1 files changed, 45 insertions, 5 deletions
diff --git a/clang/lib/Sema/SemaOpenMP.cpp b/clang/lib/Sema/SemaOpenMP.cpp
index 07417020758..a57bbfc1d53 100644
--- a/clang/lib/Sema/SemaOpenMP.cpp
+++ b/clang/lib/Sema/SemaOpenMP.cpp
@@ -887,16 +887,56 @@ bool Sema::IsOpenMPCapturedByRef(ValueDecl *D,
     //    array section, the runtime library may pass the NULL value to the
     //    device instead of the value passed to it by the compiler.
 
-    // FIXME: Right now, only implicit maps are implemented. Properly mapping
-    // values requires having the map, private, and firstprivate clauses SEMA
-    // and parsing in place, which we don't yet.
 
     if (Ty->isReferenceType())
       Ty = Ty->castAs<ReferenceType>()->getPointeeType();
-    IsByRef = !Ty->isScalarType();
+
+    // Locate map clauses and see if the variable being captured is referred to
+    // in any of those clauses. Here we only care about variables, not fields,
+    // because fields are part of aggregates.
+    bool IsVariableUsedInMapClause = false;
+    bool IsVariableAssociatedWithSection = false;
+
+    DSAStack->checkMappableExprComponentListsForDecl(
+        D, /*CurrentRegionOnly=*/true,
+        [&](OMPClauseMappableExprCommon::MappableExprComponentListRef
+                MapExprComponents) {
+
+          auto EI = MapExprComponents.rbegin();
+          auto EE = MapExprComponents.rend();
+
+          assert(EI != EE && "Invalid map expression!");
+
+          if (isa<DeclRefExpr>(EI->getAssociatedExpression()))
+            IsVariableUsedInMapClause |= EI->getAssociatedDeclaration() == D;
+
+          ++EI;
+          if (EI == EE)
+            return false;
+
+          if (isa<ArraySubscriptExpr>(EI->getAssociatedExpression()) ||
+              isa<OMPArraySectionExpr>(EI->getAssociatedExpression()) ||
+              isa<MemberExpr>(EI->getAssociatedExpression())) {
+            IsVariableAssociatedWithSection = true;
+            // There is nothing more we need to know about this variable.
+            return true;
+          }
+
+          // Keep looking for more map info.
+          return false;
+        });
+
+    if (IsVariableUsedInMapClause) {
+      // If variable is identified in a map clause it is always captured by
+      // reference except if it is a pointer that is dereferenced somehow.
+      IsByRef = !(Ty->isPointerType() && IsVariableAssociatedWithSection);
+    } else {
+      // By default, all the data that has a scalar type is mapped by copy.
+      IsByRef = !Ty->isScalarType();
+    }
   }
 
-  // When passing data by value, we need to make sure it fits the uintptr size
+  // When passing data by copy, we need to make sure it fits the uintptr size
   // and alignment, because the runtime library only deals with uintptr types.
   // If it does not fit the uintptr size, we need to pass the data by reference
   // instead.