forked from OSchip/llvm-project
104 lines
4.4 KiB
C++
104 lines
4.4 KiB
C++
//===------------------- AMDGPUCustomBehaviour.h ----------------*-C++ -* -===//
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//
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// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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// See https://llvm.org/LICENSE.txt for license information.
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// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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//
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//===----------------------------------------------------------------------===//
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/// \file
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///
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/// This file defines the AMDGPUCustomBehaviour class which inherits from
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/// CustomBehaviour. This class is used by the tool llvm-mca to enforce
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/// target specific behaviour that is not expressed well enough in the
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/// scheduling model for mca to enforce it automatically.
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///
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_LIB_TARGET_AMDGPU_MCA_AMDGPUCUSTOMBEHAVIOUR_H
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#define LLVM_LIB_TARGET_AMDGPU_MCA_AMDGPUCUSTOMBEHAVIOUR_H
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#include "llvm/ADT/SmallVector.h"
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#include "llvm/MCA/CustomBehaviour.h"
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#include "llvm/Support/TargetParser.h"
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namespace llvm {
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namespace mca {
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class AMDGPUInstrPostProcess : public InstrPostProcess {
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void processWaitCnt(std::unique_ptr<Instruction> &Inst, const MCInst &MCI);
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public:
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AMDGPUInstrPostProcess(const MCSubtargetInfo &STI, const MCInstrInfo &MCII)
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: InstrPostProcess(STI, MCII) {}
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~AMDGPUInstrPostProcess() {}
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void postProcessInstruction(std::unique_ptr<Instruction> &Inst,
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const MCInst &MCI) override;
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};
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struct WaitCntInfo {
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bool VmCnt = false;
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bool ExpCnt = false;
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bool LgkmCnt = false;
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bool VsCnt = false;
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};
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class AMDGPUCustomBehaviour : public CustomBehaviour {
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/// Whenever MCA would like to dispatch an s_waitcnt instructions,
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/// we must check all the instruction that are still executing to see if
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/// they modify the same CNT as we need to wait for. This vector
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/// gets built in the constructor and contains 1 WaitCntInfo struct
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/// for each instruction within the SrcManager. Each element
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/// tells us which CNTs that instruction may interact with.
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/// We conservatively assume some instructions interact with more
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/// CNTs than they do in reality, so we will occasionally wait
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/// longer than necessary, but we shouldn't ever wait for shorter.
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std::vector<WaitCntInfo> InstrWaitCntInfo;
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/// This method gets called from the constructor and is
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/// where we setup the InstrWaitCntInfo vector.
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/// The core logic for determining which CNTs an instruction
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/// interacts with is taken from SIInsertWaitcnts::updateEventWaitcntAfter().
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/// Unfortunately, some of the logic from that function is not avalable to us
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/// in this scope so we conservatively end up assuming that some
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/// instructions interact with more CNTs than they do in reality.
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void generateWaitCntInfo();
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/// Helper function used in generateWaitCntInfo()
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bool hasModifiersSet(const std::unique_ptr<Instruction> &Inst,
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unsigned OpName) const;
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/// Helper function used in generateWaitCntInfo()
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bool isAlwaysGDS(uint16_t Opcode) const;
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/// Helper function used in generateWaitCntInfo()
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bool isVMEM(const MCInstrDesc &MCID);
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/// This method gets called from checkCustomHazard when mca is attempting to
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/// dispatch an s_waitcnt instruction (or one of its variants). The method
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/// looks at each of the instructions that are still executing in the pipeline
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/// to determine if the waitcnt should force a wait.
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unsigned handleWaitCnt(ArrayRef<InstRef> IssuedInst, const InstRef &IR);
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/// Based on the type of s_waitcnt instruction we are looking at, and what its
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/// operands are, this method will set the values for each of the cnt
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/// references provided as arguments.
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void computeWaitCnt(const InstRef &IR, unsigned &Vmcnt, unsigned &Expcnt,
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unsigned &Lgkmcnt, unsigned &Vscnt);
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public:
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AMDGPUCustomBehaviour(const MCSubtargetInfo &STI,
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const mca::SourceMgr &SrcMgr, const MCInstrInfo &MCII);
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~AMDGPUCustomBehaviour() {}
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/// This method is used to determine if an instruction
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/// should be allowed to be dispatched. The return value is
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/// how many cycles until the instruction can be dispatched.
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/// This method is called after MCA has already checked for
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/// register and hardware dependencies so this method should only
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/// implement custom behaviour and dependencies that are not picked up
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/// by MCA naturally.
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unsigned checkCustomHazard(ArrayRef<InstRef> IssuedInst,
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const InstRef &IR) override;
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};
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} // namespace mca
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} // namespace llvm
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#endif
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