freebsd-dev/contrib/llvm/lib/Target/AMDGPU/GCNHazardRecognizer.cpp
2017-04-16 16:25:46 +00:00

576 lines
18 KiB
C++

//===-- GCNHazardRecognizers.cpp - GCN Hazard Recognizer Impls ------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements hazard recognizers for scheduling on GCN processors.
//
//===----------------------------------------------------------------------===//
#include "AMDGPUSubtarget.h"
#include "GCNHazardRecognizer.h"
#include "SIDefines.h"
#include "SIInstrInfo.h"
#include "SIRegisterInfo.h"
#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/iterator_range.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/ScheduleDAG.h"
#include "llvm/MC/MCInstrDesc.h"
#include "llvm/Support/ErrorHandling.h"
#include <algorithm>
#include <cassert>
#include <limits>
#include <set>
#include <vector>
using namespace llvm;
//===----------------------------------------------------------------------===//
// Hazard Recoginizer Implementation
//===----------------------------------------------------------------------===//
GCNHazardRecognizer::GCNHazardRecognizer(const MachineFunction &MF) :
CurrCycleInstr(nullptr),
MF(MF),
ST(MF.getSubtarget<SISubtarget>()),
TII(*ST.getInstrInfo()) {
MaxLookAhead = 5;
}
void GCNHazardRecognizer::EmitInstruction(SUnit *SU) {
EmitInstruction(SU->getInstr());
}
void GCNHazardRecognizer::EmitInstruction(MachineInstr *MI) {
CurrCycleInstr = MI;
}
static bool isDivFMas(unsigned Opcode) {
return Opcode == AMDGPU::V_DIV_FMAS_F32 || Opcode == AMDGPU::V_DIV_FMAS_F64;
}
static bool isSGetReg(unsigned Opcode) {
return Opcode == AMDGPU::S_GETREG_B32;
}
static bool isSSetReg(unsigned Opcode) {
return Opcode == AMDGPU::S_SETREG_B32 || Opcode == AMDGPU::S_SETREG_IMM32_B32;
}
static bool isRWLane(unsigned Opcode) {
return Opcode == AMDGPU::V_READLANE_B32 || Opcode == AMDGPU::V_WRITELANE_B32;
}
static bool isRFE(unsigned Opcode) {
return Opcode == AMDGPU::S_RFE_B64;
}
static bool isSMovRel(unsigned Opcode) {
switch (Opcode) {
case AMDGPU::S_MOVRELS_B32:
case AMDGPU::S_MOVRELS_B64:
case AMDGPU::S_MOVRELD_B32:
case AMDGPU::S_MOVRELD_B64:
return true;
default:
return false;
}
}
static unsigned getHWReg(const SIInstrInfo *TII, const MachineInstr &RegInstr) {
const MachineOperand *RegOp = TII->getNamedOperand(RegInstr,
AMDGPU::OpName::simm16);
return RegOp->getImm() & AMDGPU::Hwreg::ID_MASK_;
}
ScheduleHazardRecognizer::HazardType
GCNHazardRecognizer::getHazardType(SUnit *SU, int Stalls) {
MachineInstr *MI = SU->getInstr();
if (SIInstrInfo::isSMRD(*MI) && checkSMRDHazards(MI) > 0)
return NoopHazard;
if (SIInstrInfo::isVMEM(*MI) && checkVMEMHazards(MI) > 0)
return NoopHazard;
if (SIInstrInfo::isVALU(*MI) && checkVALUHazards(MI) > 0)
return NoopHazard;
if (SIInstrInfo::isDPP(*MI) && checkDPPHazards(MI) > 0)
return NoopHazard;
if (isDivFMas(MI->getOpcode()) && checkDivFMasHazards(MI) > 0)
return NoopHazard;
if (isRWLane(MI->getOpcode()) && checkRWLaneHazards(MI) > 0)
return NoopHazard;
if (isSGetReg(MI->getOpcode()) && checkGetRegHazards(MI) > 0)
return NoopHazard;
if (isSSetReg(MI->getOpcode()) && checkSetRegHazards(MI) > 0)
return NoopHazard;
if (isRFE(MI->getOpcode()) && checkRFEHazards(MI) > 0)
return NoopHazard;
if ((TII.isVINTRP(*MI) || isSMovRel(MI->getOpcode())) &&
checkReadM0Hazards(MI) > 0)
return NoopHazard;
if (checkAnyInstHazards(MI) > 0)
return NoopHazard;
return NoHazard;
}
unsigned GCNHazardRecognizer::PreEmitNoops(SUnit *SU) {
return PreEmitNoops(SU->getInstr());
}
unsigned GCNHazardRecognizer::PreEmitNoops(MachineInstr *MI) {
int WaitStates = std::max(0, checkAnyInstHazards(MI));
if (SIInstrInfo::isSMRD(*MI))
return std::max(WaitStates, checkSMRDHazards(MI));
if (SIInstrInfo::isVALU(*MI)) {
