From 6c715e1483cc2a21dd9d2076107d07b544538c89 Mon Sep 17 00:00:00 2001
From: Krzysztof Parzyszek <kparzysz@codeaurora.org>
Date: Fri, 15 Jul 2016 20:16:03 +0000
Subject: [PATCH] [Hexagon] Make MI scheduler check for stalls in previous
 packet on v60

Patch by Ikhlas Ajbar.

llvm-svn: 275606
---
 .../lib/Target/Hexagon/HexagonMachineScheduler.cpp | 28 ++++++++++++++++++++++
 llvm/lib/Target/Hexagon/HexagonMachineScheduler.h  | 16 ++++++++++---
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/llvm/lib/Target/Hexagon/HexagonMachineScheduler.cpp b/llvm/lib/Target/Hexagon/HexagonMachineScheduler.cpp
index 0cc0293..2ff1b53 100644
--- a/llvm/lib/Target/Hexagon/HexagonMachineScheduler.cpp
+++ b/llvm/lib/Target/Hexagon/HexagonMachineScheduler.cpp
@@ -105,6 +105,11 @@ void HexagonCallMutation::apply(ScheduleDAGInstrs *DAG) {
 }
 
 
+/// Save the last formed packet
+void VLIWResourceModel::savePacket() {
+  OldPacket = Packet;
+}
+
 /// Check if scheduling of this SU is possible
 /// in the current packet.
 /// It is _not_ precise (statefull), it is more like
@@ -155,6 +160,7 @@ bool VLIWResourceModel::reserveResources(SUnit *SU) {
   // Artificially reset state.
   if (!SU) {
     ResourcesModel->clearResources();
+    savePacket();
     Packet.clear();
     TotalPackets++;
     return false;
@@ -163,6 +169,7 @@ bool VLIWResourceModel::reserveResources(SUnit *SU) {
   // start a new one.
   if (!isResourceAvailable(SU)) {
     ResourcesModel->clearResources();
+    savePacket();
     Packet.clear();
     TotalPackets++;
     startNewCycle = true;
@@ -199,6 +206,7 @@ bool VLIWResourceModel::reserveResources(SUnit *SU) {
   // we start fresh.
   if (Packet.size() >= SchedModel->getIssueWidth()) {
     ResourcesModel->clearResources();
+    savePacket();
     Packet.clear();
     TotalPackets++;
     startNewCycle = true;
@@ -552,6 +560,8 @@ int ConvergingVLIWScheduler::SchedulingCost(ReadyQueue &Q, SUnit *SU,
   if (!SU || SU->isScheduled)
     return ResCount;
 
+  MachineInstr *Instr = SU->getInstr();
+
   // Forced priority is high.
   if (SU->isScheduleHigh)
     ResCount += PriorityOne;
@@ -596,6 +606,24 @@ int ConvergingVLIWScheduler::SchedulingCost(ReadyQueue &Q, SUnit *SU,
   ResCount -= (Delta.Excess.getUnitInc()*PriorityTwo);
   ResCount -= (Delta.CriticalMax.getUnitInc()*PriorityTwo);
 
+  auto &QST = DAG->MF.getSubtarget<HexagonSubtarget>();
+  auto &QII = *QST.getInstrInfo();
+
+  // Give less preference to an instruction that will cause a stall with
+  // an instruction in the previous packet.
+  if (QII.isV60VectorInstruction(Instr)) {
+    // Check for stalls in the previous packet.
+    if (Q.getID() == TopQID) {
+      for (auto J : Top.ResourceModel->OldPacket)
+        if (QII.producesStall(J->getInstr(), Instr))
+          ResCount -= PriorityOne;
+    } else {
+      for (auto J : Bot.ResourceModel->OldPacket)
+        if (QII.producesStall(Instr, J->getInstr()))
+          ResCount -= PriorityOne;
+    }
+  }
+
   DEBUG(if (verbose) dbgs() << " Total(" << ResCount << ")");
 
   return ResCount;
diff --git a/llvm/lib/Target/Hexagon/HexagonMachineScheduler.h b/llvm/lib/Target/Hexagon/HexagonMachineScheduler.h
index 1fe8d9d..611527e 100644
--- a/llvm/lib/Target/Hexagon/HexagonMachineScheduler.h
+++ b/llvm/lib/Target/Hexagon/HexagonMachineScheduler.h
@@ -53,9 +53,13 @@ class VLIWResourceModel {
   unsigned TotalPackets;
 
 public:
+  /// Save the last formed packet.
+  std::vector<SUnit*> OldPacket;
+
+public:
   VLIWResourceModel(const TargetSubtargetInfo &STI, const TargetSchedModel *SM)
       : SchedModel(SM), TotalPackets(0) {
-  ResourcesModel = STI.getInstrInfo()->CreateTargetScheduleState(STI);
+    ResourcesModel = STI.getInstrInfo()->CreateTargetScheduleState(STI);
 
     // This hard requirement could be relaxed,
     // but for now do not let it proceed.
@@ -63,6 +67,8 @@ public:
 
     Packet.resize(SchedModel->getIssueWidth());
     Packet.clear();
+    OldPacket.resize(SchedModel->getIssueWidth());
+    OldPacket.clear();
     ResourcesModel->clearResources();
   }
 
@@ -85,7 +91,12 @@ public:
 
   bool isResourceAvailable(SUnit *SU);
   bool reserveResources(SUnit *SU);
+  void savePacket();
   unsigned getTotalPackets() const { return TotalPackets; }
+
+  bool isInPacket(SUnit *SU) const {
+    return std::find(Packet.begin(), Packet.end(), SU) != Packet.end();
+  }
 };
 
 /// Extend the standard ScheduleDAGMI to provide more context and override the
@@ -99,8 +110,6 @@ public:
   /// Schedule - This is called back from ScheduleDAGInstrs::Run() when it's
   /// time to do some work.
   void schedule() override;
-  /// Perform platform-specific DAG postprocessing.
-  void postprocessDAG();
 };
 
 /// ConvergingVLIWScheduler shrinks the unscheduled zone using heuristics
@@ -166,6 +175,7 @@ class ConvergingVLIWScheduler : public MachineSchedStrategy {
     void init(VLIWMachineScheduler *dag, const TargetSchedModel *smodel) {
       DAG = dag;
       SchedModel = smodel;
+      IssueCount = 0;
     }
 
     bool isTop() const {
-- 
2.7.4