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+//===-- llvm/MC/MCSchedule.h - Scheduling -----------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the classes used to describe a subtarget's machine model
+// for scheduling and other instruction cost heuristics.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_MC_MCSCHEDULE_H
+#define LLVM_MC_MCSCHEDULE_H
+
+#include "llvm/ADT/Optional.h"
+#include "llvm/Support/DataTypes.h"
+#include <cassert>
+
+namespace llvm {
+
+struct InstrItinerary;
+class MCSubtargetInfo;
+
+/// Define a kind of processor resource that will be modeled by the scheduler.
+struct MCProcResourceDesc {
+  const char *Name;
+  unsigned NumUnits; // Number of resource of this kind
+  unsigned SuperIdx; // Index of the resources kind that contains this kind.
+
+  // Number of resources that may be buffered.
+  //
+  // Buffered resources (BufferSize != 0) may be consumed at some indeterminate
+  // cycle after dispatch. This should be used for out-of-order cpus when
+  // instructions that use this resource can be buffered in a reservaton
+  // station.
+  //
+  // Unbuffered resources (BufferSize == 0) always consume their resource some
+  // fixed number of cycles after dispatch. If a resource is unbuffered, then
+  // the scheduler will avoid scheduling instructions with conflicting resources
+  // in the same cycle. This is for in-order cpus, or the in-order portion of
+  // an out-of-order cpus.
+  int BufferSize;
+
+  // If the resource has sub-units, a pointer to the first element of an array
+  // of `NumUnits` elements containing the ProcResourceIdx of the sub units.
+  // nullptr if the resource does not have sub-units.
+  const unsigned *SubUnitsIdxBegin;
+
+  bool operator==(const MCProcResourceDesc &Other) const {
+    return NumUnits == Other.NumUnits && SuperIdx == Other.SuperIdx
+      && BufferSize == Other.BufferSize;
+  }
+};
+
+/// Identify one of the processor resource kinds consumed by a particular
+/// scheduling class for the specified number of cycles.
+struct MCWriteProcResEntry {
+  uint16_t ProcResourceIdx;
+  uint16_t Cycles;
+
+  bool operator==(const MCWriteProcResEntry &Other) const {
+    return ProcResourceIdx == Other.ProcResourceIdx && Cycles == Other.Cycles;
+  }
+};
+
+/// Specify the latency in cpu cycles for a particular scheduling class and def
+/// index. -1 indicates an invalid latency. Heuristics would typically consider
+/// an instruction with invalid latency to have infinite latency.  Also identify
+/// the WriteResources of this def. When the operand expands to a sequence of
+/// writes, this ID is the last write in the sequence.
+struct MCWriteLatencyEntry {
+  int16_t Cycles;
+  uint16_t WriteResourceID;
+
+  bool operator==(const MCWriteLatencyEntry &Other) const {
+    return Cycles == Other.Cycles && WriteResourceID == Other.WriteResourceID;
+  }
+};
+
+/// Specify the number of cycles allowed after instruction issue before a
+/// particular use operand reads its registers. This effectively reduces the
+/// write's latency. Here we allow negative cycles for corner cases where
+/// latency increases. This rule only applies when the entry's WriteResource
+/// matches the write's WriteResource.
+///
+/// MCReadAdvanceEntries are sorted first by operand index (UseIdx), then by
+/// WriteResourceIdx.
+struct MCReadAdvanceEntry {
+  unsigned UseIdx;
+  unsigned WriteResourceID;
+  int Cycles;
+
+  bool operator==(const MCReadAdvanceEntry &Other) const {
+    return UseIdx == Other.UseIdx && WriteResourceID == Other.WriteResourceID
+      && Cycles == Other.Cycles;
+  }
+};
+
+/// Summarize the scheduling resources required for an instruction of a
+/// particular scheduling class.
+///
+/// Defined as an aggregate struct for creating tables with initializer lists.
+struct MCSchedClassDesc {
+  static const unsigned short InvalidNumMicroOps = (1U << 14) - 1;
+  static const unsigned short VariantNumMicroOps = InvalidNumMicroOps - 1;
+
+#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
+  const char* Name;
+#endif
+  uint16_t NumMicroOps : 14;
+  bool     BeginGroup : 1;
+  bool     EndGroup : 1;
+  uint16_t WriteProcResIdx; // First index into WriteProcResTable.
+  uint16_t NumWriteProcResEntries;
+  uint16_t WriteLatencyIdx; // First index into WriteLatencyTable.
+  uint16_t NumWriteLatencyEntries;
+  uint16_t ReadAdvanceIdx; // First index into ReadAdvanceTable.
+  uint16_t NumReadAdvanceEntries;
+
+  bool isValid() const {
+    return NumMicroOps != InvalidNumMicroOps;
+  }
+  bool isVariant() const {
+    return NumMicroOps == VariantNumMicroOps;
+  }
+};
+
+/// Machine model for scheduling, bundling, and heuristics.
