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llvm-project/llvm/lib/Target/AMDGPU/SIInsertWaitcnts.cpp

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//===- SIInsertWaitcnts.cpp - Insert Wait Instructions --------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
/// \file
/// Insert wait instructions for memory reads and writes.
///
/// Memory reads and writes are issued asynchronously, so we need to insert
/// S_WAITCNT instructions when we want to access any of their results or
/// overwrite any register that's used asynchronously.
///
/// TODO: This pass currently keeps one timeline per hardware counter. A more
/// finely-grained approach that keeps one timeline per event type could
/// sometimes get away with generating weaker s_waitcnt instructions. For
/// example, when both SMEM and LDS are in flight and we need to wait for
/// the i-th-last LDS instruction, then an lgkmcnt(i) is actually sufficient,
/// but the pass will currently generate a conservative lgkmcnt(0) because
/// multiple event types are in flight.
//
//===----------------------------------------------------------------------===//
#include "AMDGPU.h"
#include "AMDGPUSubtarget.h"
#include "SIDefines.h"
#include "SIInstrInfo.h"
#include "SIMachineFunctionInfo.h"
#include "SIRegisterInfo.h"
#include "Utils/AMDGPUBaseInfo.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineFunctionPass.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineMemOperand.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/MachinePostDominators.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/InitializePasses.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/DebugCounter.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include <algorithm>
#include <cassert>
#include <cstdint>
#include <cstring>
#include <memory>
#include <utility>
using namespace llvm;
#define DEBUG_TYPE "si-insert-waitcnts"
DEBUG_COUNTER(ForceExpCounter, DEBUG_TYPE"-forceexp",
"Force emit s_waitcnt expcnt(0) instrs");
DEBUG_COUNTER(ForceLgkmCounter, DEBUG_TYPE"-forcelgkm",
"Force emit s_waitcnt lgkmcnt(0) instrs");
DEBUG_COUNTER(ForceVMCounter, DEBUG_TYPE"-forcevm",
"Force emit s_waitcnt vmcnt(0) instrs");
static cl::opt<bool> ForceEmitZeroFlag(
"amdgpu-waitcnt-forcezero",
cl::desc("Force all waitcnt instrs to be emitted as s_waitcnt vmcnt(0) expcnt(0) lgkmcnt(0)"),
cl::init(false), cl::Hidden);
namespace {
template <typename EnumT>
class enum_iterator
: public iterator_facade_base<enum_iterator<EnumT>,
std::forward_iterator_tag, const EnumT> {
EnumT Value;
public:
enum_iterator() = default;
enum_iterator(EnumT Value) : Value(Value) {}
enum_iterator &operator++() {
Value = static_cast<EnumT>(Value + 1);
return *this;
}
bool operator==(const enum_iterator &RHS) const { return Value == RHS.Value; }
EnumT operator*() const { return Value; }
};
// Class of object that encapsulates latest instruction counter score
// associated with the operand. Used for determining whether
// s_waitcnt instruction needs to be emited.
#define CNT_MASK(t) (1u << (t))
enum InstCounterType { VM_CNT = 0, LGKM_CNT, EXP_CNT, VS_CNT, NUM_INST_CNTS };
iterator_range<enum_iterator<InstCounterType>> inst_counter_types() {
return make_range(enum_iterator<InstCounterType>(VM_CNT),
enum_iterator<InstCounterType>(NUM_INST_CNTS));
}
using RegInterval = std::pair<int, int>;
struct {
unsigned VmcntMax;
unsigned ExpcntMax;
unsigned LgkmcntMax;
unsigned VscntMax;
} HardwareLimits;
struct {
unsigned VGPR0;
unsigned VGPRL;
unsigned SGPR0;
unsigned SGPRL;
} RegisterEncoding;
enum WaitEventType {
VMEM_ACCESS, // vector-memory read & write
VMEM_READ_ACCESS, // vector-memory read
VMEM_WRITE_ACCESS,// vector-memory write
LDS_ACCESS, // lds read & write
GDS_ACCESS, // gds read & write
SQ_MESSAGE, // send message
SMEM_ACCESS, // scalar-memory read & write
EXP_GPR_LOCK, // export holding on its data src
GDS_GPR_LOCK, // GDS holding on its data and addr src
EXP_POS_ACCESS, // write to export position
EXP_PARAM_ACCESS, // write to export parameter
VMW_GPR_LOCK, // vector-memory write holding on its data src
NUM_WAIT_EVENTS,
};
static const unsigned WaitEventMaskForInst[NUM_INST_CNTS] = {
(1 << VMEM_ACCESS) | (1 << VMEM_READ_ACCESS),
(1 << SMEM_ACCESS) | (1 << LDS_ACCESS) | (1 << GDS_ACCESS) |
(1 << SQ_MESSAGE),
(1 << EXP_GPR_LOCK) | (1 << GDS_GPR_LOCK) | (1 << VMW_GPR_LOCK) |
(1 << EXP_PARAM_ACCESS) | (1 << EXP_POS_ACCESS),
(1 << VMEM_WRITE_ACCESS)
};
// The mapping is:
// 0 .. SQ_MAX_PGM_VGPRS-1 real VGPRs
// SQ_MAX_PGM_VGPRS .. NUM_ALL_VGPRS-1 extra VGPR-like slots
// NUM_ALL_VGPRS .. NUM_ALL_VGPRS+SQ_MAX_PGM_SGPRS-1 real SGPRs
// We reserve a fixed number of VGPR slots in the scoring tables for
// special tokens like SCMEM_LDS (needed for buffer load to LDS).
enum RegisterMapping {
SQ_MAX_PGM_VGPRS = 256, // Maximum programmable VGPRs across all targets.
SQ_MAX_PGM_SGPRS = 256, // Maximum programmable SGPRs across all targets.
NUM_EXTRA_VGPRS = 1, // A reserved slot for DS.
EXTRA_VGPR_LDS = 0, // This is a placeholder the Shader algorithm uses.
NUM_ALL_VGPRS = SQ_MAX_PGM_VGPRS + NUM_EXTRA_VGPRS, // Where SGPR starts.
};
// Enumerate different types of result-returning VMEM operations. Although
// s_waitcnt orders them all with a single vmcnt counter, in the absence of
// s_waitcnt only instructions of the same VmemType are guaranteed to write
// their results in order -- so there is no need to insert an s_waitcnt between
// two instructions of the same type that write the same vgpr.
enum VmemType {
// BUF instructions and MIMG instructions without a sampler.
VMEM_NOSAMPLER,
// MIMG instructions with a sampler.
VMEM_SAMPLER,
};
VmemType getVmemType(const MachineInstr &Inst) {
assert(SIInstrInfo::isVMEM(Inst));
if (!SIInstrInfo::isMIMG(Inst))
return VMEM_NOSAMPLER;
const AMDGPU::MIMGInfo *Info = AMDGPU::getMIMGInfo(Inst.getOpcode());
return AMDGPU::getMIMGBaseOpcodeInfo(Info->BaseOpcode)->Sampler
? VMEM_SAMPLER
: VMEM_NOSAMPLER;
}
void addWait(AMDGPU::Waitcnt &Wait, InstCounterType T, unsigned Count) {
switch (T) {
case VM_CNT:
Wait.VmCnt = std::min(Wait.VmCnt, Count);
break;
case EXP_CNT:
Wait.ExpCnt = std::min(Wait.ExpCnt, Count);
break;
case LGKM_CNT:
Wait.LgkmCnt = std::min(Wait.LgkmCnt, Count);
break;
case VS_CNT:
Wait.VsCnt = std::min(Wait.VsCnt, Count);
break;
default:
llvm_unreachable("bad InstCounterType");
}
}
// This objects maintains the current score brackets of each wait counter, and
// a per-register scoreboard for each wait counter.
//
// We also maintain the latest score for every event type that can change the
// waitcnt in order to know if there are multiple types of events within
// the brackets. When multiple types of event happen in the bracket,
// wait count may get decreased out of order, therefore we need to put in
// "s_waitcnt 0" before use.
class WaitcntBrackets {
public:
WaitcntBrackets(const GCNSubtarget *SubTarget) : ST(SubTarget) {}
static unsigned getWaitCountMax(InstCounterType T) {
switch (T) {
case VM_CNT:
return HardwareLimits.VmcntMax;
case LGKM_CNT:
return HardwareLimits.LgkmcntMax;
case EXP_CNT:
return HardwareLimits.ExpcntMax;
case VS_CNT:
return HardwareLimits.VscntMax;
default:
break;
}
return 0;
}
unsigned getScoreLB(InstCounterType T) const {
assert(T < NUM_INST_CNTS);
return ScoreLBs[T];
}
unsigned getScoreUB(InstCounterType T) const {
assert(T < NUM_INST_CNTS);
return ScoreUBs[T];
}
// Mapping from event to counter.
