//===----------------------- SIFrameLowering.cpp --------------------------===//
//
// 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
//
//==-----------------------------------------------------------------------===//
#include "SIFrameLowering.h"
#include "AMDGPU.h"
#include "GCNSubtarget.h"
#include "MCTargetDesc/AMDGPUMCTargetDesc.h"
#include "SIMachineFunctionInfo.h"
#include "llvm/CodeGen/LiveRegUnits.h"
#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/RegisterScavenging.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
#define DEBUG_TYPE "frame-info"
static cl::opt<bool> EnableSpillVGPRToAGPR(
"amdgpu-spill-vgpr-to-agpr",
cl::desc("Enable spilling VGPRs to AGPRs"),
cl::ReallyHidden,
cl::init(true));
// Find a register matching \p RC from \p LiveUnits which is unused and
// available throughout the function. On failure, returns AMDGPU::NoRegister.
// TODO: Rewrite the loop here to iterate over MCRegUnits instead of
// MCRegisters. This should reduce the number of iterations and avoid redundant
// checking.
static MCRegister findUnusedRegister(MachineRegisterInfo &MRI,
const LiveRegUnits &LiveUnits,
const TargetRegisterClass &RC) {
for (MCRegister Reg : RC) {
if (!MRI.isPhysRegUsed(Reg) && LiveUnits.available(Reg) &&
!MRI.isReserved(Reg))
return Reg;
}
return MCRegister();
}
// Find a scratch register that we can use in the prologue. We avoid using
// callee-save registers since they may appear to be free when this is called
// from canUseAsPrologue (during shrink wrapping), but then no longer be free
// when this is called from emitPrologue.
static MCRegister findScratchNonCalleeSaveRegister(
MachineRegisterInfo &MRI, LiveRegUnits &LiveUnits,
const TargetRegisterClass &RC, bool Unused = false) {
// Mark callee saved registers as used so we will not choose them.
const MCPhysReg *CSRegs = MRI.getCalleeSavedRegs();
for (unsigned i = 0; CSRegs[i]; ++i)
LiveUnits.addReg(CSRegs[i]);
// We are looking for a register that can be used throughout the entire
// function, so any use is unacceptable.
if (Unused)
return findUnusedRegister(MRI, LiveUnits, RC);
for (MCRegister Reg : RC) {
if (LiveUnits.available(Reg) && !MRI.isReserved(Reg))
return Reg;
}
return MCRegister();
}
/// Query target location for spilling SGPRs
/// \p IncludeScratchCopy : Also look for free scratch SGPRs
static void getVGPRSpillLaneOrTempRegister(
MachineFunction &MF, LiveRegUnits &LiveUnits, Register SGPR,
const TargetRegisterClass &RC = AMDGPU::SReg_32_XM0_XEXECRegClass,
bool IncludeScratchCopy = true) {
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
unsigned Size = TRI->getSpillSize(RC);
Align Alignment = TRI->getSpillAlign(RC);
// We need to save and restore the given SGPR.
Register ScratchSGPR;
// 1: Try to save the given register into an unused scratch SGPR. The
// LiveUnits should have all the callee saved registers marked as used. For
// certain cases we skip copy to scratch SGPR.
if (IncludeScratchCopy)
ScratchSGPR = findUnusedRegister(MF.getRegInfo(), LiveUnits, RC);
if (!ScratchSGPR) {
int FI = FrameInfo.CreateStackObject(Size, Alignment, true, nullptr,
TargetStackID::SGPRSpill);
if (TRI->spillSGPRToVGPR() &&
MFI->allocateSGPRSpillToVGPRLane(MF, FI, /*SpillToPhysVGPRLane=*/true,
/*IsPrologEpilog=*/true)) {
// 2: There's no free lane to spill, and no free register to save the
// SGPR, so we're forced to take another VGPR to use for the spill.
MFI->addToPrologEpilogSGPRSpills(
SGPR, PrologEpilogSGPRSaveRestoreInfo(
SGPRSaveKind::SPILL_TO_VGPR_LANE, FI));
LLVM_DEBUG(auto Spill = MFI->getSGPRSpillToPhysicalVGPRLanes(FI).front();
dbgs() << printReg(SGPR, TRI) << " requires fallback spill to "
<< printReg(Spill.VGPR, TRI) << ':' << Spill.Lane
<< '\n';);
} else {
// Remove dead <FI> index
MF.getFrameInfo().RemoveStackObject(FI);
// 3: If all else fails, spill the register to memory.
FI = FrameInfo.CreateSpillStackObject(Size, Alignment);
MFI->addToPrologEpilogSGPRSpills(
SGPR,
PrologEpilogSGPRSaveRestoreInfo(SGPRSaveKind::SPILL_TO_MEM, FI));
LLVM_DEBUG(dbgs() << "Reserved FI " << FI << " for spilling "
<< printReg(SGPR, TRI) << '\n');
}
} else {
MFI->addToPrologEpilogSGPRSpills(
SGPR, PrologEpilogSGPRSaveRestoreInfo(
SGPRSaveKind::COPY_TO_SCRATCH_SGPR, ScratchSGPR));
LiveUnits.addReg(ScratchSGPR);
LLVM_DEBUG(dbgs() << "Saving " << printReg(SGPR, TRI) << " with copy to "
<< printReg(ScratchSGPR, TRI) << '\n');
}
}
// We need to specially emit stack operations here because a different frame
// register is used than in the rest of the function, as getFrameRegister would
// use.
static void buildPrologSpill(const GCNSubtarget &ST, const SIRegisterInfo &TRI,
const SIMachineFunctionInfo &FuncInfo,
LiveRegUnits &LiveUnits, MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I, const DebugLoc &DL,
Register SpillReg, int FI, Register FrameReg,
int64_t DwordOff = 0) {
unsigned Opc = ST.enableFlatScratch() ? AMDGPU::SCRATCH_STORE_DWORD_SADDR
: AMDGPU::BUFFER_STORE_DWORD_OFFSET;
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
MachinePointerInfo PtrInfo = MachinePointerInfo::getFixedStack(MF, FI);
MachineMemOperand *MMO = MF.getMachineMemOperand(
PtrInfo, MachineMemOperand::MOStore, FrameInfo.getObjectSize(FI),
FrameInfo.getObjectAlign(FI));
LiveUnits.addReg(SpillReg);
bool IsKill = !MBB.isLiveIn(SpillReg);
TRI.buildSpillLoadStore(MBB, I, DL, Opc, FI, SpillReg, IsKill, FrameReg,
DwordOff, MMO, nullptr, &LiveUnits);
if (IsKill)
LiveUnits.removeReg(SpillReg);
}
static void buildEpilogRestore(const GCNSubtarget &ST,
const SIRegisterInfo &TRI,
const SIMachineFunctionInfo &FuncInfo,
LiveRegUnits &LiveUnits, MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I,
const DebugLoc &DL, Register SpillReg, int FI,
Register FrameReg, int64_t DwordOff = 0) {
unsigned Opc = ST.enableFlatScratch() ? AMDGPU::SCRATCH_LOAD_DWORD_SADDR
: AMDGPU::BUFFER_LOAD_DWORD_OFFSET;
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
MachinePointerInfo PtrInfo = MachinePointerInfo::getFixedStack(MF, FI);
MachineMemOperand *MMO = MF.getMachineMemOperand(
PtrInfo, MachineMemOperand::MOLoad, FrameInfo.getObjectSize(FI),
FrameInfo.getObjectAlign(FI));
TRI.buildSpillLoadStore(MBB, I, DL, Opc, FI, SpillReg, false, FrameReg,
DwordOff, MMO, nullptr, &LiveUnits);
}
static void buildGitPtr(MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
const DebugLoc &DL, const SIInstrInfo *TII,
Register TargetReg) {
MachineFunction *MF = MBB.getParent();
const SIMachineFunctionInfo *MFI = MF->getInfo<SIMachineFunctionInfo>();
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32);
Register TargetLo = TRI->getSubReg(TargetReg, AMDGPU::sub0);
Register TargetHi = TRI->getSubReg(TargetReg, AMDGPU::sub1);
if (MFI->getGITPtrHigh() != 0xffffffff) {
BuildMI(MBB, I, DL, SMovB32, TargetHi)
.addImm(MFI->getGITPtrHigh())
.addReg(TargetReg, RegState::ImplicitDefine);
} else {
const MCInstrDesc &GetPC64 = TII->get(AMDGPU::S_GETPC_B64_pseudo);
BuildMI(MBB, I, DL, GetPC64, TargetReg);
}
Register GitPtrLo = MFI->getGITPtrLoReg(*MF);
MF->getRegInfo().addLiveIn(GitPtrLo);
MBB.addLiveIn(GitPtrLo);
BuildMI(MBB, I, DL, SMovB32, TargetLo)
.addReg(GitPtrLo);
}
static void initLiveUnits(LiveRegUnits &LiveUnits, const SIRegisterInfo &TRI,
const SIMachineFunctionInfo *FuncInfo,
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI, bool IsProlog) {
if (LiveUnits.empty()) {
LiveUnits.init(TRI);
if (IsProlog) {
LiveUnits.addLiveIns(MBB);
} else {
// In epilog.