+///
+/// The machine model directly provides basic information about the
+/// microarchitecture to the scheduler in the form of properties. It also
+/// optionally refers to scheduler resource tables and itinerary
+/// tables. Scheduler resource tables model the latency and cost for each
+/// instruction type. Itinerary tables are an independent mechanism that
+/// provides a detailed reservation table describing each cycle of instruction
+/// execution. Subtargets may define any or all of the above categories of data
+/// depending on the type of CPU and selected scheduler.
+struct MCSchedModel {
+  // IssueWidth is the maximum number of instructions that may be scheduled in
+  // the same per-cycle group.
+  unsigned IssueWidth;
+  static const unsigned DefaultIssueWidth = 1;
+
+  // MicroOpBufferSize is the number of micro-ops that the processor may buffer
+  // for out-of-order execution.
+  //
+  // "0" means operations that are not ready in this cycle are not considered
+  // for scheduling (they go in the pending queue). Latency is paramount. This
+  // may be more efficient if many instructions are pending in a schedule.
+  //
+  // "1" means all instructions are considered for scheduling regardless of
+  // whether they are ready in this cycle. Latency still causes issue stalls,
+  // but we balance those stalls against other heuristics.
+  //
+  // "> 1" means the processor is out-of-order. This is a machine independent
+  // estimate of highly machine specific characteristics such as the register
+  // renaming pool and reorder buffer.
+  unsigned MicroOpBufferSize;
+  static const unsigned DefaultMicroOpBufferSize = 0;
+
+  // LoopMicroOpBufferSize is the number of micro-ops that the processor may
+  // buffer for optimized loop execution. More generally, this represents the
+  // optimal number of micro-ops in a loop body. A loop may be partially
+  // unrolled to bring the count of micro-ops in the loop body closer to this
+  // number.
+  unsigned LoopMicroOpBufferSize;
+  static const unsigned DefaultLoopMicroOpBufferSize = 0;
+
+  // LoadLatency is the expected latency of load instructions.
+  unsigned LoadLatency;
+  static const unsigned DefaultLoadLatency = 4;
+
+  // HighLatency is the expected latency of "very high latency" operations.
+  // See TargetInstrInfo::isHighLatencyDef().
+  // By default, this is set to an arbitrarily high number of cycles
+  // likely to have some impact on scheduling heuristics.
+  unsigned HighLatency;
+  static const unsigned DefaultHighLatency = 10;
+
+  // MispredictPenalty is the typical number of extra cycles the processor
+  // takes to recover from a branch misprediction.
+  unsigned MispredictPenalty;
+  static const unsigned DefaultMispredictPenalty = 10;
+
+  bool PostRAScheduler; // default value is false
+
+  bool CompleteModel;
+
+  unsigned ProcID;
+  const MCProcResourceDesc *ProcResourceTable;
+  const MCSchedClassDesc *SchedClassTable;
+  unsigned NumProcResourceKinds;
+  unsigned NumSchedClasses;
+  // Instruction itinerary tables used by InstrItineraryData.
+  friend class InstrItineraryData;
+  const InstrItinerary *InstrItineraries;
+
+  unsigned getProcessorID() const { return ProcID; }
+
+  /// Does this machine model include instruction-level scheduling.
+  bool hasInstrSchedModel() const { return SchedClassTable; }
+
+  /// Return true if this machine model data for all instructions with a
+  /// scheduling class (itinerary class or SchedRW list).
+  bool isComplete() const { return CompleteModel; }
+
+  /// Return true if machine supports out of order execution.
+  bool isOutOfOrder() const { return MicroOpBufferSize > 1; }
+
+  unsigned getNumProcResourceKinds() const {
+    return NumProcResourceKinds;
+  }
+
+  const MCProcResourceDesc *getProcResource(unsigned ProcResourceIdx) const {
+    assert(hasInstrSchedModel() && "No scheduling machine model");
+
+    assert(ProcResourceIdx < NumProcResourceKinds && "bad proc resource idx");
+    return &ProcResourceTable[ProcResourceIdx];
+  }
+
+  const MCSchedClassDesc *getSchedClassDesc(unsigned SchedClassIdx) const {
+    assert(hasInstrSchedModel() && "No scheduling machine model");
+
+    assert(SchedClassIdx < NumSchedClasses && "bad scheduling class idx");
+    return &SchedClassTable[SchedClassIdx];
+  }
+
+  /// Returns the latency value for the scheduling class.
+  static int computeInstrLatency(const MCSubtargetInfo &STI,
+                                 const MCSchedClassDesc &SCDesc);
+
+  /// Returns the reciprocal throughput information from a MCSchedClassDesc.
+  static Optional<double>
+  getReciprocalThroughput(const MCSubtargetInfo &STI,
+                          const MCSchedClassDesc &SCDesc);
+
+  /// Returns the default initialized model.
+  static const MCSchedModel &GetDefaultSchedModel() { return Default; }
+  static const MCSchedModel Default;
+};
+
+} // End llvm namespace
+
+#endif