InstCounterType eventCounter(WaitEventType E) {
if (WaitEventMaskForInst[VM_CNT] & (1 << E))
return VM_CNT;
if (WaitEventMaskForInst[LGKM_CNT] & (1 << E))
return LGKM_CNT;
if (WaitEventMaskForInst[VS_CNT] & (1 << E))
return VS_CNT;
assert(WaitEventMaskForInst[EXP_CNT] & (1 << E));
return EXP_CNT;
}
unsigned getRegScore(int GprNo, InstCounterType T) {
if (GprNo < NUM_ALL_VGPRS) {
return VgprScores[T][GprNo];
}
assert(T == LGKM_CNT);
return SgprScores[GprNo - NUM_ALL_VGPRS];
}
bool merge(const WaitcntBrackets &Other);
RegInterval getRegInterval(const MachineInstr *MI, const SIInstrInfo *TII,
const MachineRegisterInfo *MRI,
const SIRegisterInfo *TRI, unsigned OpNo) const;
bool counterOutOfOrder(InstCounterType T) const;
bool simplifyWaitcnt(AMDGPU::Waitcnt &Wait) const;
bool simplifyWaitcnt(InstCounterType T, unsigned &Count) const;
void determineWait(InstCounterType T, unsigned ScoreToWait,
AMDGPU::Waitcnt &Wait) const;
void applyWaitcnt(const AMDGPU::Waitcnt &Wait);
void applyWaitcnt(InstCounterType T, unsigned Count);
void updateByEvent(const SIInstrInfo *TII, const SIRegisterInfo *TRI,
const MachineRegisterInfo *MRI, WaitEventType E,
MachineInstr &MI);
bool hasPending() const { return PendingEvents != 0; }
bool hasPendingEvent(WaitEventType E) const {
return PendingEvents & (1 << E);
}
bool hasMixedPendingEvents(InstCounterType T) const {
unsigned Events = PendingEvents & WaitEventMaskForInst[T];
// Return true if more than one bit is set in Events.
return Events & (Events - 1);
}
bool hasPendingFlat() const {
return ((LastFlat[LGKM_CNT] > ScoreLBs[LGKM_CNT] &&
LastFlat[LGKM_CNT] <= ScoreUBs[LGKM_CNT]) ||
(LastFlat[VM_CNT] > ScoreLBs[VM_CNT] &&
LastFlat[VM_CNT] <= ScoreUBs[VM_CNT]));
}
void setPendingFlat() {
LastFlat[VM_CNT] = ScoreUBs[VM_CNT];
LastFlat[LGKM_CNT] = ScoreUBs[LGKM_CNT];
}
// Return true if there might be pending writes to the specified vgpr by VMEM
// instructions with types different from V.
bool hasOtherPendingVmemTypes(int GprNo, VmemType V) const {
assert(GprNo < NUM_ALL_VGPRS);
return VgprVmemTypes[GprNo] & ~(1 << V);
}
void clearVgprVmemTypes(int GprNo) {
assert(GprNo < NUM_ALL_VGPRS);
VgprVmemTypes[GprNo] = 0;
}
void print(raw_ostream &);
void dump() { print(dbgs()); }
private:
struct MergeInfo {
unsigned OldLB;
unsigned OtherLB;
unsigned MyShift;
unsigned OtherShift;
};
static bool mergeScore(const MergeInfo &M, unsigned &Score,
unsigned OtherScore);
void setScoreLB(InstCounterType T, unsigned Val) {
assert(T < NUM_INST_CNTS);
ScoreLBs[T] = Val;
}
void setScoreUB(InstCounterType T, unsigned Val) {
assert(T < NUM_INST_CNTS);
ScoreUBs[T] = Val;
if (T == EXP_CNT) {
unsigned UB = ScoreUBs[T] - getWaitCountMax(EXP_CNT);
if (ScoreLBs[T] < UB && UB < ScoreUBs[T])
ScoreLBs[T] = UB;
}
}
void setRegScore(int GprNo, InstCounterType T, unsigned Val) {
if (GprNo < NUM_ALL_VGPRS) {
VgprUB = std::max(VgprUB, GprNo);
VgprScores[T][GprNo] = Val;
} else {
assert(T == LGKM_CNT);
SgprUB = std::max(SgprUB, GprNo - NUM_ALL_VGPRS);
SgprScores[GprNo - NUM_ALL_VGPRS] = Val;
}
}
void setExpScore(const MachineInstr *MI, const SIInstrInfo *TII,
const SIRegisterInfo *TRI, const MachineRegisterInfo *MRI,
unsigned OpNo, unsigned Val);
const GCNSubtarget *ST = nullptr;
unsigned ScoreLBs[NUM_INST_CNTS] = {0};
unsigned ScoreUBs[NUM_INST_CNTS] = {0};
unsigned PendingEvents = 0;
// Remember the last flat memory operation.
unsigned LastFlat[NUM_INST_CNTS] = {0};
// wait_cnt scores for every vgpr.
// Keep track of the VgprUB and SgprUB to make merge at join efficient.
int VgprUB = -1;
int SgprUB = -1;
unsigned VgprScores[NUM_INST_CNTS][NUM_ALL_VGPRS] = {{0}};
// Wait cnt scores for every sgpr, only lgkmcnt is relevant.
unsigned SgprScores[SQ_MAX_PGM_SGPRS] = {0};
// Bitmask of the VmemTypes of VMEM instructions that might have a pending
// write to each vgpr.
unsigned char VgprVmemTypes[NUM_ALL_VGPRS] = {0};
};
class SIInsertWaitcnts : public MachineFunctionPass {
private:
const GCNSubtarget *ST = nullptr;
const SIInstrInfo *TII = nullptr;
const SIRegisterInfo *TRI = nullptr;
const MachineRegisterInfo *MRI = nullptr;
AMDGPU::IsaVersion IV;
DenseSet<MachineInstr *> TrackedWaitcntSet;
DenseMap<const Value *, MachineBasicBlock *> SLoadAddresses;
MachinePostDominatorTree *PDT;
struct BlockInfo {
MachineBasicBlock *MBB;
std::unique_ptr<WaitcntBrackets> Incoming;
bool Dirty = true;
explicit BlockInfo(MachineBasicBlock *MBB) : MBB(MBB) {}
};
MapVector<MachineBasicBlock *, BlockInfo> BlockInfos;
// ForceEmitZeroWaitcnts: force all waitcnts insts to be s_waitcnt 0
// because of amdgpu-waitcnt-forcezero flag
bool ForceEmitZeroWaitcnts;
bool ForceEmitWaitcnt[NUM_INST_CNTS];
public:
static char ID;
SIInsertWaitcnts() : MachineFunctionPass(ID) {
(void)ForceExpCounter;
(void)ForceLgkmCounter;
(void)ForceVMCounter;
}
bool runOnMachineFunction(MachineFunction &MF) override;
StringRef getPassName() const override {
return "SI insert wait instructions";
}
void getAnalysisUsage(AnalysisUsage &AU) const override {
AU.setPreservesCFG();
AU.addRequired<MachinePostDominatorTree>();
MachineFunctionPass::getAnalysisUsage(AU);
}
bool isForceEmitWaitcnt() const {
for (auto T : inst_counter_types())
if (ForceEmitWaitcnt[T])
return true;
return false;
}
void setForceEmitWaitcnt() {
// For non-debug builds, ForceEmitWaitcnt has been initialized to false;
// For debug builds, get the debug counter info and adjust if need be
#ifndef NDEBUG
if (DebugCounter::isCounterSet(ForceExpCounter) &&
DebugCounter::shouldExecute(ForceExpCounter)) {
ForceEmitWaitcnt[EXP_CNT] = true;
} else {
ForceEmitWaitcnt[EXP_CNT] = false;
}
if (DebugCounter::isCounterSet(ForceLgkmCounter) &&
DebugCounter::shouldExecute(ForceLgkmCounter)) {
ForceEmitWaitcnt[LGKM_CNT] = true;
} else {
ForceEmitWaitcnt[LGKM_CNT] = false;
}
if (DebugCounter::isCounterSet(ForceVMCounter) &&
DebugCounter::shouldExecute(ForceVMCounter)) {
ForceEmitWaitcnt[VM_CNT] = true;
} else {
ForceEmitWaitcnt[VM_CNT] = false;
}
#endif // NDEBUG
}
bool mayAccessVMEMThroughFlat(const MachineInstr &MI) const;
bool mayAccessLDSThroughFlat(const MachineInstr &MI) const;
bool generateWaitcntInstBefore(MachineInstr &MI,
WaitcntBrackets &ScoreBrackets,
MachineInstr *OldWaitcntInstr);
void updateEventWaitcntAfter(MachineInstr &Inst,
WaitcntBrackets *ScoreBrackets);
bool insertWaitcntInBlock(MachineFunction &MF, MachineBasicBlock &Block,
WaitcntBrackets &ScoreBrackets);
};
} // end anonymous namespace
RegInterval WaitcntBrackets::getRegInterval(const MachineInstr *MI,
const SIInstrInfo *TII,
const MachineRegisterInfo *MRI,
const SIRegisterInfo *TRI,
unsigned OpNo) const {
const MachineOperand &Op = MI->getOperand(OpNo);
assert(Op.isReg());
if (!TRI->isInAllocatableClass(Op.getReg()) || TRI->isAGPR(*MRI, Op.getReg()))
return {-1, -1};
// A use via a PW operand does not need a waitcnt.
