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Diffstat (limited to 'llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp')
| -rw-r--r-- | llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp | 1049 |
1 files changed, 1049 insertions, 0 deletions
diff --git a/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp b/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp new file mode 100644 index 0000000000000..11a8d5def4296 --- /dev/null +++ b/llvm/lib/Target/AArch64/GISel/AArch64CallLowering.cpp @@ -0,0 +1,1049 @@ +//===--- AArch64CallLowering.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 "AArch64CallLowering.h" +#include "AArch64ISelLowering.h" +#include "AArch64MachineFunctionInfo.h" +#include "AArch64Subtarget.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/CodeGen/Analysis.h" +#include "llvm/CodeGen/CallingConvLower.h" +#include "llvm/CodeGen/GlobalISel/MachineIRBuilder.h" +#include "llvm/CodeGen/GlobalISel/Utils.h" +#include "llvm/CodeGen/LowLevelType.h" +#include "llvm/CodeGen/MachineBasicBlock.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineInstrBuilder.h" +#include "llvm/CodeGen/MachineMemOperand.h" +#include "llvm/CodeGen/MachineOperand.h" +#include "llvm/CodeGen/MachineRegisterInfo.h" +#include "llvm/CodeGen/TargetRegisterInfo.h" +#include "llvm/CodeGen/TargetSubtargetInfo.h" +#include "llvm/CodeGen/ValueTypes.h" +#include "llvm/IR/Argument.h" +#include "llvm/IR/Attributes.h" +#include "llvm/IR/Function.h" +#include "llvm/IR/Type.h" +#include "llvm/IR/Value.h" +#include "llvm/Support/MachineValueType.h" +#include <algorithm> +#include <cassert> +#include <cstdint> +#include <iterator> + +#define DEBUG_TYPE "aarch64-call-lowering" + +using namespace llvm; + +AArch64CallLowering::AArch64CallLowering(const AArch64TargetLowering &TLI) + : CallLowering(&TLI) {} + +namespace { +struct IncomingArgHandler : public CallLowering::ValueHandler { + IncomingArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI, + CCAssignFn *AssignFn) + : ValueHandler(MIRBuilder, MRI, AssignFn), StackUsed(0) {} + + Register getStackAddress(uint64_t Size, int64_t Offset, + MachinePointerInfo &MPO) override { + auto &MFI = MIRBuilder.getMF().getFrameInfo(); + int FI = MFI.CreateFixedObject(Size, Offset, true); + MPO = MachinePointerInfo::getFixedStack(MIRBuilder.getMF(), FI); + auto AddrReg = MIRBuilder.buildFrameIndex(LLT::pointer(0, 64), FI); + StackUsed = std::max(StackUsed, Size + Offset); + return AddrReg.getReg(0); + } + + void assignValueToReg(Register ValVReg, Register PhysReg, + CCValAssign &VA) override { + markPhysRegUsed(PhysReg); + switch (VA.getLocInfo()) { + default: + MIRBuilder.buildCopy(ValVReg, PhysReg); + break; + case CCValAssign::LocInfo::SExt: + case CCValAssign::LocInfo::ZExt: + case CCValAssign::LocInfo::AExt: { + auto Copy = MIRBuilder.buildCopy(LLT{VA.getLocVT()}, PhysReg); + MIRBuilder.buildTrunc(ValVReg, Copy); + break; + } + } + } + + void assignValueToAddress(Register ValVReg, Register Addr, uint64_t Size, + MachinePointerInfo &MPO, CCValAssign &VA) override { + MachineFunction &MF = MIRBuilder.getMF(); + auto MMO = MF.getMachineMemOperand( + MPO, MachineMemOperand::MOLoad | MachineMemOperand::MOInvariant, Size, + 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; + + bool isIncomingArgumentHandler() const override { return true; } + + uint64_t StackUsed; +}; + +struct FormalArgHandler : public IncomingArgHandler { + FormalArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI, + CCAssignFn *AssignFn) + : IncomingArgHandler(MIRBuilder, MRI, AssignFn) {} + + void