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

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//===-- llvm/lib/Target/AMDGPU/AMDGPUCallLowering.cpp - Call lowering -----===//
//
// 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
/// This file implements the lowering of LLVM calls to machine code calls for
/// GlobalISel.
///
//===----------------------------------------------------------------------===//
#include "AMDGPUCallLowering.h"
#include "AMDGPU.h"
#include "AMDGPULegalizerInfo.h"
#include "AMDGPUTargetMachine.h"
#include "SIMachineFunctionInfo.h"
#include "SIRegisterInfo.h"
#include "llvm/CodeGen/Analysis.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h"
#include "llvm/IR/IntrinsicsAMDGPU.h"
#define DEBUG_TYPE "amdgpu-call-lowering"
using namespace llvm;
namespace {
/// Wrapper around extendRegister to ensure we extend to a full 32-bit register.
static Register extendRegisterMin32(CallLowering::ValueHandler &Handler,
Register ValVReg, CCValAssign &VA) {
if (VA.getLocVT().getSizeInBits() < 32) {
// 16-bit types are reported as legal for 32-bit registers. We need to
// extend and do a 32-bit copy to avoid the verifier complaining about it.
return Handler.MIRBuilder.buildAnyExt(LLT::scalar(32), ValVReg).getReg(0);
}
return Handler.extendRegister(ValVReg, VA);
}
struct AMDGPUOutgoingValueHandler : public CallLowering::OutgoingValueHandler {
AMDGPUOutgoingValueHandler(MachineIRBuilder &B, MachineRegisterInfo &MRI,
MachineInstrBuilder MIB)
: OutgoingValueHandler(B, MRI), MIB(MIB) {}
MachineInstrBuilder MIB;
Register getStackAddress(uint64_t Size, int64_t Offset,
MachinePointerInfo &MPO,
ISD::ArgFlagsTy Flags) override {
llvm_unreachable("not implemented");
}
void assignValueToAddress(Register ValVReg, Register Addr, LLT MemTy,
MachinePointerInfo &MPO, CCValAssign &VA) override {
llvm_unreachable("not implemented");
}
void assignValueToReg(Register ValVReg, Register PhysReg,
CCValAssign VA) override {
Register ExtReg = extendRegisterMin32(*this, ValVReg, VA);
// If this is a scalar return, insert a readfirstlane just in case the value
// ends up in a VGPR.
// FIXME: Assert this is a shader return.
const SIRegisterInfo *TRI
= static_cast<const SIRegisterInfo *>(MRI.getTargetRegisterInfo());
if (TRI->isSGPRReg(MRI, PhysReg)) {
auto ToSGPR = MIRBuilder.buildIntrinsic(Intrinsic::amdgcn_readfirstlane,
{MRI.getType(ExtReg)}, false)
.addReg(ExtReg);
ExtReg = ToSGPR.getReg(0);
}
MIRBuilder.buildCopy(PhysReg, ExtReg);
MIB.addUse(PhysReg, RegState::Implicit);
}
};
struct AMDGPUIncomingArgHandler : public CallLowering::IncomingValueHandler {
uint64_t StackUsed = 0;
AMDGPUIncomingArgHandler(MachineIRBuilder &B, MachineRegisterInfo &MRI)
: IncomingValueHandler(B, MRI) {}
Register getStackAddress(uint64_t Size, int64_t Offset,
MachinePointerInfo &MPO,
ISD::ArgFlagsTy Flags) override {
auto &MFI = MIRBuilder.getMF().getFrameInfo();
// Byval is assumed to be writable memory, but other stack passed arguments
// are not.
const bool IsImmutable = !Flags.isByVal();
int FI = MFI.CreateFixedObject(Size, Offset, IsImmutable);
MPO = MachinePointerInfo::getFixedStack(MIRBuilder.getMF(), FI);
auto AddrReg = MIRBuilder.buildFrameIndex(
LLT::pointer(AMDGPUAS::PRIVATE_ADDRESS, 32), FI);
StackUsed = std::max(StackUsed, Size + Offset);
return AddrReg.getReg(0);
}
void assignValueToReg(Register ValVReg, Register PhysReg,
CCValAssign VA) override {
markPhysRegUsed(PhysReg);
if (VA.getLocVT().getSizeInBits() < 32) {
// 16-bit types are reported as legal for 32-bit registers. We need to do
// a 32-bit copy, and truncate to avoid the verifier complaining about it.
auto Copy = MIRBuilder.buildCopy(LLT::scalar(32), PhysReg);
// If we have signext/zeroext, it applies to the whole 32-bit register
// before truncation.
auto Extended =
buildExtensionHint(VA, Copy.getReg(0), LLT(VA.getLocVT()));
MIRBuilder.buildTrunc(ValVReg, Extended);
return;
}
IncomingValueHandler::assignValueToReg(ValVReg, PhysReg, VA);
}
void assignValueToAddress(Register ValVReg, Register Addr, LLT MemTy,
MachinePointerInfo &MPO, CCValAssign &VA) override {
MachineFunction &MF = MIRBuilder.getMF();
auto MMO = MF.getMachineMemOperand(
MPO, MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant, MemTy,
inferAlignFromPtrInfo(MF, MPO));
MIRBuilder.buildLoad(ValVReg, Addr, *MMO);
}
/// How the physical register gets marked varies between formal
/// parameters (it's a basic-block live-in), and a call instruction
/// (it's an implicit-def of the BL).
virtual void markPhysRegUsed(unsigned PhysReg) = 0;
};
struct FormalArgHandler : public AMDGPUIncomingArgHandler {
FormalArgHandler(MachineIRBuilder &B, MachineRegisterInfo &MRI)
: AMDGPUIncomingArgHandler(B, MRI) {}
void markPhysRegUsed(unsigned PhysReg) override {
MIRBuilder.getMBB().addLiveIn(PhysReg);
}
};
struct CallReturnHandler : public AMDGPUIncomingArgHandler {
CallReturnHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI,
MachineInstrBuilder MIB)
: AMDGPUIncomingArgHandler(MIRBuilder, MRI), MIB(MIB) {}
void markPhysRegUsed(unsigned PhysReg) override {
MIB.addDef(PhysReg, RegState::Implicit);
}
MachineInstrBuilder MIB;
};
struct AMDGPUOutgoingArgHandler : public AMDGPUOutgoingValueHandler {
/// For tail calls, the byte offset of the call's argument area from the
/// callee's. Unused elsewhere.
int FPDiff;
// Cache the SP register vreg if we need it more than once in this call site.
