| //=- 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; |
| } |
| |
| /// 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 |