WaitStates = std::max(WaitStates, checkVALUHazards(MI));
if (SIInstrInfo::isVMEM(*MI))
WaitStates = std::max(WaitStates, checkVMEMHazards(MI));
if (SIInstrInfo::isDPP(*MI))
WaitStates = std::max(WaitStates, checkDPPHazards(MI));
if (isDivFMas(MI->getOpcode()))
WaitStates = std::max(WaitStates, checkDivFMasHazards(MI));
if (isRWLane(MI->getOpcode()))
WaitStates = std::max(WaitStates, checkRWLaneHazards(MI));
if (TII.isVINTRP(*MI))
WaitStates = std::max(WaitStates, checkReadM0Hazards(MI));
return WaitStates;
}
if (isSGetReg(MI->getOpcode()))
return std::max(WaitStates, checkGetRegHazards(MI));
if (isSSetReg(MI->getOpcode()))
return std::max(WaitStates, checkSetRegHazards(MI));
if (isRFE(MI->getOpcode()))
return std::max(WaitStates, checkRFEHazards(MI));
if (TII.isVINTRP(*MI) || isSMovRel(MI->getOpcode()))
return std::max(WaitStates, checkReadM0Hazards(MI));
return WaitStates;
}
void GCNHazardRecognizer::EmitNoop() {
EmittedInstrs.push_front(nullptr);
}
void GCNHazardRecognizer::AdvanceCycle() {
// When the scheduler detects a stall, it will call AdvanceCycle() without
// emitting any instructions.
if (!CurrCycleInstr)
return;
unsigned NumWaitStates = TII.getNumWaitStates(*CurrCycleInstr);
// Keep track of emitted instructions
EmittedInstrs.push_front(CurrCycleInstr);
// Add a nullptr for each additional wait state after the first. Make sure
// not to add more than getMaxLookAhead() items to the list, since we
// truncate the list to that size right after this loop.
for (unsigned i = 1, e = std::min(NumWaitStates, getMaxLookAhead());
i < e; ++i) {
EmittedInstrs.push_front(nullptr);
}
// getMaxLookahead() is the largest number of wait states we will ever need
// to insert, so there is no point in keeping track of more than that many
// wait states.
EmittedInstrs.resize(getMaxLookAhead());
CurrCycleInstr = nullptr;
}
void GCNHazardRecognizer::RecedeCycle() {
llvm_unreachable("hazard recognizer does not support bottom-up scheduling.");
}
//===----------------------------------------------------------------------===//
// Helper Functions
//===----------------------------------------------------------------------===//
int GCNHazardRecognizer::getWaitStatesSince(
function_ref<bool(MachineInstr *)> IsHazard) {
int WaitStates = -1;
for (MachineInstr *MI : EmittedInstrs) {
++WaitStates;
if (!MI || !IsHazard(MI))
continue;
return WaitStates;
}
return std::numeric_limits<int>::max();
}
int GCNHazardRecognizer::getWaitStatesSinceDef(
unsigned Reg, function_ref<bool(MachineInstr *)> IsHazardDef) {
const SIRegisterInfo *TRI = ST.getRegisterInfo();
auto IsHazardFn = [IsHazardDef, TRI, Reg] (MachineInstr *MI) {
return IsHazardDef(MI) && MI->modifiesRegister(Reg, TRI);
};
return getWaitStatesSince(IsHazardFn);
}
int GCNHazardRecognizer::getWaitStatesSinceSetReg(
function_ref<bool(MachineInstr *)> IsHazard) {
auto IsHazardFn = [IsHazard] (MachineInstr *MI) {
return isSSetReg(MI->getOpcode()) && IsHazard(MI);
};
return getWaitStatesSince(IsHazardFn);
}
//===----------------------------------------------------------------------===//
// No-op Hazard Detection
//===----------------------------------------------------------------------===//
static void addRegsToSet(iterator_range<MachineInstr::const_mop_iterator> Ops,
std::set<unsigned> &Set) {
for (const MachineOperand &Op : Ops) {
if (Op.isReg())
Set.insert(Op.getReg());
}
}
int GCNHazardRecognizer::checkSMEMSoftClauseHazards(MachineInstr *SMEM) {
// SMEM soft clause are only present on VI+
if (ST.getGeneration() < SISubtarget::VOLCANIC_ISLANDS)
return 0;
// A soft-clause is any group of consecutive SMEM instructions. The
// instructions in this group may return out of order and/or may be
// replayed (i.e. the same instruction issued more than once).