// A partial write is not a WAW.
assert(!Op.getSubReg() || !Op.isUndef());
RegInterval Result;
unsigned Reg = TRI->getEncodingValue(AMDGPU::getMCReg(Op.getReg(), *ST));
if (TRI->isVGPR(*MRI, Op.getReg())) {
assert(Reg >= RegisterEncoding.VGPR0 && Reg <= RegisterEncoding.VGPRL);
Result.first = Reg - RegisterEncoding.VGPR0;
assert(Result.first >= 0 && Result.first < SQ_MAX_PGM_VGPRS);
} else if (TRI->isSGPRReg(*MRI, Op.getReg())) {
assert(Reg >= RegisterEncoding.SGPR0 && Reg < SQ_MAX_PGM_SGPRS);
Result.first = Reg - RegisterEncoding.SGPR0 + NUM_ALL_VGPRS;
assert(Result.first >= NUM_ALL_VGPRS &&
Result.first < SQ_MAX_PGM_SGPRS + NUM_ALL_VGPRS);
}
// TODO: Handle TTMP
// else if (TRI->isTTMP(*MRI, Reg.getReg())) ...
else
return {-1, -1};
const TargetRegisterClass *RC = TII->getOpRegClass(*MI, OpNo);
unsigned Size = TRI->getRegSizeInBits(*RC);
Result.second = Result.first + ((Size + 16) / 32);
return Result;
}
void WaitcntBrackets::setExpScore(const MachineInstr *MI,
const SIInstrInfo *TII,
const SIRegisterInfo *TRI,
const MachineRegisterInfo *MRI, unsigned OpNo,
unsigned Val) {
RegInterval Interval = getRegInterval(MI, TII, MRI, TRI, OpNo);
assert(TRI->isVGPR(*MRI, MI->getOperand(OpNo).getReg()));
for (int RegNo = Interval.first; RegNo < Interval.second; ++RegNo) {
setRegScore(RegNo, EXP_CNT, Val);
}
}
void WaitcntBrackets::updateByEvent(const SIInstrInfo *TII,
const SIRegisterInfo *TRI,
const MachineRegisterInfo *MRI,
WaitEventType E, MachineInstr &Inst) {
InstCounterType T = eventCounter(E);
unsigned CurrScore = getScoreUB(T) + 1;
if (CurrScore == 0)
report_fatal_error("InsertWaitcnt score wraparound");
// PendingEvents and ScoreUB need to be update regardless if this event
// changes the score of a register or not.
// Examples including vm_cnt when buffer-store or lgkm_cnt when send-message.
PendingEvents |= 1 << E;
setScoreUB(T, CurrScore);
if (T == EXP_CNT) {
// Put score on the source vgprs. If this is a store, just use those
// specific register(s).
if (TII->isDS(Inst) && (Inst.mayStore() || Inst.mayLoad())) {
int AddrOpIdx =
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::addr);
// All GDS operations must protect their address register (same as
// export.)
if (AddrOpIdx != -1) {
setExpScore(&Inst, TII, TRI, MRI, AddrOpIdx, CurrScore);
}
if (Inst.mayStore()) {
if (AMDGPU::getNamedOperandIdx(Inst.getOpcode(),
AMDGPU::OpName::data0) != -1) {
setExpScore(
&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::data0),
CurrScore);
}
if (AMDGPU::getNamedOperandIdx(Inst.getOpcode(),
AMDGPU::OpName::data1) != -1) {
setExpScore(&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(),
AMDGPU::OpName::data1),
CurrScore);
}
} else if (AMDGPU::getAtomicNoRetOp(Inst.getOpcode()) != -1 &&
Inst.getOpcode() != AMDGPU::DS_GWS_INIT &&
Inst.getOpcode() != AMDGPU::DS_GWS_SEMA_V &&
Inst.getOpcode() != AMDGPU::DS_GWS_SEMA_BR &&
Inst.getOpcode() != AMDGPU::DS_GWS_SEMA_P &&
Inst.getOpcode() != AMDGPU::DS_GWS_BARRIER &&
Inst.getOpcode() != AMDGPU::DS_APPEND &&
Inst.getOpcode() != AMDGPU::DS_CONSUME &&
Inst.getOpcode() != AMDGPU::DS_ORDERED_COUNT) {
for (unsigned I = 0, E = Inst.getNumOperands(); I != E; ++I) {
const MachineOperand &Op = Inst.getOperand(I);
if (Op.isReg() && !Op.isDef() && TRI->isVGPR(*MRI, Op.getReg())) {
setExpScore(&Inst, TII, TRI, MRI, I, CurrScore);
}
}
}
} else if (TII->isFLAT(Inst)) {
if (Inst.mayStore()) {
setExpScore(
&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::data),
CurrScore);
} else if (AMDGPU::getAtomicNoRetOp(Inst.getOpcode()) != -1) {
setExpScore(
&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::data),
CurrScore);
}
} else if (TII->isMIMG(Inst)) {
if (Inst.mayStore()) {
setExpScore(&Inst, TII, TRI, MRI, 0, CurrScore);
} else if (AMDGPU::getAtomicNoRetOp(Inst.getOpcode()) != -1) {
setExpScore(
&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::data),
CurrScore);
}
} else if (TII->isMTBUF(Inst)) {
if (Inst.mayStore()) {
setExpScore(&Inst, TII, TRI, MRI, 0, CurrScore);
}
} else if (TII->isMUBUF(Inst)) {
if (Inst.mayStore()) {
setExpScore(&Inst, TII, TRI, MRI, 0, CurrScore);
} else if (AMDGPU::getAtomicNoRetOp(Inst.getOpcode()) != -1) {
setExpScore(
&Inst, TII, TRI, MRI,
AMDGPU::getNamedOperandIdx(Inst.getOpcode(), AMDGPU::OpName::data),
CurrScore);
}
} else {
if (TII->isEXP(Inst)) {
// For export the destination registers are really temps that
// can be used as the actual source after export patching, so
// we need to treat them like sources and set the EXP_CNT
// score.
for (unsigned I = 0, E = Inst.getNumOperands(); I != E; ++I) {
MachineOperand &DefMO = Inst.getOperand(I);
if (DefMO.isReg() && DefMO.isDef() &&
TRI->isVGPR(*MRI, DefMO.getReg())) {
setRegScore(
TRI->getEncodingValue(AMDGPU::getMCReg(DefMO.getReg(), *ST)),
EXP_CNT, CurrScore);
}
}
}
for (unsigned I = 0, E = Inst.getNumOperands(); I != E; ++I) {
MachineOperand &MO = Inst.getOperand(I);
if (MO.isReg() && !MO.isDef() && TRI->isVGPR(*MRI, MO.getReg())) {
setExpScore(&Inst, TII, TRI, MRI, I, CurrScore);
}
}
}
#if 0 // TODO: check if this is handled by MUBUF code above.
