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

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//===-- AMDGPUSubtarget.cpp - AMDGPU Subtarget Information ----------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
/// \file
/// \brief Implements the AMDGPU specific subclass of TargetSubtarget.
//
//===----------------------------------------------------------------------===//
#include "AMDGPUSubtarget.h"
#include "SIMachineFunctionInfo.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/IR/MDBuilder.h"
#include "llvm/Target/TargetFrameLowering.h"
#include <algorithm>
using namespace llvm;
#define DEBUG_TYPE "amdgpu-subtarget"
#define GET_SUBTARGETINFO_TARGET_DESC
#define GET_SUBTARGETINFO_CTOR
#include "AMDGPUGenSubtargetInfo.inc"
AMDGPUSubtarget::~AMDGPUSubtarget() = default;
AMDGPUSubtarget &
AMDGPUSubtarget::initializeSubtargetDependencies(const Triple &TT,
StringRef GPU, StringRef FS) {
// Determine default and user-specified characteristics
// On SI+, we want FP64 denormals to be on by default. FP32 denormals can be
// enabled, but some instructions do not respect them and they run at the
// double precision rate, so don't enable by default.
//
// We want to be able to turn these off, but making this a subtarget feature
// for SI has the unhelpful behavior that it unsets everything else if you
// disable it.
SmallString<256> FullFS("+promote-alloca,+fp64-fp16-denormals,+dx10-clamp,+load-store-opt,");
if (isAmdHsaOS()) // Turn on FlatForGlobal for HSA.
FullFS += "+flat-for-global,+unaligned-buffer-access,+trap-handler,";
FullFS += FS;
ParseSubtargetFeatures(GPU, FullFS);
// Unless +-flat-for-global is specified, turn on FlatForGlobal for all OS-es
// on VI and newer hardware to avoid assertion failures due to missing ADDR64
// variants of MUBUF instructions.
if (!hasAddr64() && !FS.contains("flat-for-global")) {
FlatForGlobal = true;
}
// FIXME: I don't think think Evergreen has any useful support for
// denormals, but should be checked. Should we issue a warning somewhere
// if someone tries to enable these?
if (getGeneration() <= AMDGPUSubtarget::NORTHERN_ISLANDS) {
FP64FP16Denormals = false;
FP32Denormals = false;
}
// Set defaults if needed.
if (MaxPrivateElementSize == 0)
MaxPrivateElementSize = 4;
return *this;
}
AMDGPUSubtarget::AMDGPUSubtarget(const Triple &TT, StringRef GPU, StringRef FS,
const TargetMachine &TM)
: AMDGPUGenSubtargetInfo(TT, GPU, FS),
TargetTriple(TT),
Gen(TT.getArch() == Triple::amdgcn ? SOUTHERN_ISLANDS : R600),
IsaVersion(ISAVersion0_0_0),
WavefrontSize(64),
LocalMemorySize(0),
LDSBankCount(0),
MaxPrivateElementSize(0),
FastFMAF32(false),
HalfRate64Ops(false),
FP32Denormals(false),
FP64FP16Denormals(false),
FPExceptions(false),
DX10Clamp(false),
FlatForGlobal(false),
UnalignedScratchAccess(false),
UnalignedBufferAccess(false),
HasApertureRegs(false),
EnableXNACK(false),
TrapHandler(false),
DebuggerInsertNops(false),
DebuggerReserveRegs(false),
DebuggerEmitPrologue(false),
EnableVGPRSpilling(false),
EnablePromoteAlloca(false),
EnableLoadStoreOpt(false),
EnableUnsafeDSOffsetFolding(false),
EnableSIScheduler(false),
DumpCode(false),
FP64(false),
IsGCN(false),
GCN1Encoding(false),
GCN3Encoding(false),
CIInsts(false),
GFX9Insts(false),
SGPRInitBug(false),
HasSMemRealTime(false),
Has16BitInsts(false),
HasVOP3PInsts(false),
HasMovrel(false),
HasVGPRIndexMode(false),
HasScalarStores(false),
HasInv2PiInlineImm(false),
HasSDWA(false),
HasDPP(false),
FlatAddressSpace(false),
R600ALUInst(false),
CaymanISA(false),
CFALUBug(false),
HasVertexCache(false),
TexVTXClauseSize(0),
ScalarizeGlobal(false),
FeatureDisable(false),
InstrItins(getInstrItineraryForCPU(GPU)) {
AS = AMDGPU::getAMDGPUAS(TT);
initializeSubtargetDependencies(TT, GPU, FS);
}
unsigned AMDGPUSubtarget::getMaxLocalMemSizeWithWaveCount(unsigned NWaves,
const Function &F) const {
if (NWaves == 1)
return getLocalMemorySize();
unsigned WorkGroupSize = getFlatWorkGroupSizes(F).second;
unsigned WorkGroupsPerCu = getMaxWorkGroupsPerCU(WorkGroupSize);
unsigned MaxWaves = getMaxWavesPerEU();
return getLocalMemorySize() * MaxWaves / WorkGroupsPerCu / NWaves;
}
unsigned AMDGPUSubtarget::getOccupancyWithLocalMemSize(uint32_t Bytes,
const Function &F) const {
unsigned WorkGroupSize = getFlatWorkGroupSizes(F).second;
unsigned WorkGroupsPerCu = getMaxWorkGroupsPerCU(WorkGroupSize);
unsigned MaxWaves = getMaxWavesPerEU();
unsigned Limit = getLocalMemorySize() * MaxWaves / WorkGroupsPerCu;
unsigned NumWaves = Limit / (Bytes ? Bytes : 1u);
NumWaves = std::min(NumWaves, MaxWaves);
NumWaves = std::max(NumWaves, 1u);
return NumWaves;
}
std::pair<unsigned, unsigned> AMDGPUSubtarget::getFlatWorkGroupSizes(
const Function &F) const {
// Default minimum/maximum flat work group sizes.