Register SPReg;
bool IsTailCall;
AMDGPUOutgoingArgHandler(MachineIRBuilder &MIRBuilder,
MachineRegisterInfo &MRI, MachineInstrBuilder MIB,
bool IsTailCall = false, int FPDiff = 0)
: AMDGPUOutgoingValueHandler(MIRBuilder, MRI, MIB), FPDiff(FPDiff),
IsTailCall(IsTailCall) {}
Register getStackAddress(uint64_t Size, int64_t Offset,
MachinePointerInfo &MPO,
ISD::ArgFlagsTy Flags) override {
MachineFunction &MF = MIRBuilder.getMF();
const LLT PtrTy = LLT::pointer(AMDGPUAS::PRIVATE_ADDRESS, 32);
const LLT S32 = LLT::scalar(32);
if (IsTailCall) {
Offset += FPDiff;
int FI = MF.getFrameInfo().CreateFixedObject(Size, Offset, true);
auto FIReg = MIRBuilder.buildFrameIndex(PtrTy, FI);
MPO = MachinePointerInfo::getFixedStack(MF, FI);
return FIReg.getReg(0);
}
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
if (!SPReg)
SPReg = MIRBuilder.buildCopy(PtrTy, MFI->getStackPtrOffsetReg()).getReg(0);
auto OffsetReg = MIRBuilder.buildConstant(S32, Offset);
auto AddrReg = MIRBuilder.buildPtrAdd(PtrTy, SPReg, OffsetReg);
MPO = MachinePointerInfo::getStack(MF, Offset);
return AddrReg.getReg(0);
}
void assignValueToReg(Register ValVReg, Register PhysReg,
CCValAssign VA) override {
MIB.addUse(PhysReg, RegState::Implicit);
Register ExtReg = extendRegisterMin32(*this, ValVReg, VA);
MIRBuilder.buildCopy(PhysReg, ExtReg);
}
void assignValueToAddress(Register ValVReg, Register Addr, LLT MemTy,
MachinePointerInfo &MPO, CCValAssign &VA) override {
MachineFunction &MF = MIRBuilder.getMF();
uint64_t LocMemOffset = VA.getLocMemOffset();
const auto &ST = MF.getSubtarget<GCNSubtarget>();
auto MMO = MF.getMachineMemOperand(
MPO, MachineMemOperand::MOStore, MemTy,
commonAlignment(ST.getStackAlignment(), LocMemOffset));
MIRBuilder.buildStore(ValVReg, Addr, *MMO);
}
void assignValueToAddress(const CallLowering::ArgInfo &Arg,
unsigned ValRegIndex, Register Addr, LLT MemTy,
MachinePointerInfo &MPO, CCValAssign &VA) override {
Register ValVReg = VA.getLocInfo() != CCValAssign::LocInfo::FPExt
? extendRegister(Arg.Regs[ValRegIndex], VA)
: Arg.Regs[ValRegIndex];
assignValueToAddress(ValVReg, Addr, MemTy, MPO, VA);
}
};
}
AMDGPUCallLowering::AMDGPUCallLowering(const AMDGPUTargetLowering &TLI)
: CallLowering(&TLI) {
}
// FIXME: Compatibility shim
static ISD::NodeType extOpcodeToISDExtOpcode(unsigned MIOpc) {
switch (MIOpc) {
case TargetOpcode::G_SEXT:
return ISD::SIGN_EXTEND;
case TargetOpcode::G_ZEXT:
return ISD::ZERO_EXTEND;
case TargetOpcode::G_ANYEXT:
return ISD::ANY_EXTEND;
default:
llvm_unreachable("not an extend opcode");
}
}
bool AMDGPUCallLowering::canLowerReturn(MachineFunction &MF,
CallingConv::ID CallConv,
SmallVectorImpl<BaseArgInfo> &Outs,
bool IsVarArg) const {
// For shaders. Vector types should be explicitly handled by CC.
if (AMDGPU::isEntryFunctionCC(CallConv))
return true;
SmallVector<CCValAssign, 16> ArgLocs;
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
CCState CCInfo(CallConv, IsVarArg, MF, ArgLocs,
MF.getFunction().getContext());
return checkReturn(CCInfo, Outs, TLI.CCAssignFnForReturn(CallConv, IsVarArg));
}
/// Lower the return value for the already existing \p Ret. This assumes that
/// \p B's insertion point is correct.
bool AMDGPUCallLowering::lowerReturnVal(MachineIRBuilder &B,
const Value *Val, ArrayRef<Register> VRegs,
MachineInstrBuilder &Ret) const {
if (!Val)
return true;
auto &MF = B.getMF();
const auto &F = MF.getFunction();
const DataLayout &DL = MF.getDataLayout();
MachineRegisterInfo *MRI = B.getMRI();
LLVMContext &Ctx = F.getContext();
CallingConv::ID CC = F.getCallingConv();
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
SmallVector<EVT, 8> SplitEVTs;
ComputeValueVTs(TLI, DL, Val->getType(), SplitEVTs);
assert(VRegs.size() == SplitEVTs.size() &&
"For each split Type there should be exactly one VReg.");
SmallVector<ArgInfo, 8> SplitRetInfos;
for (unsigned i = 0; i < SplitEVTs.size(); ++i) {
EVT VT = SplitEVTs[i];
Register Reg = VRegs[i];
ArgInfo RetInfo(Reg, VT.getTypeForEVT(Ctx), 0);
setArgFlags(RetInfo, AttributeList::ReturnIndex, DL, F);
if (VT.isScalarInteger()) {
unsigned ExtendOp = TargetOpcode::G_ANYEXT;
if (RetInfo.Flags[0].isSExt()) {
assert(RetInfo.Regs.size() == 1 && "expect only simple return values");
ExtendOp = TargetOpcode::G_SEXT;
} else if (RetInfo.Flags[0].isZExt()) {
assert(RetInfo.Regs.size() == 1 && "expect only simple return values");
ExtendOp = TargetOpcode::G_ZEXT;
}
EVT ExtVT = TLI.getTypeForExtReturn(Ctx, VT,
extOpcodeToISDExtOpcode(ExtendOp));
if (ExtVT != VT) {
RetInfo.Ty = ExtVT.getTypeForEVT(Ctx);
LLT ExtTy = getLLTForType(*RetInfo.Ty, DL);
Reg = B.buildInstr(ExtendOp, {ExtTy}, {Reg}).getReg(0);
}
}
if (Reg != RetInfo.Regs[0]) {
RetInfo.Regs[0] = Reg;
// Reset the arg flags after modifying Reg.
setArgFlags(RetInfo, AttributeList::ReturnIndex, DL, F);
}
splitToValueTypes(RetInfo, SplitRetInfos, DL, CC);
}
CCAssignFn *AssignFn = TLI.CCAssignFnForReturn(CC, F.isVarArg());
OutgoingValueAssigner Assigner(AssignFn);
AMDGPUOutgoingValueHandler RetHandler(B, *MRI, Ret);
return determineAndHandleAssignments(RetHandler, Assigner, SplitRetInfos, B,
CC, F.isVarArg());
}
bool AMDGPUCallLowering::lowerReturn(MachineIRBuilder &B, const Value *Val,
ArrayRef<Register> VRegs,
FunctionLoweringInfo &FLI) const {
MachineFunction &MF = B.getMF();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
MFI->setIfReturnsVoid(!Val);
assert(!Val == VRegs.empty() && "Return value without a vreg");
CallingConv::ID CC = B.getMF().getFunction().getCallingConv();
const bool IsShader = AMDGPU::isShader(CC);
const bool IsWaveEnd =
(IsShader && MFI->returnsVoid()) || AMDGPU::isKernel(CC);
if (IsWaveEnd) {
B.buildInstr(AMDGPU::S_ENDPGM)
.addImm(0);
return true;
}
auto const &ST = MF.getSubtarget<GCNSubtarget>();
unsigned ReturnOpc =
IsShader ? AMDGPU::SI_RETURN_TO_EPILOG : AMDGPU::S_SETPC_B64_return;
auto Ret = B.buildInstrNoInsert(ReturnOpc);
Register ReturnAddrVReg;
if (ReturnOpc == AMDGPU::S_SETPC_B64_return) {
ReturnAddrVReg = MRI.createVirtualRegister(&AMDGPU::CCR_SGPR_64RegClass);
Ret.addUse(ReturnAddrVReg);
}
if (!FLI.CanLowerReturn)
insertSRetStores(B, Val->getType(), VRegs, FLI.DemoteRegister);
else if (!lowerReturnVal(B, Val, VRegs, Ret))
return false;
if (ReturnOpc == AMDGPU::S_SETPC_B64_return) {
const SIRegisterInfo *TRI = ST.getRegisterInfo();
Register LiveInReturn = MF.addLiveIn(TRI->getReturnAddressReg(MF),
&AMDGPU::SGPR_64RegClass);
B.buildCopy(ReturnAddrVReg, LiveInReturn);
}
// TODO: Handle CalleeSavedRegsViaCopy.