} else if (Inst.getOpcode() == AMDGPU::BUFFER_STORE_DWORD ||
Inst.getOpcode() == AMDGPU::BUFFER_STORE_DWORDX2 ||
Inst.getOpcode() == AMDGPU::BUFFER_STORE_DWORDX4) {
MachineOperand *MO = TII->getNamedOperand(Inst, AMDGPU::OpName::data);
unsigned OpNo;//TODO: find the OpNo for this operand;
RegInterval Interval = getRegInterval(&Inst, TII, MRI, TRI, OpNo);
for (int RegNo = Interval.first; RegNo < Interval.second;
++RegNo) {
setRegScore(RegNo + NUM_ALL_VGPRS, t, CurrScore);
}
#endif
} else {
// Match the score to the destination registers.
for (unsigned I = 0, E = Inst.getNumOperands(); I != E; ++I) {
auto &Op = Inst.getOperand(I);
if (!Op.isReg() || !Op.isDef())
continue;
RegInterval Interval = getRegInterval(&Inst, TII, MRI, TRI, I);
if (T == VM_CNT) {
if (Interval.first >= NUM_ALL_VGPRS)
continue;
if (SIInstrInfo::isVMEM(Inst)) {
VmemType V = getVmemType(Inst);
for (int RegNo = Interval.first; RegNo < Interval.second; ++RegNo)
VgprVmemTypes[RegNo] |= 1 << V;
}
}
for (int RegNo = Interval.first; RegNo < Interval.second; ++RegNo) {
setRegScore(RegNo, T, CurrScore);
}
}
if (TII->isDS(Inst) && Inst.mayStore()) {
setRegScore(SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS, T, CurrScore);
}
}
}
void WaitcntBrackets::print(raw_ostream &OS) {
OS << '\n';
for (auto T : inst_counter_types()) {
unsigned LB = getScoreLB(T);
unsigned UB = getScoreUB(T);
switch (T) {
case VM_CNT:
OS << " VM_CNT(" << UB - LB << "): ";
break;
case LGKM_CNT:
OS << " LGKM_CNT(" << UB - LB << "): ";
break;
case EXP_CNT:
OS << " EXP_CNT(" << UB - LB << "): ";
break;
case VS_CNT:
OS << " VS_CNT(" << UB - LB << "): ";
break;
default:
OS << " UNKNOWN(" << UB - LB << "): ";
break;
}
if (LB < UB) {
// Print vgpr scores.
for (int J = 0; J <= VgprUB; J++) {
unsigned RegScore = getRegScore(J, T);
if (RegScore <= LB)
continue;
unsigned RelScore = RegScore - LB - 1;
if (J < SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS) {
OS << RelScore << ":v" << J << " ";
} else {
OS << RelScore << ":ds ";
}
}
// Also need to print sgpr scores for lgkm_cnt.
if (T == LGKM_CNT) {
for (int J = 0; J <= SgprUB; J++) {
unsigned RegScore = getRegScore(J + NUM_ALL_VGPRS, LGKM_CNT);
if (RegScore <= LB)
continue;
unsigned RelScore = RegScore - LB - 1;
OS << RelScore << ":s" << J << " ";
}
}
}
OS << '\n';
}
OS << '\n';
}
/// Simplify the waitcnt, in the sense of removing redundant counts, and return
/// whether a waitcnt instruction is needed at all.
bool WaitcntBrackets::simplifyWaitcnt(AMDGPU::Waitcnt &Wait) const {
return simplifyWaitcnt(VM_CNT, Wait.VmCnt) |
simplifyWaitcnt(EXP_CNT, Wait.ExpCnt) |
simplifyWaitcnt(LGKM_CNT, Wait.LgkmCnt) |
simplifyWaitcnt(VS_CNT, Wait.VsCnt);
}
bool WaitcntBrackets::simplifyWaitcnt(InstCounterType T,
unsigned &Count) const {
const unsigned LB = getScoreLB(T);
const unsigned UB = getScoreUB(T);
if (Count < UB && UB - Count > LB)
return true;
Count = ~0u;
return false;
}
void WaitcntBrackets::determineWait(InstCounterType T, unsigned ScoreToWait,
AMDGPU::Waitcnt &Wait) const {
// If the score of src_operand falls within the bracket, we need an
// s_waitcnt instruction.
const unsigned LB = getScoreLB(T);
const unsigned UB = getScoreUB(T);
if ((UB >= ScoreToWait) && (ScoreToWait > LB)) {
if ((T == VM_CNT || T == LGKM_CNT) &&
hasPendingFlat() &&
!ST->hasFlatLgkmVMemCountInOrder()) {
// If there is a pending FLAT operation, and this is a VMem or LGKM
// waitcnt and the target can report early completion, then we need
// to force a waitcnt 0.
addWait(Wait, T, 0);
} else if (counterOutOfOrder(T)) {
// Counter can get decremented out-of-order when there
// are multiple types event in the bracket. Also emit an s_wait counter
// with a conservative value of 0 for the counter.
addWait(Wait, T, 0);
} else {
// If a counter has been maxed out avoid overflow by waiting for
// MAX(CounterType) - 1 instead.
unsigned NeededWait = std::min(UB - ScoreToWait, getWaitCountMax(T) - 1);
addWait(Wait, T, NeededWait);
}
}
}
void WaitcntBrackets::applyWaitcnt(const AMDGPU::Waitcnt &Wait) {
applyWaitcnt(VM_CNT, Wait.VmCnt);
applyWaitcnt(EXP_CNT, Wait.ExpCnt);
applyWaitcnt(LGKM_CNT, Wait.LgkmCnt);
applyWaitcnt(VS_CNT, Wait.VsCnt);
}
void WaitcntBrackets::applyWaitcnt(InstCounterType T, unsigned Count) {
const unsigned UB = getScoreUB(T);
if (Count >= UB)
return;
if (Count != 0) {
if (counterOutOfOrder(T))
return;
setScoreLB(T, std::max(getScoreLB(T), UB - Count));
} else {
setScoreLB(T, UB);
PendingEvents &= ~WaitEventMaskForInst[T];
}
}
// Where there are multiple types of event in the bracket of a counter,
// the decrement may go out of order.
bool WaitcntBrackets::counterOutOfOrder(InstCounterType T) const {
// Scalar memory read always can go out of order.
if (T == LGKM_CNT && hasPendingEvent(SMEM_ACCESS))
return true;
return hasMixedPendingEvents(T);
}
INITIALIZE_PASS_BEGIN(SIInsertWaitcnts, DEBUG_TYPE, "SI Insert Waitcnts", false,
false)
INITIALIZE_PASS_DEPENDENCY(MachinePostDominatorTree)
INITIALIZE_PASS_END(SIInsertWaitcnts, DEBUG_TYPE, "SI Insert Waitcnts", false,
false)
char SIInsertWaitcnts::ID = 0;
char &llvm::SIInsertWaitcntsID = SIInsertWaitcnts::ID;
FunctionPass *llvm::createSIInsertWaitcntsPass() {
return new SIInsertWaitcnts();
}
static bool readsVCCZ(const MachineInstr &MI) {
unsigned Opc = MI.getOpcode();
return (Opc == AMDGPU::S_CBRANCH_VCCNZ || Opc == AMDGPU::S_CBRANCH_VCCZ) &&
!MI.getOperand(1).isUndef();
}
/// \returns true if the callee inserts an s_waitcnt 0 on function entry.
static bool callWaitsOnFunctionEntry(const MachineInstr &MI) {
// Currently all conventions wait, but this may not always be the case.
//
// TODO: If IPRA is enabled, and the callee is isSafeForNoCSROpt, it may make
// senses to omit the wait and do it in the caller.
return true;
}
/// \returns true if the callee is expected to wait for any outstanding waits
/// before returning.
static bool callWaitsOnFunctionReturn(const MachineInstr &MI) {
return true;
}
/// Generate s_waitcnt instruction to be placed before cur_Inst.
/// Instructions of a given type are returned in order,
/// but instructions of different types can complete out of order.
/// We rely on this in-order completion
/// and simply assign a score to the memory access instructions.
/// We keep track of the active "score bracket" to determine
/// if an access of a memory read requires an s_waitcnt
/// and if so what the value of each counter is.
/// The "score bracket" is bound by the lower bound and upper bound
/// scores (*_score_LB and *_score_ub respectively).
bool SIInsertWaitcnts::generateWaitcntInstBefore(
MachineInstr &MI, WaitcntBrackets &ScoreBrackets,
MachineInstr *OldWaitcntInstr) {
setForceEmitWaitcnt();
bool IsForceEmitWaitcnt = isForceEmitWaitcnt();
if (MI.isMetaInstruction())
return false;
AMDGPU::Waitcnt Wait;
// See if this instruction has a forced S_WAITCNT VM.
// TODO: Handle other cases of NeedsWaitcntVmBefore()
if (MI.getOpcode() == AMDGPU::BUFFER_WBINVL1 ||
MI.getOpcode() == AMDGPU::BUFFER_WBINVL1_SC ||
MI.getOpcode() == AMDGPU::BUFFER_WBINVL1_VOL ||
MI.getOpcode() == AMDGPU::BUFFER_GL0_INV ||
MI.getOpcode() == AMDGPU::BUFFER_GL1_INV) {
Wait.VmCnt = 0;
}
// All waits must be resolved at call return.