LiveUnits.addLiveOuts(MBB);
LiveUnits.stepBackward(*MBBI);
}
}
}
namespace llvm {
// SpillBuilder to save/restore special SGPR spills like the one needed for FP,
// BP, etc. These spills are delayed until the current function's frame is
// finalized. For a given register, the builder uses the
// PrologEpilogSGPRSaveRestoreInfo to decide the spill method.
class PrologEpilogSGPRSpillBuilder {
MachineBasicBlock::iterator MI;
MachineBasicBlock &MBB;
MachineFunction &MF;
const GCNSubtarget &ST;
MachineFrameInfo &MFI;
SIMachineFunctionInfo *FuncInfo;
const SIInstrInfo *TII;
const SIRegisterInfo &TRI;
Register SuperReg;
const PrologEpilogSGPRSaveRestoreInfo SI;
LiveRegUnits &LiveUnits;
const DebugLoc &DL;
Register FrameReg;
ArrayRef<int16_t> SplitParts;
unsigned NumSubRegs;
unsigned EltSize = 4;
void saveToMemory(const int FI) const {
MachineRegisterInfo &MRI = MF.getRegInfo();
assert(!MFI.isDeadObjectIndex(FI));
initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MI, /*IsProlog*/ true);
MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister(
MRI, LiveUnits, AMDGPU::VGPR_32RegClass);
if (!TmpVGPR)
report_fatal_error("failed to find free scratch register");
for (unsigned I = 0, DwordOff = 0; I < NumSubRegs; ++I) {
Register SubReg = NumSubRegs == 1
? SuperReg
: Register(TRI.getSubReg(SuperReg, SplitParts[I]));
BuildMI(MBB, MI, DL, TII->get(AMDGPU::V_MOV_B32_e32), TmpVGPR)
.addReg(SubReg);
buildPrologSpill(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MI, DL, TmpVGPR,
FI, FrameReg, DwordOff);
DwordOff += 4;
}
}
void saveToVGPRLane(const int FI) const {
assert(!MFI.isDeadObjectIndex(FI));
assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill);
ArrayRef<SIRegisterInfo::SpilledReg> Spill =
FuncInfo->getSGPRSpillToPhysicalVGPRLanes(FI);
assert(Spill.size() == NumSubRegs);
for (unsigned I = 0; I < NumSubRegs; ++I) {
Register SubReg = NumSubRegs == 1
? SuperReg
: Register(TRI.getSubReg(SuperReg, SplitParts[I]));
BuildMI(MBB, MI, DL, TII->get(AMDGPU::SI_SPILL_S32_TO_VGPR),
Spill[I].VGPR)
.addReg(SubReg)
.addImm(Spill[I].Lane)
.addReg(Spill[I].VGPR, RegState::Undef);
}
}
void copyToScratchSGPR(Register DstReg) const {
BuildMI(MBB, MI, DL, TII->get(AMDGPU::COPY), DstReg)
.addReg(SuperReg)
.setMIFlag(MachineInstr::FrameSetup);
}
void restoreFromMemory(const int FI) {
MachineRegisterInfo &MRI = MF.getRegInfo();
initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MI, /*IsProlog*/ false);
MCPhysReg TmpVGPR = findScratchNonCalleeSaveRegister(
MRI, LiveUnits, AMDGPU::VGPR_32RegClass);
if (!TmpVGPR)
report_fatal_error("failed to find free scratch register");
for (unsigned I = 0, DwordOff = 0; I < NumSubRegs; ++I) {
Register SubReg = NumSubRegs == 1
? SuperReg
: Register(TRI.getSubReg(SuperReg, SplitParts[I]));
buildEpilogRestore(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MI, DL,
TmpVGPR, FI, FrameReg, DwordOff);
BuildMI(MBB, MI, DL, TII->get(AMDGPU::V_READFIRSTLANE_B32), SubReg)
.addReg(TmpVGPR, RegState::Kill);
DwordOff += 4;
}
}
void restoreFromVGPRLane(const int FI) {
assert(MFI.getStackID(FI) == TargetStackID::SGPRSpill);
ArrayRef<SIRegisterInfo::SpilledReg> Spill =
FuncInfo->getSGPRSpillToPhysicalVGPRLanes(FI);
assert(Spill.size() == NumSubRegs);
for (unsigned I = 0; I < NumSubRegs; ++I) {
Register SubReg = NumSubRegs == 1
? SuperReg
: Register(TRI.getSubReg(SuperReg, SplitParts[I]));
BuildMI(MBB, MI, DL, TII->get(AMDGPU::SI_RESTORE_S32_FROM_VGPR), SubReg)
.addReg(Spill[I].VGPR)
.addImm(Spill[I].Lane);
}
}
void copyFromScratchSGPR(Register SrcReg) const {
BuildMI(MBB, MI, DL, TII->get(AMDGPU::COPY), SuperReg)
.addReg(SrcReg)
.setMIFlag(MachineInstr::FrameDestroy);
}
public:
PrologEpilogSGPRSpillBuilder(Register Reg,
const PrologEpilogSGPRSaveRestoreInfo SI,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MI,
const DebugLoc &DL, const SIInstrInfo *TII,
const SIRegisterInfo &TRI,
LiveRegUnits &LiveUnits, Register FrameReg)
: MI(MI), MBB(MBB), MF(*MBB.getParent()),
ST(MF.getSubtarget<GCNSubtarget>()), MFI(MF.getFrameInfo()),
FuncInfo(MF.getInfo<SIMachineFunctionInfo>()), TII(TII), TRI(TRI),
SuperReg(Reg), SI(SI), LiveUnits(LiveUnits), DL(DL),
FrameReg(FrameReg) {
const TargetRegisterClass *RC = TRI.getPhysRegBaseClass(SuperReg);
SplitParts = TRI.getRegSplitParts(RC, EltSize);
NumSubRegs = SplitParts.empty() ? 1 : SplitParts.size();
assert(SuperReg != AMDGPU::M0 && "m0 should never spill");
}
void save() {
switch (SI.getKind()) {
case SGPRSaveKind::SPILL_TO_MEM:
return saveToMemory(SI.getIndex());
case SGPRSaveKind::SPILL_TO_VGPR_LANE:
return saveToVGPRLane(SI.getIndex());
case SGPRSaveKind::COPY_TO_SCRATCH_SGPR:
return copyToScratchSGPR(SI.getReg());
}
}
void restore() {
switch (SI.getKind()) {
case SGPRSaveKind::SPILL_TO_MEM:
return restoreFromMemory(SI.getIndex());
case SGPRSaveKind::SPILL_TO_VGPR_LANE:
return restoreFromVGPRLane(SI.getIndex());
case SGPRSaveKind::COPY_TO_SCRATCH_SGPR:
return copyFromScratchSGPR(SI.getReg());
}
}
};
} // namespace llvm
// Emit flat scratch setup code, assuming `MFI->hasFlatScratchInit()`
void SIFrameLowering::emitEntryFunctionFlatScratchInit(
MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
const DebugLoc &DL, Register ScratchWaveOffsetReg) const {
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
// We don't need this if we only have spills since there is no user facing
// scratch.
// TODO: If we know we don't have flat instructions earlier, we can omit
// this from the input registers.
//
// TODO: We only need to know if we access scratch space through a flat
// pointer. Because we only detect if flat instructions are used at all,
// this will be used more often than necessary on VI.
Register FlatScrInitLo;
Register FlatScrInitHi;
if (ST.isAmdPalOS()) {
// Extract the scratch offset from the descriptor in the GIT
LiveRegUnits LiveUnits;
LiveUnits.init(*TRI);
LiveUnits.addLiveIns(MBB);
// Find unused reg to load flat scratch init into
MachineRegisterInfo &MRI = MF.getRegInfo();
Register FlatScrInit = AMDGPU::NoRegister;
ArrayRef<MCPhysReg> AllSGPR64s = TRI->getAllSGPR64(MF);
unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 1) / 2;
AllSGPR64s = AllSGPR64s.slice(
std::min(static_cast<unsigned>(AllSGPR64s.size()), NumPreloaded));
Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
for (MCPhysReg Reg : AllSGPR64s) {
if (LiveUnits.available(Reg) && !MRI.isReserved(Reg) &&
MRI.isAllocatable(Reg) && !TRI->isSubRegisterEq(Reg, GITPtrLoReg)) {
FlatScrInit = Reg;
break;
}
}
assert(FlatScrInit && "Failed to find free register for scratch init");
FlatScrInitLo = TRI->getSubReg(FlatScrInit, AMDGPU::sub0);
FlatScrInitHi = TRI->getSubReg(FlatScrInit, AMDGPU::sub1);
buildGitPtr(MBB, I, DL, TII, FlatScrInit);
// We now have the GIT ptr - now get the scratch descriptor from the entry
// at offset 0 (or offset 16 for a compute shader).
MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM);
auto *MMO = MF.getMachineMemOperand(
PtrInfo,
MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
MachineMemOperand::MODereferenceable,
8, Align(4));
unsigned Offset =
MF.getFunction().getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0;
const GCNSubtarget &Subtarget = MF.getSubtarget<GCNSubtarget>();
unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset);
BuildMI(MBB, I, DL, LoadDwordX2, FlatScrInit)
.addReg(FlatScrInit)
.addImm(EncodedOffset) // offset
.addImm(0) // cpol
.addMemOperand(MMO);
// Mask the offset in [47:0] of the descriptor
const MCInstrDesc &SAndB32 = TII->get(AMDGPU::S_AND_B32);
auto And = BuildMI(MBB, I, DL, SAndB32, FlatScrInitHi)
.addReg(FlatScrInitHi)
.addImm(0xffff);
And->getOperand(3).setIsDead(); // Mark SCC as dead.