std::pair<unsigned, unsigned> Default =
AMDGPU::isCompute(F.getCallingConv()) ?
std::pair<unsigned, unsigned>(getWavefrontSize() * 2,
getWavefrontSize() * 4) :
std::pair<unsigned, unsigned>(1, getWavefrontSize());
// TODO: Do not process "amdgpu-max-work-group-size" attribute once mesa
// starts using "amdgpu-flat-work-group-size" attribute.
Default.second = AMDGPU::getIntegerAttribute(
F, "amdgpu-max-work-group-size", Default.second);
Default.first = std::min(Default.first, Default.second);
// Requested minimum/maximum flat work group sizes.
std::pair<unsigned, unsigned> Requested = AMDGPU::getIntegerPairAttribute(
F, "amdgpu-flat-work-group-size", Default);
// Make sure requested minimum is less than requested maximum.
if (Requested.first > Requested.second)
return Default;
// Make sure requested values do not violate subtarget's specifications.
if (Requested.first < getMinFlatWorkGroupSize())
return Default;
if (Requested.second > getMaxFlatWorkGroupSize())
return Default;
return Requested;
}
std::pair<unsigned, unsigned> AMDGPUSubtarget::getWavesPerEU(
const Function &F) const {
// Default minimum/maximum number of waves per execution unit.
std::pair<unsigned, unsigned> Default(1, getMaxWavesPerEU());
// Default/requested minimum/maximum flat work group sizes.
std::pair<unsigned, unsigned> FlatWorkGroupSizes = getFlatWorkGroupSizes(F);
// If minimum/maximum flat work group sizes were explicitly requested using
// "amdgpu-flat-work-group-size" attribute, then set default minimum/maximum
// number of waves per execution unit to values implied by requested
// minimum/maximum flat work group sizes.
unsigned MinImpliedByFlatWorkGroupSize =
getMaxWavesPerEU(FlatWorkGroupSizes.second);
bool RequestedFlatWorkGroupSize = false;
// TODO: Do not process "amdgpu-max-work-group-size" attribute once mesa
// starts using "amdgpu-flat-work-group-size" attribute.
if (F.hasFnAttribute("amdgpu-max-work-group-size") ||
F.hasFnAttribute("amdgpu-flat-work-group-size")) {
Default.first = MinImpliedByFlatWorkGroupSize;
RequestedFlatWorkGroupSize = true;
}
// Requested minimum/maximum number of waves per execution unit.
std::pair<unsigned, unsigned> Requested = AMDGPU::getIntegerPairAttribute(
F, "amdgpu-waves-per-eu", Default, true);
// Make sure requested minimum is less than requested maximum.
if (Requested.second && Requested.first > Requested.second)
return Default;
// Make sure requested values do not violate subtarget's specifications.
if (Requested.first < getMinWavesPerEU() ||
Requested.first > getMaxWavesPerEU())
return Default;
if (Requested.second > getMaxWavesPerEU())
return Default;
// Make sure requested values are compatible with values implied by requested
// minimum/maximum flat work group sizes.
if (RequestedFlatWorkGroupSize &&
Requested.first > MinImpliedByFlatWorkGroupSize)
return Default;
return Requested;
}
bool AMDGPUSubtarget::makeLIDRangeMetadata(Instruction *I) const {
Function *Kernel = I->getParent()->getParent();
unsigned MinSize = 0;
unsigned MaxSize = getFlatWorkGroupSizes(*Kernel).second;
bool IdQuery = false;
// If reqd_work_group_size is present it narrows value down.
