[OPENMP50]Add parsing/sema for acq_rel clause.

Added basic support (representation + parsing/sema/(de)serialization)
for acq_rel clause in flush/atomic directives.
diff --git a/clang/lib/AST/OpenMPClause.cpp b/clang/lib/AST/OpenMPClause.cpp
index c7e7f33..b1f9ad1 100644
--- a/clang/lib/AST/OpenMPClause.cpp
+++ b/clang/lib/AST/OpenMPClause.cpp
@@ -116,6 +116,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_threads:
   case OMPC_simd:
@@ -190,6 +191,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_device:
   case OMPC_threads:
@@ -1334,6 +1336,10 @@
   OS << "seq_cst";
 }
 
+void OMPClausePrinter::VisitOMPAcqRelClause(OMPAcqRelClause *) {
+  OS << "acq_rel";
+}
+
 void OMPClausePrinter::VisitOMPThreadsClause(OMPThreadsClause *) {
   OS << "threads";
 }
diff --git a/clang/lib/AST/StmtProfile.cpp b/clang/lib/AST/StmtProfile.cpp
index 4625374..a39bc9a 100644
--- a/clang/lib/AST/StmtProfile.cpp
+++ b/clang/lib/AST/StmtProfile.cpp
@@ -517,6 +517,8 @@
 
 void OMPClauseProfiler::VisitOMPSeqCstClause(const OMPSeqCstClause *) {}
 
+void OMPClauseProfiler::VisitOMPAcqRelClause(const OMPAcqRelClause *) {}
+
 void OMPClauseProfiler::VisitOMPThreadsClause(const OMPThreadsClause *) {}
 
 void OMPClauseProfiler::VisitOMPSIMDClause(const OMPSIMDClause *) {}
diff --git a/clang/lib/Basic/OpenMPKinds.cpp b/clang/lib/Basic/OpenMPKinds.cpp
index 3204e22..8937e87 100644
--- a/clang/lib/Basic/OpenMPKinds.cpp
+++ b/clang/lib/Basic/OpenMPKinds.cpp
@@ -214,6 +214,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_device:
   case OMPC_threads:
   case OMPC_simd:
@@ -426,6 +427,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_device:
   case OMPC_threads:
   case OMPC_simd:
@@ -577,9 +579,22 @@
     }
     break;
   case OMPD_flush:
-    return CKind == OMPC_flush;
+    if (CKind == OMPC_flush)
+      return true;
+    if (OpenMPVersion < 50)
+      return false;
+    switch (CKind) {
+#define OPENMP_FLUSH_CLAUSE(Name)                                              \
+  case OMPC_##Name:                                                            \
+    return true;
+#include "clang/Basic/OpenMPKinds.def"
+    default:
+      break;
+    }
     break;
   case OMPD_atomic:
+    if (OpenMPVersion < 50 && CKind == OMPC_acq_rel)
+      return false;
     switch (CKind) {
 #define OPENMP_ATOMIC_CLAUSE(Name)                                             \
   case OMPC_##Name:                                                            \
diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index 827ea213..b315421 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -21,6 +21,7 @@
 #include "clang/AST/OpenMPClause.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/StmtOpenMP.h"
+#include "clang/Basic/OpenMPKinds.h"
 #include "clang/Basic/PrettyStackTrace.h"
 #include "llvm/Frontend/OpenMP/OMPIRBuilder.h"
 using namespace clang;
@@ -4434,6 +4435,7 @@
   case OMPC_collapse:
   case OMPC_default:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_shared:
   case OMPC_linear:
   case OMPC_aligned:
@@ -4483,8 +4485,9 @@
   bool IsSeqCst = S.getSingleClause<OMPSeqCstClause>();
   OpenMPClauseKind Kind = OMPC_unknown;
   for (const OMPClause *C : S.clauses()) {
-    // Find first clause (skip seq_cst clause, if it is first).
-    if (C->getClauseKind() != OMPC_seq_cst) {
+    // Find first clause (skip seq_cst|acq_rel clause, if it is first).
+    if (C->getClauseKind() != OMPC_seq_cst &&
+        C->getClauseKind() != OMPC_acq_rel) {
       Kind = C->getClauseKind();
       break;
     }
diff --git a/clang/lib/Parse/ParseOpenMP.cpp b/clang/lib/Parse/ParseOpenMP.cpp
index ed2e52a..8ac0471 100644
--- a/clang/lib/Parse/ParseOpenMP.cpp
+++ b/clang/lib/Parse/ParseOpenMP.cpp
@@ -1720,7 +1720,6 @@
   DeclarationNameInfo DirName;
   StmtResult Directive = StmtError();
   bool HasAssociatedStatement = true;
-  bool FlushHasClause = false;
 
