LLVM 17.0.0git
Go to the documentation of this file.
1//===------------------- AMDGPUCustomBehaviour.h ----------------*-C++ -* -===//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
8/// \file
10/// This file defines the AMDGPUCustomBehaviour class which inherits from
11/// CustomBehaviour. This class is used by the tool llvm-mca to enforce
12/// target specific behaviour that is not expressed well enough in the
13/// scheduling model for mca to enforce it automatically.
24namespace llvm {
25namespace mca {
28 void processWaitCnt(std::unique_ptr<Instruction> &Inst, const MCInst &MCI);
36 void postProcessInstruction(std::unique_ptr<Instruction> &Inst,
37 const MCInst &MCI) override;
41 bool VmCnt = false;
42 bool ExpCnt = false;
43 bool LgkmCnt = false;
44 bool VsCnt = false;
48 /// Whenever MCA would like to dispatch an s_waitcnt instructions,
49 /// we must check all the instruction that are still executing to see if
50 /// they modify the same CNT as we need to wait for. This vector
51 /// gets built in the constructor and contains 1 WaitCntInfo struct
52 /// for each instruction within the SrcManager. Each element
53 /// tells us which CNTs that instruction may interact with.
54 /// We conservatively assume some instructions interact with more
55 /// CNTs than they do in reality, so we will occasionally wait
56 /// longer than necessary, but we shouldn't ever wait for shorter.
57 std::vector<WaitCntInfo> InstrWaitCntInfo;
59 /// This method gets called from the constructor and is
60 /// where we setup the InstrWaitCntInfo vector.
61 /// The core logic for determining which CNTs an instruction
62 /// interacts with is taken from SIInsertWaitcnts::updateEventWaitcntAfter().
63 /// Unfortunately, some of the logic from that function is not available to us
64 /// in this scope so we conservatively end up assuming that some
65 /// instructions interact with more CNTs than they do in reality.
66 void generateWaitCntInfo();
67 /// Helper function used in generateWaitCntInfo()
68 bool hasModifiersSet(const std::unique_ptr<Instruction> &Inst,
69 unsigned OpName) const;
70 /// Helper function used in generateWaitCntInfo()
71 bool isAlwaysGDS(uint16_t Opcode) const;
72 /// Helper function used in generateWaitCntInfo()
73 bool isVMEM(const MCInstrDesc &MCID);
74 /// This method gets called from checkCustomHazard when mca is attempting to
75 /// dispatch an s_waitcnt instruction (or one of its variants). The method
76 /// looks at each of the instructions that are still executing in the pipeline
77 /// to determine if the waitcnt should force a wait.
78 unsigned handleWaitCnt(ArrayRef<InstRef> IssuedInst, const InstRef &IR);
79 /// Based on the type of s_waitcnt instruction we are looking at, and what its
80 /// operands are, this method will set the values for each of the cnt
81 /// references provided as arguments.
82 void computeWaitCnt(const InstRef &IR, unsigned &Vmcnt, unsigned &Expcnt,
83 unsigned &Lgkmcnt, unsigned &Vscnt);
87 const mca::SourceMgr &SrcMgr, const MCInstrInfo &MCII);
90 /// This method is used to determine if an instruction
91 /// should be allowed to be dispatched. The return value is
92 /// how many cycles until the instruction can be dispatched.
93 /// This method is called after MCA has already checked for
94 /// register and hardware dependencies so this method should only
95 /// implement custom behaviour and dependencies that are not picked up
96 /// by MCA naturally.
97 unsigned checkCustomHazard(ArrayRef<InstRef> IssuedInst,
98 const InstRef &IR) override;
100} // namespace mca
101} // namespace llvm
This file defines the base class CustomBehaviour which can be inherited from by specific targets (ex.
Statically lint checks LLVM IR
Definition: Lint.cpp:746
This file defines the SmallVector class.
ArrayRef - Represent a constant reference to an array (0 or more elements consecutively in memory),...
Definition: ArrayRef.h:41
Instances of this class represent a single low-level machine instruction.
Definition: MCInst.h:184
Describe properties that are true of each instruction in the target description file.
Definition: MCInstrDesc.h:198
Interface to description of machine instruction set.
Definition: MCInstrInfo.h:26
Generic base class for all target subtargets.
unsigned checkCustomHazard(ArrayRef< InstRef > IssuedInst, const InstRef &IR) override
This method is used to determine if an instruction should be allowed to be dispatched.
void postProcessInstruction(std::unique_ptr< Instruction > &Inst, const MCInst &MCI) override
This method can be overriden by targets to modify the mca::Instruction object after it has been lower...
AMDGPUInstrPostProcess(const MCSubtargetInfo &STI, const MCInstrInfo &MCII)
Class which can be overriden by targets to enforce instruction dependencies and behaviours that aren'...
const MCInstrInfo & MCII
const mca::SourceMgr & SrcMgr
const MCSubtargetInfo & STI
An InstRef contains both a SourceMgr index and Instruction pair.
Definition: Instruction.h:720
Class which can be overriden by targets to modify the mca::Instruction objects before the pipeline st...
const MCSubtargetInfo & STI
const MCInstrInfo & MCII
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
Abstracting the input code sequence (a sequence of MCInst) and assigning unique identifiers to every ...
Definition: SourceMgr.h:29