// NOTE: this could be improved with knowledge of all call sites or
// with knowledge of the called routines.
if (MI.getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG ||
MI.getOpcode() == AMDGPU::S_SETPC_B64_return ||
(MI.isReturn() && MI.isCall() && !callWaitsOnFunctionEntry(MI))) {
Wait = Wait.combined(AMDGPU::Waitcnt::allZero(ST->hasVscnt()));
}
// Resolve vm waits before gs-done.
else if ((MI.getOpcode() == AMDGPU::S_SENDMSG ||
MI.getOpcode() == AMDGPU::S_SENDMSGHALT) &&
((MI.getOperand(0).getImm() & AMDGPU::SendMsg::ID_MASK_) ==
AMDGPU::SendMsg::ID_GS_DONE)) {
Wait.VmCnt = 0;
}
#if 0 // TODO: the following blocks of logic when we have fence.
else if (MI.getOpcode() == SC_FENCE) {
const unsigned int group_size =
context->shader_info->GetMaxThreadGroupSize();
// group_size == 0 means thread group size is unknown at compile time
const bool group_is_multi_wave =
(group_size == 0 || group_size > target_info->GetWaveFrontSize());
const bool fence_is_global = !((SCInstInternalMisc*)Inst)->IsGroupFence();
for (unsigned int i = 0; i < Inst->NumSrcOperands(); i++) {
SCRegType src_type = Inst->GetSrcType(i);
switch (src_type) {
case SCMEM_LDS:
if (group_is_multi_wave ||
context->OptFlagIsOn(OPT_R1100_LDSMEM_FENCE_CHICKEN_BIT)) {
EmitWaitcnt |= ScoreBrackets->updateByWait(LGKM_CNT,
ScoreBrackets->getScoreUB(LGKM_CNT));
// LDS may have to wait for VM_CNT after buffer load to LDS
if (target_info->HasBufferLoadToLDS()) {
EmitWaitcnt |= ScoreBrackets->updateByWait(VM_CNT,
ScoreBrackets->getScoreUB(VM_CNT));
}
}
break;
case SCMEM_GDS:
if (group_is_multi_wave || fence_is_global) {
EmitWaitcnt |= ScoreBrackets->updateByWait(EXP_CNT,
ScoreBrackets->getScoreUB(EXP_CNT));
EmitWaitcnt |= ScoreBrackets->updateByWait(LGKM_CNT,
ScoreBrackets->getScoreUB(LGKM_CNT));
}
break;
case SCMEM_UAV:
case SCMEM_TFBUF:
case SCMEM_RING:
case SCMEM_SCATTER:
if (group_is_multi_wave || fence_is_global) {
EmitWaitcnt |= ScoreBrackets->updateByWait(EXP_CNT,
ScoreBrackets->getScoreUB(EXP_CNT));
EmitWaitcnt |= ScoreBrackets->updateByWait(VM_CNT,
ScoreBrackets->getScoreUB(VM_CNT));
}
break;
case SCMEM_SCRATCH:
default:
break;
}
}
}
#endif
// Export & GDS instructions do not read the EXEC mask until after the export
// is granted (which can occur well after the instruction is issued).
// The shader program must flush all EXP operations on the export-count
// before overwriting the EXEC mask.
else {
if (MI.modifiesRegister(AMDGPU::EXEC, TRI)) {
// Export and GDS are tracked individually, either may trigger a waitcnt
// for EXEC.
if (ScoreBrackets.hasPendingEvent(EXP_GPR_LOCK) ||
ScoreBrackets.hasPendingEvent(EXP_PARAM_ACCESS) ||
ScoreBrackets.hasPendingEvent(EXP_POS_ACCESS) ||
ScoreBrackets.hasPendingEvent(GDS_GPR_LOCK)) {
Wait.ExpCnt = 0;
}
}
if (MI.isCall() && callWaitsOnFunctionEntry(MI)) {
// The function is going to insert a wait on everything in its prolog.
// This still needs to be careful if the call target is a load (e.g. a GOT
// load). We also need to check WAW depenancy with saved PC.
Wait = AMDGPU::Waitcnt();
int CallAddrOpIdx =
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::src0);
if (MI.getOperand(CallAddrOpIdx).isReg()) {
RegInterval CallAddrOpInterval =
ScoreBrackets.getRegInterval(&MI, TII, MRI, TRI, CallAddrOpIdx);
for (int RegNo = CallAddrOpInterval.first;
RegNo < CallAddrOpInterval.second; ++RegNo)
ScoreBrackets.determineWait(
LGKM_CNT, ScoreBrackets.getRegScore(RegNo, LGKM_CNT), Wait);
int RtnAddrOpIdx =
AMDGPU::getNamedOperandIdx(MI.getOpcode(), AMDGPU::OpName::dst);
if (RtnAddrOpIdx != -1) {
RegInterval RtnAddrOpInterval =
ScoreBrackets.getRegInterval(&MI, TII, MRI, TRI, RtnAddrOpIdx);
for (int RegNo = RtnAddrOpInterval.first;
RegNo < RtnAddrOpInterval.second; ++RegNo)
ScoreBrackets.determineWait(
LGKM_CNT, ScoreBrackets.getRegScore(RegNo, LGKM_CNT), Wait);
}
}
} else {
// FIXME: Should not be relying on memoperands.
// Look at the source operands of every instruction to see if
// any of them results from a previous memory operation that affects
// its current usage. If so, an s_waitcnt instruction needs to be
// emitted.
// If the source operand was defined by a load, add the s_waitcnt
// instruction.
//
// Two cases are handled for destination operands:
// 1) If the destination operand was defined by a load, add the s_waitcnt
// instruction to guarantee the right WAW order.
// 2) If a destination operand that was used by a recent export/store ins,
// add s_waitcnt on exp_cnt to guarantee the WAR order.
for (const MachineMemOperand *Memop : MI.memoperands()) {
const Value *Ptr = Memop->getValue();
if (Memop->isStore() && SLoadAddresses.count(Ptr)) {
addWait(Wait, LGKM_CNT, 0);
if (PDT->dominates(MI.getParent(), SLoadAddresses.find(Ptr)->second))
SLoadAddresses.erase(Ptr);
}
unsigned AS = Memop->getAddrSpace();
if (AS != AMDGPUAS::LOCAL_ADDRESS)
continue;
unsigned RegNo = SQ_MAX_PGM_VGPRS + EXTRA_VGPR_LDS;
// VM_CNT is only relevant to vgpr or LDS.
ScoreBrackets.determineWait(
VM_CNT, ScoreBrackets.getRegScore(RegNo, VM_CNT), Wait);
if (Memop->isStore()) {
ScoreBrackets.determineWait(
EXP_CNT, ScoreBrackets.getRegScore(RegNo, EXP_CNT), Wait);
}
}
// Loop over use and def operands.
for (unsigned I = 0, E = MI.getNumOperands(); I != E; ++I) {
MachineOperand &Op = MI.getOperand(I);
if (!Op.isReg())
continue;
RegInterval Interval =
ScoreBrackets.getRegInterval(&MI, TII, MRI, TRI, I);
const bool IsVGPR = TRI->isVGPR(*MRI, Op.getReg());
for (int RegNo = Interval.first; RegNo < Interval.second; ++RegNo) {
if (IsVGPR) {
// RAW always needs an s_waitcnt. WAW needs an s_waitcnt unless the
// previous write and this write are the same type of VMEM
// instruction, in which case they're guaranteed to write their
// results in order anyway.
if (Op.isUse() || !SIInstrInfo::isVMEM(MI) ||
ScoreBrackets.hasOtherPendingVmemTypes(RegNo,
getVmemType(MI))) {
ScoreBrackets.determineWait(
VM_CNT, ScoreBrackets.getRegScore(RegNo, VM_CNT), Wait);
ScoreBrackets.clearVgprVmemTypes(RegNo);
}
if (Op.isDef()) {
ScoreBrackets.determineWait(
EXP_CNT, ScoreBrackets.getRegScore(RegNo, EXP_CNT), Wait);
}
}
ScoreBrackets.determineWait(
LGKM_CNT, ScoreBrackets.getRegScore(RegNo, LGKM_CNT), Wait);
}
}
}
}
// Check to see if this is an S_BARRIER, and if an implicit S_WAITCNT 0
// occurs before the instruction. Doing it here prevents any additional
// S_WAITCNTs from being emitted if the instruction was marked as
// requiring a WAITCNT beforehand.
if (MI.getOpcode() == AMDGPU::S_BARRIER &&
!ST->hasAutoWaitcntBeforeBarrier()) {
Wait = Wait.combined(AMDGPU::Waitcnt::allZero(ST->hasVscnt()));
}
// TODO: Remove this work-around, enable the assert for Bug 457939
// after fixing the scheduler. Also, the Shader Compiler code is
// independent of target.
if (readsVCCZ(MI) && ST->hasReadVCCZBug()) {
if (ScoreBrackets.getScoreLB(LGKM_CNT) <
ScoreBrackets.getScoreUB(LGKM_CNT) &&
ScoreBrackets.hasPendingEvent(SMEM_ACCESS)) {
Wait.LgkmCnt = 0;
}
}
// Early-out if no wait is indicated.