//
// In order to handle these situations correctly we need to make sure
// that when a clause has more than one instruction, no instruction in the
// clause writes to a register that is read another instruction in the clause
// (including itself). If we encounter this situaion, we need to break the
// clause by inserting a non SMEM instruction.
std::set<unsigned> ClauseDefs;
std::set<unsigned> ClauseUses;
for (MachineInstr *MI : EmittedInstrs) {
// When we hit a non-SMEM instruction then we have passed the start of the
// clause and we can stop.
if (!MI || !SIInstrInfo::isSMRD(*MI))
break;
addRegsToSet(MI->defs(), ClauseDefs);
addRegsToSet(MI->uses(), ClauseUses);
}
if (ClauseDefs.empty())
return 0;
// FIXME: When we support stores, we need to make sure not to put loads and
// stores in the same clause if they use the same address. For now, just
// start a new clause whenever we see a store.
if (SMEM->mayStore())
return 1;
addRegsToSet(SMEM->defs(), ClauseDefs);
addRegsToSet(SMEM->uses(), ClauseUses);
std::vector<unsigned> Result(std::max(ClauseDefs.size(), ClauseUses.size()));
std::vector<unsigned>::iterator End;
End = std::set_intersection(ClauseDefs.begin(), ClauseDefs.end(),
ClauseUses.begin(), ClauseUses.end(), Result.begin());
// If the set of defs and uses intersect then we cannot add this instruction
// to the clause, so we have a hazard.
if (End != Result.begin())
return 1;
return 0;
}
int GCNHazardRecognizer::checkSMRDHazards(MachineInstr *SMRD) {
const SISubtarget &ST = MF.getSubtarget<SISubtarget>();
int WaitStatesNeeded = 0;
WaitStatesNeeded = checkSMEMSoftClauseHazards(SMRD);
// This SMRD hazard only affects SI.
if (ST.getGeneration() != SISubtarget::SOUTHERN_ISLANDS)
return WaitStatesNeeded;
// A read of an SGPR by SMRD instruction requires 4 wait states when the
// SGPR was written by a VALU instruction.
int SmrdSgprWaitStates = 4;
auto IsHazardDefFn = [this] (MachineInstr *MI) { return TII.isVALU(*MI); };
for (const MachineOperand &Use : SMRD->uses()) {
if (!Use.isReg())
continue;
int WaitStatesNeededForUse =
SmrdSgprWaitStates - getWaitStatesSinceDef(Use.getReg(), IsHazardDefFn);
WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForUse);
}
return WaitStatesNeeded;
}
int GCNHazardRecognizer::checkVMEMHazards(MachineInstr* VMEM) {
const SIInstrInfo *TII = ST.getInstrInfo();
if (ST.getGeneration() < SISubtarget::VOLCANIC_ISLANDS)
return 0;
const SIRegisterInfo &TRI = TII->getRegisterInfo();
// A read of an SGPR by a VMEM instruction requires 5 wait states when the
// SGPR was written by a VALU Instruction.
int VmemSgprWaitStates = 5;
int WaitStatesNeeded = 0;
auto IsHazardDefFn = [TII] (MachineInstr *MI) { return TII->isVALU(*MI); };
for (const MachineOperand &Use : VMEM->uses()) {
if (!Use.isReg() || TRI.isVGPR(MF.getRegInfo(), Use.getReg()))
continue;
int WaitStatesNeededForUse =
VmemSgprWaitStates - getWaitStatesSinceDef(Use.getReg(), IsHazardDefFn);
WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForUse);
}
return WaitStatesNeeded;
}
int GCNHazardRecognizer::checkDPPHazards(MachineInstr *DPP) {
const SIRegisterInfo *TRI = ST.getRegisterInfo();
// Check for DPP VGPR read after VALU VGPR write.
