1 files changed, 26 insertions, 20 deletions

diff --git a/clang/lib/CodeGen/CGStmtOpenMP.cpp b/clang/lib/CodeGen/CGStmtOpenMP.cpp
index b378cc6dea5..1a9ff6eacd4 100644
--- a/clang/lib/CodeGen/CGStmtOpenMP.cpp
+++ b/clang/lib/CodeGen/CGStmtOpenMP.cpp
@@ -376,14 +376,23 @@ bool CodeGenFunction::EmitOMPFirstprivateClause(const OMPExecutableDirective &D,
                                                 OMPPrivateScope &PrivateScope) {
   if (!HaveInsertPoint())
     return false;
+  bool FirstprivateIsLastprivate = false;
+  llvm::DenseSet<const VarDecl *> Lastprivates;
+  for (const auto *C : D.getClausesOfKind<OMPLastprivateClause>()) {
+    for (const auto *D : C->varlists())
+      Lastprivates.insert(
+          cast<VarDecl>(cast<DeclRefExpr>(D)->getDecl())->getCanonicalDecl());
+  }
   llvm::DenseSet<const VarDecl *> EmittedAsFirstprivate;
   for (const auto *C : D.getClausesOfKind<OMPFirstprivateClause>()) {
     auto IRef = C->varlist_begin();
     auto InitsRef = C->inits().begin();
     for (auto IInit : C->private_copies()) {
       auto *OrigVD = cast<VarDecl>(cast<DeclRefExpr>(*IRef)->getDecl());
-      if (EmittedAsFirstprivate.count(OrigVD) == 0) {
-        EmittedAsFirstprivate.insert(OrigVD);
+      FirstprivateIsLastprivate =
+          FirstprivateIsLastprivate ||
+          (Lastprivates.count(OrigVD->getCanonicalDecl()) > 0);
+      if (EmittedAsFirstprivate.insert(OrigVD->getCanonicalDecl()).second) {
         auto *VD = cast<VarDecl>(cast<DeclRefExpr>(IInit)->getDecl());
         auto *VDInit = cast<VarDecl>(cast<DeclRefExpr>(*InitsRef)->getDecl());
         bool IsRegistered;
@@ -443,7 +452,7 @@ bool CodeGenFunction::EmitOMPFirstprivateClause(const OMPExecutableDirective &D,
       ++IRef, ++InitsRef;
     }
   }
-  return !EmittedAsFirstprivate.empty();
+  return FirstprivateIsLastprivate && !EmittedAsFirstprivate.empty();
 }
 