B.insertInstr(Ret);
return true;
}
void AMDGPUCallLowering::lowerParameterPtr(Register DstReg, MachineIRBuilder &B,
uint64_t Offset) const {
MachineFunction &MF = B.getMF();
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
MachineRegisterInfo &MRI = MF.getRegInfo();
Register KernArgSegmentPtr =
MFI->getPreloadedReg(AMDGPUFunctionArgInfo::KERNARG_SEGMENT_PTR);
Register KernArgSegmentVReg = MRI.getLiveInVirtReg(KernArgSegmentPtr);
auto OffsetReg = B.buildConstant(LLT::scalar(64), Offset);
B.buildPtrAdd(DstReg, KernArgSegmentVReg, OffsetReg);
}
void AMDGPUCallLowering::lowerParameter(MachineIRBuilder &B, ArgInfo &OrigArg,
uint64_t Offset,
Align Alignment) const {
MachineFunction &MF = B.getMF();
const Function &F = MF.getFunction();
const DataLayout &DL = F.getParent()->getDataLayout();
MachinePointerInfo PtrInfo(AMDGPUAS::CONSTANT_ADDRESS);
LLT PtrTy = LLT::pointer(AMDGPUAS::CONSTANT_ADDRESS, 64);
SmallVector<ArgInfo, 32> SplitArgs;
SmallVector<uint64_t> FieldOffsets;
splitToValueTypes(OrigArg, SplitArgs, DL, F.getCallingConv(), &FieldOffsets);
unsigned Idx = 0;
for (ArgInfo &SplitArg : SplitArgs) {
Register PtrReg = B.getMRI()->createGenericVirtualRegister(PtrTy);
lowerParameterPtr(PtrReg, B, Offset + FieldOffsets[Idx]);
LLT ArgTy = getLLTForType(*SplitArg.Ty, DL);
if (SplitArg.Flags[0].isPointer()) {
// Compensate for losing pointeriness in splitValueTypes.
LLT PtrTy = LLT::pointer(SplitArg.Flags[0].getPointerAddrSpace(),
ArgTy.getScalarSizeInBits());
ArgTy = ArgTy.isVector() ? LLT::vector(ArgTy.getElementCount(), PtrTy)
: PtrTy;
}
MachineMemOperand *MMO = MF.getMachineMemOperand(
PtrInfo,
MachineMemOperand::MOLoad | MachineMemOperand::MODereferenceable |
MachineMemOperand::MOInvariant,
ArgTy, commonAlignment(Alignment, FieldOffsets[Idx]));
assert(SplitArg.Regs.size() == 1);
B.buildLoad(SplitArg.Regs[0], PtrReg, *MMO);
++Idx;
}
}
// Allocate special inputs passed in user SGPRs.
static void allocateHSAUserSGPRs(CCState &CCInfo,
MachineIRBuilder &B,
MachineFunction &MF,
const SIRegisterInfo &TRI,
SIMachineFunctionInfo &Info) {
// FIXME: How should these inputs interact with inreg / custom SGPR inputs?
if (Info.hasPrivateSegmentBuffer()) {
Register PrivateSegmentBufferReg = Info.addPrivateSegmentBuffer(TRI);
MF.addLiveIn(PrivateSegmentBufferReg, &AMDGPU::SGPR_128RegClass);
CCInfo.AllocateReg(PrivateSegmentBufferReg);
}
if (Info.hasDispatchPtr()) {
Register DispatchPtrReg = Info.addDispatchPtr(TRI);
MF.addLiveIn(DispatchPtrReg, &AMDGPU::SGPR_64RegClass);
CCInfo.AllocateReg(DispatchPtrReg);
}
if (Info.hasQueuePtr()) {
Register QueuePtrReg = Info.addQueuePtr(TRI);
MF.addLiveIn(QueuePtrReg, &AMDGPU::SGPR_64RegClass);
CCInfo.AllocateReg(QueuePtrReg);
}
if (Info.hasKernargSegmentPtr()) {
MachineRegisterInfo &MRI = MF.getRegInfo();
Register InputPtrReg = Info.addKernargSegmentPtr(TRI);
const LLT P4 = LLT::pointer(AMDGPUAS::CONSTANT_ADDRESS, 64);
Register VReg = MRI.createGenericVirtualRegister(P4);
MRI.addLiveIn(InputPtrReg, VReg);
B.getMBB().addLiveIn(InputPtrReg);
B.buildCopy(VReg, InputPtrReg);
CCInfo.AllocateReg(InputPtrReg);
}
if (Info.hasDispatchID()) {
Register DispatchIDReg = Info.addDispatchID(TRI);
MF.addLiveIn(DispatchIDReg, &AMDGPU::SGPR_64RegClass);
CCInfo.AllocateReg(DispatchIDReg);
}
if (Info.hasFlatScratchInit()) {
Register FlatScratchInitReg = Info.addFlatScratchInit(TRI);
MF.addLiveIn(FlatScratchInitReg, &AMDGPU::SGPR_64RegClass);
CCInfo.AllocateReg(FlatScratchInitReg);
}
// TODO: Add GridWorkGroupCount user SGPRs when used. For now with HSA we read
// these from the dispatch pointer.
}
bool AMDGPUCallLowering::lowerFormalArgumentsKernel(
MachineIRBuilder &B, const Function &F,
ArrayRef<ArrayRef<Register>> VRegs) const {
MachineFunction &MF = B.getMF();
const GCNSubtarget *Subtarget = &MF.getSubtarget<GCNSubtarget>();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *Info = MF.getInfo<SIMachineFunctionInfo>();
const SIRegisterInfo *TRI = Subtarget->getRegisterInfo();
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
const DataLayout &DL = F.getParent()->getDataLayout();
Info->allocateModuleLDSGlobal(F.getParent());
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(F.getCallingConv(), F.isVarArg(), MF, ArgLocs, F.getContext());
allocateHSAUserSGPRs(CCInfo, B, MF, *TRI, *Info);
unsigned i = 0;
const Align KernArgBaseAlign(16);
const unsigned BaseOffset = Subtarget->getExplicitKernelArgOffset(F);
uint64_t ExplicitArgOffset = 0;
// TODO: Align down to dword alignment and extract bits for extending loads.