} else {
Register FlatScratchInitReg =
MFI->getPreloadedReg(AMDGPUFunctionArgInfo::FLAT_SCRATCH_INIT);
assert(FlatScratchInitReg);
MachineRegisterInfo &MRI = MF.getRegInfo();
MRI.addLiveIn(FlatScratchInitReg);
MBB.addLiveIn(FlatScratchInitReg);
FlatScrInitLo = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub0);
FlatScrInitHi = TRI->getSubReg(FlatScratchInitReg, AMDGPU::sub1);
}
// Do a 64-bit pointer add.
if (ST.flatScratchIsPointer()) {
if (ST.getGeneration() >= AMDGPUSubtarget::GFX10) {
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), FlatScrInitLo)
.addReg(FlatScrInitLo)
.addReg(ScratchWaveOffsetReg);
auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32),
FlatScrInitHi)
.addReg(FlatScrInitHi)
.addImm(0);
Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)).
addReg(FlatScrInitLo).
addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_LO |
(31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_)));
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_SETREG_B32)).
addReg(FlatScrInitHi).
addImm(int16_t(AMDGPU::Hwreg::ID_FLAT_SCR_HI |
(31 << AMDGPU::Hwreg::WIDTH_M1_SHIFT_)));
return;
}
// For GFX9.
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), AMDGPU::FLAT_SCR_LO)
.addReg(FlatScrInitLo)
.addReg(ScratchWaveOffsetReg);
auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32),
AMDGPU::FLAT_SCR_HI)
.addReg(FlatScrInitHi)
.addImm(0);
Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
return;
}
assert(ST.getGeneration() < AMDGPUSubtarget::GFX9);
// Copy the size in bytes.
BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), AMDGPU::FLAT_SCR_LO)
.addReg(FlatScrInitHi, RegState::Kill);
// Add wave offset in bytes to private base offset.
// See comment in AMDKernelCodeT.h for enable_sgpr_flat_scratch_init.
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_I32), FlatScrInitLo)
.addReg(FlatScrInitLo)
.addReg(ScratchWaveOffsetReg);
// Convert offset to 256-byte units.
auto LShr = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_LSHR_B32),
AMDGPU::FLAT_SCR_HI)
.addReg(FlatScrInitLo, RegState::Kill)
.addImm(8);
LShr->getOperand(3).setIsDead(); // Mark SCC as dead.
}
// Note SGPRSpill stack IDs should only be used for SGPR spilling to VGPRs, not
// memory. They should have been removed by now.
static bool allStackObjectsAreDead(const MachineFrameInfo &MFI) {
for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd();
I != E; ++I) {
if (!MFI.isDeadObjectIndex(I))
return false;
}
return true;
}
// Shift down registers reserved for the scratch RSRC.
Register SIFrameLowering::getEntryFunctionReservedScratchRsrcReg(
MachineFunction &MF) const {
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
assert(MFI->isEntryFunction());
Register ScratchRsrcReg = MFI->getScratchRSrcReg();
if (!ScratchRsrcReg || (!MRI.isPhysRegUsed(ScratchRsrcReg) &&
allStackObjectsAreDead(MF.getFrameInfo())))
return Register();
if (ST.hasSGPRInitBug() ||
ScratchRsrcReg != TRI->reservedPrivateSegmentBufferReg(MF))
return ScratchRsrcReg;
// We reserved the last registers for this. Shift it down to the end of those
// which were actually used.
//
// FIXME: It might be safer to use a pseudoregister before replacement.
// FIXME: We should be able to eliminate unused input registers. We only
// cannot do this for the resources required for scratch access. For now we
// skip over user SGPRs and may leave unused holes.
unsigned NumPreloaded = (MFI->getNumPreloadedSGPRs() + 3) / 4;
ArrayRef<MCPhysReg> AllSGPR128s = TRI->getAllSGPR128(MF);
AllSGPR128s = AllSGPR128s.slice(std::min(static_cast<unsigned>(AllSGPR128s.size()), NumPreloaded));
// Skip the last N reserved elements because they should have already been
// reserved for VCC etc.
Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
for (MCPhysReg Reg : AllSGPR128s) {
// Pick the first unallocated one. Make sure we don't clobber the other
// reserved input we needed. Also for PAL, make sure we don't clobber
// the GIT pointer passed in SGPR0 or SGPR8.
if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) &&
(!GITPtrLoReg || !TRI->isSubRegisterEq(Reg, GITPtrLoReg))) {
MRI.replaceRegWith(ScratchRsrcReg, Reg);
MFI->setScratchRSrcReg(Reg);
return Reg;
}
}
return ScratchRsrcReg;
}
static unsigned getScratchScaleFactor(const GCNSubtarget &ST) {
return ST.enableFlatScratch() ? 1 : ST.getWavefrontSize();
}
void SIFrameLowering::emitEntryFunctionPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
assert(&MF.front() == &MBB && "Shrink-wrapping not yet supported");
// FIXME: If we only have SGPR spills, we won't actually be using scratch
// memory since these spill to VGPRs. We should be cleaning up these unused
// SGPR spill frame indices somewhere.
// FIXME: We still have implicit uses on SGPR spill instructions in case they
// need to spill to vector memory. It's likely that will not happen, but at
// this point it appears we need the setup. This part of the prolog should be
// emitted after frame indices are eliminated.
// FIXME: Remove all of the isPhysRegUsed checks
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
const Function &F = MF.getFunction();
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
assert(MFI->isEntryFunction());
Register PreloadedScratchWaveOffsetReg = MFI->getPreloadedReg(
AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_WAVE_BYTE_OFFSET);
// We need to do the replacement of the private segment buffer register even
// if there are no stack objects. There could be stores to undef or a
// constant without an associated object.
//
// This will return `Register()` in cases where there are no actual
// uses of the SRSRC.
Register ScratchRsrcReg;
if (!ST.enableFlatScratch())
ScratchRsrcReg = getEntryFunctionReservedScratchRsrcReg(MF);
// Make the selected register live throughout the function.
if (ScratchRsrcReg) {
for (MachineBasicBlock &OtherBB : MF) {
if (&OtherBB != &MBB) {
OtherBB.addLiveIn(ScratchRsrcReg);
}
}
}
// Now that we have fixed the reserved SRSRC we need to locate the
// (potentially) preloaded SRSRC.
Register PreloadedScratchRsrcReg;
if (ST.isAmdHsaOrMesa(F)) {
PreloadedScratchRsrcReg =
MFI->getPreloadedReg(AMDGPUFunctionArgInfo::PRIVATE_SEGMENT_BUFFER);
if (ScratchRsrcReg && PreloadedScratchRsrcReg) {
// We added live-ins during argument lowering, but since they were not
// used they were deleted. We're adding the uses now, so add them back.
MRI.addLiveIn(PreloadedScratchRsrcReg);
MBB.addLiveIn(PreloadedScratchRsrcReg);
}
}
// Debug location must be unknown since the first debug location is used to
// determine the end of the prologue.
DebugLoc DL;
MachineBasicBlock::iterator I = MBB.begin();
// We found the SRSRC first because it needs four registers and has an
// alignment requirement. If the SRSRC that we found is clobbering with
// the scratch wave offset, which may be in a fixed SGPR or a free SGPR
// chosen by SITargetLowering::allocateSystemSGPRs, COPY the scratch
// wave offset to a free SGPR.
Register ScratchWaveOffsetReg;
if (PreloadedScratchWaveOffsetReg &&
TRI->isSubRegisterEq(ScratchRsrcReg, PreloadedScratchWaveOffsetReg)) {
ArrayRef<MCPhysReg> AllSGPRs = TRI->getAllSGPR32(MF);
unsigned NumPreloaded = MFI->getNumPreloadedSGPRs();
AllSGPRs = AllSGPRs.slice(
std::min(static_cast<unsigned>(AllSGPRs.size()), NumPreloaded));
Register GITPtrLoReg = MFI->getGITPtrLoReg(MF);
for (MCPhysReg Reg : AllSGPRs) {
if (!MRI.isPhysRegUsed(Reg) && MRI.isAllocatable(Reg) &&
!TRI->isSubRegisterEq(ScratchRsrcReg, Reg) && GITPtrLoReg != Reg) {
ScratchWaveOffsetReg = Reg;
BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchWaveOffsetReg)
.addReg(PreloadedScratchWaveOffsetReg, RegState::Kill);
break;
}
}
} else {
ScratchWaveOffsetReg = PreloadedScratchWaveOffsetReg;
}
assert(ScratchWaveOffsetReg || !PreloadedScratchWaveOffsetReg);
if (requiresStackPointerReference(MF)) {
Register SPReg = MFI->getStackPtrOffsetReg();
assert(SPReg != AMDGPU::SP_REG);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), SPReg)
.addImm(FrameInfo.getStackSize() * getScratchScaleFactor(ST));
}
if (hasFP(MF)) {
Register FPReg = MFI->getFrameOffsetReg();
assert(FPReg != AMDGPU::FP_REG);
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_MOV_B32), FPReg).addImm(0);
}
bool NeedsFlatScratchInit =
MFI->getUserSGPRInfo().hasFlatScratchInit() &&
(MRI.isPhysRegUsed(AMDGPU::FLAT_SCR) || FrameInfo.hasCalls() ||
(!allStackObjectsAreDead(FrameInfo) && ST.enableFlatScratch()));
if ((NeedsFlatScratchInit || ScratchRsrcReg) &&
PreloadedScratchWaveOffsetReg && !ST.flatScratchIsArchitected()) {
MRI.addLiveIn(PreloadedScratchWaveOffsetReg);
MBB.addLiveIn(PreloadedScratchWaveOffsetReg);
}
if (NeedsFlatScratchInit) {
emitEntryFunctionFlatScratchInit(MF, MBB, I, DL, ScratchWaveOffsetReg);
}
if (ScratchRsrcReg) {
emitEntryFunctionScratchRsrcRegSetup(MF, MBB, I, DL,
PreloadedScratchRsrcReg,
ScratchRsrcReg, ScratchWaveOffsetReg);
}
}
// Emit scratch RSRC setup code, assuming `ScratchRsrcReg != AMDGPU::NoReg`
void SIFrameLowering::emitEntryFunctionScratchRsrcRegSetup(
MachineFunction &MF, MachineBasicBlock &MBB, MachineBasicBlock::iterator I,
const DebugLoc &DL, Register PreloadedScratchRsrcReg,
Register ScratchRsrcReg, Register ScratchWaveOffsetReg) const {
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = &TII->getRegisterInfo();
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
const Function &Fn = MF.getFunction();
if (ST.isAmdPalOS()) {
// The pointer to the GIT is formed from the offset passed in and either
// the amdgpu-git-ptr-high function attribute or the top part of the PC
Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1);
Register Rsrc03 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
buildGitPtr(MBB, I, DL, TII, Rsrc01);
// We now have the GIT ptr - now get the scratch descriptor from the entry
// at offset 0 (or offset 16 for a compute shader).
MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
const MCInstrDesc &LoadDwordX4 = TII->get(AMDGPU::S_LOAD_DWORDX4_IMM);
auto MMO = MF.getMachineMemOperand(PtrInfo,
MachineMemOperand::MOLoad |
MachineMemOperand::MOInvariant |
MachineMemOperand::MODereferenceable,
16, Align(4));
unsigned Offset = Fn.getCallingConv() == CallingConv::AMDGPU_CS ? 16 : 0;
const GCNSubtarget &Subtarget = MF.getSubtarget<GCNSubtarget>();
unsigned EncodedOffset = AMDGPU::convertSMRDOffsetUnits(Subtarget, Offset);
BuildMI(MBB, I, DL, LoadDwordX4, ScratchRsrcReg)
.addReg(Rsrc01)
.addImm(EncodedOffset) // offset
.addImm(0) // cpol
.addReg(ScratchRsrcReg, RegState::ImplicitDefine)
.addMemOperand(MMO);
// The driver will always set the SRD for wave 64 (bits 118:117 of
// descriptor / bits 22:21 of third sub-reg will be 0b11)
// If the shader is actually wave32 we have to modify the const_index_stride
// field of the descriptor 3rd sub-reg (bits 22:21) to 0b10 (stride=32). The
// reason the driver does this is that there can be cases where it presents
// 2 shaders with different wave size (e.g. VsFs).
// TODO: convert to using SCRATCH instructions or multiple SRD buffers
if (ST.isWave32()) {
const MCInstrDesc &SBitsetB32 = TII->get(AMDGPU::S_BITSET0_B32);
BuildMI(MBB, I, DL, SBitsetB32, Rsrc03)
.addImm(21)
.addReg(Rsrc03);
}
} else if (ST.isMesaGfxShader(Fn) || !PreloadedScratchRsrcReg) {
assert(!ST.isAmdHsaOrMesa(Fn));
const MCInstrDesc &SMovB32 = TII->get(AMDGPU::S_MOV_B32);
Register Rsrc2 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub2);
Register Rsrc3 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub3);
// Use relocations to get the pointer, and setup the other bits manually.
uint64_t Rsrc23 = TII->getScratchRsrcWords23();
if (MFI->getUserSGPRInfo().hasImplicitBufferPtr()) {
Register Rsrc01 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0_sub1);
if (AMDGPU::isCompute(MF.getFunction().getCallingConv())) {
const MCInstrDesc &Mov64 = TII->get(AMDGPU::S_MOV_B64);
BuildMI(MBB, I, DL, Mov64, Rsrc01)
.addReg(MFI->getImplicitBufferPtrUserSGPR())
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
} else {
const MCInstrDesc &LoadDwordX2 = TII->get(AMDGPU::S_LOAD_DWORDX2_IMM);
MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
auto MMO = MF.getMachineMemOperand(
PtrInfo,
MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant |
MachineMemOperand::MODereferenceable,
8, Align(4));
BuildMI(MBB, I, DL, LoadDwordX2, Rsrc01)
.addReg(MFI->getImplicitBufferPtrUserSGPR())
.addImm(0) // offset
.addImm(0) // cpol
.addMemOperand(MMO)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
MF.getRegInfo().addLiveIn(MFI->getImplicitBufferPtrUserSGPR());
MBB.addLiveIn(MFI->getImplicitBufferPtrUserSGPR());
}
} else {
Register Rsrc0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
Register Rsrc1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
BuildMI(MBB, I, DL, SMovB32, Rsrc0)
.addExternalSymbol("SCRATCH_RSRC_DWORD0")
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
BuildMI(MBB, I, DL, SMovB32, Rsrc1)
.addExternalSymbol("SCRATCH_RSRC_DWORD1")
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
}
BuildMI(MBB, I, DL, SMovB32, Rsrc2)
.addImm(Rsrc23 & 0xffffffff)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
BuildMI(MBB, I, DL, SMovB32, Rsrc3)
.addImm(Rsrc23 >> 32)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
} else if (ST.isAmdHsaOrMesa(Fn)) {
assert(PreloadedScratchRsrcReg);
if (ScratchRsrcReg != PreloadedScratchRsrcReg) {
BuildMI(MBB, I, DL, TII->get(AMDGPU::COPY), ScratchRsrcReg)
.addReg(PreloadedScratchRsrcReg, RegState::Kill);
}
}
// Add the scratch wave offset into the scratch RSRC.
//
// We only want to update the first 48 bits, which is the base address
// pointer, without touching the adjacent 16 bits of flags. We know this add
// cannot carry-out from bit 47, otherwise the scratch allocation would be
// impossible to fit in the 48-bit global address space.
//
// TODO: Evaluate if it is better to just construct an SRD using the flat
// scratch init and some constants rather than update the one we are passed.
Register ScratchRsrcSub0 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub0);
Register ScratchRsrcSub1 = TRI->getSubReg(ScratchRsrcReg, AMDGPU::sub1);
// We cannot Kill ScratchWaveOffsetReg here because we allow it to be used in
// the kernel body via inreg arguments.
BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_U32), ScratchRsrcSub0)
.addReg(ScratchRsrcSub0)
.addReg(ScratchWaveOffsetReg)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
auto Addc = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADDC_U32), ScratchRsrcSub1)
.addReg(ScratchRsrcSub1)
.addImm(0)
.addReg(ScratchRsrcReg, RegState::ImplicitDefine);
Addc->getOperand(3).setIsDead(); // Mark SCC as dead.
}
bool SIFrameLowering::isSupportedStackID(TargetStackID::Value ID) const {
switch (ID) {
case TargetStackID::Default:
case TargetStackID::NoAlloc:
case TargetStackID::SGPRSpill:
return true;
case TargetStackID::ScalableVector:
case TargetStackID::WasmLocal:
return false;
}
llvm_unreachable("Invalid TargetStackID::Value");
}
// Activate only the inactive lanes when \p EnableInactiveLanes is true.
// Otherwise, activate all lanes. It returns the saved exec.
static Register buildScratchExecCopy(LiveRegUnits &LiveUnits,
MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI,
const DebugLoc &DL, bool IsProlog,
bool EnableInactiveLanes) {
Register ScratchExecCopy;
MachineRegisterInfo &MRI = MF.getRegInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, IsProlog);
ScratchExecCopy = findScratchNonCalleeSaveRegister(
MRI, LiveUnits, *TRI.getWaveMaskRegClass());
if (!ScratchExecCopy)
report_fatal_error("failed to find free scratch register");
LiveUnits.addReg(ScratchExecCopy);
const unsigned SaveExecOpc =
ST.isWave32() ? (EnableInactiveLanes ? AMDGPU::S_XOR_SAVEEXEC_B32
: AMDGPU::S_OR_SAVEEXEC_B32)
: (EnableInactiveLanes ? AMDGPU::S_XOR_SAVEEXEC_B64
: AMDGPU::S_OR_SAVEEXEC_B64);
auto SaveExec =
BuildMI(MBB, MBBI, DL, TII->get(SaveExecOpc), ScratchExecCopy).addImm(-1);
SaveExec->getOperand(3).setIsDead(); // Mark SCC as dead.
return ScratchExecCopy;
}
void SIFrameLowering::emitCSRSpillStores(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI, DebugLoc &DL, LiveRegUnits &LiveUnits,
Register FrameReg, Register FramePtrRegScratchCopy) const {
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
// Spill Whole-Wave Mode VGPRs. Save only the inactive lanes of the scratch
// registers. However, save all lanes of callee-saved VGPRs. Due to this, we
// might end up flipping the EXEC bits twice.
