TargetSchedModel API. Implement latency lookup, disabled.

llvm-svn: 164098

llvm/include/llvm/CodeGen/ScheduleDAGInstrs.h

@@ -18,6 +18,7 @@
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/ScheduleDAG.h"
+#include "llvm/CodeGen/TargetSchedule.h"
 #include "llvm/Support/Compiler.h"
 #include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/ADT/SmallSet.h"
@@ -181,6 +182,9 @@ namespace llvm {
     /// Live Intervals provides reaching defs in preRA scheduling.
     LiveIntervals *LIS;
 
+    /// TargetSchedModel provides an interface to the machine model.
+    TargetSchedModel SchedModel;
+
     /// isPostRA flag indicates vregs cannot be present.
     bool IsPostRA;
 

llvm/include/llvm/CodeGen/TargetSchedule.h

@@ -45,17 +45,33 @@ public:
   /// Return true if this machine model includes an instruction-level scheduling
   /// model. This is more detailed than the course grain IssueWidth and default
   /// latency properties, but separate from the per-cycle itinerary data.
-  bool hasInstrSchedModel() const {
-    return SchedModel.hasInstrSchedModel();
-  }
+  bool hasInstrSchedModel() const { return SchedModel.hasInstrSchedModel(); }
 
   /// Return true if this machine model includes cycle-to-cycle itinerary
   /// data. This models scheduling at each stage in the processor pipeline.
-  bool hasInstrItineraries() const {
-    return SchedModel.hasInstrItineraries();
-  }
+  bool hasInstrItineraries() const { return !InstrItins.isEmpty(); }
+
+  /// computeOperandLatency - Compute and return the latency of the given data
+  /// dependent def and use when the operand indices are already known. UseMI
+  /// may be NULL for an unknown user.
+  ///
+  /// FindMin may be set to get the minimum vs. expected latency. Minimum
+  /// latency is used for scheduling groups, while expected latency is for
+  /// instruction cost and critical path.
+  unsigned computeOperandLatency(const MachineInstr *DefMI, unsigned DefOperIdx,
+                                 const MachineInstr *UseMI, unsigned UseOperIdx,
+                                 bool FindMin) const;
 
   unsigned getProcessorID() const { return SchedModel.getProcessorID(); }
+
+private:
+  /// getDefLatency is a helper for computeOperandLatency. Return the
+  /// instruction's latency if operand lookup is not required.
+  /// Otherwise return -1.
+  int getDefLatency(const MachineInstr *DefMI, bool FindMin) const;
+
+  /// Return the MCSchedClassDesc for this instruction.
+  const MCSchedClassDesc *resolveSchedClass(const MachineInstr *MI) const;
 };
 
 } // namespace llvm

llvm/include/llvm/MC/MCSchedule.h

@@ -208,14 +208,7 @@ public:
   unsigned getProcessorID() const { return ProcID; }
 
   /// Does this machine model include instruction-level scheduling.
-  bool hasInstrSchedModel() const {
-    return SchedClassTable;
-  }
-
-  /// Does this machine model include cycle-to-cycle itineraries.
-  bool hasInstrItineraries() const {
-    return InstrItineraries;
-  }
+  bool hasInstrSchedModel() const { return SchedClassTable != NULL; }
 
   const MCProcResourceDesc *getProcResource(unsigned ProcResourceIdx) const {
     assert(hasInstrSchedModel() && "No scheduling machine model");

llvm/include/llvm/Target/TargetInstrInfo.h

@@ -824,6 +824,9 @@ public:
   unsigned defaultDefLatency(const MCSchedModel *SchedModel,
                              const MachineInstr *DefMI) const;
 
+  int computeDefOperandLatency(const InstrItineraryData *ItinData,
+                               const MachineInstr *DefMI, bool FindMin) const;
+
   /// isHighLatencyDef - Return true if this opcode has high latency to its
   /// result.
   virtual bool isHighLatencyDef(int opc) const { return false; }

llvm/lib/CodeGen/TargetInstrInfoImpl.cpp

@@ -606,13 +606,13 @@ getOperandLatency(const InstrItineraryData *ItinData,
 
 /// If we can determine the operand latency from the def only, without itinerary
 /// lookup, do so. Otherwise return -1.
-static int computeDefOperandLatency(
-  const TargetInstrInfo *TII, const InstrItineraryData *ItinData,
-  const MachineInstr *DefMI, bool FindMin) {
+int TargetInstrInfo::computeDefOperandLatency(
+  const InstrItineraryData *ItinData,
+  const MachineInstr *DefMI, bool FindMin) const {
 