for (auto &Arg : F.args()) {
const bool IsByRef = Arg.hasByRefAttr();
Type *ArgTy = IsByRef ? Arg.getParamByRefType() : Arg.getType();
unsigned AllocSize = DL.getTypeAllocSize(ArgTy);
if (AllocSize == 0)
continue;
MaybeAlign ABIAlign = IsByRef ? Arg.getParamAlign() : None;
if (!ABIAlign)
ABIAlign = DL.getABITypeAlign(ArgTy);
uint64_t ArgOffset = alignTo(ExplicitArgOffset, ABIAlign) + BaseOffset;
ExplicitArgOffset = alignTo(ExplicitArgOffset, ABIAlign) + AllocSize;
if (Arg.use_empty()) {
++i;
continue;
}
Align Alignment = commonAlignment(KernArgBaseAlign, ArgOffset);
if (IsByRef) {
unsigned ByRefAS = cast<PointerType>(Arg.getType())->getAddressSpace();
assert(VRegs[i].size() == 1 &&
"expected only one register for byval pointers");
if (ByRefAS == AMDGPUAS::CONSTANT_ADDRESS) {
lowerParameterPtr(VRegs[i][0], B, ArgOffset);
} else {
const LLT ConstPtrTy = LLT::pointer(AMDGPUAS::CONSTANT_ADDRESS, 64);
Register PtrReg = MRI.createGenericVirtualRegister(ConstPtrTy);
lowerParameterPtr(PtrReg, B, ArgOffset);
B.buildAddrSpaceCast(VRegs[i][0], PtrReg);
}
} else {
ArgInfo OrigArg(VRegs[i], Arg, i);
const unsigned OrigArgIdx = i + AttributeList::FirstArgIndex;
setArgFlags(OrigArg, OrigArgIdx, DL, F);
lowerParameter(B, OrigArg, ArgOffset, Alignment);
}
++i;
}
TLI.allocateSpecialEntryInputVGPRs(CCInfo, MF, *TRI, *Info);
TLI.allocateSystemSGPRs(CCInfo, MF, *Info, F.getCallingConv(), false);
return true;
}
bool AMDGPUCallLowering::lowerFormalArguments(
MachineIRBuilder &B, const Function &F, ArrayRef<ArrayRef<Register>> VRegs,
FunctionLoweringInfo &FLI) const {
CallingConv::ID CC = F.getCallingConv();
// The infrastructure for normal calling convention lowering is essentially
// useless for kernels. We want to avoid any kind of legalization or argument
// splitting.
if (CC == CallingConv::AMDGPU_KERNEL)
return lowerFormalArgumentsKernel(B, F, VRegs);
const bool IsGraphics = AMDGPU::isGraphics(CC);
const bool IsEntryFunc = AMDGPU::isEntryFunctionCC(CC);
MachineFunction &MF = B.getMF();
MachineBasicBlock &MBB = B.getMBB();
MachineRegisterInfo &MRI = MF.getRegInfo();
SIMachineFunctionInfo *Info = MF.getInfo<SIMachineFunctionInfo>();
const GCNSubtarget &Subtarget = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = Subtarget.getRegisterInfo();
const DataLayout &DL = F.getParent()->getDataLayout();
Info->allocateModuleLDSGlobal(F.getParent());
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(CC, F.isVarArg(), MF, ArgLocs, F.getContext());
if (!IsEntryFunc) {
Register ReturnAddrReg = TRI->getReturnAddressReg(MF);
Register LiveInReturn = MF.addLiveIn(ReturnAddrReg,
&AMDGPU::SGPR_64RegClass);
MBB.addLiveIn(ReturnAddrReg);
B.buildCopy(LiveInReturn, ReturnAddrReg);
}
if (Info->hasImplicitBufferPtr()) {
Register ImplicitBufferPtrReg = Info->addImplicitBufferPtr(*TRI);
MF.addLiveIn(ImplicitBufferPtrReg, &AMDGPU::SGPR_64RegClass);
CCInfo.AllocateReg(ImplicitBufferPtrReg);
}
SmallVector<ArgInfo, 32> SplitArgs;
unsigned Idx = 0;
unsigned PSInputNum = 0;
// Insert the hidden sret parameter if the return value won't fit in the
// return registers.
if (!FLI.CanLowerReturn)
insertSRetIncomingArgument(F, SplitArgs, FLI.DemoteRegister, MRI, DL);
for (auto &Arg : F.args()) {
if (DL.getTypeStoreSize(Arg.getType()) == 0)
continue;
const bool InReg = Arg.hasAttribute(Attribute::InReg);
// SGPR arguments to functions not implemented.
if (!IsGraphics && InReg)
return false;
if (Arg.hasAttribute(Attribute::SwiftSelf) ||
Arg.hasAttribute(Attribute::SwiftError) ||
Arg.hasAttribute(Attribute::Nest))
return false;
if (CC == CallingConv::AMDGPU_PS && !InReg && PSInputNum <= 15) {
const bool ArgUsed = !Arg.use_empty();
bool SkipArg = !ArgUsed && !Info->isPSInputAllocated(PSInputNum);
if (!SkipArg) {
Info->markPSInputAllocated(PSInputNum);
if (ArgUsed)
Info->markPSInputEnabled(PSInputNum);
}
++PSInputNum;
if (SkipArg) {
for (int I = 0, E = VRegs[Idx].size(); I != E; ++I)
B.buildUndef(VRegs[Idx][I]);
++Idx;
continue;
}
}
ArgInfo OrigArg(VRegs[Idx], Arg, Idx);
const unsigned OrigArgIdx = Idx + AttributeList::FirstArgIndex;
setArgFlags(OrigArg, OrigArgIdx, DL, F);
splitToValueTypes(OrigArg, SplitArgs, DL, CC);
++Idx;
}
// At least one interpolation mode must be enabled or else the GPU will
// hang.
//
// Check PSInputAddr instead of PSInputEnable. The idea is that if the user
// set PSInputAddr, the user wants to enable some bits after the compilation
// based on run-time states. Since we can't know what the final PSInputEna
// will look like, so we shouldn't do anything here and the user should take
// responsibility for the correct programming.
//
// Otherwise, the following restrictions apply:
// - At least one of PERSP_* (0xF) or LINEAR_* (0x70) must be enabled.
// - If POS_W_FLOAT (11) is enabled, at least one of PERSP_* must be
// enabled too.
if (CC == CallingConv::AMDGPU_PS) {
if ((Info->getPSInputAddr() & 0x7F) == 0 ||
((Info->getPSInputAddr() & 0xF) == 0 &&
Info->isPSInputAllocated(11))) {
CCInfo.AllocateReg(AMDGPU::VGPR0);
CCInfo.AllocateReg(AMDGPU::VGPR1);
Info->markPSInputAllocated(0);
Info->markPSInputEnabled(0);
}
if (Subtarget.isAmdPalOS()) {
// For isAmdPalOS, the user does not enable some bits after compilation
// based on run-time states; the register values being generated here are
// the final ones set in hardware. Therefore we need to apply the
// workaround to PSInputAddr and PSInputEnable together. (The case where
// a bit is set in PSInputAddr but not PSInputEnable is where the frontend
// set up an input arg for a particular interpolation mode, but nothing
// uses that input arg. Really we should have an earlier pass that removes
// such an arg.)
unsigned PsInputBits = Info->getPSInputAddr() & Info->getPSInputEnable();
if ((PsInputBits & 0x7F) == 0 ||
((PsInputBits & 0xF) == 0 &&
(PsInputBits >> 11 & 1)))
Info->markPSInputEnabled(
countTrailingZeros(Info->getPSInputAddr(), ZB_Undefined));
}
}
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
CCAssignFn *AssignFn = TLI.CCAssignFnForCall(CC, F.isVarArg());
if (!MBB.empty())
B.setInstr(*MBB.begin());
if (!IsEntryFunc) {
// For the fixed ABI, pass workitem IDs in the last argument register.
if (AMDGPUTargetMachine::EnableFixedFunctionABI)
TLI.allocateSpecialInputVGPRsFixed(CCInfo, MF, *TRI, *Info);
}
IncomingValueAssigner Assigner(AssignFn);
if (!determineAssignments(Assigner, SplitArgs, CCInfo))
return false;
FormalArgHandler Handler(B, MRI);
if (!handleAssignments(Handler, SplitArgs, CCInfo, ArgLocs, B))
return false;
uint64_t StackOffset = Assigner.StackOffset;
if (!IsEntryFunc && !AMDGPUTargetMachine::EnableFixedFunctionABI) {
// Special inputs come after user arguments.
