MIsched: Improve the interface to SchedDFS analysis (subtrees).

Allow the strategy to select SchedDFS. Allow the results of SchedDFS
to affect initialization of the scheduler state.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173425 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/CodeGen/MachineScheduler.h

@@ -316,12 +316,9 @@ public:
 
   const SUnit *getNextClusterSucc() const { return NextClusterSucc; }
 
-  /// Initialize a DFSResult after DAG building is complete, and before any
+  /// Compute a DFSResult after DAG building is complete, and before any
   /// queue comparisons.
-  void initDFSResult();
-
-  /// Compute DFS result once all interesting roots are discovered.
-  void computeDFSResult(ArrayRef<SUnit*> Roots);
+  void computeDFSResult();
 
   /// Return a non-null DFS result if the scheduling strategy initialized it.
   const SchedDFSResult *getDFSResult() const { return DFSResult; }
@@ -341,8 +338,8 @@ protected:
   /// instances of ScheduleDAGMI to perform custom DAG postprocessing.
   void postprocessDAG();
 
-  /// Identify DAG roots and setup scheduler queues.
-  void initQueues();
+  /// Release ExitSU predecessors and setup scheduler queues.
+  void initQueues(ArrayRef<SUnit*> TopRoots, ArrayRef<SUnit*> BotRoots);
 
   /// Move an instruction and update register pressure.
   void scheduleMI(SUnit *SU, bool IsTopNode);
@@ -365,7 +362,8 @@ protected:
   void moveInstruction(MachineInstr *MI, MachineBasicBlock::iterator InsertPos);
   bool checkSchedLimit();
 
-  void releaseRoots();
+  void findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
+                             SmallVectorImpl<SUnit*> &BotRoots);
 
   void releaseSucc(SUnit *SU, SDep *SuccEdge);
   void releaseSuccessors(SUnit *SU);

include/llvm/CodeGen/ScheduleDFS.h

@@ -127,7 +127,7 @@ public:
   }
 
   /// \brief Compute various metrics for the DAG with given roots.
-  void compute(ArrayRef<SUnit *> Roots);
+  void compute(ArrayRef<SUnit> SUnits);
 
   /// \brief Get the ILP value for a DAG node.
   ///
@@ -140,7 +140,12 @@ public:
   unsigned getNumSubtrees() const { return SubtreeConnectLevels.size(); }
 
   /// \brief Get the ID of the subtree the given DAG node belongs to.
+  ///
+  /// For convenience, if DFSResults have not been computed yet, give everything
+  /// tree ID 0.
   unsigned getSubtreeID(const SUnit *SU) const {
+    if (empty())
+      return 0;
     assert(SU->NodeNum < DFSData.size() &&  "New Node");
     return DFSData[SU->NodeNum].SubtreeID;
   }

lib/CodeGen/MachineScheduler.cpp

@@ -510,10 +510,19 @@ void ScheduleDAGMI::schedule() {
 
   postprocessDAG();
 
+  SmallVector<SUnit*, 8> TopRoots, BotRoots;
+  findRootsAndBiasEdges(TopRoots, BotRoots);
+
+  // Initialize the strategy before modifying the DAG.
+  // This may initialize a DFSResult to be used for queue priority.
+  SchedImpl->initialize(this);
+
   DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
           SUnits[su].dumpAll(this));
+  if (ViewMISchedDAGs) viewGraph();
 
-  initQueues();
+  // Initialize ready queues now that the DAG and priority data are finalized.
+  initQueues(TopRoots, BotRoots);
 
   bool IsTopNode = false;
   while (SUnit *SU = SchedImpl->pickNode(IsTopNode)) {
@@ -561,25 +570,18 @@ void ScheduleDAGMI::postprocessDAG() {
   }
 }
 
-void ScheduleDAGMI::initDFSResult() {
+void ScheduleDAGMI::computeDFSResult() {
   if (!DFSResult)
     DFSResult = new SchedDFSResult(/*BottomU*/true, MinSubtreeSize);
   DFSResult->clear();
-  DFSResult->resize(SUnits.size());
   ScheduledTrees.clear();
-}
-
-void ScheduleDAGMI::computeDFSResult(ArrayRef<SUnit*> Roots) {
-  DFSResult->compute(Roots);
+  DFSResult->resize(SUnits.size());
+  DFSResult->compute(SUnits);
   ScheduledTrees.resize(DFSResult->getNumSubtrees());
 }
 
-// Release all DAG roots for scheduling.
-//
-// Nodes with unreleased weak edges can still be roots.
-void ScheduleDAGMI::releaseRoots() {
-  SmallVector<SUnit*, 16> BotRoots;
-
+void ScheduleDAGMI::findRootsAndBiasEdges(SmallVectorImpl<SUnit*> &TopRoots,
+                                          SmallVectorImpl<SUnit*> &BotRoots) {
   for (std::vector<SUnit>::iterator
          I = SUnits.begin(), E = SUnits.end(); I != E; ++I) {
     SUnit *SU = &(*I);
@@ -589,28 +591,33 @@ void ScheduleDAGMI::releaseRoots() {
 
     // A SUnit is ready to top schedule if it has no predecessors.
     if (!I->NumPredsLeft && SU != &EntrySU)
-      SchedImpl->releaseTopNode(SU);
+      TopRoots.push_back(SU);
     // A SUnit is ready to bottom schedule if it has no successors.
     if (!I->NumSuccsLeft && SU != &ExitSU)
       BotRoots.push_back(SU);
   }
-  // Release bottom roots in reverse order so the higher priority nodes appear
-  // first. This is more natural and slightly more efficient.
-  for (SmallVectorImpl<SUnit*>::const_reverse_iterator
-         I = BotRoots.rbegin(), E = BotRoots.rend(); I != E; ++I)
-    SchedImpl->releaseBottomNode(*I);
 }
 