if (auto *CI = dyn_cast<CallInst>(I)) {
const Function *F = CI->getCalledFunction();
if (F) {
unsigned Dim = UINT_MAX;
switch (F->getIntrinsicID()) {
case Intrinsic::amdgcn_workitem_id_x:
case Intrinsic::r600_read_tidig_x:
IdQuery = true;
case Intrinsic::r600_read_local_size_x:
Dim = 0;
break;
case Intrinsic::amdgcn_workitem_id_y:
case Intrinsic::r600_read_tidig_y:
IdQuery = true;
case Intrinsic::r600_read_local_size_y:
Dim = 1;
break;
case Intrinsic::amdgcn_workitem_id_z:
case Intrinsic::r600_read_tidig_z:
IdQuery = true;
case Intrinsic::r600_read_local_size_z:
Dim = 2;
break;
default:
break;
}
if (Dim <= 3) {
if (auto Node = Kernel->getMetadata("reqd_work_group_size"))
if (Node->getNumOperands() == 3)
MinSize = MaxSize = mdconst::extract<ConstantInt>(
Node->getOperand(Dim))->getZExtValue();
}
}
}
if (!MaxSize)
return false;
// Range metadata is [Lo, Hi). For ID query we need to pass max size
// as Hi. For size query we need to pass Hi + 1.
if (IdQuery)
MinSize = 0;
else
++MaxSize;
MDBuilder MDB(I->getContext());
MDNode *MaxWorkGroupSizeRange = MDB.createRange(APInt(32, MinSize),
APInt(32, MaxSize));
I->setMetadata(LLVMContext::MD_range, MaxWorkGroupSizeRange);
return true;
}
R600Subtarget::R600Subtarget(const Triple &TT, StringRef GPU, StringRef FS,
const TargetMachine &TM) :
AMDGPUSubtarget(TT, GPU, FS, TM),
InstrInfo(*this),
FrameLowering(TargetFrameLowering::StackGrowsUp, getStackAlignment(), 0),
TLInfo(TM, *this) {}
SISubtarget::SISubtarget(const Triple &TT, StringRef GPU, StringRef FS,
const TargetMachine &TM) :
AMDGPUSubtarget(TT, GPU, FS, TM),
InstrInfo(*this),
FrameLowering(TargetFrameLowering::StackGrowsUp, getStackAlignment(), 0),
TLInfo(TM, *this) {}
void SISubtarget::overrideSchedPolicy(MachineSchedPolicy &Policy,
unsigned NumRegionInstrs) const {
// Track register pressure so the scheduler can try to decrease
// pressure once register usage is above the threshold defined by
// SIRegisterInfo::getRegPressureSetLimit()
Policy.ShouldTrackPressure = true;
// Enabling both top down and bottom up scheduling seems to give us less
// register spills than just using one of these approaches on its own.
Policy.OnlyTopDown = false;
Policy.OnlyBottomUp = false;
// Enabling ShouldTrackLaneMasks crashes the SI Machine Scheduler.
if (!enableSIScheduler())
Policy.ShouldTrackLaneMasks = true;
}
bool SISubtarget::isVGPRSpillingEnabled(const Function& F) const {
return EnableVGPRSpilling || !AMDGPU::isShader(F.getCallingConv());
}
unsigned SISubtarget::getKernArgSegmentSize(const MachineFunction &MF,
unsigned ExplicitArgBytes) const {
unsigned ImplicitBytes = getImplicitArgNumBytes(MF);
if (ImplicitBytes == 0)
return ExplicitArgBytes;
unsigned Alignment = getAlignmentForImplicitArgPtr();
return alignTo(ExplicitArgBytes, Alignment) + ImplicitBytes;
}
unsigned SISubtarget::getOccupancyWithNumSGPRs(unsigned SGPRs) const {
if (getGeneration() >= SISubtarget::VOLCANIC_ISLANDS) {
if (SGPRs <= 80)
return 10;
if (SGPRs <= 88)
return 9;
if (SGPRs <= 100)
return 8;
return 7;
}
if (SGPRs <= 48)
return 10;
if (SGPRs <= 56)
return 9;
if (SGPRs <= 64)
return 8;
if (SGPRs <= 72)
return 7;
if (SGPRs <= 80)
return 6;
return 5;
}
unsigned SISubtarget::getOccupancyWithNumVGPRs(unsigned VGPRs) const {
if (VGPRs <= 24)
return 10;
if (VGPRs <= 28)
return 9;
if (VGPRs <= 32)
return 8;
if (VGPRs <= 36)
return 7;
if (VGPRs <= 40)
return 6;
if (VGPRs <= 48)
return 5;
if (VGPRs <= 64)
return 4;
if (VGPRs <= 84)
return 3;
if (VGPRs <= 128)
return 2;
return 1;
}
unsigned SISubtarget::getReservedNumSGPRs(const MachineFunction &MF) const {
const SIMachineFunctionInfo &MFI = *MF.getInfo<SIMachineFunctionInfo>();
if (MFI.hasFlatScratchInit()) {
if (getGeneration() >= AMDGPUSubtarget::VOLCANIC_ISLANDS)
return 6; // FLAT_SCRATCH, XNACK, VCC (in that order).