TLI.allocateSpecialInputVGPRs(CCInfo, MF, *TRI, *Info);
}
// Start adding system SGPRs.
if (IsEntryFunc) {
TLI.allocateSystemSGPRs(CCInfo, MF, *Info, CC, IsGraphics);
} else {
if (!Subtarget.enableFlatScratch())
CCInfo.AllocateReg(Info->getScratchRSrcReg());
TLI.allocateSpecialInputSGPRs(CCInfo, MF, *TRI, *Info);
}
// When we tail call, we need to check if the callee's arguments will fit on
// the caller's stack. So, whenever we lower formal arguments, we should keep
// track of this information, since we might lower a tail call in this
// function later.
Info->setBytesInStackArgArea(StackOffset);
// Move back to the end of the basic block.
B.setMBB(MBB);
return true;
}
bool AMDGPUCallLowering::passSpecialInputs(MachineIRBuilder &MIRBuilder,
CCState &CCInfo,
SmallVectorImpl<std::pair<MCRegister, Register>> &ArgRegs,
CallLoweringInfo &Info) const {
MachineFunction &MF = MIRBuilder.getMF();
// If there's no call site, this doesn't correspond to a call from the IR and
// doesn't need implicit inputs.
if (!Info.CB)
return true;
const AMDGPUFunctionArgInfo *CalleeArgInfo
= &AMDGPUArgumentUsageInfo::FixedABIFunctionInfo;
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
const AMDGPUFunctionArgInfo &CallerArgInfo = MFI->getArgInfo();
// TODO: Unify with private memory register handling. This is complicated by
// the fact that at least in kernels, the input argument is not necessarily
// in the same location as the input.
AMDGPUFunctionArgInfo::PreloadedValue InputRegs[] = {
AMDGPUFunctionArgInfo::DISPATCH_PTR,
AMDGPUFunctionArgInfo::QUEUE_PTR,
AMDGPUFunctionArgInfo::IMPLICIT_ARG_PTR,
AMDGPUFunctionArgInfo::DISPATCH_ID,
AMDGPUFunctionArgInfo::WORKGROUP_ID_X,
AMDGPUFunctionArgInfo::WORKGROUP_ID_Y,
AMDGPUFunctionArgInfo::WORKGROUP_ID_Z
};
static constexpr StringLiteral ImplicitAttrNames[] = {
"amdgpu-no-dispatch-ptr",
"amdgpu-no-queue-ptr",
"amdgpu-no-implicitarg-ptr",
"amdgpu-no-dispatch-id",
"amdgpu-no-workgroup-id-x",
"amdgpu-no-workgroup-id-y",
"amdgpu-no-workgroup-id-z"
};
MachineRegisterInfo &MRI = MF.getRegInfo();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const AMDGPULegalizerInfo *LI
= static_cast<const AMDGPULegalizerInfo*>(ST.getLegalizerInfo());
unsigned I = 0;
for (auto InputID : InputRegs) {
const ArgDescriptor *OutgoingArg;
const TargetRegisterClass *ArgRC;
LLT ArgTy;
// If the callee does not use the attribute value, skip copying the value.
if (Info.CB->hasFnAttr(ImplicitAttrNames[I++]))
continue;
std::tie(OutgoingArg, ArgRC, ArgTy) =
CalleeArgInfo->getPreloadedValue(InputID);
if (!OutgoingArg)
continue;
const ArgDescriptor *IncomingArg;
const TargetRegisterClass *IncomingArgRC;
std::tie(IncomingArg, IncomingArgRC, ArgTy) =
CallerArgInfo.getPreloadedValue(InputID);
assert(IncomingArgRC == ArgRC);
Register InputReg = MRI.createGenericVirtualRegister(ArgTy);
if (IncomingArg) {
LI->loadInputValue(InputReg, MIRBuilder, IncomingArg, ArgRC, ArgTy);
} else {
assert(InputID == AMDGPUFunctionArgInfo::IMPLICIT_ARG_PTR);
LI->getImplicitArgPtr(InputReg, MRI, MIRBuilder);
}
if (OutgoingArg->isRegister()) {
ArgRegs.emplace_back(OutgoingArg->getRegister(), InputReg);
if (!CCInfo.AllocateReg(OutgoingArg->getRegister()))
report_fatal_error("failed to allocate implicit input argument");
} else {
LLVM_DEBUG(dbgs() << "Unhandled stack passed implicit input argument\n");
return false;
}
}
// Pack workitem IDs into a single register or pass it as is if already
// packed.
const ArgDescriptor *OutgoingArg;
const TargetRegisterClass *ArgRC;
LLT ArgTy;
std::tie(OutgoingArg, ArgRC, ArgTy) =
CalleeArgInfo->getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_X);
if (!OutgoingArg)
std::tie(OutgoingArg, ArgRC, ArgTy) =
CalleeArgInfo->getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_Y);
if (!OutgoingArg)
std::tie(OutgoingArg, ArgRC, ArgTy) =
CalleeArgInfo->getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_Z);
if (!OutgoingArg)
return false;
auto WorkitemIDX =
CallerArgInfo.getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_X);
auto WorkitemIDY =
CallerArgInfo.getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_Y);
auto WorkitemIDZ =
CallerArgInfo.getPreloadedValue(AMDGPUFunctionArgInfo::WORKITEM_ID_Z);
const ArgDescriptor *IncomingArgX = std::get<0>(WorkitemIDX);
const ArgDescriptor *IncomingArgY = std::get<0>(WorkitemIDY);
const ArgDescriptor *IncomingArgZ = std::get<0>(WorkitemIDZ);
const LLT S32 = LLT::scalar(32);
const bool NeedWorkItemIDX = !Info.CB->hasFnAttr("amdgpu-no-workitem-id-x");
const bool NeedWorkItemIDY = !Info.CB->hasFnAttr("amdgpu-no-workitem-id-y");
const bool NeedWorkItemIDZ = !Info.CB->hasFnAttr("amdgpu-no-workitem-id-z");
// If incoming ids are not packed we need to pack them.
// FIXME: Should consider known workgroup size to eliminate known 0 cases.
Register InputReg;
if (IncomingArgX && !IncomingArgX->isMasked() && CalleeArgInfo->WorkItemIDX &&
NeedWorkItemIDX) {
InputReg = MRI.createGenericVirtualRegister(S32);
LI->loadInputValue(InputReg, MIRBuilder, IncomingArgX,
std::get<1>(WorkitemIDX), std::get<2>(WorkitemIDX));
}
if (IncomingArgY && !IncomingArgY->isMasked() && CalleeArgInfo->WorkItemIDY &&
NeedWorkItemIDY) {
Register Y = MRI.createGenericVirtualRegister(S32);
LI->loadInputValue(Y, MIRBuilder, IncomingArgY, std::get<1>(WorkitemIDY),
std::get<2>(WorkitemIDY));
Y = MIRBuilder.buildShl(S32, Y, MIRBuilder.buildConstant(S32, 10)).getReg(0);
InputReg = InputReg ? MIRBuilder.buildOr(S32, InputReg, Y).getReg(0) : Y;
}
if (IncomingArgZ && !IncomingArgZ->isMasked() && CalleeArgInfo->WorkItemIDZ &&
NeedWorkItemIDZ) {
Register Z = MRI.createGenericVirtualRegister(S32);
LI->loadInputValue(Z, MIRBuilder, IncomingArgZ, std::get<1>(WorkitemIDZ),
std::get<2>(WorkitemIDZ));
Z = MIRBuilder.buildShl(S32, Z, MIRBuilder.buildConstant(S32, 20)).getReg(0);
InputReg = InputReg ? MIRBuilder.buildOr(S32, InputReg, Z).getReg(0) : Z;
}
if (!InputReg && (NeedWorkItemIDX || NeedWorkItemIDY || NeedWorkItemIDZ)) {
InputReg = MRI.createGenericVirtualRegister(S32);
// Workitem ids are already packed, any of present incoming arguments will
// carry all required fields.