if (!ScoreBrackets.simplifyWaitcnt(Wait) && !IsForceEmitWaitcnt) {
bool Modified = false;
if (OldWaitcntInstr) {
for (auto II = OldWaitcntInstr->getIterator(), NextI = std::next(II);
&*II != &MI; II = NextI, ++NextI) {
if (II->isDebugInstr())
continue;
if (TrackedWaitcntSet.count(&*II)) {
TrackedWaitcntSet.erase(&*II);
II->eraseFromParent();
Modified = true;
} else if (II->getOpcode() == AMDGPU::S_WAITCNT) {
int64_t Imm = II->getOperand(0).getImm();
ScoreBrackets.applyWaitcnt(AMDGPU::decodeWaitcnt(IV, Imm));
} else {
assert(II->getOpcode() == AMDGPU::S_WAITCNT_VSCNT);
assert(II->getOperand(0).getReg() == AMDGPU::SGPR_NULL);
auto W = TII->getNamedOperand(*II, AMDGPU::OpName::simm16)->getImm();
ScoreBrackets.applyWaitcnt(AMDGPU::Waitcnt(~0u, ~0u, ~0u, W));
}
}
}
return Modified;
}
if (ForceEmitZeroWaitcnts)
Wait = AMDGPU::Waitcnt::allZero(ST->hasVscnt());
if (ForceEmitWaitcnt[VM_CNT])
Wait.VmCnt = 0;
if (ForceEmitWaitcnt[EXP_CNT])
Wait.ExpCnt = 0;
if (ForceEmitWaitcnt[LGKM_CNT])
Wait.LgkmCnt = 0;
if (ForceEmitWaitcnt[VS_CNT])
Wait.VsCnt = 0;
ScoreBrackets.applyWaitcnt(Wait);
AMDGPU::Waitcnt OldWait;
bool Modified = false;
if (OldWaitcntInstr) {
for (auto II = OldWaitcntInstr->getIterator(), NextI = std::next(II);
&*II != &MI; II = NextI, NextI++) {
if (II->isDebugInstr())
continue;
if (II->getOpcode() == AMDGPU::S_WAITCNT) {
unsigned IEnc = II->getOperand(0).getImm();
AMDGPU::Waitcnt IWait = AMDGPU::decodeWaitcnt(IV, IEnc);
OldWait = OldWait.combined(IWait);
if (!TrackedWaitcntSet.count(&*II))
Wait = Wait.combined(IWait);
unsigned NewEnc = AMDGPU::encodeWaitcnt(IV, Wait);
if (IEnc != NewEnc) {
II->getOperand(0).setImm(NewEnc);
Modified = true;
}
Wait.VmCnt = ~0u;
Wait.LgkmCnt = ~0u;
Wait.ExpCnt = ~0u;
} else {
assert(II->getOpcode() == AMDGPU::S_WAITCNT_VSCNT);
assert(II->getOperand(0).getReg() == AMDGPU::SGPR_NULL);
unsigned ICnt = TII->getNamedOperand(*II, AMDGPU::OpName::simm16)
->getImm();
OldWait.VsCnt = std::min(OldWait.VsCnt, ICnt);
if (!TrackedWaitcntSet.count(&*II))
Wait.VsCnt = std::min(Wait.VsCnt, ICnt);
if (Wait.VsCnt != ICnt) {
TII->getNamedOperand(*II, AMDGPU::OpName::simm16)->setImm(Wait.VsCnt);
Modified = true;
}
Wait.VsCnt = ~0u;
}
LLVM_DEBUG(dbgs() << "generateWaitcntInstBefore\n"
<< "Old Instr: " << MI
<< "New Instr: " << *II << '\n');
if (!Wait.hasWait())
return Modified;
}
}
if (Wait.VmCnt != ~0u || Wait.LgkmCnt != ~0u || Wait.ExpCnt != ~0u) {
unsigned Enc = AMDGPU::encodeWaitcnt(IV, Wait);
auto SWaitInst = BuildMI(*MI.getParent(), MI.getIterator(),
MI.getDebugLoc(), TII->get(AMDGPU::S_WAITCNT))
.addImm(Enc);
TrackedWaitcntSet.insert(SWaitInst);
Modified = true;
LLVM_DEBUG(dbgs() << "generateWaitcntInstBefore\n"
<< "Old Instr: " << MI
<< "New Instr: " << *SWaitInst << '\n');
}
if (Wait.VsCnt != ~0u) {
assert(ST->hasVscnt());
auto SWaitInst =
BuildMI(*MI.getParent(), MI.getIterator(), MI.getDebugLoc(),
TII->get(AMDGPU::S_WAITCNT_VSCNT))
.addReg(AMDGPU::SGPR_NULL, RegState::Undef)
.addImm(Wait.VsCnt);
TrackedWaitcntSet.insert(SWaitInst);
Modified = true;
LLVM_DEBUG(dbgs() << "generateWaitcntInstBefore\n"
<< "Old Instr: " << MI
<< "New Instr: " << *SWaitInst << '\n');
}
return Modified;
}
// This is a flat memory operation. Check to see if it has memory tokens other
// than LDS. Other address spaces supported by flat memory operations involve
// global memory.
bool SIInsertWaitcnts::mayAccessVMEMThroughFlat(const MachineInstr &MI) const {
assert(TII->isFLAT(MI));
// All flat instructions use the VMEM counter.
assert(TII->usesVM_CNT(MI));
// If there are no memory operands then conservatively assume the flat
// operation may access VMEM.
if (MI.memoperands_empty())
return true;
// See if any memory operand specifies an address space that involves VMEM.
// Flat operations only supported FLAT, LOCAL (LDS), or address spaces
// involving VMEM such as GLOBAL, CONSTANT, PRIVATE (SCRATCH), etc. The REGION
// (GDS) address space is not supported by flat operations. Therefore, simply
// return true unless only the LDS address space is found.
for (const MachineMemOperand *Memop : MI.memoperands()) {
unsigned AS = Memop->getAddrSpace();
assert(AS != AMDGPUAS::REGION_ADDRESS);
if (AS != AMDGPUAS::LOCAL_ADDRESS)
return true;
}
return false;
}
// This is a flat memory operation. Check to see if it has memory tokens for
// either LDS or FLAT.
bool SIInsertWaitcnts::mayAccessLDSThroughFlat(const MachineInstr &MI) const {
assert(TII->isFLAT(MI));
// Flat instruction such as SCRATCH and GLOBAL do not use the lgkm counter.
if (!TII->usesLGKM_CNT(MI))
return false;
// If there are no memory operands then conservatively assume the flat
// operation may access LDS.
if (MI.memoperands_empty())
return true;
// See if any memory operand specifies an address space that involves LDS.
for (const MachineMemOperand *Memop : MI.memoperands()) {
unsigned AS = Memop->getAddrSpace();
if (AS == AMDGPUAS::LOCAL_ADDRESS || AS == AMDGPUAS::FLAT_ADDRESS)
return true;
}
return false;
}
void SIInsertWaitcnts::updateEventWaitcntAfter(MachineInstr &Inst,
WaitcntBrackets *ScoreBrackets) {
// Now look at the instruction opcode. If it is a memory access
// instruction, update the upper-bound of the appropriate counter's
// bracket and the destination operand scores.
// TODO: Use the (TSFlags & SIInstrFlags::LGKM_CNT) property everywhere.
if (TII->isDS(Inst) && TII->usesLGKM_CNT(Inst)) {
if (TII->isAlwaysGDS(Inst.getOpcode()) ||
TII->hasModifiersSet(Inst, AMDGPU::OpName::gds)) {
ScoreBrackets->updateByEvent(TII, TRI, MRI, GDS_ACCESS, Inst);
ScoreBrackets->updateByEvent(TII, TRI, MRI, GDS_GPR_LOCK, Inst);
} else {
ScoreBrackets->updateByEvent(TII, TRI, MRI, LDS_ACCESS, Inst);
}
} else if (TII->isFLAT(Inst)) {
assert(Inst.mayLoadOrStore());
int FlatASCount = 0;
if (mayAccessVMEMThroughFlat(Inst)) {
++FlatASCount;
if (!ST->hasVscnt())
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_ACCESS, Inst);
else if (Inst.mayLoad() &&
AMDGPU::getAtomicRetOp(Inst.getOpcode()) == -1)
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_READ_ACCESS, Inst);
else
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_WRITE_ACCESS, Inst);
}
if (mayAccessLDSThroughFlat(Inst)) {
++FlatASCount;
ScoreBrackets->updateByEvent(TII, TRI, MRI, LDS_ACCESS, Inst);
}
// A Flat memory operation must access at least one address space.
assert(FlatASCount);
// This is a flat memory operation that access both VMEM and LDS, so note it
// - it will require that both the VM and LGKM be flushed to zero if it is
// pending when a VM or LGKM dependency occurs.
if (FlatASCount > 1)
ScoreBrackets->setPendingFlat();
} else if (SIInstrInfo::isVMEM(Inst) &&
// TODO: get a better carve out.
