-TREE:   OmpClause -> Contains -> OmpContainsClause -> OmpDirectiveNameEntry -> llvm::omp::Directive = workshare
-!PARSE-TREE:   OmpDirectiveNameEntry -> llvm::omp::Directive = task
+!PARSE-TREE:   OmpClauseList -> OmpClause -> Absent -> OmpAbsentClause -> llvm::omp::Directive = allocate
+!PARSE-TREE:   OmpClause -> Contains -> OmpContainsClause -> llvm::omp::Directive = workshare
+!PARSE-TREE:   llvm::omp::Directive = task
  !$omp assume absent(allocate), contains(workshare, task)
 !CHECK: !$OMP ASSUME HOLDS(1==1)
   !$omp assume holds(1.eq.1)
@@ -32,35 +31,27 @@ end subroutine sub1
 
 subroutine sub2
   integer :: r
-!CHECK !$OMP ASSUMES NO_OPENMP
-!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumesConstruct
-!PARSE-TREE: OmpAssumesDirective
+!CHECK !$OMP BEGIN ASSUMES NO_OPENMP
+!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPBeginAssumesConstruct
+!PARSE-TREE: OmpBeginAssumesDirective
 !PARSE-TREE: Verbatim
 !PARSE-TREE: OmpClauseList -> OmpClause -> NoOpenmp
 !PARSE-TREE: OpenMPAssumesPartConstruct -> Block
 !PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> AssignmentStmt
 !PARSE-TREE: Expr -> Add
 !PARSE-TREE: OmpEndAssumesDirective
-  !$omp assumes no_openmp
+  !$omp begin assumes no_openmp
   r = r + 1
 !CHECK !$OMP END ASSUMES
   !$omp end assumes
 end subroutine sub2
-
-subroutine sub3
-  integer :: r
+  
+program p
 !CHECK !$OMP ASSUMES NO_OPENMP
-!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> OpenMPConstruct -> OpenMPAssumesConstruct
-!PARSE-TREE: OmpAssumesDirective
+!PARSE-TREE: SpecificationPart
+!PARSE-TREE:   OpenMPDeclarativeConstruct -> OpenMPAssumesConstruct
 !PARSE-TREE: Verbatim
 !PARSE-TREE: OmpClauseList -> OmpClause -> NoOpenmp
-!PARSE-TREE: OpenMPAssumesPartConstruct -> Block
-!PARSE-TREE: ExecutionPartConstruct -> ExecutableConstruct -> ActionStmt -> AssignmentStmt
-!PARSE-TREE: Expr -> Add
-!PARSE-TREE: OmpEndAssumesDirective
-  !$omp begin assumes no_openmp
-  r = r + 1
-!CHECK !$OMP END ASSUMES
-  !$omp end assumes
-end subroutine sub3
+  !$omp assumes no_openmp
+end program p
   



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