2 files changed, 28 insertions, 0 deletions
diff --git a/llvm/include/llvm/CodeGen/DFAPacketizer.h b/llvm/include/llvm/CodeGen/DFAPacketizer.h
index 2145884658e..8de140e91bf 100644
--- a/llvm/include/llvm/CodeGen/DFAPacketizer.h
+++ b/llvm/include/llvm/CodeGen/DFAPacketizer.h
@@ -28,6 +28,7 @@
 
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
+#include "llvm/CodeGen/ScheduleDAGMutation.h"
 #include <map>
 
 namespace llvm {
@@ -199,6 +200,9 @@ public:
   virtual bool isLegalToPruneDependencies(SUnit *SUI, SUnit *SUJ) {
     return false;
   }
+
+  // Add a DAG mutation to be done before the packetization begins.
+  void addMutation(std::unique_ptr<ScheduleDAGMutation> Mutation);
 };
 
 } // namespace llvm
diff --git a/llvm/lib/CodeGen/DFAPacketizer.cpp b/llvm/lib/CodeGen/DFAPacketizer.cpp
index a4ed61b98ce..205ebf80c59 100644
--- a/llvm/lib/CodeGen/DFAPacketizer.cpp
+++ b/llvm/lib/CodeGen/DFAPacketizer.cpp
@@ -155,11 +155,20 @@ namespace llvm {
 class DefaultVLIWScheduler : public ScheduleDAGInstrs {
 private:
   AliasAnalysis *AA;
+  /// Ordered list of DAG postprocessing steps.
+  std::vector<std::unique_ptr<ScheduleDAGMutation>> Mutations;
 public:
   DefaultVLIWScheduler(MachineFunction &MF, MachineLoopInfo &MLI,
                        AliasAnalysis *AA);
   // Actual scheduling work.
   void schedule() override;
+
+  /// DefaultVLIWScheduler takes ownership of the Mutation object.
+  void addMutation(std::unique_ptr<ScheduleDAGMutation> Mutation) {
+    Mutations.push_back(std::move(Mutation));
+  }
+protected:
+  void postprocessDAG();
 };
 }
 
@@ -172,9 +181,17 @@ DefaultVLIWScheduler::DefaultVLIWScheduler(MachineFunction &MF,
 }
 
 
+/// Apply each ScheduleDAGMutation step in order.
+void DefaultVLIWScheduler::postprocessDAG() {
+  for (auto &M : Mutations)
+    M->apply(this);
+}
+
+
 void DefaultVLIWScheduler::schedule() {
   // Build the scheduling graph.
   buildSchedGraph(AA);
+  postprocessDAG();
 }
 
 
@@ -272,3 +289,10 @@ void VLIWPacketizerList::PacketizeMIs(MachineBasicBlock *MBB,
   VLIWScheduler->exitRegion();
   VLIWScheduler->finishBlock();
 }
+
+
+// Add a DAG mutation object to the ordered list.
+void VLIWPacketizerList::addMutation(
+      std::unique_ptr<ScheduleDAGMutation> Mutation) {
+  VLIWScheduler->addMutation(std::move(Mutation));
+}