   switch (DKind) {
   case OMPD_threadprivate: {
@@ -1831,13 +1830,6 @@
     break;
   }
   case OMPD_flush:
-    if (PP.LookAhead(0).is(tok::l_paren)) {
-      FlushHasClause = true;
-      // Push copy of the current token back to stream to properly parse
-      // pseudo-clause OMPFlushClause.
-      PP.EnterToken(Tok, /*IsReinject*/ true);
-    }
-    LLVM_FALLTHROUGH;
   case OMPD_taskyield:
   case OMPD_barrier:
   case OMPD_taskwait:
@@ -1897,6 +1889,10 @@
   case OMPD_target_teams_distribute_parallel_for:
   case OMPD_target_teams_distribute_parallel_for_simd:
   case OMPD_target_teams_distribute_simd: {
+    // Special processing for flush clause.
+    Token FlushTok;
+    if (DKind == OMPD_flush)
+      FlushTok = Tok;
     ConsumeToken();
     // Parse directive name of the 'critical' directive if any.
     if (DKind == OMPD_critical) {
@@ -1926,6 +1922,15 @@
     Actions.StartOpenMPDSABlock(DKind, DirName, Actions.getCurScope(), Loc);
 
     while (Tok.isNot(tok::annot_pragma_openmp_end)) {
+      bool FlushHasClause = false;
+      if (DKind == OMPD_flush && Tok.is(tok::l_paren)) {
+        FlushHasClause = true;
+        // Push copy of the current token back to stream to properly parse
+        // pseudo-clause OMPFlushClause.
+        PP.EnterToken(Tok, /*IsReinject*/ true);
+        PP.EnterToken(FlushTok, /*IsReinject*/ true);
+        ConsumeAnyToken();
+      }
       OpenMPClauseKind CKind =
           Tok.isAnnotation()
               ? OMPC_unknown
@@ -2084,7 +2089,8 @@
 ///       thread_limit-clause | priority-clause | grainsize-clause |
 ///       nogroup-clause | num_tasks-clause | hint-clause | to-clause |
 ///       from-clause | is_device_ptr-clause | task_reduction-clause |
-///       in_reduction-clause | allocator-clause | allocate-clause
+///       in_reduction-clause | allocator-clause | allocate-clause |
+///       acq_rel-clause
 ///
 OMPClause *Parser::ParseOpenMPClause(OpenMPDirectiveKind DKind,
                                      OpenMPClauseKind CKind, bool FirstClause) {
@@ -2193,6 +2199,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_threads:
   case OMPC_simd:
   case OMPC_nogroup:
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index df76b42..aa61971 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -4987,6 +4987,7 @@
       case OMPC_update:
       case OMPC_capture:
       case OMPC_seq_cst:
+      case OMPC_acq_rel:
       case OMPC_depend:
       case OMPC_threads:
       case OMPC_simd:
@@ -8562,7 +8563,21 @@
 StmtResult Sema::ActOnOpenMPFlushDirective(ArrayRef<OMPClause *> Clauses,
                                            SourceLocation StartLoc,
                                            SourceLocation EndLoc) {
-  assert(Clauses.size() <= 1 && "Extra clauses in flush directive");
+  OMPFlushClause *FC = nullptr;
+  OMPClause *OrderClause = nullptr;
+  for (OMPClause *C : Clauses) {
+    if (C->getClauseKind() == OMPC_flush)
+      FC = cast<OMPFlushClause>(C);
+    else
+      OrderClause = C;
+  }
+  if (FC && OrderClause) {
+    Diag(FC->getLParenLoc(), diag::err_omp_flush_order_clause_and_list)
+        << getOpenMPClauseName(OrderClause->getClauseKind());
+    Diag(OrderClause->getBeginLoc(), diag::note_omp_flush_order_clause_here)
+        << getOpenMPClauseName(OrderClause->getClauseKind());
+    return StmtError();
+  }
   return OMPFlushDirective::Create(Context, StartLoc, EndLoc, Clauses);
 }
 
