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//=- llvm/CodeGen/ScoreboardHazardRecognizer.h - Schedule Support -*- 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 ScoreboardHazardRecognizer class, which
// encapsulates hazard-avoidance heuristics for scheduling, based on the
// scheduling itineraries specified for the target.
#include "llvm/CodeGen/ScheduleHazardRecognizer.h"
#include "llvm/Support/DataTypes.h"
#include <cassert>
#include <cstring>
namespace llvm {
class InstrItineraryData;
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 {
unsigned *Data;
// 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;
// Indices into the Scoreboard that represent the current cycle.
size_t Head;
Scoreboard():Data(nullptr), Depth(0), Head(0) { }
~Scoreboard() {
delete[] Data;
size_t getDepth() const { return Depth; }
unsigned& 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 unsigned[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;
#ifndef NDEBUG
// Support for tracing ScoreboardHazardRecognizer as a component within
// another module. Follows the current thread-unsafe model of tracing.
static const char *DebugType;
// Itinerary data for the target.
const InstrItineraryData *ItinData;
const ScheduleDAG *DAG;
/// IssueWidth - Max issue per cycle. 0=Unknown.
unsigned IssueWidth;
/// IssueCount - Count instructions issued in this cycle.
unsigned IssueCount;
Scoreboard ReservedScoreboard;
Scoreboard RequiredScoreboard;
ScoreboardHazardRecognizer(const InstrItineraryData *ItinData,
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;