ArgDescriptor IncomingArg = ArgDescriptor::createArg(
IncomingArgX ? *IncomingArgX :
IncomingArgY ? *IncomingArgY : *IncomingArgZ, ~0u);
LI->loadInputValue(InputReg, MIRBuilder, &IncomingArg,
&AMDGPU::VGPR_32RegClass, S32);
}
if (OutgoingArg->isRegister()) {
if (InputReg)
ArgRegs.emplace_back(OutgoingArg->getRegister(), InputReg);
if (!CCInfo.AllocateReg(OutgoingArg->getRegister()))
report_fatal_error("failed to allocate implicit input argument");
} else {
LLVM_DEBUG(dbgs() << "Unhandled stack passed implicit input argument\n");
return false;
}
return true;
}
/// Returns a pair containing the fixed CCAssignFn and the vararg CCAssignFn for
/// CC.
static std::pair<CCAssignFn *, CCAssignFn *>
getAssignFnsForCC(CallingConv::ID CC, const SITargetLowering &TLI) {
return {TLI.CCAssignFnForCall(CC, false), TLI.CCAssignFnForCall(CC, true)};
}
static unsigned getCallOpcode(const MachineFunction &CallerF, bool IsIndirect,
bool IsTailCall) {
return IsTailCall ? AMDGPU::SI_TCRETURN : AMDGPU::SI_CALL;
}
// Add operands to call instruction to track the callee.
static bool addCallTargetOperands(MachineInstrBuilder &CallInst,
MachineIRBuilder &MIRBuilder,
AMDGPUCallLowering::CallLoweringInfo &Info) {
if (Info.Callee.isReg()) {
CallInst.addReg(Info.Callee.getReg());
CallInst.addImm(0);
} else if (Info.Callee.isGlobal() && Info.Callee.getOffset() == 0) {
// The call lowering lightly assumed we can directly encode a call target in
// the instruction, which is not the case. Materialize the address here.
const GlobalValue *GV = Info.Callee.getGlobal();
auto Ptr = MIRBuilder.buildGlobalValue(
LLT::pointer(GV->getAddressSpace(), 64), GV);
CallInst.addReg(Ptr.getReg(0));
CallInst.add(Info.Callee);
} else
return false;
return true;
}
bool AMDGPUCallLowering::doCallerAndCalleePassArgsTheSameWay(
CallLoweringInfo &Info, MachineFunction &MF,
SmallVectorImpl<ArgInfo> &InArgs) const {
const Function &CallerF = MF.getFunction();
CallingConv::ID CalleeCC = Info.CallConv;
CallingConv::ID CallerCC = CallerF.getCallingConv();
// If the calling conventions match, then everything must be the same.
if (CalleeCC == CallerCC)
return true;
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
// Make sure that the caller and callee preserve all of the same registers.
auto TRI = ST.getRegisterInfo();
const uint32_t *CallerPreserved = TRI->getCallPreservedMask(MF, CallerCC);
const uint32_t *CalleePreserved = TRI->getCallPreservedMask(MF, CalleeCC);
if (!TRI->regmaskSubsetEqual(CallerPreserved, CalleePreserved))
return false;
// Check if the caller and callee will handle arguments in the same way.
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
CCAssignFn *CalleeAssignFnFixed;
CCAssignFn *CalleeAssignFnVarArg;
std::tie(CalleeAssignFnFixed, CalleeAssignFnVarArg) =
getAssignFnsForCC(CalleeCC, TLI);
CCAssignFn *CallerAssignFnFixed;
CCAssignFn *CallerAssignFnVarArg;
std::tie(CallerAssignFnFixed, CallerAssignFnVarArg) =
getAssignFnsForCC(CallerCC, TLI);
// FIXME: We are not accounting for potential differences in implicitly passed
// inputs, but only the fixed ABI is supported now anyway.
IncomingValueAssigner CalleeAssigner(CalleeAssignFnFixed,
CalleeAssignFnVarArg);
IncomingValueAssigner CallerAssigner(CallerAssignFnFixed,
CallerAssignFnVarArg);
return resultsCompatible(Info, MF, InArgs, CalleeAssigner, CallerAssigner);
}
bool AMDGPUCallLowering::areCalleeOutgoingArgsTailCallable(
CallLoweringInfo &Info, MachineFunction &MF,
SmallVectorImpl<ArgInfo> &OutArgs) const {
// If there are no outgoing arguments, then we are done.
if (OutArgs.empty())
return true;
const Function &CallerF = MF.getFunction();
CallingConv::ID CalleeCC = Info.CallConv;
CallingConv::ID CallerCC = CallerF.getCallingConv();
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
CCAssignFn *AssignFnFixed;
CCAssignFn *AssignFnVarArg;
std::tie(AssignFnFixed, AssignFnVarArg) = getAssignFnsForCC(CalleeCC, TLI);
// We have outgoing arguments. Make sure that we can tail call with them.
SmallVector<CCValAssign, 16> OutLocs;
CCState OutInfo(CalleeCC, false, MF, OutLocs, CallerF.getContext());
OutgoingValueAssigner Assigner(AssignFnFixed, AssignFnVarArg);
if (!determineAssignments(Assigner, OutArgs, OutInfo)) {
LLVM_DEBUG(dbgs() << "... Could not analyze call operands.\n");
return false;
}
// Make sure that they can fit on the caller's stack.
const SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
if (OutInfo.getNextStackOffset() > FuncInfo->getBytesInStackArgArea()) {
LLVM_DEBUG(dbgs() << "... Cannot fit call operands on caller's stack.\n");
return false;
}
// Verify that the parameters in callee-saved registers match.