   // Let the target hook getInstrLatency handle missing itineraries.
   if (!ItinData)
-    return TII->getInstrLatency(ItinData, DefMI);
+    return getInstrLatency(ItinData, DefMI);
 
   // Return a latency based on the itinerary properties and defining instruction
   // if possible. Some common subtargets don't require per-operand latency,
@@ -621,7 +621,7 @@ static int computeDefOperandLatency(
     // If MinLatency is valid, call getInstrLatency. This uses Stage latency if
     // it exists before defaulting to MinLatency.
     if (ItinData->SchedModel->MinLatency >= 0)
-      return TII->getInstrLatency(ItinData, DefMI);
+      return getInstrLatency(ItinData, DefMI);
 
     // If MinLatency is invalid, OperandLatency is interpreted as MinLatency.
     // For empty itineraries, short-cirtuit the check and default to one cycle.
@@ -629,7 +629,7 @@ static int computeDefOperandLatency(
       return 1;
   }
   else if(ItinData->isEmpty())
-    return TII->defaultDefLatency(ItinData->SchedModel, DefMI);
+    return defaultDefLatency(ItinData->SchedModel, DefMI);
 
   // ...operand lookup required
   return -1;
@@ -652,7 +652,7 @@ computeOperandLatency(const InstrItineraryData *ItinData,
                       const MachineInstr *UseMI, unsigned UseIdx,
                       bool FindMin) const {
 
-  int DefLatency = computeDefOperandLatency(this, ItinData, DefMI, FindMin);
+  int DefLatency = computeDefOperandLatency(ItinData, DefMI, FindMin);
   if (DefLatency >= 0)
     return DefLatency;
 

llvm/lib/CodeGen/TargetSchedule.cpp

@@ -14,6 +14,7 @@
 
 #include "llvm/CodeGen/TargetSchedule.h"
 #include "llvm/Target/TargetInstrInfo.h"
+#include "llvm/Target/TargetRegisterInfo.h"
 #include "llvm/Target/TargetSubtargetInfo.h"
 #include "llvm/Support/CommandLine.h"
 
@@ -22,6 +23,9 @@ using namespace llvm;
 static cl::opt<bool> EnableSchedModel("schedmodel", cl::Hidden, cl::init(false),
   cl::desc("Use TargetSchedModel for latency lookup"));
 