markPhysRegUsed(unsigned PhysReg) override { + MIRBuilder.getMRI()->addLiveIn(PhysReg); + MIRBuilder.getMBB().addLiveIn(PhysReg); + } +}; + +struct CallReturnHandler : public IncomingArgHandler { + CallReturnHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI, + MachineInstrBuilder MIB, CCAssignFn *AssignFn) + : IncomingArgHandler(MIRBuilder, MRI, AssignFn), MIB(MIB) {} + + void markPhysRegUsed(unsigned PhysReg) override { + MIB.addDef(PhysReg, RegState::Implicit); + } + + MachineInstrBuilder MIB; +}; + +struct OutgoingArgHandler : public CallLowering::ValueHandler { + OutgoingArgHandler(MachineIRBuilder &MIRBuilder, MachineRegisterInfo &MRI, + MachineInstrBuilder MIB, CCAssignFn *AssignFn, + CCAssignFn *AssignFnVarArg, bool IsTailCall = false, + int FPDiff = 0) + : ValueHandler(MIRBuilder, MRI, AssignFn), MIB(MIB), + AssignFnVarArg(AssignFnVarArg), IsTailCall(IsTailCall), FPDiff(FPDiff), + StackSize(0), SPReg(0) {} + + bool isIncomingArgumentHandler() const override { return false; } + + Register getStackAddress(uint64_t Size, int64_t Offset, + MachinePointerInfo &MPO) override { + MachineFunction &MF = MIRBuilder.getMF(); + LLT p0 = LLT::pointer(0, 64); + LLT s64 = LLT::scalar(64); + + if (IsTailCall) { + Offset += FPDiff; + int FI = MF.getFrameInfo().CreateFixedObject(Size, Offset, true); + auto FIReg = MIRBuilder.buildFrameIndex(p0, FI); + MPO = MachinePointerInfo::getFixedStack(MF, FI); + return FIReg.getReg(0); + } + + if (!SPReg) + SPReg = MIRBuilder.buildCopy(p0, Register(AArch64::SP)).getReg(0); + + auto OffsetReg = MIRBuilder.buildConstant(s64, Offset); + + auto AddrReg = MIRBuilder.buildPtrAdd(p0, 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 = extendRegister(ValVReg, VA); + MIRBuilder.buildCopy(PhysReg, ExtReg); + } + + void assignValueToAddress(Register ValVReg, Register Addr, uint64_t Size, + MachinePointerInfo &MPO, CCValAssign &VA) override { + MachineFunction &MF = MIRBuilder.getMF(); + auto MMO = MF.getMachineMemOperand(MPO, MachineMemOperand::MOStore, Size, + inferAlignFromPtrInfo(MF, MPO)); + MIRBuilder.buildStore(ValVReg, Addr, *MMO); + } + + void assignValueToAddress(const CallLowering::ArgInfo &Arg, Register Addr, + uint64_t Size, MachinePointerInfo &MPO, + CCValAssign &VA) override { + unsigned MaxSize = Size * 8; + // For varargs, we always want to extend them to 8 bytes, in which case + // we disable setting a max. + if (!Arg.IsFixed) + MaxSize = 0; + + Register ValVReg = VA.getLocInfo() != CCValAssign::LocInfo::FPExt + ? extendRegister(Arg.Regs[0], VA, MaxSize) + : Arg.Regs[0]; + + // If we extended we might need to adjust the MMO's Size. + const LLT RegTy = MRI.getType(ValVReg); + if (RegTy.getSizeInBytes() > Size) + Size = RegTy.getSizeInBytes(); + + assignValueToAddress(ValVReg, Addr, Size, MPO, VA); + } + + bool assignArg(unsigned ValNo, MVT ValVT, MVT LocVT, + CCValAssign::LocInfo LocInfo, + const CallLowering::ArgInfo &Info, + ISD::ArgFlagsTy Flags, + CCState &State) override { + bool Res; + if (Info.IsFixed) + Res = AssignFn(ValNo, ValVT, LocVT, LocInfo, Flags, State); + else + Res = AssignFnVarArg(ValNo, ValVT, LocVT, LocInfo, Flags, State); + + StackSize = State.getNextStackOffset(); + return Res; + } + + MachineInstrBuilder MIB; + CCAssignFn *AssignFnVarArg; + bool IsTailCall; + + /// For tail calls, the byte offset of the call's argument area from the + /// callee's. Unused elsewhere. + int FPDiff; + uint64_t StackSize; + + // Cache the SP register vreg if we need it more than once in this call site. + Register SPReg; +}; +} // namespace + +static bool doesCalleeRestoreStack(CallingConv::ID