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const uint32_t *CallerPreservedMask = TRI->getCallPreservedMask(MF, CallerCC);
MachineRegisterInfo &MRI = MF.getRegInfo();
return parametersInCSRMatch(MRI, CallerPreservedMask, OutLocs, OutArgs);
}
/// Return true if the calling convention is one that we can guarantee TCO for.
static bool canGuaranteeTCO(CallingConv::ID CC) {
return CC == CallingConv::Fast;
}
/// Return true if we might ever do TCO for calls with this calling convention.
static bool mayTailCallThisCC(CallingConv::ID CC) {
switch (CC) {
case CallingConv::C:
case CallingConv::AMDGPU_Gfx:
return true;
default:
return canGuaranteeTCO(CC);
}
}
bool AMDGPUCallLowering::isEligibleForTailCallOptimization(
MachineIRBuilder &B, CallLoweringInfo &Info,
SmallVectorImpl<ArgInfo> &InArgs, SmallVectorImpl<ArgInfo> &OutArgs) const {
// Must pass all target-independent checks in order to tail call optimize.
if (!Info.IsTailCall)
return false;
MachineFunction &MF = B.getMF();
const Function &CallerF = MF.getFunction();
CallingConv::ID CalleeCC = Info.CallConv;
CallingConv::ID CallerCC = CallerF.getCallingConv();
const SIRegisterInfo *TRI = MF.getSubtarget<GCNSubtarget>().getRegisterInfo();
const uint32_t *CallerPreserved = TRI->getCallPreservedMask(MF, CallerCC);
// Kernels aren't callable, and don't have a live in return address so it
// doesn't make sense to do a tail call with entry functions.
if (!CallerPreserved)
return false;
if (!mayTailCallThisCC(CalleeCC)) {
LLVM_DEBUG(dbgs() << "... Calling convention cannot be tail called.\n");
return false;
}
if (any_of(CallerF.args(), [](const Argument &A) {
return A.hasByValAttr() || A.hasSwiftErrorAttr();
})) {
LLVM_DEBUG(dbgs() << "... Cannot tail call from callers with byval "
"or swifterror arguments\n");
return false;
}
// If we have -tailcallopt, then we're done.
if (MF.getTarget().Options.GuaranteedTailCallOpt)
return canGuaranteeTCO(CalleeCC) && CalleeCC == CallerF.getCallingConv();
// Verify that the incoming and outgoing arguments from the callee are
// safe to tail call.
if (!doCallerAndCalleePassArgsTheSameWay(Info, MF, InArgs)) {
LLVM_DEBUG(
dbgs()
<< "... Caller and callee have incompatible calling conventions.\n");
return false;
}
if (!areCalleeOutgoingArgsTailCallable(Info, MF, OutArgs))
return false;
LLVM_DEBUG(dbgs() << "... Call is eligible for tail call optimization.\n");
return true;
}
// Insert outgoing implicit arguments for a call, by inserting copies to the
// implicit argument registers and adding the necessary implicit uses to the
// call instruction.
void AMDGPUCallLowering::handleImplicitCallArguments(
MachineIRBuilder &MIRBuilder, MachineInstrBuilder &CallInst,
const GCNSubtarget &ST, const SIMachineFunctionInfo &FuncInfo,
ArrayRef<std::pair<MCRegister, Register>> ImplicitArgRegs) const {
if (!ST.enableFlatScratch()) {
// Insert copies for the SRD. In the HSA case, this should be an identity
// copy.
auto ScratchRSrcReg = MIRBuilder.buildCopy(LLT::fixed_vector(4, 32),
FuncInfo.getScratchRSrcReg());
MIRBuilder.buildCopy(AMDGPU::SGPR0_SGPR1_SGPR2_SGPR3, ScratchRSrcReg);
CallInst.addReg(AMDGPU::SGPR0_SGPR1_SGPR2_SGPR3, RegState::Implicit);
}
for (std::pair<MCRegister, Register> ArgReg : ImplicitArgRegs) {
MIRBuilder.buildCopy((Register)ArgReg.first, ArgReg.second);
CallInst.addReg(ArgReg.first, RegState::Implicit);
}
}
bool AMDGPUCallLowering::lowerTailCall(
MachineIRBuilder &MIRBuilder, CallLoweringInfo &Info,
SmallVectorImpl<ArgInfo> &OutArgs) const {
MachineFunction &MF = MIRBuilder.getMF();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
SIMachineFunctionInfo *FuncInfo = MF.getInfo<SIMachineFunctionInfo>();
const Function &F = MF.getFunction();
MachineRegisterInfo &MRI = MF.getRegInfo();
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
// True when we're tail calling, but without -tailcallopt.
bool IsSibCall = !MF.getTarget().Options.GuaranteedTailCallOpt;
// Find out which ABI gets to decide where things go.
CallingConv::ID CalleeCC = Info.CallConv;
CCAssignFn *AssignFnFixed;
CCAssignFn *AssignFnVarArg;
std::tie(AssignFnFixed, AssignFnVarArg) = getAssignFnsForCC(CalleeCC, TLI);
MachineInstrBuilder CallSeqStart;
if (!IsSibCall)
CallSeqStart = MIRBuilder.buildInstr(AMDGPU::ADJCALLSTACKUP);
unsigned Opc = getCallOpcode(MF, Info.Callee.isReg(), true);
auto MIB = MIRBuilder.buildInstrNoInsert(Opc);
if (!addCallTargetOperands(MIB, MIRBuilder, Info))
return false;
// Byte offset for the tail call. When we are sibcalling, this will always
// be 0.
MIB.addImm(0);
// Tell the call which registers are clobbered.
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const uint32_t *Mask = TRI->getCallPreservedMask(MF, CalleeCC);
MIB.addRegMask(Mask);
// FPDiff is the byte offset of the call's argument area from the callee's.
// Stores to callee stack arguments will be placed in FixedStackSlots offset
// by this amount for a tail call. In a sibling call it must be 0 because the
// caller will deallocate the entire stack and the callee still expects its
// arguments to begin at SP+0.
int FPDiff = 0;
// This will be 0 for sibcalls, potentially nonzero for tail calls produced
// by -tailcallopt. For sibcalls, the memory operands for the call are
// already available in the caller's incoming argument space.
unsigned NumBytes = 0;
if (!IsSibCall) {
// We aren't sibcalling, so we need to compute FPDiff. We need to do this
// before handling assignments, because FPDiff must be known for memory
// arguments.
unsigned NumReusableBytes = FuncInfo->getBytesInStackArgArea();
SmallVector<CCValAssign, 16> OutLocs;
CCState OutInfo(CalleeCC, false, MF, OutLocs, F.getContext());
// FIXME: Not accounting for callee implicit inputs
OutgoingValueAssigner CalleeAssigner(AssignFnFixed, AssignFnVarArg);
if (!determineAssignments(CalleeAssigner, OutArgs, OutInfo))
return false;
// The callee will pop the argument stack as a tail call. Thus, we must
// keep it 16-byte aligned.
NumBytes = alignTo(OutInfo.getNextStackOffset(), ST.getStackAlignment());
// FPDiff will be negative if this tail call requires more space than we
// would automatically have in our incoming argument space. Positive if we
// actually shrink the stack.
FPDiff = NumReusableBytes - NumBytes;
// The stack pointer must be 16-byte aligned at all times it's used for a
// memory operation, which in practice means at *all* times and in
// particular across call boundaries. Therefore our own arguments started at
// a 16-byte aligned SP and the delta applied for the tail call should
// satisfy the same constraint.
assert(isAligned(ST.getStackAlignment(), FPDiff) &&
"unaligned stack on tail call");
}
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(Info.CallConv, Info.IsVarArg, MF, ArgLocs, F.getContext());
// We could pass MIB and directly add the implicit uses to the call
// now. However, as an aesthetic choice, place implicit argument operands
// after the ordinary user argument registers.
SmallVector<std::pair<MCRegister, Register>, 12> ImplicitArgRegs;
if (AMDGPUTargetMachine::EnableFixedFunctionABI &&
Info.CallConv != CallingConv::AMDGPU_Gfx) {
// With a fixed ABI, allocate fixed registers before user arguments.
if (!passSpecialInputs(MIRBuilder, CCInfo, ImplicitArgRegs, Info))
return false;
}
OutgoingValueAssigner Assigner(AssignFnFixed, AssignFnVarArg);
if (!determineAssignments(Assigner, OutArgs, CCInfo))
return false;
// Do the actual argument marshalling.