Register ScratchExecCopy;
SmallVector<std::pair<Register, int>, 2> WWMCalleeSavedRegs, WWMScratchRegs;
FuncInfo->splitWWMSpillRegisters(MF, WWMCalleeSavedRegs, WWMScratchRegs);
if (!WWMScratchRegs.empty())
ScratchExecCopy =
buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
/*IsProlog*/ true, /*EnableInactiveLanes*/ true);
auto StoreWWMRegisters =
[&](SmallVectorImpl<std::pair<Register, int>> &WWMRegs) {
for (const auto &Reg : WWMRegs) {
Register VGPR = Reg.first;
int FI = Reg.second;
buildPrologSpill(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MBBI, DL,
VGPR, FI, FrameReg);
}
};
StoreWWMRegisters(WWMScratchRegs);
if (!WWMCalleeSavedRegs.empty()) {
if (ScratchExecCopy) {
unsigned MovOpc = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64;
BuildMI(MBB, MBBI, DL, TII->get(MovOpc), TRI.getExec()).addImm(-1);
} else {
ScratchExecCopy = buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
/*IsProlog*/ true,
/*EnableInactiveLanes*/ false);
}
}
StoreWWMRegisters(WWMCalleeSavedRegs);
if (ScratchExecCopy) {
// FIXME: Split block and make terminator.
unsigned ExecMov = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64;
BuildMI(MBB, MBBI, DL, TII->get(ExecMov), TRI.getExec())
.addReg(ScratchExecCopy, RegState::Kill);
LiveUnits.addReg(ScratchExecCopy);
}
Register FramePtrReg = FuncInfo->getFrameOffsetReg();
for (const auto &Spill : FuncInfo->getPrologEpilogSGPRSpills()) {
// Special handle FP spill:
// Skip if FP is saved to a scratch SGPR, the save has already been emitted.
// Otherwise, FP has been moved to a temporary register and spill it
// instead.
Register Reg =
Spill.first == FramePtrReg ? FramePtrRegScratchCopy : Spill.first;
if (!Reg)
continue;
PrologEpilogSGPRSpillBuilder SB(Reg, Spill.second, MBB, MBBI, DL, TII, TRI,
LiveUnits, FrameReg);
SB.save();
}
// If a copy to scratch SGPR has been chosen for any of the SGPR spills, make
// such scratch registers live throughout the function.
SmallVector<Register, 1> ScratchSGPRs;
FuncInfo->getAllScratchSGPRCopyDstRegs(ScratchSGPRs);
if (!ScratchSGPRs.empty()) {
for (MachineBasicBlock &MBB : MF) {
for (MCPhysReg Reg : ScratchSGPRs)
MBB.addLiveIn(Reg);
MBB.sortUniqueLiveIns();
}
if (!LiveUnits.empty()) {
for (MCPhysReg Reg : ScratchSGPRs)
LiveUnits.addReg(Reg);
}
}
}
void SIFrameLowering::emitCSRSpillRestores(
MachineFunction &MF, MachineBasicBlock &MBB,
MachineBasicBlock::iterator MBBI, DebugLoc &DL, LiveRegUnits &LiveUnits,
Register FrameReg, Register FramePtrRegScratchCopy) const {
const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
Register FramePtrReg = FuncInfo->getFrameOffsetReg();
for (const auto &Spill : FuncInfo->getPrologEpilogSGPRSpills()) {
// Special handle FP restore:
// Skip if FP needs to be restored from the scratch SGPR. Otherwise, restore
// the FP value to a temporary register. The frame pointer should be
// overwritten only at the end when all other spills are restored from
// current frame.
Register Reg =
Spill.first == FramePtrReg ? FramePtrRegScratchCopy : Spill.first;
if (!Reg)
continue;
PrologEpilogSGPRSpillBuilder SB(Reg, Spill.second, MBB, MBBI, DL, TII, TRI,
LiveUnits, FrameReg);
SB.restore();
}
// Restore Whole-Wave Mode VGPRs. Restore only the inactive lanes of the
// scratch registers. However, restore all lanes of callee-saved VGPRs. Due to
// this, we might end up flipping the EXEC bits twice.
Register ScratchExecCopy;
SmallVector<std::pair<Register, int>, 2> WWMCalleeSavedRegs, WWMScratchRegs;
FuncInfo->splitWWMSpillRegisters(MF, WWMCalleeSavedRegs, WWMScratchRegs);
if (!WWMScratchRegs.empty())
ScratchExecCopy =
buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
/*IsProlog*/ false, /*EnableInactiveLanes*/ true);
auto RestoreWWMRegisters =
[&](SmallVectorImpl<std::pair<Register, int>> &WWMRegs) {
for (const auto &Reg : WWMRegs) {
Register VGPR = Reg.first;
int FI = Reg.second;
buildEpilogRestore(ST, TRI, *FuncInfo, LiveUnits, MF, MBB, MBBI, DL,
VGPR, FI, FrameReg);
}
};
RestoreWWMRegisters(WWMScratchRegs);
if (!WWMCalleeSavedRegs.empty()) {
if (ScratchExecCopy) {
unsigned MovOpc = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64;
BuildMI(MBB, MBBI, DL, TII->get(MovOpc), TRI.getExec()).addImm(-1);
} else {
ScratchExecCopy = buildScratchExecCopy(LiveUnits, MF, MBB, MBBI, DL,
/*IsProlog*/ false,
/*EnableInactiveLanes*/ false);
}
}
RestoreWWMRegisters(WWMCalleeSavedRegs);
if (ScratchExecCopy) {
// FIXME: Split block and make terminator.
unsigned ExecMov = ST.isWave32() ? AMDGPU::S_MOV_B32 : AMDGPU::S_MOV_B64;
BuildMI(MBB, MBBI, DL, TII->get(ExecMov), TRI.getExec())
.addReg(ScratchExecCopy, RegState::Kill);
}
}
void SIFrameLowering::emitPrologue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
if (FuncInfo->isEntryFunction()) {
emitEntryFunctionPrologue(MF, MBB);
return;
}
MachineFrameInfo &MFI = MF.getFrameInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
Register StackPtrReg = FuncInfo->getStackPtrOffsetReg();
Register FramePtrReg = FuncInfo->getFrameOffsetReg();
Register BasePtrReg =
TRI.hasBasePointer(MF) ? TRI.getBaseRegister() : Register();
LiveRegUnits LiveUnits;
MachineBasicBlock::iterator MBBI = MBB.begin();
// DebugLoc must be unknown since the first instruction with DebugLoc is used
// to determine the end of the prologue.
DebugLoc DL;
if (FuncInfo->isChainFunction()) {
// Functions with the amdgpu_cs_chain[_preserve] CC don't receive a SP, but
// are free to set one up if they need it.
bool UseSP = requiresStackPointerReference(MF);
if (UseSP) {
assert(StackPtrReg != AMDGPU::SP_REG);
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_MOV_B32), StackPtrReg)
.addImm(MFI.getStackSize() * getScratchScaleFactor(ST));
}
}
bool HasFP = false;
bool HasBP = false;
uint32_t NumBytes = MFI.getStackSize();
uint32_t RoundedSize = NumBytes;
if (TRI.hasStackRealignment(MF))
HasFP = true;
Register FramePtrRegScratchCopy;
if (!HasFP && !hasFP(MF)) {
// Emit the CSR spill stores with SP base register.
emitCSRSpillStores(MF, MBB, MBBI, DL, LiveUnits,
FuncInfo->isChainFunction() ? Register() : StackPtrReg,
FramePtrRegScratchCopy);
} else {
// CSR spill stores will use FP as base register.
Register SGPRForFPSaveRestoreCopy =
FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, /*IsProlog*/ true);
if (SGPRForFPSaveRestoreCopy) {
// Copy FP to the scratch register now and emit the CFI entry. It avoids
// the extra FP copy needed in the other two cases when FP is spilled to
// memory or to a VGPR lane.
PrologEpilogSGPRSpillBuilder SB(
FramePtrReg,
FuncInfo->getPrologEpilogSGPRSaveRestoreInfo(FramePtrReg), MBB, MBBI,
DL, TII, TRI, LiveUnits, FramePtrReg);
SB.save();
LiveUnits.addReg(SGPRForFPSaveRestoreCopy);
} else {
// Copy FP into a new scratch register so that its previous value can be
// spilled after setting up the new frame.
FramePtrRegScratchCopy = findScratchNonCalleeSaveRegister(
MRI, LiveUnits, AMDGPU::SReg_32_XM0_XEXECRegClass);
if (!FramePtrRegScratchCopy)
report_fatal_error("failed to find free scratch register");
LiveUnits.addReg(FramePtrRegScratchCopy);
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrRegScratchCopy)
.addReg(FramePtrReg);
}
}
if (HasFP) {
const unsigned Alignment = MFI.getMaxAlign().value();
RoundedSize += Alignment;
if (LiveUnits.empty()) {
LiveUnits.init(TRI);
LiveUnits.addLiveIns(MBB);
}
// s_add_i32 s33, s32, NumBytes
// s_and_b32 s33, s33, 0b111...0000
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_I32), FramePtrReg)
.addReg(StackPtrReg)
.addImm((Alignment - 1) * getScratchScaleFactor(ST))
.setMIFlag(MachineInstr::FrameSetup);
auto And = BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_AND_B32), FramePtrReg)
.addReg(FramePtrReg, RegState::Kill)
.addImm(-Alignment * getScratchScaleFactor(ST))
.setMIFlag(MachineInstr::FrameSetup);
And->getOperand(3).setIsDead(); // Mark SCC as dead.
