llvm-6502/include/llvm/CodeGen/ScheduleHazardRecognizer.h

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//=- llvm/CodeGen/ScheduleHazardRecognizer.h - Scheduling 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 implements the ScheduleHazardRecognizer class, which implements
// hazard-avoidance heuristics for scheduling.
//
//===----------------------------------------------------------------------===//
#ifndef LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
#define LLVM_CODEGEN_SCHEDULEHAZARDRECOGNIZER_H
namespace llvm {
class SUnit;
/// HazardRecognizer - This determines whether or not an instruction can be
/// issued this cycle, and whether or not a noop needs to be inserted to handle
/// the hazard.
class ScheduleHazardRecognizer {
public:
virtual ~ScheduleHazardRecognizer();
enum HazardType {
NoHazard, // This instruction can be emitted at this cycle.
Hazard, // This instruction can't be emitted at this cycle.
NoopHazard // This instruction can't be emitted, and needs noops.
};
/// getHazardType - Return the hazard type of emitting this node. There are
/// three possible results. Either:
/// * NoHazard: it is legal to issue this instruction on this cycle.
/// * Hazard: issuing this instruction would stall the machine. If some
/// other instruction is available, issue it first.
/// * NoopHazard: issuing this instruction would break the program. If
/// some other instruction can be issued, do so, otherwise issue a noop.
virtual HazardType getHazardType(SUnit *) {
return NoHazard;
}
/// Reset - This callback is invoked when a new block of
/// instructions is about to be schedule. The hazard state should be
/// set to an initialized state.
virtual void Reset() {}
/// EmitInstruction - This callback is invoked when an instruction is
/// emitted, to advance the hazard state.
virtual void EmitInstruction(SUnit *) {}
/// AdvanceCycle - This callback is invoked when no instructions can be
/// issued on this cycle without a hazard. This should increment the
/// internal state of the hazard recognizer so that previously "Hazard"
/// instructions will now not be hazards.
virtual void AdvanceCycle() {}
/// EmitNoop - This callback is invoked when a noop was added to the
/// instruction stream.
virtual void EmitNoop() {
// Default implementation: count it as a cycle.
AdvanceCycle();
}
};
}
#endif