Index: lib/CodeGen/IslAst.cpp
===================================================================
--- lib/CodeGen/IslAst.cpp
+++ lib/CodeGen/IslAst.cpp
@@ -124,6 +124,9 @@
   /// @brief Flag to indicate that we are inside a parallel for node.
   bool InParallelFor;
 
+  /// @brief Flag to indicate that we met a SIMD mark.
+  bool SIMDMark;
+
   /// @brief The last iterator id created for the current SCoP.
   isl_id *LastForNodeId;
 };
@@ -254,14 +257,41 @@
   Id = isl_id_set_free_user(Id, freeIslAstUserPayload);
   BuildInfo->LastForNodeId = Id;
 
+  if (BuildInfo->SIMDMark) {
+    BuildInfo->SIMDMark = false;
+    Payload->IsInnermost = true;
+    Payload->IsInnermostParallel = true;
+  }
+
   // Test for parallelism only if we are not already inside a parallel loop
-  if (!BuildInfo->InParallelFor)
-    BuildInfo->InParallelFor = Payload->IsOutermostParallel =
-        astScheduleDimIsParallel(Build, BuildInfo->Deps, Payload);
+  if (!BuildInfo->InParallelFor) {
+    if (Payload->IsInnermostParallel)
+      BuildInfo->InParallelFor = Payload->IsOutermostParallel = true;
+    else
+      BuildInfo->InParallelFor = Payload->IsOutermostParallel =
+          astScheduleDimIsParallel(Build, BuildInfo->Deps, Payload);
+  }
 
   return Id;
 }
 
+// This method is executed before the construction of a mark node. It sets
+// the 'SIMDMark' flag, if we met a mark node, which isl_id has name 'SIMD'.
+// This helps to skip parallelism checks.
+//
+static isl_stat astBuildBeforeMark(__isl_keep isl_id *MarkId,
+                                   __isl_keep isl_ast_build *Build,
+                                   void *User) {
+  if (!MarkId)
+    return isl_stat_error;
+
+  AstBuildUserInfo *BuildInfo = (AstBuildUserInfo *)User;
+  if (!strcmp(isl_id_get_name(MarkId), "SIMD"))
+    BuildInfo->SIMDMark = true;
+
+  return isl_stat_ok;
+}
+
 // This method is executed after the construction of a for node.
 //
 // It performs the following actions:
@@ -285,7 +315,8 @@
   // Innermost loops that are surrounded by parallel loops have not yet been
   // tested for parallelism. Test them here to ensure we check all innermost
   // loops for parallelism.
-  if (Payload->IsInnermost && BuildInfo->InParallelFor) {
+  if (Payload->IsInnermost && BuildInfo->InParallelFor &&
+      !Payload->IsInnermostParallel) {
     if (Payload->IsOutermostParallel)
       Payload->IsInnermostParallel = true;
     else
@@ -407,9 +438,14 @@
   if (PerformParallelTest) {
     BuildInfo.Deps = &D;
     BuildInfo.InParallelFor = 0;
+    BuildInfo.SIMDMark = 0;
 
     Build = isl_ast_build_set_before_each_for(Build, &astBuildBeforeFor,
                                               &BuildInfo);
+
+    Build = isl_ast_build_set_before_each_mark(Build, &astBuildBeforeMark,
+                                               &BuildInfo);
+
     Build =
         isl_ast_build_set_after_each_for(Build, &astBuildAfterFor, &BuildInfo);
   }
Index: lib/Transform/ScheduleOptimizer.cpp
===================================================================
--- lib/Transform/ScheduleOptimizer.cpp
+++ lib/Transform/ScheduleOptimizer.cpp
@@ -289,6 +289,10 @@
       Node, isl_union_set_read_from_str(Ctx, "{ unroll[x]: 1 = 0 }"));
   Node = isl_schedule_node_band_sink(Node);
   Node = isl_schedule_node_child(Node, 0);
+  if (isl_schedule_node_get_type(Node) == isl_schedule_node_leaf)
+    Node = isl_schedule_node_parent(Node);
+  isl_id *LoopMarker = isl_id_alloc(Ctx, "SIMD", nullptr);
+  Node = isl_schedule_node_insert_mark(Node, LoopMarker);
   return Node;
 }