 /// Identify DAG roots and setup scheduler queues.
-void ScheduleDAGMI::initQueues() {
+void ScheduleDAGMI::initQueues(ArrayRef<SUnit*> TopRoots,
+                               ArrayRef<SUnit*> BotRoots) {
   NextClusterSucc = NULL;
   NextClusterPred = NULL;
 
-  // Initialize the strategy before modifying the DAG.
-  SchedImpl->initialize(this);
-
   // Release all DAG roots for scheduling, not including EntrySU/ExitSU.
-  releaseRoots();
+  //
+  // Nodes with unreleased weak edges can still be roots.
+  // Release top roots in forward order.
+  for (SmallVectorImpl<SUnit*>::const_iterator
+         I = TopRoots.begin(), E = TopRoots.end(); I != E; ++I) {
+    SchedImpl->releaseTopNode(*I);
+  }
+  // Release bottom roots in reverse order so the higher priority nodes appear
+  // first. This is more natural and slightly more efficient.
+  for (SmallVectorImpl<SUnit*>::const_reverse_iterator
+         I = BotRoots.rbegin(), E = BotRoots.rend(); I != E; ++I) {
+    SchedImpl->releaseBottomNode(*I);
+  }
 
   releaseSuccessors(&EntrySU);
   releasePredecessors(&ExitSU);
@@ -1216,7 +1223,7 @@ void ConvergingScheduler::initialize(ScheduleDAGMI *dag) {
   Top.init(DAG, SchedModel, &Rem);
   Bot.init(DAG, SchedModel, &Rem);
 
-  DAG->initDFSResult();
+  DAG->computeDFSResult();
 
   // Initialize resource counts.
 
@@ -1278,8 +1285,6 @@ void ConvergingScheduler::registerRoots() {
       Rem.CriticalPath = (*I)->getDepth();
   }
   DEBUG(dbgs() << "Critical Path: " << Rem.CriticalPath << '\n');
-
-  DAG->computeDFSResult(Bot.Available.elements());
 }
 
 /// Does this SU have a hazard within the current instruction group.
@@ -2140,14 +2145,13 @@ public:
 
   virtual void initialize(ScheduleDAGMI *dag) {
     DAG = dag;
-    DAG->initDFSResult();
+    DAG->computeDFSResult();
     Cmp.DFSResult = DAG->getDFSResult();
     Cmp.ScheduledTrees = &DAG->getScheduledTrees();
     ReadyQ.clear();
   }
 
   virtual void registerRoots() {
-    DAG->computeDFSResult(ReadyQ);
     // Restore the heap in ReadyQ with the updated DFS results.
     std::make_heap(ReadyQ.begin(), ReadyQ.end(), Cmp);
   }

lib/CodeGen/ScheduleDAGInstrs.cpp

@@ -1188,16 +1188,20 @@ static bool hasDataSucc(const SUnit *SU) {
 
 /// Compute an ILP metric for all nodes in the subDAG reachable via depth-first
 /// search from this root.
-void SchedDFSResult::compute(ArrayRef<SUnit *> Roots) {
+void SchedDFSResult::compute(ArrayRef<SUnit> SUnits) {
   if (!IsBottomUp)
     llvm_unreachable("Top-down ILP metric is unimplemnted");
 
   SchedDFSImpl Impl(*this);
-  for (ArrayRef<const SUnit*>::const_iterator
-         RootI = Roots.begin(), RootE = Roots.end(); RootI != RootE; ++RootI) {
+  for (ArrayRef<SUnit>::const_iterator
+         SI = SUnits.begin(), SE = SUnits.end(); SI != SE; ++SI) {
+    const SUnit *SU = &*SI;
+    if (Impl.isVisited(SU) || hasDataSucc(SU))
+      continue;
+
     SchedDAGReverseDFS DFS;
-    Impl.visitPreorder(*RootI);
-    DFS.follow(*RootI);
+    Impl.visitPreorder(SU);
+    DFS.follow(SU);
     for (;;) {
       // Traverse the leftmost path as far as possible.
       while (DFS.getPred() != DFS.getPredEnd()) {

lib/Target/Hexagon/HexagonMachineScheduler.cpp

@@ -152,6 +152,12 @@ void VLIWMachineScheduler::schedule() {
   // Postprocess the DAG to add platform specific artificial dependencies.
   postprocessDAG();
 
+  SmallVector<SUnit*, 8> TopRoots, BotRoots;
+  findRootsAndBiasEdges(TopRoots, BotRoots);
+
+  // Initialize the strategy before modifying the DAG.
+  SchedImpl->initialize(this);
+
   // To view Height/Depth correctly, they should be accessed at least once.
   DEBUG(unsigned maxH = 0;
         for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
@@ -166,7 +172,7 @@ void VLIWMachineScheduler::schedule() {
   DEBUG(for (unsigned su = 0, e = SUnits.size(); su != e; ++su)
           SUnits[su].dumpAll(this));
 
-  initQueues();
+  initQueues(TopRoots, BotRoots);
 
   bool IsTopNode = false;
   while (SUnit *SU = SchedImpl->pickNode(IsTopNode)) {

test/CodeGen/X86/misched-matrix.ll

@@ -8,9 +8,6 @@
 ; RUN:          -misched=ilpmax -verify-machineinstrs \
 ; RUN:     | FileCheck %s -check-prefix=ILPMAX
 ;
-; Very temporary xfail during SchedDFSResult churn.
-; XFAIL: *
-;
 ; Verify that the MI scheduler minimizes register pressure for a
 ; uniform set of bottom-up subtrees (unrolled matrix multiply).
 ;