1 files changed, 117 insertions, 12 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZMachineScheduler.cpp b/llvm/lib/Target/SystemZ/SystemZMachineScheduler.cpp
index 8342463c108..4b0f9256763 100644
--- a/llvm/lib/Target/SystemZ/SystemZMachineScheduler.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZMachineScheduler.cpp
@@ -11,7 +11,8 @@
 // SystemZPostRASchedStrategy is a scheduling strategy which is plugged into
 // the MachineScheduler. It has a sorted Available set of SUs and a pickNode()
 // implementation that looks to optimize decoder grouping and balance the
-// usage of processor resources.
+// usage of processor resources. Scheduler states are saved for the end
+// region of each MBB, so that a successor block can learn from it.
 //===----------------------------------------------------------------------===//
 
 #include "SystemZMachineScheduler.h"
@@ -34,14 +35,118 @@ dump(SystemZHazardRecognizer &HazardRec) const {
 }
 #endif
 
+// Try to find a single predecessor that would be interesting for the
+// scheduler in the top-most region of MBB.
+static MachineBasicBlock *getSingleSchedPred(MachineBasicBlock *MBB,
+                                             const MachineLoop *Loop) {
+  MachineBasicBlock *PredMBB = nullptr;
+  if (MBB->pred_size() == 1)
+    PredMBB = *MBB->pred_begin();
+
+  // The loop header has two predecessors, return the latch, but not for a
+  // single block loop.
+  if (MBB->pred_size() == 2 && Loop != nullptr && Loop->getHeader() == MBB) {
+    for (auto I = MBB->pred_begin(); I != MBB->pred_end(); ++I)
+      if (Loop->contains(*I))
+        PredMBB = (*I == MBB ? nullptr : *I);
+  }
+
+  assert ((PredMBB == nullptr || !Loop || Loop->contains(PredMBB))
+          && "Loop MBB should not consider predecessor outside of loop.");
+
+  return PredMBB;
+}
+
+void SystemZPostRASchedStrategy::
+advanceTo(MachineBasicBlock::iterator NextBegin) {
+  MachineBasicBlock::iterator LastEmittedMI = HazardRec->getLastEmittedMI();
+  MachineBasicBlock::iterator I =
+    ((LastEmittedMI != nullptr && LastEmittedMI->getParent() == MBB) ?
+     std::next(LastEmittedMI) : MBB->begin());
+
+  for (; I != NextBegin; ++I) {
+    if (I->isPosition() || I->isDebugValue())
+      continue;
+    HazardRec->emitInstruction(&*I);
+  }
+}
+
+void SystemZPostRASchedStrategy::enterMBB(MachineBasicBlock *NextMBB) {
+  assert ((SchedStates.find(NextMBB) == SchedStates.end()) &&
+          "Entering MBB twice?");
+  DEBUG (dbgs() << "+++ Entering MBB#" << NextMBB->getNumber());
+
+  MBB = NextMBB;
+  /// Create a HazardRec for MBB, save it in SchedStates and set HazardRec to
+  /// point to it.
+  HazardRec = SchedStates[MBB] = new SystemZHazardRecognizer(TII, &SchedModel);
+  DEBUG (const MachineLoop *Loop = MLI->getLoopFor(MBB);
+         if(Loop && Loop->getHeader() == MBB)
+           dbgs() << " (Loop header)";
+         dbgs() << ":\n";);
+
+  // Try to take over the state from a single predecessor, if it has been
+  // scheduled. If this is not possible, we are done.
+  MachineBasicBlock *SinglePredMBB =
+    getSingleSchedPred(MBB, MLI->getLoopFor(MBB));
+  if (SinglePredMBB == nullptr ||
+      SchedStates.find(SinglePredMBB) == SchedStates.end())
+    return;
+
+  DEBUG (dbgs() << "+++ Continued scheduling from MBB#"
+         << SinglePredMBB->getNumber() << "\n";);
+
+  HazardRec->copyState(SchedStates[SinglePredMBB]);
+
+  // Emit incoming terminator(s). Be optimistic and assume that branch
+  // prediction will generally do "the right thing".
+  for (MachineBasicBlock::iterator I = SinglePredMBB->getFirstTerminator();
+       I != SinglePredMBB->end(); I++) {
+    DEBUG (dbgs() << "+++ Emitting incoming branch: "; I->dump(););
+    bool TakenBranch = (I->isBranch() &&
+      (TII->getBranchInfo(*I).Target->isReg() || // Relative branch
+       TII->getBranchInfo(*I).Target->getMBB() == MBB));
+    HazardRec->emitInstruction(&*I, TakenBranch);
+    if (TakenBranch)
+      break;
+  }
+}
+
+void SystemZPostRASchedStrategy::leaveMBB() {
+  DEBUG (dbgs() << "+++ Leaving MBB#" << MBB->getNumber() << "\n";);
+
+  // Advance to first terminator. The successor block will handle terminators
+  // dependent on CFG layout (T/NT branch etc).
+  advanceTo(MBB->getFirstTerminator());
+}
+
 SystemZPostRASchedStrategy::
 SystemZPostRASchedStrategy(const MachineSchedContext *C)
-  : DAG(nullptr), HazardRec(C) {}
+  : MLI(C->MLI),
+    TII(static_cast<const SystemZInstrInfo *>
+        (C->MF->getSubtarget().getInstrInfo())), 
+    MBB(nullptr), HazardRec(nullptr) {
+  const TargetSubtargetInfo *ST = &C->MF->getSubtarget();
+  SchedModel.init(ST->getSchedModel(), ST, TII);
+}
+
+SystemZPostRASchedStrategy::~SystemZPostRASchedStrategy() {
+  // Delete hazard recognizers kept around for each MBB.
+  for (auto I : SchedStates) {
+    SystemZHazardRecognizer *hazrec = I.second;
+    delete hazrec;
+  }
+}
+
+void SystemZPostRASchedStrategy::initPolicy(MachineBasicBlock::iterator Begin,
+                                            MachineBasicBlock::iterator End,
+                                            unsigned NumRegionInstrs) {
+  // Don't emit the terminators.
+  if (Begin->isTerminator())
+    return;
 