FuncInfo->setIsStackRealigned(true);
} else if ((HasFP = hasFP(MF))) {
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg)
.addReg(StackPtrReg)
.setMIFlag(MachineInstr::FrameSetup);
}
// If FP is used, emit the CSR spills with FP base register.
if (HasFP) {
emitCSRSpillStores(MF, MBB, MBBI, DL, LiveUnits, FramePtrReg,
FramePtrRegScratchCopy);
if (FramePtrRegScratchCopy)
LiveUnits.removeReg(FramePtrRegScratchCopy);
}
// If we need a base pointer, set it up here. It's whatever the value of
// the stack pointer is at this point. Any variable size objects will be
// allocated after this, so we can still use the base pointer to reference
// the incoming arguments.
if ((HasBP = TRI.hasBasePointer(MF))) {
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), BasePtrReg)
.addReg(StackPtrReg)
.setMIFlag(MachineInstr::FrameSetup);
}
if (HasFP && RoundedSize != 0) {
auto Add = BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_I32), StackPtrReg)
.addReg(StackPtrReg)
.addImm(RoundedSize * getScratchScaleFactor(ST))
.setMIFlag(MachineInstr::FrameSetup);
Add->getOperand(3).setIsDead(); // Mark SCC as dead.
}
bool FPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(FramePtrReg);
(void)FPSaved;
assert((!HasFP || FPSaved) &&
"Needed to save FP but didn't save it anywhere");
// If we allow spilling to AGPRs we may have saved FP but then spill
// everything into AGPRs instead of the stack.
assert((HasFP || !FPSaved || EnableSpillVGPRToAGPR) &&
"Saved FP but didn't need it");
bool BPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(BasePtrReg);
(void)BPSaved;
assert((!HasBP || BPSaved) &&
"Needed to save BP but didn't save it anywhere");
assert((HasBP || !BPSaved) && "Saved BP but didn't need it");
}
void SIFrameLowering::emitEpilogue(MachineFunction &MF,
MachineBasicBlock &MBB) const {
const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
if (FuncInfo->isEntryFunction())
return;
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo &TRI = TII->getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
LiveRegUnits LiveUnits;
// Get the insert location for the epilogue. If there were no terminators in
// the block, get the last instruction.
MachineBasicBlock::iterator MBBI = MBB.end();
DebugLoc DL;
if (!MBB.empty()) {
MBBI = MBB.getLastNonDebugInstr();
if (MBBI != MBB.end())
DL = MBBI->getDebugLoc();
MBBI = MBB.getFirstTerminator();
}
const MachineFrameInfo &MFI = MF.getFrameInfo();
uint32_t NumBytes = MFI.getStackSize();
uint32_t RoundedSize = FuncInfo->isStackRealigned()
? NumBytes + MFI.getMaxAlign().value()
: NumBytes;
const Register StackPtrReg = FuncInfo->getStackPtrOffsetReg();
Register FramePtrReg = FuncInfo->getFrameOffsetReg();
bool FPSaved = FuncInfo->hasPrologEpilogSGPRSpillEntry(FramePtrReg);
Register FramePtrRegScratchCopy;
Register SGPRForFPSaveRestoreCopy =
FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
if (FPSaved) {
// CSR spill restores should use FP as base register. If
// SGPRForFPSaveRestoreCopy is not true, restore the previous value of FP
// into a new scratch register and copy to FP later when other registers are
// restored from the current stack frame.
initLiveUnits(LiveUnits, TRI, FuncInfo, MF, MBB, MBBI, /*IsProlog*/ false);
if (SGPRForFPSaveRestoreCopy) {
LiveUnits.addReg(SGPRForFPSaveRestoreCopy);
} else {
FramePtrRegScratchCopy = findScratchNonCalleeSaveRegister(
MRI, LiveUnits, AMDGPU::SReg_32_XM0_XEXECRegClass);
if (!FramePtrRegScratchCopy)
report_fatal_error("failed to find free scratch register");
LiveUnits.addReg(FramePtrRegScratchCopy);
}
emitCSRSpillRestores(MF, MBB, MBBI, DL, LiveUnits, FramePtrReg,
FramePtrRegScratchCopy);
}
if (RoundedSize != 0 && hasFP(MF)) {
auto Add = BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::S_ADD_I32), StackPtrReg)
.addReg(StackPtrReg)
.addImm(-static_cast<int64_t>(RoundedSize * getScratchScaleFactor(ST)))
.setMIFlag(MachineInstr::FrameDestroy);
Add->getOperand(3).setIsDead(); // Mark SCC as dead.
}
if (FPSaved) {
// Insert the copy to restore FP.
Register SrcReg = SGPRForFPSaveRestoreCopy ? SGPRForFPSaveRestoreCopy
: FramePtrRegScratchCopy;
MachineInstrBuilder MIB =
BuildMI(MBB, MBBI, DL, TII->get(AMDGPU::COPY), FramePtrReg)
.addReg(SrcReg);
if (SGPRForFPSaveRestoreCopy)
MIB.setMIFlag(MachineInstr::FrameDestroy);
} else {
// Insert the CSR spill restores with SP as the base register.
emitCSRSpillRestores(MF, MBB, MBBI, DL, LiveUnits, StackPtrReg,
FramePtrRegScratchCopy);
}
}
#ifndef NDEBUG
static bool allSGPRSpillsAreDead(const MachineFunction &MF) {
const MachineFrameInfo &MFI = MF.getFrameInfo();
const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
for (int I = MFI.getObjectIndexBegin(), E = MFI.getObjectIndexEnd();
I != E; ++I) {
if (!MFI.isDeadObjectIndex(I) &&
MFI.getStackID(I) == TargetStackID::SGPRSpill &&
!FuncInfo->checkIndexInPrologEpilogSGPRSpills(I)) {
return false;
}
}
return true;
}
#endif
StackOffset SIFrameLowering::getFrameIndexReference(const MachineFunction &MF,
int FI,
Register &FrameReg) const {
const SIRegisterInfo *RI = MF.getSubtarget<GCNSubtarget>().getRegisterInfo();
FrameReg = RI->getFrameRegister(MF);
return StackOffset::getFixed(MF.getFrameInfo().getObjectOffset(FI));
}
void SIFrameLowering::processFunctionBeforeFrameFinalized(
MachineFunction &MF,
RegScavenger *RS) const {
MachineFrameInfo &MFI = MF.getFrameInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
// Allocate spill slots for WWM reserved VGPRs.
// For chain functions, we only need to do this if we have calls to
// llvm.amdgcn.cs.chain.
bool IsChainWithoutCalls =
FuncInfo->isChainFunction() && !MF.getFrameInfo().hasTailCall();
if (!FuncInfo->isEntryFunction() && !IsChainWithoutCalls) {
for (Register Reg : FuncInfo->getWWMReservedRegs()) {
const TargetRegisterClass *RC = TRI->getPhysRegBaseClass(Reg);
FuncInfo->allocateWWMSpill(MF, Reg, TRI->getSpillSize(*RC),
TRI->getSpillAlign(*RC));
}
}
const bool SpillVGPRToAGPR = ST.hasMAIInsts() && FuncInfo->hasSpilledVGPRs()
&& EnableSpillVGPRToAGPR;
if (SpillVGPRToAGPR) {
// To track the spill frame indices handled in this pass.
BitVector SpillFIs(MFI.getObjectIndexEnd(), false);
BitVector NonVGPRSpillFIs(MFI.getObjectIndexEnd(), false);
bool SeenDbgInstr = false;
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : llvm::make_early_inc_range(MBB)) {
int FrameIndex;
if (MI.isDebugInstr())
SeenDbgInstr = true;
if (TII->isVGPRSpill(MI)) {
// Try to eliminate stack used by VGPR spills before frame
// finalization.
unsigned FIOp = AMDGPU::getNamedOperandIdx(MI.getOpcode(),
AMDGPU::OpName::vaddr);
int FI = MI.getOperand(FIOp).getIndex();
Register VReg =
TII->getNamedOperand(MI, AMDGPU::OpName::vdata)->getReg();
if (FuncInfo->allocateVGPRSpillToAGPR(MF, FI,
TRI->isAGPR(MRI, VReg))) {
assert(RS != nullptr);
RS->enterBasicBlockEnd(MBB);
RS->backward(std::next(MI.getIterator()));
TRI->eliminateFrameIndex(MI, 0, FIOp, RS);
SpillFIs.set(FI);
continue;
}
} else if (TII->isStoreToStackSlot(MI, FrameIndex) ||
TII->isLoadFromStackSlot(MI, FrameIndex))
if (!MFI.isFixedObjectIndex(FrameIndex))
NonVGPRSpillFIs.set(FrameIndex);
}
}
// Stack slot coloring may assign different objects to the same stack slot.