Inst.getOpcode() != AMDGPU::BUFFER_WBINVL1 &&
Inst.getOpcode() != AMDGPU::BUFFER_WBINVL1_SC &&
Inst.getOpcode() != AMDGPU::BUFFER_WBINVL1_VOL &&
Inst.getOpcode() != AMDGPU::BUFFER_GL0_INV &&
Inst.getOpcode() != AMDGPU::BUFFER_GL1_INV) {
if (!ST->hasVscnt())
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_ACCESS, Inst);
else if ((Inst.mayLoad() &&
AMDGPU::getAtomicRetOp(Inst.getOpcode()) == -1) ||
/* IMAGE_GET_RESINFO / IMAGE_GET_LOD */
(TII->isMIMG(Inst) && !Inst.mayLoad() && !Inst.mayStore()))
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_READ_ACCESS, Inst);
else if (Inst.mayStore())
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMEM_WRITE_ACCESS, Inst);
if (ST->vmemWriteNeedsExpWaitcnt() &&
(Inst.mayStore() || AMDGPU::getAtomicNoRetOp(Inst.getOpcode()) != -1)) {
ScoreBrackets->updateByEvent(TII, TRI, MRI, VMW_GPR_LOCK, Inst);
}
} else if (TII->isSMRD(Inst)) {
ScoreBrackets->updateByEvent(TII, TRI, MRI, SMEM_ACCESS, Inst);
} else if (Inst.isCall()) {
if (callWaitsOnFunctionReturn(Inst)) {
// Act as a wait on everything
ScoreBrackets->applyWaitcnt(AMDGPU::Waitcnt::allZero(ST->hasVscnt()));
} else {
// May need to way wait for anything.
ScoreBrackets->applyWaitcnt(AMDGPU::Waitcnt());
}
} else if (SIInstrInfo::isEXP(Inst)) {
int Imm = TII->getNamedOperand(Inst, AMDGPU::OpName::tgt)->getImm();
if (Imm >= AMDGPU::Exp::ET_PARAM0 && Imm <= AMDGPU::Exp::ET_PARAM31)
ScoreBrackets->updateByEvent(TII, TRI, MRI, EXP_PARAM_ACCESS, Inst);
else if (Imm >= AMDGPU::Exp::ET_POS0 && Imm <= AMDGPU::Exp::ET_POS_LAST)
ScoreBrackets->updateByEvent(TII, TRI, MRI, EXP_POS_ACCESS, Inst);
else
ScoreBrackets->updateByEvent(TII, TRI, MRI, EXP_GPR_LOCK, Inst);
} else {
switch (Inst.getOpcode()) {
case AMDGPU::S_SENDMSG:
case AMDGPU::S_SENDMSGHALT:
ScoreBrackets->updateByEvent(TII, TRI, MRI, SQ_MESSAGE, Inst);
break;
case AMDGPU::S_MEMTIME:
case AMDGPU::S_MEMREALTIME:
ScoreBrackets->updateByEvent(TII, TRI, MRI, SMEM_ACCESS, Inst);
break;
}
}
}
bool WaitcntBrackets::mergeScore(const MergeInfo &M, unsigned &Score,
unsigned OtherScore) {
unsigned MyShifted = Score <= M.OldLB ? 0 : Score + M.MyShift;
unsigned OtherShifted =
OtherScore <= M.OtherLB ? 0 : OtherScore + M.OtherShift;
Score = std::max(MyShifted, OtherShifted);
return OtherShifted > MyShifted;
}
/// Merge the pending events and associater score brackets of \p Other into
/// this brackets status.
///
/// Returns whether the merge resulted in a change that requires tighter waits
/// (i.e. the merged brackets strictly dominate the original brackets).
bool WaitcntBrackets::merge(const WaitcntBrackets &Other) {
bool StrictDom = false;
VgprUB = std::max(VgprUB, Other.VgprUB);
SgprUB = std::max(SgprUB, Other.SgprUB);
for (auto T : inst_counter_types()) {
// Merge event flags for this counter
const bool OldOutOfOrder = counterOutOfOrder(T);
const unsigned OldEvents = PendingEvents & WaitEventMaskForInst[T];
const unsigned OtherEvents = Other.PendingEvents & WaitEventMaskForInst[T];
if (OtherEvents & ~OldEvents)
StrictDom = true;
PendingEvents |= OtherEvents;
// Merge scores for this counter
const unsigned MyPending = ScoreUBs[T] - ScoreLBs[T];
const unsigned OtherPending = Other.ScoreUBs[T] - Other.ScoreLBs[T];
const unsigned NewUB = ScoreLBs[T] + std::max(MyPending, OtherPending);
if (NewUB < ScoreLBs[T])
report_fatal_error("waitcnt score overflow");
MergeInfo M;
M.OldLB = ScoreLBs[T];
M.OtherLB = Other.ScoreLBs[T];
M.MyShift = NewUB - ScoreUBs[T];
M.OtherShift = NewUB - Other.ScoreUBs[T];
ScoreUBs[T] = NewUB;
StrictDom |= mergeScore(M, LastFlat[T], Other.LastFlat[T]);
bool RegStrictDom = false;
for (int J = 0; J <= VgprUB; J++) {
RegStrictDom |= mergeScore(M, VgprScores[T][J], Other.VgprScores[T][J]);
}
if (T == VM_CNT) {
for (int J = 0; J <= VgprUB; J++) {
unsigned char NewVmemTypes = VgprVmemTypes[J] | Other.VgprVmemTypes[J];
RegStrictDom |= NewVmemTypes != VgprVmemTypes[J];
VgprVmemTypes[J] = NewVmemTypes;
}
}
if (T == LGKM_CNT) {
for (int J = 0; J <= SgprUB; J++) {
RegStrictDom |= mergeScore(M, SgprScores[J], Other.SgprScores[J]);
}
}
if (RegStrictDom && !OldOutOfOrder)
StrictDom = true;
}
return StrictDom;
}
// Generate s_waitcnt instructions where needed.
bool SIInsertWaitcnts::insertWaitcntInBlock(MachineFunction &MF,
MachineBasicBlock &Block,
WaitcntBrackets &ScoreBrackets) {
bool Modified = false;
LLVM_DEBUG({
dbgs() << "*** Block" << Block.getNumber() << " ***";
ScoreBrackets.dump();
});
// Track the correctness of vccz through this basic block. There are two
// reasons why it might be incorrect; see ST->hasReadVCCZBug() and
// ST->partialVCCWritesUpdateVCCZ().
bool VCCZCorrect = true;
if (ST->hasReadVCCZBug()) {
// vccz could be incorrect at a basic block boundary if a predecessor wrote
// to vcc and then issued an smem load.
VCCZCorrect = false;
} else if (!ST->partialVCCWritesUpdateVCCZ()) {
// vccz could be incorrect at a basic block boundary if a predecessor wrote
// to vcc_lo or vcc_hi.
VCCZCorrect = false;
}
// Walk over the instructions.
MachineInstr *OldWaitcntInstr = nullptr;
for (MachineBasicBlock::instr_iterator Iter = Block.instr_begin(),
E = Block.instr_end();
Iter != E;) {
MachineInstr &Inst = *Iter;
// Track pre-existing waitcnts from earlier iterations.
if (Inst.getOpcode() == AMDGPU::S_WAITCNT ||
(Inst.getOpcode() == AMDGPU::S_WAITCNT_VSCNT &&
Inst.getOperand(0).isReg() &&
Inst.getOperand(0).getReg() == AMDGPU::SGPR_NULL)) {
if (!OldWaitcntInstr)
OldWaitcntInstr = &Inst;
++Iter;
continue;
}
// Generate an s_waitcnt instruction to be placed before Inst, if needed.
Modified |= generateWaitcntInstBefore(Inst, ScoreBrackets, OldWaitcntInstr);
OldWaitcntInstr = nullptr;
// Restore vccz if it's not known to be correct already.
bool RestoreVCCZ = !VCCZCorrect && readsVCCZ(Inst);
// Don't examine operands unless we need to track vccz correctness.
if (ST->hasReadVCCZBug() || !ST->partialVCCWritesUpdateVCCZ()) {
if (Inst.definesRegister(AMDGPU::VCC_LO) ||
Inst.definesRegister(AMDGPU::VCC_HI)) {
// Up to gfx9, writes to vcc_lo and vcc_hi don't update vccz.
if (!ST->partialVCCWritesUpdateVCCZ())
VCCZCorrect = false;
} else if (Inst.definesRegister(AMDGPU::VCC)) {
// There is a hardware bug on CI/SI where SMRD instruction may corrupt
// vccz bit, so when we detect that an instruction may read from a
// corrupt vccz bit, we need to:
// 1. Insert s_waitcnt lgkm(0) to wait for all outstanding SMRD
// operations to complete.