-void SystemZPostRASchedStrategy::initialize(ScheduleDAGMI *dag) {
-  DAG = dag;
-  HazardRec.setDAG(dag);
-  HazardRec.Reset();
+  // Emit any instructions before start of region.
+  advanceTo(Begin);
 }
 
 // Pick the next node to schedule.
@@ -55,25 +160,25 @@ SUnit *SystemZPostRASchedStrategy::pickNode(bool &IsTopNode) {
   // If only one choice, return it.
   if (Available.size() == 1) {
     DEBUG (dbgs() << "+++ Only one: ";
-           HazardRec.dumpSU(*Available.begin(), dbgs()); dbgs() << "\n";);
+           HazardRec->dumpSU(*Available.begin(), dbgs()); dbgs() << "\n";);
     return *Available.begin();
   }
 
   // All nodes that are possible to schedule are stored by in the
   // Available set.
-  DEBUG(dbgs() << "+++ Available: "; Available.dump(HazardRec););
+  DEBUG(dbgs() << "+++ Available: "; Available.dump(*HazardRec););
 
   Candidate Best;
   for (auto *SU : Available) {
 
     // SU is the next candidate to be compared against current Best.
-    Candidate c(SU, HazardRec);
+    Candidate c(SU, *HazardRec);
 
     // Remeber which SU is the best candidate.
     if (Best.SU == nullptr || c < Best) {
       Best = c;
       DEBUG(dbgs() << "+++ Best sofar: ";
-            HazardRec.dumpSU(Best.SU, dbgs());
+            HazardRec->dumpSU(Best.SU, dbgs());
             if (Best.GroupingCost != 0)
               dbgs() << "\tGrouping cost:" << Best.GroupingCost;
             if (Best.ResourcesCost != 0)
@@ -138,13 +243,13 @@ void SystemZPostRASchedStrategy::schedNode(SUnit *SU, bool IsTopNode) {
 
   // Remove SU from Available set and update HazardRec.
   Available.erase(SU);
-  HazardRec.EmitInstruction(SU);
+  HazardRec->EmitInstruction(SU);
 }
 
 void SystemZPostRASchedStrategy::releaseTopNode(SUnit *SU) {
   // Set isScheduleHigh flag on all SUs that we want to consider first in
   // pickNode().
-  const MCSchedClassDesc *SC = DAG->getSchedClass(SU);
+  const MCSchedClassDesc *SC = HazardRec->getSchedClass(SU);
   bool AffectsGrouping = (SC->isValid() && (SC->BeginGroup || SC->EndGroup));
   SU->isScheduleHigh = (AffectsGrouping || SU->isUnbuffered);