 void CodeGenFunction::EmitOMPPrivateClause(
@@ -490,7 +499,6 @@ bool CodeGenFunction::EmitOMPCopyinClause(const OMPExecutableDirective &D) {
       auto *VD = cast<VarDecl>(cast<DeclRefExpr>(*IRef)->getDecl());
       QualType Type = VD->getType();
       if (CopiedVars.insert(VD->getCanonicalDecl()).second) {
-
         // Get the address of the master variable. If we are emitting code with
         // TLS support, the address is passed from the master as field in the
         // captured declaration.
@@ -964,12 +972,11 @@ void CodeGenFunction::EmitOMPParallelDirective(const OMPParallelDirective &S) {
   auto &&CodeGen = [&S](CodeGenFunction &CGF) {
     OMPPrivateScope PrivateScope(CGF);
     bool Copyins = CGF.EmitOMPCopyinClause(S);
-    bool Firstprivates = CGF.EmitOMPFirstprivateClause(S, PrivateScope);
-    if (Copyins || Firstprivates) {
+    (void)CGF.EmitOMPFirstprivateClause(S, PrivateScope);
+    if (Copyins) {
       // Emit implicit barrier to synchronize threads and avoid data races on
-      // initialization of firstprivate variables or propagation master's thread
-      // values of threadprivate variables to local instances of that variables
-      // of all other implicit threads.
+      // propagation master's thread values of threadprivate variables to local
+      // instances of that variables of all other implicit threads.
       CGF.CGM.getOpenMPRuntime().emitBarrierCall(
           CGF, S.getLocStart(), OMPD_unknown, /*EmitChecks=*/false,
           /*ForceSimpleCall=*/true);
@@ -1605,7 +1612,8 @@ bool CodeGenFunction::EmitOMPWorksharingLoop(const OMPLoopDirective &S) {
       OMPPrivateScope LoopScope(*this);
       if (EmitOMPFirstprivateClause(S, LoopScope)) {
         // Emit implicit barrier to synchronize threads and avoid data races on
-        // initialization of firstprivate variables.
+        // initialization of firstprivate variables and post-update of
+        // lastprivate variables.
         CGM.getOpenMPRuntime().emitBarrierCall(
             *this, S.getLocStart(), OMPD_unknown, /*EmitChecks=*/false,
             /*ForceSimpleCall=*/true);
@@ -1804,7 +1812,8 @@ CodeGenFunction::EmitSections(const OMPExecutableDirective &S) {
     CodeGenFunction::OMPPrivateScope LoopScope(CGF);
     if (CGF.EmitOMPFirstprivateClause(S, LoopScope)) {
       // Emit implicit barrier to synchronize threads and avoid data races on
-      // initialization of firstprivate variables.
+      // initialization of firstprivate variables and post-update of lastprivate
+      // variables.
       CGF.CGM.getOpenMPRuntime().emitBarrierCall(
           CGF, S.getLocStart(), OMPD_unknown, /*EmitChecks=*/false,
           /*ForceSimpleCall=*/true);
@@ -1883,8 +1892,7 @@ void CodeGenFunction::EmitOMPSingleDirective(const OMPSingleDirective &S) {
   llvm::SmallVector<const Expr *, 8> SrcExprs;
   llvm::SmallVector<const Expr *, 8> AssignmentOps;
   // Check if there are any 'copyprivate' clauses associated with this
-  // 'single'
-  // construct.
+  // 'single' construct.
   // Build a list of copyprivate variables along with helper expressions
   // (<source>, <destination>, <destination>=<source> expressions)
   for (const auto *C : S.getClausesOfKind<OMPCopyprivateClause>()) {
@@ -1897,10 +1905,9 @@ void CodeGenFunction::EmitOMPSingleDirective(const OMPSingleDirective &S) {
   }
   LexicalScope Scope(*this, S.getSourceRange());
   // Emit code for 'single' region along with 'copyprivate' clauses
-  bool HasFirstprivates;
-  auto &&CodeGen = [&S, &HasFirstprivates](CodeGenFunction &CGF) {
+  auto &&CodeGen = [&S](CodeGenFunction &CGF) {
     CodeGenFunction::OMPPrivateScope SingleScope(CGF);
-    HasFirstprivates = CGF.EmitOMPFirstprivateClause(S, SingleScope);
+    (void)CGF.EmitOMPFirstprivateClause(S, SingleScope);
     CGF.EmitOMPPrivateClause(S, SingleScope);
     (void)SingleScope.Privatize();
 
@@ -1909,10 +1916,9 @@ void CodeGenFunction::EmitOMPSingleDirective(const OMPSingleDirective &S) {
   CGM.getOpenMPRuntime().emitSingleRegion(*this, CodeGen, S.getLocStart(),
                                           CopyprivateVars, DestExprs, SrcExprs,
                                           AssignmentOps);
-  // Emit an implicit barrier at the end (to avoid data race on firstprivate
-  // init or if no 'nowait' clause was specified and no 'copyprivate' clause).
-  if ((!S.getSingleClause<OMPNowaitClause>() || HasFirstprivates) &&
-      CopyprivateVars.empty()) {
+  // Emit an implicit barrier at the end (to avoid data race if no 'nowait'
+  // clause was specified and no 'copyprivate' clause).
+  if (!S.getSingleClause<OMPNowaitClause>() && CopyprivateVars.empty()) {
     CGM.getOpenMPRuntime().emitBarrierCall(
         *this, S.getLocStart(),
         S.getSingleClause<OMPNowaitClause>() ? OMPD_unknown : OMPD_single);