CallConv, bool TailCallOpt) { + return CallConv == CallingConv::Fast && TailCallOpt; +} + +void AArch64CallLowering::splitToValueTypes( + const ArgInfo &OrigArg, SmallVectorImpl<ArgInfo> &SplitArgs, + const DataLayout &DL, MachineRegisterInfo &MRI, CallingConv::ID CallConv) const { + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + LLVMContext &Ctx = OrigArg.Ty->getContext(); + + SmallVector<EVT, 4> SplitVTs; + SmallVector<uint64_t, 4> Offsets; + ComputeValueVTs(TLI, DL, OrigArg.Ty, SplitVTs, &Offsets, 0); + + if (SplitVTs.size() == 0) + return; + + if (SplitVTs.size() == 1) { + // No splitting to do, but we want to replace the original type (e.g. [1 x + // double] -> double). + SplitArgs.emplace_back(OrigArg.Regs[0], SplitVTs[0].getTypeForEVT(Ctx), + OrigArg.Flags[0], OrigArg.IsFixed); + return; + } + + // Create one ArgInfo for each virtual register in the original ArgInfo. + assert(OrigArg.Regs.size() == SplitVTs.size() && "Regs / types mismatch"); + + bool NeedsRegBlock = TLI.functionArgumentNeedsConsecutiveRegisters( + OrigArg.Ty, CallConv, false); + for (unsigned i = 0, e = SplitVTs.size(); i < e; ++i) { + Type *SplitTy = SplitVTs[i].getTypeForEVT(Ctx); + SplitArgs.emplace_back(OrigArg.Regs[i], SplitTy, OrigArg.Flags[0], + OrigArg.IsFixed); + if (NeedsRegBlock) + SplitArgs.back().Flags[0].setInConsecutiveRegs(); + } + + SplitArgs.back().Flags[0].setInConsecutiveRegsLast(); +} + +bool AArch64CallLowering::lowerReturn(MachineIRBuilder &MIRBuilder, + const Value *Val, + ArrayRef<Register> VRegs, + Register SwiftErrorVReg) const { + auto MIB = MIRBuilder.buildInstrNoInsert(AArch64::RET_ReallyLR); + assert(((Val && !VRegs.empty()) || (!Val && VRegs.empty())) && + "Return value without a vreg"); + + bool Success = true; + if (!VRegs.empty()) { + MachineFunction &MF = MIRBuilder.getMF(); + const Function &F = MF.getFunction(); + + MachineRegisterInfo &MRI = MF.getRegInfo(); + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + CCAssignFn *AssignFn = TLI.CCAssignFnForReturn(F.getCallingConv()); + auto &DL = F.getParent()->getDataLayout(); + LLVMContext &Ctx = Val->getType()->getContext(); + + SmallVector<EVT, 4> 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> SplitArgs; + CallingConv::ID CC = F.getCallingConv(); + + for (unsigned i = 0; i < SplitEVTs.size(); ++i) { + if (TLI.getNumRegistersForCallingConv(Ctx, CC, SplitEVTs[i]) > 1) { + LLVM_DEBUG(dbgs() << "Can't handle extended arg types which need split"); + return false; + } + + Register CurVReg = VRegs[i]; + ArgInfo CurArgInfo = ArgInfo{CurVReg, SplitEVTs[i].getTypeForEVT(Ctx)}; + setArgFlags(CurArgInfo, AttributeList::ReturnIndex, DL, F); + + // i1 is a special case because SDAG i1 true is naturally zero extended + // when widened using ANYEXT. We need to do it explicitly here. + if (MRI.getType(CurVReg).getSizeInBits() == 1) { + CurVReg = MIRBuilder.buildZExt(LLT::scalar(8), CurVReg).getReg(0); + } else { + // Some types will need extending as specified by the CC. + MVT NewVT = TLI.getRegisterTypeForCallingConv(Ctx, CC, SplitEVTs[i]); + if (EVT(NewVT) != SplitEVTs[i]) { + unsigned ExtendOp = TargetOpcode::G_ANYEXT; + if (F.getAttributes().hasAttribute(AttributeList::ReturnIndex, + Attribute::SExt)) + ExtendOp = TargetOpcode::G_SEXT; + else if (F.getAttributes().hasAttribute(AttributeList::ReturnIndex, + Attribute::ZExt)) + ExtendOp = TargetOpcode::G_ZEXT; + + LLT NewLLT(NewVT); + LLT OldLLT(MVT::getVT(CurArgInfo.Ty)); + CurArgInfo.Ty = EVT(NewVT).getTypeForEVT(Ctx); + // Instead of an extend, we might have a vector type which needs + // padding with more