@@ -8901,6 +8916,8 @@
   // longjmp() and throw() must not violate the entry/exit criteria.
   OpenMPClauseKind AtomicKind = OMPC_unknown;
   SourceLocation AtomicKindLoc;
+  OpenMPClauseKind MemOrderKind = OMPC_unknown;
+  SourceLocation MemOrderLoc;
   for (const OMPClause *C : Clauses) {
     if (C->getClauseKind() == OMPC_read || C->getClauseKind() == OMPC_write ||
         C->getClauseKind() == OMPC_update ||
@@ -8915,6 +8932,18 @@
         AtomicKindLoc = C->getBeginLoc();
       }
     }
+    if (C->getClauseKind() == OMPC_seq_cst ||
+        C->getClauseKind() == OMPC_acq_rel) {
+      if (MemOrderKind != OMPC_unknown) {
+        Diag(C->getBeginLoc(), diag::err_omp_atomic_several_mem_order_clauses)
+            << SourceRange(C->getBeginLoc(), C->getEndLoc());
+        Diag(MemOrderLoc, diag::note_omp_atomic_previous_clause)
+            << getOpenMPClauseName(MemOrderKind);
+      } else {
+        MemOrderKind = C->getClauseKind();
+        MemOrderLoc = C->getBeginLoc();
+      }
+    }
   }
 
   Stmt *Body = CS->getCapturedStmt();
@@ -10841,6 +10870,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_threads:
   case OMPC_simd:
@@ -11553,6 +11583,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_threads:
   case OMPC_simd:
@@ -11975,6 +12006,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_device:
   case OMPC_threads:
@@ -12175,6 +12207,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_depend:
   case OMPC_device:
   case OMPC_threads:
@@ -12348,6 +12381,9 @@
   case OMPC_seq_cst:
     Res = ActOnOpenMPSeqCstClause(StartLoc, EndLoc);
     break;
+  case OMPC_acq_rel:
+    Res = ActOnOpenMPAcqRelClause(StartLoc, EndLoc);
+    break;
   case OMPC_threads:
     Res = ActOnOpenMPThreadsClause(StartLoc, EndLoc);
     break;
@@ -12461,6 +12497,11 @@
   return new (Context) OMPSeqCstClause(StartLoc, EndLoc);
 }
 
+OMPClause *Sema::ActOnOpenMPAcqRelClause(SourceLocation StartLoc,
+                                         SourceLocation EndLoc) {
+  return new (Context) OMPAcqRelClause(StartLoc, EndLoc);
+}
+
 OMPClause *Sema::ActOnOpenMPThreadsClause(SourceLocation StartLoc,
                                           SourceLocation EndLoc) {
   return new (Context) OMPThreadsClause(StartLoc, EndLoc);
@@ -12617,6 +12658,7 @@
   case OMPC_update:
   case OMPC_capture:
   case OMPC_seq_cst:
+  case OMPC_acq_rel:
   case OMPC_device:
   case OMPC_threads:
   case OMPC_simd:
diff --git a/clang/lib/Sema/TreeTransform.h b/clang/lib/Sema/TreeTransform.h
index c00c06e..bd0df00 100644
--- a/clang/lib/Sema/TreeTransform.h
+++ b/clang/lib/Sema/TreeTransform.h
@@ -8806,6 +8806,13 @@
 
 template <typename Derived>
 OMPClause *
+TreeTransform<Derived>::TransformOMPAcqRelClause(OMPAcqRelClause *C) {
+  // No need to rebuild this clause, no template-dependent parameters.
+  return C;
+}
+
+template <typename Derived>
+OMPClause *
 TreeTransform<Derived>::TransformOMPThreadsClause(OMPThreadsClause *C) {
   // No need to rebuild this clause, no template-dependent parameters.
   return C;
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index 0921190..c25ce49 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -11666,6 +11666,9 @@
   case OMPC_seq_cst:
     C = new (Context) OMPSeqCstClause();
     break;
+  case OMPC_acq_rel:
+    C = new (Context) OMPAcqRelClause();
+    break;
   case OMPC_threads:
     C = new (Context) OMPThreadsClause();
     break;
@@ -11928,6 +11931,8 @@
 
 void OMPClauseReader::VisitOMPSeqCstClause(OMPSeqCstClause *) {}
 
+void OMPClauseReader::VisitOMPAcqRelClause(OMPAcqRelClause *) {}
+
 void OMPClauseReader::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseReader::VisitOMPSIMDClause(OMPSIMDClause *) {}
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 123f83a..2e19d73 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -6147,6 +6147,8 @@
 
 void OMPClauseWriter::VisitOMPSeqCstClause(OMPSeqCstClause *) {}
 
+void OMPClauseWriter::VisitOMPAcqRelClause(OMPAcqRelClause *) {}
+
 void OMPClauseWriter::VisitOMPThreadsClause(OMPThreadsClause *) {}
 
 void OMPClauseWriter::VisitOMPSIMDClause(OMPSIMDClause *) {}