// If not, then the VGPR to AGPR spill slot is dead.
for (unsigned FI : SpillFIs.set_bits())
if (!NonVGPRSpillFIs.test(FI))
FuncInfo->setVGPRToAGPRSpillDead(FI);
for (MachineBasicBlock &MBB : MF) {
for (MCPhysReg Reg : FuncInfo->getVGPRSpillAGPRs())
MBB.addLiveIn(Reg);
for (MCPhysReg Reg : FuncInfo->getAGPRSpillVGPRs())
MBB.addLiveIn(Reg);
MBB.sortUniqueLiveIns();
if (!SpillFIs.empty() && SeenDbgInstr) {
// FIXME: The dead frame indices are replaced with a null register from
// the debug value instructions. We should instead, update it with the
// correct register value. But not sure the register value alone is
for (MachineInstr &MI : MBB) {
if (MI.isDebugValue() && MI.getOperand(0).isFI() &&
!MFI.isFixedObjectIndex(MI.getOperand(0).getIndex()) &&
SpillFIs[MI.getOperand(0).getIndex()]) {
MI.getOperand(0).ChangeToRegister(Register(), false /*isDef*/);
}
}
}
}
}
// At this point we've already allocated all spilled SGPRs to VGPRs if we
// can. Any remaining SGPR spills will go to memory, so move them back to the
// default stack.
bool HaveSGPRToVMemSpill =
FuncInfo->removeDeadFrameIndices(MFI, /*ResetSGPRSpillStackIDs*/ true);
assert(allSGPRSpillsAreDead(MF) &&
"SGPR spill should have been removed in SILowerSGPRSpills");
// FIXME: The other checks should be redundant with allStackObjectsAreDead,
// but currently hasNonSpillStackObjects is set only from source
// allocas. Stack temps produced from legalization are not counted currently.
if (!allStackObjectsAreDead(MFI)) {
assert(RS && "RegScavenger required if spilling");
// Add an emergency spill slot
RS->addScavengingFrameIndex(FuncInfo->getScavengeFI(MFI, *TRI));
// If we are spilling SGPRs to memory with a large frame, we may need a
// second VGPR emergency frame index.
if (HaveSGPRToVMemSpill &&
allocateScavengingFrameIndexesNearIncomingSP(MF)) {
RS->addScavengingFrameIndex(MFI.CreateStackObject(4, Align(4), false));
}
}
}
void SIFrameLowering::processFunctionBeforeFrameIndicesReplaced(
MachineFunction &MF, RegScavenger *RS) const {
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
if (ST.hasMAIInsts() && !ST.hasGFX90AInsts()) {
// On gfx908, we had initially reserved highest available VGPR for AGPR
// copy. Now since we are done with RA, check if there exist an unused VGPR
// which is lower than the eariler reserved VGPR before RA. If one exist,
// use it for AGPR copy instead of one reserved before RA.
Register VGPRForAGPRCopy = FuncInfo->getVGPRForAGPRCopy();
Register UnusedLowVGPR =
TRI->findUnusedRegister(MRI, &AMDGPU::VGPR_32RegClass, MF);
if (UnusedLowVGPR && (TRI->getHWRegIndex(UnusedLowVGPR) <
TRI->getHWRegIndex(VGPRForAGPRCopy))) {
// Reserve this newly identified VGPR (for AGPR copy)
// reserved registers should already be frozen at this point
// so we can avoid calling MRI.freezeReservedRegs and just use
// MRI.reserveReg
FuncInfo->setVGPRForAGPRCopy(UnusedLowVGPR);
MRI.reserveReg(UnusedLowVGPR, TRI);
}
}
// We initally reserved the highest available SGPR pair for long branches
// now, after RA, we shift down to a lower unused one if one exists
Register LongBranchReservedReg = FuncInfo->getLongBranchReservedReg();
Register UnusedLowSGPR =
TRI->findUnusedRegister(MRI, &AMDGPU::SGPR_64RegClass, MF);
// If LongBranchReservedReg is null then we didn't find a long branch
// and never reserved a register to begin with so there is nothing to
// shift down. Then if UnusedLowSGPR is null, there isn't available lower
// register to use so just keep the original one we set.
if (LongBranchReservedReg && UnusedLowSGPR) {
FuncInfo->setLongBranchReservedReg(UnusedLowSGPR);
MRI.reserveReg(UnusedLowSGPR, TRI);
}
}
// The special SGPR spills like the one needed for FP, BP or any reserved
// registers delayed until frame lowering.
void SIFrameLowering::determinePrologEpilogSGPRSaves(
MachineFunction &MF, BitVector &SavedVGPRs,
bool NeedExecCopyReservedReg) const {
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
LiveRegUnits LiveUnits;
LiveUnits.init(*TRI);
// Initially mark callee saved registers as used so we will not choose them
// while looking for scratch SGPRs.
const MCPhysReg *CSRegs = MF.getRegInfo().getCalleeSavedRegs();
for (unsigned I = 0; CSRegs[I]; ++I)
LiveUnits.addReg(CSRegs[I]);
const TargetRegisterClass &RC = *TRI->getWaveMaskRegClass();
if (NeedExecCopyReservedReg) {
Register ReservedReg = MFI->getSGPRForEXECCopy();
assert(ReservedReg && "Should have reserved an SGPR for EXEC copy.");
Register UnusedScratchReg = findUnusedRegister(MRI, LiveUnits, RC);
if (UnusedScratchReg) {
// If found any unused scratch SGPR, reserve the register itself for Exec
// copy and there is no need for any spills in that case.
MFI->setSGPRForEXECCopy(UnusedScratchReg);
LiveUnits.addReg(UnusedScratchReg);
} else {
// Needs spill.
assert(!MFI->hasPrologEpilogSGPRSpillEntry(ReservedReg) &&
"Re-reserving spill slot for EXEC copy register");
getVGPRSpillLaneOrTempRegister(MF, LiveUnits, ReservedReg, RC,
/*IncludeScratchCopy=*/false);
}
}
// hasFP only knows about stack objects that already exist. We're now
// determining the stack slots that will be created, so we have to predict
// them. Stack objects force FP usage with calls.
//
// Note a new VGPR CSR may be introduced if one is used for the spill, but we
// don't want to report it here.
//
// FIXME: Is this really hasReservedCallFrame?
const bool WillHaveFP =
FrameInfo.hasCalls() &&
(SavedVGPRs.any() || !allStackObjectsAreDead(FrameInfo));
if (WillHaveFP || hasFP(MF)) {
Register FramePtrReg = MFI->getFrameOffsetReg();
assert(!MFI->hasPrologEpilogSGPRSpillEntry(FramePtrReg) &&
"Re-reserving spill slot for FP");
getVGPRSpillLaneOrTempRegister(MF, LiveUnits, FramePtrReg);
}
if (TRI->hasBasePointer(MF)) {
Register BasePtrReg = TRI->getBaseRegister();
assert(!MFI->hasPrologEpilogSGPRSpillEntry(BasePtrReg) &&
"Re-reserving spill slot for BP");
getVGPRSpillLaneOrTempRegister(MF, LiveUnits, BasePtrReg);
}
}
// Only report VGPRs to generic code.
void SIFrameLowering::determineCalleeSaves(MachineFunction &MF,
BitVector &SavedVGPRs,
RegScavenger *RS) const {
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
// If this is a function with the amdgpu_cs_chain[_preserve] calling
// convention and it doesn't contain any calls to llvm.amdgcn.cs.chain, then
// we don't need to save and restore anything.
if (MFI->isChainFunction() && !MF.getFrameInfo().hasTailCall())
return;
MFI->shiftSpillPhysVGPRsToLowestRange(MF);
TargetFrameLowering::determineCalleeSaves(MF, SavedVGPRs, RS);
if (MFI->isEntryFunction())
return;
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const SIInstrInfo *TII = ST.getInstrInfo();
bool NeedExecCopyReservedReg = false;
MachineInstr *ReturnMI = nullptr;
for (MachineBasicBlock &MBB : MF) {
for (MachineInstr &MI : MBB) {
// WRITELANE instructions used for SGPR spills can overwrite the inactive
// lanes of VGPRs and callee must spill and restore them even if they are
// marked Caller-saved.
// TODO: Handle this elsewhere at an early point. Walking through all MBBs
// here would be a bad heuristic. A better way should be by calling
// allocateWWMSpill during the regalloc pipeline whenever a physical
// register is allocated for the intended virtual registers.
if (MI.getOpcode() == AMDGPU::SI_SPILL_S32_TO_VGPR)
MFI->allocateWWMSpill(MF, MI.getOperand(0).getReg());
else if (MI.getOpcode() == AMDGPU::SI_RESTORE_S32_FROM_VGPR)
MFI->allocateWWMSpill(MF, MI.getOperand(1).getReg());
else if (TII->isWWMRegSpillOpcode(MI.getOpcode()))
NeedExecCopyReservedReg = true;
else if (MI.getOpcode() == AMDGPU::SI_RETURN ||
MI.getOpcode() == AMDGPU::SI_RETURN_TO_EPILOG ||
(MFI->isChainFunction() &&
TII->isChainCallOpcode(MI.getOpcode()))) {
// We expect all return to be the same size.
assert(!ReturnMI ||
(count_if(MI.operands(), [](auto Op) { return Op.isReg(); }) ==
count_if(ReturnMI->operands(), [](auto Op) { return Op.isReg(); })));
ReturnMI = &MI;
}
}
}
// Remove any VGPRs used in the return value because these do not need to be saved.
// This prevents CSR restore from clobbering return VGPRs.
if (ReturnMI) {
for (auto &Op : ReturnMI->operands()) {
if (Op.isReg())
SavedVGPRs.reset(Op.getReg());
}
}
// Ignore the SGPRs the default implementation found.
SavedVGPRs.clearBitsNotInMask(TRI->getAllVectorRegMask());
// Do not save AGPRs prior to GFX90A because there was no easy way to do so.