elements, e.g. <2 x half> -> <4 x half>. + if (NewVT.isVector()) { + if (OldLLT.isVector()) { + if (NewLLT.getNumElements() > OldLLT.getNumElements()) { + // We don't handle VA types which are not exactly twice the + // size, but can easily be done in future. + if (NewLLT.getNumElements() != OldLLT.getNumElements() * 2) { + LLVM_DEBUG(dbgs() << "Outgoing vector ret has too many elts"); + return false; + } + auto Undef = MIRBuilder.buildUndef({OldLLT}); + CurVReg = + MIRBuilder.buildMerge({NewLLT}, {CurVReg, Undef}).getReg(0); + } else { + // Just do a vector extend. + CurVReg = MIRBuilder.buildInstr(ExtendOp, {NewLLT}, {CurVReg}) + .getReg(0); + } + } else if (NewLLT.getNumElements() == 2) { + // We need to pad a <1 x S> type to <2 x S>. Since we don't have + // <1 x S> vector types in GISel we use a build_vector instead + // of a vector merge/concat. + auto Undef = MIRBuilder.buildUndef({OldLLT}); + CurVReg = + MIRBuilder + .buildBuildVector({NewLLT}, {CurVReg, Undef.getReg(0)}) + .getReg(0); + } else { + LLVM_DEBUG(dbgs() << "Could not handle ret ty"); + return false; + } + } else { + // A scalar extend. + CurVReg = + MIRBuilder.buildInstr(ExtendOp, {NewLLT}, {CurVReg}).getReg(0); + } + } + } + if (CurVReg != CurArgInfo.Regs[0]) { + CurArgInfo.Regs[0] = CurVReg; + // Reset the arg flags after modifying CurVReg. + setArgFlags(CurArgInfo, AttributeList::ReturnIndex, DL, F); + } + splitToValueTypes(CurArgInfo, SplitArgs, DL, MRI, CC); + } + + OutgoingArgHandler Handler(MIRBuilder, MRI, MIB, AssignFn, AssignFn); + Success = handleAssignments(MIRBuilder, SplitArgs, Handler); + } + + if (SwiftErrorVReg) { + MIB.addUse(AArch64::X21, RegState::Implicit); + MIRBuilder.buildCopy(AArch64::X21, SwiftErrorVReg); + } + + MIRBuilder.insertInstr(MIB); + return Success; +} + +/// Helper function to compute forwarded registers for musttail calls. Computes +/// the forwarded registers, sets MBB liveness, and emits COPY instructions that +/// can be used to save + restore registers later. +static void handleMustTailForwardedRegisters(MachineIRBuilder &MIRBuilder, + CCAssignFn *AssignFn) { + MachineBasicBlock &MBB = MIRBuilder.getMBB(); + MachineFunction &MF = MIRBuilder.getMF(); + MachineFrameInfo &MFI = MF.getFrameInfo(); + + if (!MFI.hasMustTailInVarArgFunc()) + return; + + AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>(); + const Function &F = MF.getFunction(); + assert(F.isVarArg() && "Expected F to be vararg?"); + + // Compute the set of forwarded registers. The rest are scratch. + SmallVector<CCValAssign, 16> ArgLocs; + CCState CCInfo(F.getCallingConv(), /*IsVarArg=*/true, MF, ArgLocs, + F.getContext()); + SmallVector<MVT, 2> RegParmTypes; + RegParmTypes.push_back(MVT::i64); + RegParmTypes.push_back(MVT::f128); + + // Later on, we can use this vector to restore the registers if necessary. + SmallVectorImpl<ForwardedRegister> &Forwards = + FuncInfo->getForwardedMustTailRegParms(); + CCInfo.analyzeMustTailForwardedRegisters(Forwards, RegParmTypes, AssignFn); + + // Conservatively forward X8, since it might be used for an aggregate + // return. + if (!CCInfo.isAllocated(AArch64::X8)) { + unsigned X8VReg = MF.addLiveIn(AArch64::X8, &AArch64::GPR64RegClass); + Forwards.push_back(ForwardedRegister(X8VReg, AArch64::X8, MVT::i64)); + } + + // Add the forwards to the MachineBasicBlock and MachineFunction. + for (const auto &F : Forwards) { + MBB.addLiveIn(F.PReg); + MIRBuilder.buildCopy(Register(F.VReg), Register(F.PReg)); + } +} + +bool AArch64CallLowering::fallBackToDAGISel(const Function &F) const { + if (isa<ScalableVectorType>(F.getReturnType())) + return