3 files changed, 31 insertions, 19 deletions
diff --git a/llvm/lib/CodeGen/TargetSchedule.cpp b/llvm/lib/CodeGen/TargetSchedule.cpp
index 2709df5697b..3cff31ad493 100644
--- a/llvm/lib/CodeGen/TargetSchedule.cpp
+++ b/llvm/lib/CodeGen/TargetSchedule.cpp
@@ -322,7 +322,7 @@ computeOutputLatency(const MachineInstr *DefMI, unsigned DefOperIdx,
   return 0;
 }
 
-Optional<double>
+double
 TargetSchedModel::computeReciprocalThroughput(const MachineInstr *MI) const {
   if (hasInstrItineraries()) {
     unsigned SchedClass = MI->getDesc().getSchedClass();
@@ -332,10 +332,11 @@ TargetSchedModel::computeReciprocalThroughput(const MachineInstr *MI) const {
 
   if (hasInstrSchedModel())
     return MCSchedModel::getReciprocalThroughput(*STI, *resolveSchedClass(MI));
-  return Optional<double>();
+
+  return 0.0;
 }
 
-Optional<double>
+double
 TargetSchedModel::computeReciprocalThroughput(unsigned Opcode) const {
   unsigned SchedClass = TII->get(Opcode).getSchedClass();
   if (hasInstrItineraries())
@@ -346,10 +347,11 @@ TargetSchedModel::computeReciprocalThroughput(unsigned Opcode) const {
     if (SCDesc.isValid() && !SCDesc.isVariant())
       return MCSchedModel::getReciprocalThroughput(*STI, SCDesc);
   }
-  return Optional<double>();
+
+  return 0.0;
 }
 
-Optional<double>
+double
 TargetSchedModel::computeReciprocalThroughput(const MCInst &MI) const {
   if (hasInstrSchedModel())
     return SchedModel.getReciprocalThroughput(*STI, *TII, MI);
diff --git a/llvm/lib/CodeGen/TargetSubtargetInfo.cpp b/llvm/lib/CodeGen/TargetSubtargetInfo.cpp
index 97ca707a738..fa29c05fd6c 100644
--- a/llvm/lib/CodeGen/TargetSubtargetInfo.cpp
+++ b/llvm/lib/CodeGen/TargetSubtargetInfo.cpp
@@ -67,13 +67,12 @@ bool TargetSubtargetInfo::useAA() const {
   return false;
 }
 
-static std::string createSchedInfoStr(unsigned Latency,
-                                      Optional<double> RThroughput) {
+static std::string createSchedInfoStr(unsigned Latency, double RThroughput) {
   static const char *SchedPrefix = " sched: [";
   std::string Comment;
   raw_string_ostream CS(Comment);
-  if (RThroughput.hasValue())
-    CS << SchedPrefix << Latency << format(":%2.2f", RThroughput.getValue())
+  if (RThroughput != 0.0)
+    CS << SchedPrefix << Latency << format(":%2.2f", RThroughput)
        << "]";
   else
     CS << SchedPrefix << Latency << ":?]";
@@ -90,7 +89,7 @@ std::string TargetSubtargetInfo::getSchedInfoStr(const MachineInstr &MI) const {
   TargetSchedModel TSchedModel;
   TSchedModel.init(this);
   unsigned Latency = TSchedModel.computeInstrLatency(&MI);
-  Optional<double> RThroughput = TSchedModel.computeReciprocalThroughput(&MI);
+  double RThroughput = TSchedModel.computeReciprocalThroughput(&MI);
   return createSchedInfoStr(Latency, RThroughput);
 }
 
@@ -109,8 +108,7 @@ std::string TargetSubtargetInfo::getSchedInfoStr(MCInst const &MCI) const {
         getInstrInfo()->get(MCI.getOpcode()).getSchedClass());
   } else
     return std::string();
-  Optional<double> RThroughput =
-      TSchedModel.computeReciprocalThroughput(MCI);
+  double RThroughput = TSchedModel.computeReciprocalThroughput(MCI);
   return createSchedInfoStr(Latency, RThroughput);
 }
 
diff --git a/llvm/lib/MC/MCSchedule.cpp b/llvm/lib/MC/MCSchedule.cpp
index e3fa76ee03c..929bd7f6046 100644
--- a/llvm/lib/MC/MCSchedule.cpp
+++ b/llvm/lib/MC/MCSchedule.cpp
@@ -85,7 +85,7 @@ int MCSchedModel::computeInstrLatency(const MCSubtargetInfo &STI,
   llvm_unreachable("unsupported variant scheduling class");
 }
 
-Optional<double>
+double
 MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
                                       const MCSchedClassDesc &SCDesc) {
   Optional<double> Throughput;
@@ -99,18 +99,25 @@ MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
     double Temp = NumUnits * 1.0 / I->Cycles;
     Throughput = Throughput ? std::min(Throughput.getValue(), Temp) : Temp;
   }
-  return Throughput ? 1 / Throughput.getValue() : Throughput;
+  if (Throughput.hasValue())
+    return 1.0 / Throughput.getValue();
+
+  // If no throughput value was calculated, assume that we can execute at the
+  // maximum issue width scaled by number of micro-ops for the schedule class.
+  return ((double)SCDesc.NumMicroOps) / SM.IssueWidth;
 }
 
-Optional<double>
+double
 MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
                                       const MCInstrInfo &MCII,
                                       const MCInst &Inst) const {
-  Optional<double> Throughput;
   unsigned SchedClass = MCII.get(Inst.getOpcode()).getSchedClass();
   const MCSchedClassDesc *SCDesc = getSchedClassDesc(SchedClass);
+
+  // If there's no valid class, assume that the instruction executes/completes
+  // at the maximum issue width.
   if (!SCDesc->isValid())
-    return Throughput;
+    return 1.0 / IssueWidth;
 
   unsigned CPUID = getProcessorID();
   while (SCDesc->isVariant()) {
@@ -124,7 +131,7 @@ MCSchedModel::getReciprocalThroughput(const MCSubtargetInfo &STI,
   llvm_unreachable("unsupported variant scheduling class");
 }
 
-Optional<double>
+double
 MCSchedModel::getReciprocalThroughput(unsigned SchedClass,
                                       const InstrItineraryData &IID) {
   Optional<double> Throughput;
@@ -136,5 +143,10 @@ MCSchedModel::getReciprocalThroughput(unsigned SchedClass,
     double Temp = countPopulation(I->getUnits()) * 1.0 / I->getCycles();
     Throughput = Throughput ? std::min(Throughput.getValue(), Temp) : Temp;
   }
-  return Throughput ? 1 / Throughput.getValue() : Throughput;
+  if (Throughput.hasValue())
+    return 1.0 / Throughput.getValue();
+
+  // If there are no execution resources specified for this class, then assume
+  // that it can execute at the maximum default issue width.
+  return 1.0 / DefaultIssueWidth;
 }