// 2. Restore the correct value of vccz by writing the current value
// of vcc back to vcc.
if (ST->hasReadVCCZBug() &&
ScoreBrackets.getScoreLB(LGKM_CNT) <
ScoreBrackets.getScoreUB(LGKM_CNT) &&
ScoreBrackets.hasPendingEvent(SMEM_ACCESS)) {
// Writes to vcc while there's an outstanding smem read may get
// clobbered as soon as any read completes.
VCCZCorrect = false;
} else {
// Writes to vcc will fix any incorrect value in vccz.
VCCZCorrect = true;
}
}
}
if (TII->isSMRD(Inst)) {
for (const MachineMemOperand *Memop : Inst.memoperands()) {
const Value *Ptr = Memop->getValue();
SLoadAddresses.insert(std::make_pair(Ptr, Inst.getParent()));
}
if (ST->hasReadVCCZBug()) {
// This smem read could complete and clobber vccz at any time.
VCCZCorrect = false;
}
}
updateEventWaitcntAfter(Inst, &ScoreBrackets);
#if 0 // TODO: implement resource type check controlled by options with ub = LB.
// If this instruction generates a S_SETVSKIP because it is an
// indexed resource, and we are on Tahiti, then it will also force
// an S_WAITCNT vmcnt(0)
if (RequireCheckResourceType(Inst, context)) {
// Force the score to as if an S_WAITCNT vmcnt(0) is emitted.
ScoreBrackets->setScoreLB(VM_CNT,
ScoreBrackets->getScoreUB(VM_CNT));
}
#endif
LLVM_DEBUG({
Inst.print(dbgs());
ScoreBrackets.dump();
});
// TODO: Remove this work-around after fixing the scheduler and enable the
// assert above.
if (RestoreVCCZ) {
// Restore the vccz bit. Any time a value is written to vcc, the vcc
// bit is updated, so we can restore the bit by reading the value of
// vcc and then writing it back to the register.
BuildMI(Block, Inst, Inst.getDebugLoc(),
TII->get(ST->isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64),
TRI->getVCC())
.addReg(TRI->getVCC());
VCCZCorrect = true;
Modified = true;
}
++Iter;
}
return Modified;
}
bool SIInsertWaitcnts::runOnMachineFunction(MachineFunction &MF) {
ST = &MF.getSubtarget<GCNSubtarget>();
TII = ST->getInstrInfo();
TRI = &TII->getRegisterInfo();
MRI = &MF.getRegInfo();
IV = AMDGPU::getIsaVersion(ST->getCPU());
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
PDT = &getAnalysis<MachinePostDominatorTree>();
ForceEmitZeroWaitcnts = ForceEmitZeroFlag;
for (auto T : inst_counter_types())
ForceEmitWaitcnt[T] = false;
HardwareLimits.VmcntMax = AMDGPU::getVmcntBitMask(IV);
HardwareLimits.ExpcntMax = AMDGPU::getExpcntBitMask(IV);
HardwareLimits.LgkmcntMax = AMDGPU::getLgkmcntBitMask(IV);
HardwareLimits.VscntMax = ST->hasVscnt() ? 63 : 0;
unsigned NumVGPRsMax = ST->getAddressableNumVGPRs();
unsigned NumSGPRsMax = ST->getAddressableNumSGPRs();
assert(NumVGPRsMax <= SQ_MAX_PGM_VGPRS);
assert(NumSGPRsMax <= SQ_MAX_PGM_SGPRS);
RegisterEncoding.VGPR0 = TRI->getEncodingValue(AMDGPU::VGPR0);
RegisterEncoding.VGPRL = RegisterEncoding.VGPR0 + NumVGPRsMax - 1;
RegisterEncoding.SGPR0 = TRI->getEncodingValue(AMDGPU::SGPR0);
RegisterEncoding.SGPRL = RegisterEncoding.SGPR0 + NumSGPRsMax - 1;
TrackedWaitcntSet.clear();
BlockInfos.clear();
// Keep iterating over the blocks in reverse post order, inserting and
// updating s_waitcnt where needed, until a fix point is reached.
for (auto *MBB : ReversePostOrderTraversal<MachineFunction *>(&MF))
BlockInfos.insert({MBB, BlockInfo(MBB)});
std::unique_ptr<WaitcntBrackets> Brackets;
bool Modified = false;
bool Repeat;
do {
Repeat = false;
for (auto BII = BlockInfos.begin(), BIE = BlockInfos.end(); BII != BIE;
++BII) {
BlockInfo &BI = BII->second;
if (!BI.Dirty)
continue;
if (BI.Incoming) {
if (!Brackets)
Brackets = std::make_unique<WaitcntBrackets>(*BI.Incoming);
else
*Brackets = *BI.Incoming;
} else {
if (!Brackets)
Brackets = std::make_unique<WaitcntBrackets>(ST);
else
*Brackets = WaitcntBrackets(ST);
}
Modified |= insertWaitcntInBlock(MF, *BI.MBB, *Brackets);
BI.Dirty = false;
if (Brackets->hasPending()) {
BlockInfo *MoveBracketsToSucc = nullptr;
for (MachineBasicBlock *Succ : BI.MBB->successors()) {
auto SuccBII = BlockInfos.find(Succ);
BlockInfo &SuccBI = SuccBII->second;
if (!SuccBI.Incoming) {
SuccBI.Dirty = true;
if (SuccBII <= BII)
Repeat = true;
if (!MoveBracketsToSucc) {
MoveBracketsToSucc = &SuccBI;
} else {
SuccBI.Incoming = std::make_unique<WaitcntBrackets>(*Brackets);
}
} else if (SuccBI.Incoming->merge(*Brackets)) {
SuccBI.Dirty = true;
if (SuccBII <= BII)
Repeat = true;
}
}
if (MoveBracketsToSucc)
MoveBracketsToSucc->Incoming = std::move(Brackets);
}
}
} while (Repeat);
SmallVector<MachineBasicBlock *, 4> EndPgmBlocks;
bool HaveScalarStores = false;
for (MachineFunction::iterator BI = MF.begin(), BE = MF.end(); BI != BE;
++BI) {
MachineBasicBlock &MBB = *BI;
for (MachineBasicBlock::iterator I = MBB.begin(), E = MBB.end(); I != E;
++I) {
if (!HaveScalarStores && TII->isScalarStore(*I))
HaveScalarStores = true;
if (I->getOpcode() == AMDGPU::S_ENDPGM ||
I->getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG)
EndPgmBlocks.push_back(&MBB);
}
}
if (HaveScalarStores) {
// If scalar writes are used, the cache must be flushed or else the next
// wave to reuse the same scratch memory can be clobbered.
//
// Insert s_dcache_wb at wave termination points if there were any scalar
// stores, and only if the cache hasn't already been flushed. This could be
// improved by looking across blocks for flushes in postdominating blocks
// from the stores but an explicitly requested flush is probably very rare.
for (MachineBasicBlock *MBB : EndPgmBlocks) {
bool SeenDCacheWB = false;
for (MachineBasicBlock::iterator I = MBB->begin(), E = MBB->end(); I != E;
++I) {
if (I->getOpcode() == AMDGPU::S_DCACHE_WB)
SeenDCacheWB = true;
else if (TII->isScalarStore(*I))
SeenDCacheWB = false;
// FIXME: It would be better to insert this before a waitcnt if any.
if ((I->getOpcode() == AMDGPU::S_ENDPGM ||
I->getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG) &&
!SeenDCacheWB) {
Modified = true;
BuildMI(*MBB, I, I->getDebugLoc(), TII->get(AMDGPU::S_DCACHE_WB));
}
}
}
}
if (!MFI->isEntryFunction()) {
// Wait for any outstanding memory operations that the input registers may
// depend on. We can't track them and it's better to the wait after the
// costly call sequence.
// TODO: Could insert earlier and schedule more liberally with operations
// that only use caller preserved registers.
MachineBasicBlock &EntryBB = MF.front();
MachineBasicBlock::iterator I = EntryBB.begin();
for (MachineBasicBlock::iterator E = EntryBB.end();
I != E && (I->isPHI() || I->isMetaInstruction()); ++I)
;
BuildMI(EntryBB, I, DebugLoc(), TII->get(AMDGPU::S_WAITCNT)).addImm(0);
if (ST->hasVscnt())
BuildMI(EntryBB, I, DebugLoc(), TII->get(AMDGPU::S_WAITCNT_VSCNT))
.addReg(AMDGPU::SGPR_NULL, RegState::Undef)
.addImm(0);
Modified = true;
}
return Modified;
}
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