true; + return llvm::any_of(F.args(), [](const Argument &A) { + return isa<ScalableVectorType>(A.getType()); + }); +} + +bool AArch64CallLowering::lowerFormalArguments( + MachineIRBuilder &MIRBuilder, const Function &F, + ArrayRef<ArrayRef<Register>> VRegs) const { + MachineFunction &MF = MIRBuilder.getMF(); + MachineBasicBlock &MBB = MIRBuilder.getMBB(); + MachineRegisterInfo &MRI = MF.getRegInfo(); + auto &DL = F.getParent()->getDataLayout(); + + SmallVector<ArgInfo, 8> SplitArgs; + unsigned i = 0; + for (auto &Arg : F.args()) { + if (DL.getTypeStoreSize(Arg.getType()).isZero()) + continue; + + ArgInfo OrigArg{VRegs[i], Arg.getType()}; + setArgFlags(OrigArg, i + AttributeList::FirstArgIndex, DL, F); + + splitToValueTypes(OrigArg, SplitArgs, DL, MRI, F.getCallingConv()); + ++i; + } + + if (!MBB.empty()) + MIRBuilder.setInstr(*MBB.begin()); + + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + CCAssignFn *AssignFn = + TLI.CCAssignFnForCall(F.getCallingConv(), /*IsVarArg=*/false); + + FormalArgHandler Handler(MIRBuilder, MRI, AssignFn); + if (!handleAssignments(MIRBuilder, SplitArgs, Handler)) + return false; + + AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>(); + uint64_t StackOffset = Handler.StackUsed; + if (F.isVarArg()) { + auto &Subtarget = MF.getSubtarget<AArch64Subtarget>(); + if (!Subtarget.isTargetDarwin()) { + // FIXME: we need to reimplement saveVarArgsRegisters from + // AArch64ISelLowering. + return false; + } + + // We currently pass all varargs at 8-byte alignment, or 4 in ILP32. + StackOffset = alignTo(Handler.StackUsed, Subtarget.isTargetILP32() ? 4 : 8); + + auto &MFI = MIRBuilder.getMF().getFrameInfo(); + FuncInfo->setVarArgsStackIndex(MFI.CreateFixedObject(4, StackOffset, true)); + } + + if (doesCalleeRestoreStack(F.getCallingConv(), + MF.getTarget().Options.GuaranteedTailCallOpt)) { + // We have a non-standard ABI, so why not make full use of the stack that + // we're going to pop? It must be aligned to 16 B in any case. + StackOffset = alignTo(StackOffset, 16); + + // If we're expected to restore the stack (e.g. fastcc), then we'll be + // adding a multiple of 16. + FuncInfo->setArgumentStackToRestore(StackOffset); + + // Our own callers will guarantee that the space is free by giving an + // aligned value to CALLSEQ_START. + } + + // 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. + FuncInfo->setBytesInStackArgArea(StackOffset); + + auto &Subtarget = MF.getSubtarget<AArch64Subtarget>(); + if (Subtarget.hasCustomCallingConv()) + Subtarget.getRegisterInfo()->UpdateCustomCalleeSavedRegs(MF); + + handleMustTailForwardedRegisters(MIRBuilder, AssignFn); + + // Move back to the end of the basic block. + MIRBuilder.setMBB(MBB); + + return true; +} + +/// 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::PreserveMost: + case CallingConv::Swift: + return true; + default: + return canGuaranteeTCO(CC); + } +} + +/// Returns a pair containing the fixed CCAssignFn and the vararg CCAssignFn for +/// CC. +static std::pair<CCAssignFn *, CCAssignFn *> +getAssignFnsForCC(CallingConv::ID CC, const AArch64TargetLowering &TLI) { + return {TLI.CCAssignFnForCall(CC, false), TLI.CCAssignFnForCall(CC, true)}; +} + +bool AArch64CallLowering::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; + + // Check if the caller and callee will handle arguments in the same way. + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + CCAssignFn *CalleeAssignFnFixed; + CCAssignFn *CalleeAssignFnVarArg; + std::tie(CalleeAssignFnFixed, CalleeAssignFnVarArg) = + getAssignFnsForCC(CalleeCC, TLI); + + CCAssignFn *CallerAssignFnFixed; + CCAssignFn *CallerAssignFnVarArg; + std::tie(CallerAssignFnFixed, CallerAssignFnVarArg) = + getAssignFnsForCC(CallerCC, TLI); + + if (!resultsCompatible(Info, MF, InArgs, *CalleeAssignFnFixed, + *CalleeAssignFnVarArg, *CallerAssignFnFixed, + *CallerAssignFnVarArg)) + return false; + + // Make sure that the caller and callee preserve all of the same registers. + auto TRI = MF.getSubtarget<AArch64Subtarget>().getRegisterInfo(); + const uint32_t *CallerPreserved = TRI->getCallPreservedMask(MF, CallerCC); + const uint32_t *CalleePreserved = TRI->getCallPreservedMask(MF, CalleeCC); + if (MF.getSubtarget<AArch64Subtarget>().hasCustomCallingConv()) { + TRI->UpdateCustomCallPreservedMask(MF, &CallerPreserved); + TRI->UpdateCustomCallPreservedMask(MF, &CalleePreserved); + } + + return TRI->regmaskSubsetEqual(CallerPreserved, CalleePreserved); +} + +bool AArch64CallLowering::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 AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + + 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()); + + if (!analyzeArgInfo(OutInfo, OutArgs, *AssignFnFixed, *AssignFnVarArg)) { + LLVM_DEBUG(dbgs() << "... Could not analyze call operands.\n"); + return false; + } + + // Make sure that they can fit on the caller's stack. + const AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>(); + 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. + // TODO: Port this over to CallLowering as general code once swiftself is + // supported. + auto TRI = MF.getSubtarget<AArch64Subtarget>().getRegisterInfo(); + const uint32_t *CallerPreservedMask = TRI->getCallPreservedMask(MF, CallerCC); + MachineRegisterInfo &MRI = MF.getRegInfo(); + + for (unsigned i = 0; i < OutLocs.size(); ++i) { + auto &ArgLoc = OutLocs[i]; + // If it's not a register, it's fine. + if (!ArgLoc.isRegLoc()) { + if (Info.IsVarArg) { + // Be conservative and disallow variadic memory operands to match SDAG's + // behaviour. + // FIXME: If the caller's calling convention is C, then we can + // potentially use its argument area. However, for cases like fastcc, + // we can't do anything. + LLVM_DEBUG( + dbgs() + << "... Cannot tail call vararg function with stack arguments\n"); + return false; + } + continue; + } + + Register Reg = ArgLoc.getLocReg(); + + // Only look at callee-saved registers. + if (MachineOperand::clobbersPhysReg(CallerPreservedMask, Reg)) + continue; + + LLVM_DEBUG( + dbgs() + << "... Call has an argument passed in a callee-saved register.\n"); + + // Check if it was copied from. + ArgInfo &OutInfo = OutArgs[i]; + + if (OutInfo.Regs.size() > 1) { + LLVM_DEBUG( + dbgs() << "... Cannot handle arguments in multiple registers.\n"); + return false; + } + + // Check if we copy the register, walking through copies from virtual + // registers. Note that getDefIgnoringCopies does not ignore copies from + // physical registers. + MachineInstr *RegDef = getDefIgnoringCopies(OutInfo.Regs[0], MRI); + if (!RegDef || RegDef->getOpcode() != TargetOpcode::COPY) { + LLVM_DEBUG( + dbgs() + << "... Parameter was not copied into a VReg, cannot tail call.\n"); + return false; + } + + // Got a copy. Verify that it's the same as the register we want. + Register CopyRHS = RegDef->getOperand(1).getReg(); + if (CopyRHS != Reg) { + LLVM_DEBUG(dbgs() << "... Callee-saved register was not copied into " + "VReg, cannot tail call.