if (getGeneration() == AMDGPUSubtarget::SEA_ISLANDS)
return 4; // FLAT_SCRATCH, VCC (in that order).
}
if (isXNACKEnabled())
return 4; // XNACK, VCC (in that order).
return 2; // VCC.
}
unsigned SISubtarget::getMaxNumSGPRs(const MachineFunction &MF) const {
const Function &F = *MF.getFunction();
const SIMachineFunctionInfo &MFI = *MF.getInfo<SIMachineFunctionInfo>();
// Compute maximum number of SGPRs function can use using default/requested
// minimum number of waves per execution unit.
std::pair<unsigned, unsigned> WavesPerEU = MFI.getWavesPerEU();
unsigned MaxNumSGPRs = getMaxNumSGPRs(WavesPerEU.first, false);
unsigned MaxAddressableNumSGPRs = getMaxNumSGPRs(WavesPerEU.first, true);
// Check if maximum number of SGPRs was explicitly requested using
// "amdgpu-num-sgpr" attribute.
if (F.hasFnAttribute("amdgpu-num-sgpr")) {
unsigned Requested = AMDGPU::getIntegerAttribute(
F, "amdgpu-num-sgpr", MaxNumSGPRs);
// Make sure requested value does not violate subtarget's specifications.
if (Requested && (Requested <= getReservedNumSGPRs(MF)))
Requested = 0;
// If more SGPRs are required to support the input user/system SGPRs,
// increase to accommodate them.
//
// FIXME: This really ends up using the requested number of SGPRs + number
// of reserved special registers in total. Theoretically you could re-use
// the last input registers for these special registers, but this would
// require a lot of complexity to deal with the weird aliasing.
unsigned InputNumSGPRs = MFI.getNumPreloadedSGPRs();
if (Requested && Requested < InputNumSGPRs)
Requested = InputNumSGPRs;
// Make sure requested value is compatible with values implied by
// default/requested minimum/maximum number of waves per execution unit.
if (Requested && Requested > getMaxNumSGPRs(WavesPerEU.first, false))
Requested = 0;
if (WavesPerEU.second &&
Requested && Requested < getMinNumSGPRs(WavesPerEU.second))
Requested = 0;
if (Requested)
MaxNumSGPRs = Requested;
}
if (hasSGPRInitBug())
MaxNumSGPRs = AMDGPU::IsaInfo::FIXED_NUM_SGPRS_FOR_INIT_BUG;
return std::min(MaxNumSGPRs - getReservedNumSGPRs(MF),
MaxAddressableNumSGPRs);
}
unsigned SISubtarget::getMaxNumVGPRs(const MachineFunction &MF) const {
const Function &F = *MF.getFunction();
const SIMachineFunctionInfo &MFI = *MF.getInfo<SIMachineFunctionInfo>();
// Compute maximum number of VGPRs function can use using default/requested
// minimum number of waves per execution unit.
std::pair<unsigned, unsigned> WavesPerEU = MFI.getWavesPerEU();
unsigned MaxNumVGPRs = getMaxNumVGPRs(WavesPerEU.first);
// Check if maximum number of VGPRs was explicitly requested using
// "amdgpu-num-vgpr" attribute.
if (F.hasFnAttribute("amdgpu-num-vgpr")) {
unsigned Requested = AMDGPU::getIntegerAttribute(
F, "amdgpu-num-vgpr", MaxNumVGPRs);
// Make sure requested value does not violate subtarget's specifications.
if (Requested && Requested <= getReservedNumVGPRs(MF))
Requested = 0;
// Make sure requested value is compatible with values implied by
// default/requested minimum/maximum number of waves per execution unit.
if (Requested && Requested > getMaxNumVGPRs(WavesPerEU.first))
Requested = 0;
if (WavesPerEU.second &&
Requested && Requested < getMinNumVGPRs(WavesPerEU.second))
Requested = 0;
if (Requested)
MaxNumVGPRs = Requested;
}
return MaxNumVGPRs - getReservedNumVGPRs(MF);
}
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