+static cl::opt<bool> EnableSchedItins("scheditins", cl::Hidden, cl::init(true),
+  cl::desc("Use InstrItineraryData for latency lookup"));
+
 void TargetSchedModel::init(const MCSchedModel &sm,
                             const TargetSubtargetInfo *sti,
                             const TargetInstrInfo *tii) {
@@ -30,3 +34,139 @@ void TargetSchedModel::init(const MCSchedModel &sm,
   TII = tii;
   STI->initInstrItins(InstrItins);
 }
+
+/// If we can determine the operand latency from the def only, without machine
+/// model or itinerary lookup, do so. Otherwise return -1.
+int TargetSchedModel::getDefLatency(const MachineInstr *DefMI,
+                                    bool FindMin) const {
+
+  // Return a latency based on the itinerary properties and defining instruction
+  // if possible. Some common subtargets don't require per-operand latency,
+  // especially for minimum latencies.
+  if (FindMin) {
+    // If MinLatency is invalid, then use the itinerary for MinLatency. If no
+    // itinerary exists either, then use single cycle latency.
+    if (SchedModel.MinLatency < 0
+        && !(EnableSchedItins && hasInstrItineraries())) {
+      return 1;
+    }
+    return SchedModel.MinLatency;
+  }
+  else if (!(EnableSchedModel && hasInstrSchedModel())
+           && !(EnableSchedItins && hasInstrItineraries())) {
+    return TII->defaultDefLatency(&SchedModel, DefMI);
+  }
+  // ...operand lookup required
+  return -1;
+}
+
+/// Return the MCSchedClassDesc for this instruction. Some SchedClasses require
+/// evaluation of predicates that depend on instruction operands or flags.
+const MCSchedClassDesc *TargetSchedModel::
+resolveSchedClass(const MachineInstr *MI) const {
+
+  // Get the definition's scheduling class descriptor from this machine model.
+  unsigned SchedClass = MI->getDesc().getSchedClass();
+  const MCSchedClassDesc *SCDesc = SchedModel.getSchedClassDesc(SchedClass);
+
+#ifndef NDEBUG
+  unsigned NIter = 0;
+#endif
+  while (SCDesc->isVariant()) {
+    assert(++NIter < 6 && "Variants are nested deeper than the magic number");
+
+    SchedClass = STI->resolveSchedClass(SchedClass, MI, this);
+    SCDesc = SchedModel.getSchedClassDesc(SchedClass);
+  }
+  return SCDesc;
+}
+
+/// Find the def index of this operand. This index maps to the machine model and
+/// is independent of use operands. Def operands may be reordered with uses or
+/// merged with uses without affecting the def index (e.g. before/after
+/// regalloc). However, an instruction's def operands must never be reordered
+/// with respect to each other.
+static unsigned findDefIdx(const MachineInstr *MI, unsigned DefOperIdx) {
+  unsigned DefIdx = 0;
+  for (unsigned i = 0; i != DefOperIdx; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    if (MO.isReg() && MO.isDef())
+      ++DefIdx;
+  }
+  return DefIdx;
+}
+
+/// Find the use index of this operand. This is independent of the instruction's
+/// def operands.
+static unsigned findUseIdx(const MachineInstr *MI, unsigned UseOperIdx) {
+  unsigned UseIdx = 0;
+  for (unsigned i = 0; i != UseOperIdx; ++i) {
+    const MachineOperand &MO = MI->getOperand(i);
+    if (MO.isReg() && MO.isUse())
+      ++UseIdx;
+  }
+  return UseIdx;
+}
+
+// Top-level API for clients that know the operand indices.
+unsigned TargetSchedModel::computeOperandLatency(
+  const MachineInstr *DefMI, unsigned DefOperIdx,
+  const MachineInstr *UseMI, unsigned UseOperIdx,
+  bool FindMin) const {
+
+  int DefLatency = getDefLatency(DefMI, FindMin);
+  if (DefLatency >= 0)
+    return DefLatency;
+
+  if (!FindMin && EnableSchedModel && hasInstrSchedModel()) {
+    const MCSchedClassDesc *SCDesc = resolveSchedClass(DefMI);
+    unsigned DefIdx = findDefIdx(DefMI, DefOperIdx);
+    if (DefIdx < SCDesc->NumWriteLatencyEntries) {
+
+      // Lookup the definition's write latency in SubtargetInfo.
+      const MCWriteLatencyEntry *WLEntry =
+        STI->getWriteLatencyEntry(SCDesc, DefIdx);
+      unsigned WriteID = WLEntry->WriteResourceID;
+      unsigned Latency = WLEntry->Cycles;
+      if (!UseMI)
+        return Latency;
+
+      // Lookup the use's latency adjustment in SubtargetInfo.
+      const MCSchedClassDesc *UseDesc = resolveSchedClass(UseMI);
+      if (UseDesc->NumReadAdvanceEntries == 0)
+        return Latency;
+      unsigned UseIdx = findUseIdx(UseMI, UseOperIdx);
+      return Latency - STI->getReadAdvanceCycles(UseDesc, UseIdx, WriteID);
+    }
+    // If DefIdx does not exist in the model (e.g. implicit defs), then return
+    // unit latency (defaultDefLatency may be too conservative).
+    // TODO: For unknown defs, we may want to use the subtarget's model
+    // for WAW latency here instead of 1 cycle.
+    assert((!SCDesc->isValid() || DefMI->getOperand(DefOperIdx).isImplicit()) &&
+           "DefIdx exceeds machine model def operand list");
+    return 1;
+  }
+  assert(EnableSchedItins && hasInstrItineraries() &&
+         "operand latency requires itinerary");
+
+  int OperLatency = 0;
+  if (UseMI) {
+    OperLatency =
+      TII->getOperandLatency(&InstrItins, DefMI, DefOperIdx, UseMI, UseOperIdx);
+  }
+  else {
+    unsigned DefClass = DefMI->getDesc().getSchedClass();
+    OperLatency = InstrItins.getOperandCycle(DefClass, DefOperIdx);
+  }
+  if (OperLatency >= 0)
+    return OperLatency;
+
+  // No operand latency was found.
+  unsigned InstrLatency = TII->getInstrLatency(&InstrItins, DefMI);
+
+  // Expected latency is the max of the stage latency and itinerary props.
+  if (!FindMin)
+    InstrLatency = std::max(InstrLatency,
+                            TII->defaultDefLatency(&SchedModel, DefMI));
+  return InstrLatency;
+}

llvm/lib/MC/MCSubtargetInfo.cpp

@@ -113,5 +113,5 @@ MCSubtargetInfo::getInstrItineraryForCPU(StringRef CPU) const {
 /// Initialize an InstrItineraryData instance.
 void MCSubtargetInfo::initInstrItins(InstrItineraryData &InstrItins) const {
   InstrItins =
-    InstrItineraryData(0, Stages, OperandCycles, ForwardingPaths);
+    InstrItineraryData(CPUSchedModel, Stages, OperandCycles, ForwardingPaths);
 }