[Hexagon] Add a scheduling DAG mutation

- Remove output dependencies on USR_OVF register.
- Update chain edge latencies between v60 vector loads/stores.

llvm-svn: 275586

llvm/lib/Target/Hexagon/HexagonMachineScheduler.cpp

@@ -13,7 +13,9 @@
 //===----------------------------------------------------------------------===//
 
 #include "HexagonMachineScheduler.h"
+#include "HexagonSubtarget.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
+#include "llvm/CodeGen/ScheduleDAGMutation.h"
 #include "llvm/IR/Function.h"
 
 using namespace llvm;
@@ -223,6 +225,8 @@ void ConvergingVLIWScheduler::initialize(ScheduleDAGMI *dag) {
 
   assert((!llvm::ForceTopDown || !llvm::ForceBottomUp) &&
          "-misched-topdown incompatible with -misched-bottomup");
+
+  DAG->addMutation(make_unique<HexagonSubtarget::HexagonDAGMutation>());
 }
 
 void ConvergingVLIWScheduler::releaseTopNode(SUnit *SU) {

llvm/lib/Target/Hexagon/HexagonSubtarget.cpp

@@ -14,6 +14,8 @@
 #include "HexagonSubtarget.h"
 #include "Hexagon.h"
 #include "HexagonRegisterInfo.h"
+#include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/ScheduleDAGInstrs.h"
 #include "llvm/Support/CommandLine.h"
 #include "llvm/Support/ErrorHandling.h"
 #include <map>
@@ -119,6 +121,57 @@ HexagonSubtarget::HexagonSubtarget(const Triple &TT, StringRef CPU,
   UseBSBScheduling = hasV60TOps() && EnableBSBSched;
 }
 
+
+void HexagonSubtarget::HexagonDAGMutation::apply(ScheduleDAGInstrs *DAG) {
+  for (auto &SU : DAG->SUnits) {
+    if (!SU.isInstr())
+      continue;
+    SmallVector<SDep, 4> Erase;
+    for (auto &D : SU.Preds)
+      if (D.getKind() == SDep::Output && D.getReg() == Hexagon::USR_OVF)
+        Erase.push_back(D);
+    for (auto &E : Erase)
+      SU.removePred(E);
+  }
+
+  for (auto &SU : DAG->SUnits) {
+    // Update the latency of chain edges between v60 vector load or store
+    // instructions to be 1. These instructions cannot be scheduled in the
+    // same packet.
+    MachineInstr *MI1 = SU.getInstr();
+    auto *QII = static_cast<const HexagonInstrInfo*>(DAG->TII);
+    bool IsStoreMI1 = MI1->mayStore();
+    bool IsLoadMI1 = MI1->mayLoad();
+    if (!QII->isV60VectorInstruction(MI1) || !(IsStoreMI1 || IsLoadMI1))
+      continue;
+    for (auto &SI : SU.Succs) {
+      if (SI.getKind() != SDep::Order || SI.getLatency() != 0)
+        continue;
+      MachineInstr *MI2 = SI.getSUnit()->getInstr();
+      if (!QII->isV60VectorInstruction(MI2))
+        continue;
+      if ((IsStoreMI1 && MI2->mayStore()) || (IsLoadMI1 && MI2->mayLoad())) {
+        SI.setLatency(1);
+        SU.setHeightDirty();
+        // Change the dependence in the opposite direction too.
+        for (auto &PI : SI.getSUnit()->Preds) {
+          if (PI.getSUnit() != &SU || PI.getKind() != SDep::Order)
+            continue;
+          PI.setLatency(1);
+          SI.getSUnit()->setDepthDirty();
+        }
+      }
+    }
+  }
+}
+
+
+void HexagonSubtarget::getPostRAMutations(
+      std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations) const {
+  Mutations.push_back(make_unique<HexagonSubtarget::HexagonDAGMutation>());
+}
+
+
 // Pin the vtable to this file.
 void HexagonSubtarget::anchor() {}
 

llvm/lib/Target/Hexagon/HexagonSubtarget.h

@@ -18,7 +18,6 @@
 #include "HexagonISelLowering.h"
 #include "HexagonInstrInfo.h"
 #include "HexagonSelectionDAGInfo.h"
-#include "llvm/IR/DataLayout.h"
 #include "llvm/Target/TargetMachine.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include <string>
@@ -47,6 +46,11 @@ public:
   /// default for V60.
   bool UseBSBScheduling;
 
+  class HexagonDAGMutation : public ScheduleDAGMutation {
+  public:
+    void apply(ScheduleDAGInstrs *DAG) override;
+  };
+
 private:
   std::string CPUString;
   HexagonInstrInfo InstrInfo;
@@ -119,6 +123,10 @@ public:
   const HexagonArchEnum &getHexagonArchVersion() const {
     return HexagonArchVersion;
   }
+
+  void getPostRAMutations(
+      std::vector<std::unique_ptr<ScheduleDAGMutation>> &Mutations)
+      const override;
 };
 
 } // end namespace llvm

llvm/lib/Target/Hexagon/HexagonVLIWPacketizer.cpp

@@ -108,6 +108,8 @@ HexagonPacketizerList::HexagonPacketizerList(MachineFunction &MF,
     : VLIWPacketizerList(MF, MLI, AA), MBPI(MBPI), MLI(&MLI) {
   HII = MF.getSubtarget<HexagonSubtarget>().getInstrInfo();
   HRI = MF.getSubtarget<HexagonSubtarget>().getRegisterInfo();
+
+  addMutation(make_unique<HexagonSubtarget::HexagonDAGMutation>());
 }
 
 // Check if FirstI modifies a register that SecondI reads.