AMDGPUOutgoingArgHandler Handler(MIRBuilder, MRI, MIB, true, FPDiff);
if (!handleAssignments(Handler, OutArgs, CCInfo, ArgLocs, MIRBuilder))
return false;
handleImplicitCallArguments(MIRBuilder, MIB, ST, *FuncInfo, ImplicitArgRegs);
// If we have -tailcallopt, we need to adjust the stack. We'll do the call
// sequence start and end here.
if (!IsSibCall) {
MIB->getOperand(1).setImm(FPDiff);
CallSeqStart.addImm(NumBytes).addImm(0);
// End the call sequence *before* emitting the call. Normally, we would
// tidy the frame up after the call. However, here, we've laid out the
// parameters so that when SP is reset, they will be in the correct
// location.
MIRBuilder.buildInstr(AMDGPU::ADJCALLSTACKDOWN).addImm(NumBytes).addImm(0);
}
// Now we can add the actual call instruction to the correct basic block.
MIRBuilder.insertInstr(MIB);
// If Callee is a reg, since it is used by a target specific
// instruction, it must have a register class matching the
// constraint of that instruction.
// FIXME: We should define regbankselectable call instructions to handle
// divergent call targets.
if (MIB->getOperand(0).isReg()) {
MIB->getOperand(0).setReg(constrainOperandRegClass(
MF, *TRI, MRI, *ST.getInstrInfo(), *ST.getRegBankInfo(), *MIB,
MIB->getDesc(), MIB->getOperand(0), 0));
}
MF.getFrameInfo().setHasTailCall();
Info.LoweredTailCall = true;
return true;
}
bool AMDGPUCallLowering::lowerCall(MachineIRBuilder &MIRBuilder,
CallLoweringInfo &Info) const {
if (Info.IsVarArg) {
LLVM_DEBUG(dbgs() << "Variadic functions not implemented\n");
return false;
}
MachineFunction &MF = MIRBuilder.getMF();
const GCNSubtarget &ST = MF.getSubtarget<GCNSubtarget>();
const SIRegisterInfo *TRI = ST.getRegisterInfo();
const Function &F = MF.getFunction();
MachineRegisterInfo &MRI = MF.getRegInfo();
const SITargetLowering &TLI = *getTLI<SITargetLowering>();
const DataLayout &DL = F.getParent()->getDataLayout();
if (!AMDGPUTargetMachine::EnableFixedFunctionABI &&
Info.CallConv != CallingConv::AMDGPU_Gfx) {
LLVM_DEBUG(dbgs() << "Variable function ABI not implemented\n");
return false;
}
SmallVector<ArgInfo, 8> OutArgs;
for (auto &OrigArg : Info.OrigArgs)
splitToValueTypes(OrigArg, OutArgs, DL, Info.CallConv);
SmallVector<ArgInfo, 8> InArgs;
if (Info.CanLowerReturn && !Info.OrigRet.Ty->isVoidTy())
splitToValueTypes(Info.OrigRet, InArgs, DL, Info.CallConv);
// If we can lower as a tail call, do that instead.
bool CanTailCallOpt =
isEligibleForTailCallOptimization(MIRBuilder, Info, InArgs, OutArgs);
// We must emit a tail call if we have musttail.
if (Info.IsMustTailCall && !CanTailCallOpt) {
LLVM_DEBUG(dbgs() << "Failed to lower musttail call as tail call\n");
return false;
}
if (CanTailCallOpt)
return lowerTailCall(MIRBuilder, Info, OutArgs);
// Find out which ABI gets to decide where things go.
CCAssignFn *AssignFnFixed;
CCAssignFn *AssignFnVarArg;
std::tie(AssignFnFixed, AssignFnVarArg) =
getAssignFnsForCC(Info.CallConv, TLI);
MIRBuilder.buildInstr(AMDGPU::ADJCALLSTACKUP)
.addImm(0)
.addImm(0);
// Create a temporarily-floating call instruction so we can add the implicit
// uses of arg registers.
unsigned Opc = getCallOpcode(MF, Info.Callee.isReg(), false);
auto MIB = MIRBuilder.buildInstrNoInsert(Opc);
MIB.addDef(TRI->getReturnAddressReg(MF));
if (!addCallTargetOperands(MIB, MIRBuilder, Info))
return false;
// Tell the call which registers are clobbered.
const uint32_t *Mask = TRI->getCallPreservedMask(MF, Info.CallConv);
MIB.addRegMask(Mask);
SmallVector<CCValAssign, 16> ArgLocs;
CCState CCInfo(Info.CallConv, Info.IsVarArg, MF, ArgLocs, F.getContext());
// We could pass MIB and directly add the implicit uses to the call
// now. However, as an aesthetic choice, place implicit argument operands
// after the ordinary user argument registers.
SmallVector<std::pair<MCRegister, Register>, 12> ImplicitArgRegs;
if (AMDGPUTargetMachine::EnableFixedFunctionABI &&
Info.CallConv != CallingConv::AMDGPU_Gfx) {
// With a fixed ABI, allocate fixed registers before user arguments.
if (!passSpecialInputs(MIRBuilder, CCInfo, ImplicitArgRegs, Info))
return false;
}
// Do the actual argument marshalling.
SmallVector<Register, 8> PhysRegs;
OutgoingValueAssigner Assigner(AssignFnFixed, AssignFnVarArg);
if (!determineAssignments(Assigner, OutArgs, CCInfo))
return false;
AMDGPUOutgoingArgHandler Handler(MIRBuilder, MRI, MIB, false);
if (!handleAssignments(Handler, OutArgs, CCInfo, ArgLocs, MIRBuilder))
return false;
const SIMachineFunctionInfo *MFI = MF.getInfo<SIMachineFunctionInfo>();
handleImplicitCallArguments(MIRBuilder, MIB, ST, *MFI, ImplicitArgRegs);
// Get a count of how many bytes are to be pushed on the stack.
unsigned NumBytes = CCInfo.getNextStackOffset();
// If Callee is a reg, since it is used by a target specific
// instruction, it must have a register class matching the
// constraint of that instruction.
// FIXME: We should define regbankselectable call instructions to handle
// divergent call targets.
if (MIB->getOperand(1).isReg()) {
MIB->getOperand(1).setReg(constrainOperandRegClass(
MF, *TRI, MRI, *ST.getInstrInfo(),
*ST.getRegBankInfo(), *MIB, MIB->getDesc(), MIB->getOperand(1),
1));
}
// Now we can add the actual call instruction to the correct position.
MIRBuilder.insertInstr(MIB);
// Finally we can copy the returned value back into its virtual-register. In
// symmetry with the arguments, the physical register must be an
// implicit-define of the call instruction.
if (Info.CanLowerReturn && !Info.OrigRet.Ty->isVoidTy()) {
CCAssignFn *RetAssignFn = TLI.CCAssignFnForReturn(Info.CallConv,
Info.IsVarArg);
IncomingValueAssigner Assigner(RetAssignFn);
CallReturnHandler Handler(MIRBuilder, MRI, MIB);
if (!determineAndHandleAssignments(Handler, Assigner, InArgs, MIRBuilder,
Info.CallConv, Info.IsVarArg))
return false;
}
uint64_t CalleePopBytes = NumBytes;
MIRBuilder.buildInstr(AMDGPU::ADJCALLSTACKDOWN)
.addImm(0)
.addImm(CalleePopBytes);
if (!Info.CanLowerReturn) {
insertSRetLoads(MIRBuilder, Info.OrigRet.Ty, Info.OrigRet.Regs,
Info.DemoteRegister, Info.DemoteStackIndex);
}
return true;
}
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