// In gfx908 there was do AGPR loads and stores and thus spilling also
// require a temporary VGPR.
if (!ST.hasGFX90AInsts())
SavedVGPRs.clearBitsInMask(TRI->getAllAGPRRegMask());
determinePrologEpilogSGPRSaves(MF, SavedVGPRs, NeedExecCopyReservedReg);
// The Whole-Wave VGPRs need to be specially inserted in the prolog, so don't
// allow the default insertion to handle them.
for (auto &Reg : MFI->getWWMSpills())
SavedVGPRs.reset(Reg.first);
// Mark all lane VGPRs as BB LiveIns.
for (MachineBasicBlock &MBB : MF) {
for (auto &Reg : MFI->getWWMSpills())
MBB.addLiveIn(Reg.first);
MBB.sortUniqueLiveIns();
}
}
void SIFrameLowering::determineCalleeSavesSGPR(MachineFunction &MF,
BitVector &SavedRegs,
RegScavenger *RS) const {
TargetFrameLowering::determineCalleeSaves(MF, SavedRegs, RS);
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
if (MFI->isEntryFunction())
return;
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
// The SP is specifically managed and we don't want extra spills of it.
SavedRegs.reset(MFI->getStackPtrOffsetReg());
const BitVector AllSavedRegs = SavedRegs;
SavedRegs.clearBitsInMask(TRI->getAllVectorRegMask());
// We have to anticipate introducing CSR VGPR spills or spill of caller
// save VGPR reserved for SGPR spills as we now always create stack entry
// for it, if we don't have any stack objects already, since we require a FP
// if there is a call and stack. We will allocate a VGPR for SGPR spills if
// there are any SGPR spills. Whether they are CSR spills or otherwise.
MachineFrameInfo &FrameInfo = MF.getFrameInfo();
const bool WillHaveFP =
FrameInfo.hasCalls() && (AllSavedRegs.any() || MFI->hasSpilledSGPRs());
// FP will be specially managed like SP.
if (WillHaveFP || hasFP(MF))
SavedRegs.reset(MFI->getFrameOffsetReg());
// Return address use with return instruction is hidden through the SI_RETURN
// pseudo. Given that and since the IPRA computes actual register usage and
// does not use CSR list, the clobbering of return address by function calls
// (D117243) or otherwise (D120922) is ignored/not seen by the IPRA's register
// usage collection. This will ensure save/restore of return address happens
// in those scenarios.
const MachineRegisterInfo &MRI = MF.getRegInfo();
Register RetAddrReg = TRI->getReturnAddressReg(MF);
if (!MFI->isEntryFunction() &&
(FrameInfo.hasCalls() || MRI.isPhysRegModified(RetAddrReg))) {
SavedRegs.set(TRI->getSubReg(RetAddrReg, AMDGPU::sub0));
SavedRegs.set(TRI->getSubReg(RetAddrReg, AMDGPU::sub1));
}
}
bool SIFrameLowering::assignCalleeSavedSpillSlots(
MachineFunction &MF, const TargetRegisterInfo *TRI,
std::vector<CalleeSavedInfo> &CSI) const {
if (CSI.empty())
return true; // Early exit if no callee saved registers are modified!
const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *RI = ST.getRegisterInfo();
Register FramePtrReg = FuncInfo->getFrameOffsetReg();
Register BasePtrReg = RI->getBaseRegister();
Register SGPRForFPSaveRestoreCopy =
FuncInfo->getScratchSGPRCopyDstReg(FramePtrReg);
Register SGPRForBPSaveRestoreCopy =
FuncInfo->getScratchSGPRCopyDstReg(BasePtrReg);
if (!SGPRForFPSaveRestoreCopy && !SGPRForBPSaveRestoreCopy)
return false;
unsigned NumModifiedRegs = 0;
if (SGPRForFPSaveRestoreCopy)
NumModifiedRegs++;
if (SGPRForBPSaveRestoreCopy)
NumModifiedRegs++;
for (auto &CS : CSI) {
if (CS.getReg() == FramePtrReg && SGPRForFPSaveRestoreCopy) {
CS.setDstReg(SGPRForFPSaveRestoreCopy);
if (--NumModifiedRegs)
break;
} else if (CS.getReg() == BasePtrReg && SGPRForBPSaveRestoreCopy) {
CS.setDstReg(SGPRForBPSaveRestoreCopy);
if (--NumModifiedRegs)
break;
}
}
return false;
}
bool SIFrameLowering::allocateScavengingFrameIndexesNearIncomingSP(
const MachineFunction &MF) const {
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const MachineFrameInfo &MFI = MF.getFrameInfo();
const SIInstrInfo *TII = ST.getInstrInfo();
uint64_t EstStackSize = MFI.estimateStackSize(MF);
uint64_t MaxOffset = EstStackSize - 1;
// We need the emergency stack slots to be allocated in range of the
// MUBUF/flat scratch immediate offset from the base register, so assign these
// first at the incoming SP position.
//
// TODO: We could try sorting the objects to find a hole in the first bytes
// rather than allocating as close to possible. This could save a lot of space
// on frames with alignment requirements.
if (ST.enableFlatScratch()) {
if (TII->isLegalFLATOffset(MaxOffset, AMDGPUAS::PRIVATE_ADDRESS,
SIInstrFlags::FlatScratch))
return false;
} else {
if (TII->isLegalMUBUFImmOffset(MaxOffset))
return false;
}
return true;
}
MachineBasicBlock::iterator SIFrameLowering::eliminateCallFramePseudoInstr(
MachineFunction &MF,
MachineBasicBlock &MBB,
MachineBasicBlock::iterator I) const {
int64_t Amount = I->getOperand(0).getImm();
if (Amount == 0)
return MBB.erase(I);
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIInstrInfo *TII = ST.getInstrInfo();
const DebugLoc &DL = I->getDebugLoc();
unsigned Opc = I->getOpcode();
bool IsDestroy = Opc == TII->getCallFrameDestroyOpcode();
uint64_t CalleePopAmount = IsDestroy ? I->getOperand(1).getImm() : 0;
if (!hasReservedCallFrame(MF)) {
Amount = alignTo(Amount, getStackAlign());
assert(isUInt<32>(Amount) && "exceeded stack address space size");
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
Register SPReg = MFI->getStackPtrOffsetReg();
Amount *= getScratchScaleFactor(ST);
if (IsDestroy)
Amount = -Amount;
auto Add = BuildMI(MBB, I, DL, TII->get(AMDGPU::S_ADD_I32), SPReg)
.addReg(SPReg)
.addImm(Amount);
Add->getOperand(3).setIsDead(); // Mark SCC as dead.
} else if (CalleePopAmount != 0) {
llvm_unreachable("is this used?");
}
return MBB.erase(I);
}
/// Returns true if the frame will require a reference to the stack pointer.
///
/// This is the set of conditions common to setting up the stack pointer in a
/// kernel, and for using a frame pointer in a callable function.
///
/// FIXME: Should also check hasOpaqueSPAdjustment and if any inline asm
/// references SP.
static bool frameTriviallyRequiresSP(const MachineFrameInfo &MFI) {
return MFI.hasVarSizedObjects() || MFI.hasStackMap() || MFI.hasPatchPoint();
}
// The FP for kernels is always known 0, so we never really need to setup an
// explicit register for it. However, DisableFramePointerElim will force us to
// use a register for it.
bool SIFrameLowering::hasFP(const MachineFunction &MF) const {
const MachineFrameInfo &MFI = MF.getFrameInfo();
// For entry & chain functions we can use an immediate offset in most cases,
// so the presence of calls doesn't imply we need a distinct frame pointer.
if (MFI.hasCalls() &&
!MF.getInfo<SIMachineFunctionInfo>()->isEntryFunction() &&
!MF.getInfo<SIMachineFunctionInfo>()->isChainFunction()) {
// All offsets are unsigned, so need to be addressed in the same direction
// as stack growth.
// FIXME: This function is pretty broken, since it can be called before the
// frame layout is determined or CSR spills are inserted.
return MFI.getStackSize() != 0;
}
return frameTriviallyRequiresSP(MFI) || MFI.isFrameAddressTaken() ||
MF.getSubtarget<GCNSubtarget>().getRegisterInfo()->hasStackRealignment(
MF) ||
MF.getTarget().Options.DisableFramePointerElim(MF);
}
// This is essentially a reduced version of hasFP for entry functions. Since the
// stack pointer is known 0 on entry to kernels, we never really need an FP
// register. We may need to initialize the stack pointer depending on the frame
// properties, which logically overlaps many of the cases where an ordinary
// function would require an FP.
// Also used for chain functions. While not technically entry functions, chain
// functions may need to set up a stack pointer in some situations.
bool SIFrameLowering::requiresStackPointerReference(
const MachineFunction &MF) const {
// Callable functions always require a stack pointer reference.
assert((MF.getInfo<SIMachineFunctionInfo>()->isEntryFunction() ||
MF.getInfo<SIMachineFunctionInfo>()->isChainFunction()) &&
"only expected to call this for entry points and chain functions");
const MachineFrameInfo &MFI = MF.getFrameInfo();
// Entry points ordinarily don't need to initialize SP. We have to set it up
// for callees if there are any. Also note tail calls are impossible/don't
// make any sense for kernels.
if (MFI.hasCalls())
return true;
// We still need to initialize the SP if we're doing anything weird that
// references the SP, like variable sized stack objects.
return frameTriviallyRequiresSP(MFI);
}