int DppVgprWaitStates = 2;
int WaitStatesNeeded = 0;
for (const MachineOperand &Use : DPP->uses()) {
if (!Use.isReg() || !TRI->isVGPR(MF.getRegInfo(), Use.getReg()))
continue;
int WaitStatesNeededForUse =
DppVgprWaitStates - getWaitStatesSinceDef(Use.getReg());
WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForUse);
}
return WaitStatesNeeded;
}
int GCNHazardRecognizer::checkDivFMasHazards(MachineInstr *DivFMas) {
const SIInstrInfo *TII = ST.getInstrInfo();
// v_div_fmas requires 4 wait states after a write to vcc from a VALU
// instruction.
const int DivFMasWaitStates = 4;
auto IsHazardDefFn = [TII] (MachineInstr *MI) { return TII->isVALU(*MI); };
int WaitStatesNeeded = getWaitStatesSinceDef(AMDGPU::VCC, IsHazardDefFn);
return DivFMasWaitStates - WaitStatesNeeded;
}
int GCNHazardRecognizer::checkGetRegHazards(MachineInstr *GetRegInstr) {
const SIInstrInfo *TII = ST.getInstrInfo();
unsigned GetRegHWReg = getHWReg(TII, *GetRegInstr);
const int GetRegWaitStates = 2;
auto IsHazardFn = [TII, GetRegHWReg] (MachineInstr *MI) {
return GetRegHWReg == getHWReg(TII, *MI);
};
int WaitStatesNeeded = getWaitStatesSinceSetReg(IsHazardFn);
return GetRegWaitStates - WaitStatesNeeded;
}
int GCNHazardRecognizer::checkSetRegHazards(MachineInstr *SetRegInstr) {
const SIInstrInfo *TII = ST.getInstrInfo();
unsigned HWReg = getHWReg(TII, *SetRegInstr);
const int SetRegWaitStates =
ST.getGeneration() <= AMDGPUSubtarget::SEA_ISLANDS ? 1 : 2;
auto IsHazardFn = [TII, HWReg] (MachineInstr *MI) {
return HWReg == getHWReg(TII, *MI);
};
int WaitStatesNeeded = getWaitStatesSinceSetReg(IsHazardFn);
return SetRegWaitStates - WaitStatesNeeded;
}
int GCNHazardRecognizer::createsVALUHazard(const MachineInstr &MI) {
if (!MI.mayStore())
return -1;
const SIInstrInfo *TII = ST.getInstrInfo();
unsigned Opcode = MI.getOpcode();
const MCInstrDesc &Desc = MI.getDesc();
int VDataIdx = AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::vdata);
int VDataRCID = -1;
if (VDataIdx != -1)
VDataRCID = Desc.OpInfo[VDataIdx].RegClass;
if (TII->isMUBUF(MI) || TII->isMTBUF(MI)) {
// There is no hazard if the instruction does not use vector regs
// (like wbinvl1)
if (VDataIdx == -1)
return -1;
// For MUBUF/MTBUF instructions this hazard only exists if the
// instruction is not using a register in the soffset field.
const MachineOperand *SOffset =
TII->getNamedOperand(MI, AMDGPU::OpName::soffset);
// If we have no soffset operand, then assume this field has been
// hardcoded to zero.
if (AMDGPU::getRegBitWidth(VDataRCID) > 64 &&
(!SOffset || !SOffset->isReg()))
return VDataIdx;
}
// MIMG instructions create a hazard if they don't use a 256-bit T# and
// the store size is greater than 8 bytes and they have more than two bits
// of their dmask set.
