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//=- llvm/CodeGen/ScoreboardHazardRecognizer.h - Schedule Support -*- C++ -*-=//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file defines the ScoreboardHazardRecognizer class, which
// encapsulates hazard-avoidance heuristics for scheduling, based on the
// scheduling itineraries specified for the target.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
#define LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/MC/MCInstrItineraries.h"
#include <cassert>
#include <cstddef>
#include <cstring>
namespace llvm {
class ScheduleDAG;
class SUnit;
class ScoreboardHazardRecognizer : public ScheduleHazardRecognizer {
// Scoreboard to track function unit usage. Scoreboard[0] is a
// mask of the FUs in use in the cycle currently being
// schedule. Scoreboard[1] is a mask for the next cycle. The
// Scoreboard is used as a circular buffer with the current cycle
// indicated by Head.
//
// Scoreboard always counts cycles in forward execution order. If used by a
// bottom-up scheduler, then the scoreboard cycles are the inverse of the
// scheduler's cycles.
class Scoreboard {
InstrStage::FuncUnits *Data = nullptr;
// The maximum number of cycles monitored by the Scoreboard. This
// value is determined based on the target itineraries to ensure
// that all hazards can be tracked.
size_t Depth = 0;
// Indices into the Scoreboard that represent the current cycle.
size_t Head = 0;
public:
Scoreboard() = default;
Scoreboard &operator=(const Scoreboard &other) = delete;
Scoreboard(const Scoreboard &other) = delete;
~Scoreboard() {
delete[] Data;
}
size_t getDepth() const { return Depth; }
InstrStage::FuncUnits& operator[](size_t idx) const {
// Depth is expected to be a power-of-2.
assert(Depth && !(Depth & (Depth - 1)) &&
"Scoreboard was not initialized properly!");
return Data[(Head + idx) & (Depth-1)];
}
void reset(size_t d = 1) {
if (!Data) {
Depth = d;
Data = new InstrStage::FuncUnits[Depth];
}
memset(Data, 0, Depth * sizeof(Data[0]));
Head = 0;
}
void advance() {
Head = (Head + 1) & (Depth-1);
}
void recede() {
Head = (Head - 1) & (Depth-1);
}
// Print the scoreboard.
void dump() const;
};
// Support for tracing ScoreboardHazardRecognizer as a component within
// another module.
const char *DebugType;
// Itinerary data for the target.
const InstrItineraryData *ItinData;
const ScheduleDAG *DAG;
/// IssueWidth - Max issue per cycle. 0=Unknown.
unsigned IssueWidth = 0;
/// IssueCount - Count instructions issued in this cycle.
unsigned IssueCount = 0;
Scoreboard ReservedScoreboard;
Scoreboard RequiredScoreboard;
public:
ScoreboardHazardRecognizer(const InstrItineraryData *II,
const ScheduleDAG *DAG,
const char *ParentDebugType = "");
/// atIssueLimit - Return true if no more instructions may be issued in this
/// cycle.
bool atIssueLimit() const override;
// Stalls provides an cycle offset at which SU will be scheduled. It will be
// negative for bottom-up scheduling.
HazardType getHazardType(SUnit *SU, int Stalls) override;
void Reset() override;
void EmitInstruction(SUnit *SU) override;
void AdvanceCycle() override;
void RecedeCycle() override;
};
} // end namespace llvm
#endif // LLVM_CODEGEN_SCOREBOARDHAZARDRECOGNIZER_H
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