// All our MIMG definitions use a 256-bit T#, so we can skip checking for them.
if (TII->isMIMG(MI)) {
int SRsrcIdx = AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::srsrc);
assert(SRsrcIdx != -1 &&
AMDGPU::getRegBitWidth(Desc.OpInfo[SRsrcIdx].RegClass) == 256);
(void)SRsrcIdx;
}
if (TII->isFLAT(MI)) {
int DataIdx = AMDGPU::getNamedOperandIdx(Opcode, AMDGPU::OpName::vdata);
if (AMDGPU::getRegBitWidth(Desc.OpInfo[DataIdx].RegClass) > 64)
return DataIdx;
}
return -1;
}
int GCNHazardRecognizer::checkVALUHazards(MachineInstr *VALU) {
// This checks for the hazard where VMEM instructions that store more than
// 8 bytes can have there store data over written by the next instruction.
if (!ST.has12DWordStoreHazard())
return 0;
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const MachineRegisterInfo &MRI = VALU->getParent()->getParent()->getRegInfo();
const int VALUWaitStates = 1;
int WaitStatesNeeded = 0;
for (const MachineOperand &Def : VALU->defs()) {
if (!TRI->isVGPR(MRI, Def.getReg()))
continue;
unsigned Reg = Def.getReg();
auto IsHazardFn = [this, Reg, TRI] (MachineInstr *MI) {
int DataIdx = createsVALUHazard(*MI);
return DataIdx >= 0 &&
TRI->regsOverlap(MI->getOperand(DataIdx).getReg(), Reg);
};
int WaitStatesNeededForDef =
VALUWaitStates - getWaitStatesSince(IsHazardFn);
WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForDef);
}
return WaitStatesNeeded;
}
int GCNHazardRecognizer::checkRWLaneHazards(MachineInstr *RWLane) {
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const MachineRegisterInfo &MRI =
RWLane->getParent()->getParent()->getRegInfo();
const MachineOperand *LaneSelectOp =
TII->getNamedOperand(*RWLane, AMDGPU::OpName::src1);
if (!LaneSelectOp->isReg() || !TRI->isSGPRReg(MRI, LaneSelectOp->getReg()))
return 0;
unsigned LaneSelectReg = LaneSelectOp->getReg();
auto IsHazardFn = [TII] (MachineInstr *MI) {
return TII->isVALU(*MI);
};
const int RWLaneWaitStates = 4;
int WaitStatesSince = getWaitStatesSinceDef(LaneSelectReg, IsHazardFn);
return RWLaneWaitStates - WaitStatesSince;
}
int GCNHazardRecognizer::checkRFEHazards(MachineInstr *RFE) {
if (ST.getGeneration() < AMDGPUSubtarget::VOLCANIC_ISLANDS)
return 0;
const SIInstrInfo *TII = ST.getInstrInfo();
const int RFEWaitStates = 1;
auto IsHazardFn = [TII] (MachineInstr *MI) {
return getHWReg(TII, *MI) == AMDGPU::Hwreg::ID_TRAPSTS;
};
int WaitStatesNeeded = getWaitStatesSinceSetReg(IsHazardFn);
return RFEWaitStates - WaitStatesNeeded;
}
int GCNHazardRecognizer::checkAnyInstHazards(MachineInstr *MI) {
if (MI->isDebugValue())
return 0;
const SIRegisterInfo *TRI = ST.getRegisterInfo();
if (!ST.hasSMovFedHazard())
return 0;
// Check for any instruction reading an SGPR after a write from
// s_mov_fed_b32.
int MovFedWaitStates = 1;
int WaitStatesNeeded = 0;
for (const MachineOperand &Use : MI->uses()) {
if (!Use.isReg() || TRI->isVGPR(MF.getRegInfo(), Use.getReg()))
continue;
auto IsHazardFn = [] (MachineInstr *MI) {
return MI->getOpcode() == AMDGPU::S_MOV_FED_B32;
};
int WaitStatesNeededForUse =
MovFedWaitStates - getWaitStatesSinceDef(Use.getReg(), IsHazardFn);
WaitStatesNeeded = std::max(WaitStatesNeeded, WaitStatesNeededForUse);
}
return WaitStatesNeeded;
}
int GCNHazardRecognizer::checkReadM0Hazards(MachineInstr *MI) {
if (!ST.hasReadM0Hazard())
return 0;
const SIInstrInfo *TII = ST.getInstrInfo();
int SMovRelWaitStates = 1;
auto IsHazardFn = [TII] (MachineInstr *MI) {
return TII->isSALU(*MI);
};
return SMovRelWaitStates - getWaitStatesSinceDef(AMDGPU::M0, IsHazardFn);
}