\n"); + return false; + } + } + + return true; +} + +bool AArch64CallLowering::isEligibleForTailCallOptimization( + MachineIRBuilder &MIRBuilder, 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; + + CallingConv::ID CalleeCC = Info.CallConv; + MachineFunction &MF = MIRBuilder.getMF(); + const Function &CallerF = MF.getFunction(); + + LLVM_DEBUG(dbgs() << "Attempting to lower call as tail call\n"); + + if (Info.SwiftErrorVReg) { + // TODO: We should handle this. + // Note that this is also handled by the check for no outgoing arguments. + // Proactively disabling this though, because the swifterror handling in + // lowerCall inserts a COPY *after* the location of the call. + LLVM_DEBUG(dbgs() << "... Cannot handle tail calls with swifterror yet.\n"); + return false; + } + + if (!mayTailCallThisCC(CalleeCC)) { + LLVM_DEBUG(dbgs() << "... Calling convention cannot be tail called.\n"); + return false; + } + + // Byval parameters hand the function a pointer directly into the stack area + // we want to reuse during a tail call. Working around this *is* possible (see + // X86). + // + // FIXME: In AArch64ISelLowering, this isn't worked around. Can/should we try + // it? + // + // On Windows, "inreg" attributes signify non-aggregate indirect returns. + // In this case, it is necessary to save/restore X0 in the callee. Tail + // call opt interferes with this. So we disable tail call opt when the + // caller has an argument with "inreg" attribute. + // + // FIXME: Check whether the callee also has an "inreg" argument. + // + // When the caller has a swifterror argument, we don't want to tail call + // because would have to move into the swifterror register before the + // tail call. + if (any_of(CallerF.args(), [](const Argument &A) { + return A.hasByValAttr() || A.hasInRegAttr() || A.hasSwiftErrorAttr(); + })) { + LLVM_DEBUG(dbgs() << "... Cannot tail call from callers with byval, " + "inreg, or swifterror arguments\n"); + return false; + } + + // Externally-defined functions with weak linkage should not be + // tail-called on AArch64 when the OS does not support dynamic + // pre-emption of symbols, as the AAELF spec requires normal calls + // to undefined weak functions to be replaced with a NOP or jump to the + // next instruction. The behaviour of branch instructions in this + // situation (as used for tail calls) is implementation-defined, so we + // cannot rely on the linker replacing the tail call with a return. + if (Info.Callee.isGlobal()) { + const GlobalValue *GV = Info.Callee.getGlobal(); + const Triple &TT = MF.getTarget().getTargetTriple(); + if (GV->hasExternalWeakLinkage() && + (!TT.isOSWindows() || TT.isOSBinFormatELF() || + TT.isOSBinFormatMachO())) { + LLVM_DEBUG(dbgs() << "... Cannot tail call externally-defined function " + "with weak linkage for this OS.\n"); + return false; + } + } + + // If we have -tailcallopt, then we're done. + if (MF.getTarget().Options.GuaranteedTailCallOpt) + return canGuaranteeTCO(CalleeCC) && CalleeCC == CallerF.getCallingConv(); + + // We don't have -tailcallopt, so we're allowed to change the ABI (sibcall). + // Try to find cases where we can do that. + + // I want anyone implementing a new calling convention to think long and hard + // about this assert. + assert((!Info.IsVarArg || CalleeCC == CallingConv::C) && + "Unexpected variadic calling convention"); + + // 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; +} + +static unsigned getCallOpcode(const MachineFunction &CallerF, bool IsIndirect, + bool IsTailCall) { + if (!IsTailCall) + return IsIndirect ? getBLRCallOpcode(CallerF) : (unsigned)AArch64::BL; + + if (!IsIndirect) + return AArch64::TCRETURNdi; + + // When BTI is enabled, we need to use TCRETURNriBTI to make sure that we use + // x16 or x17. + if (CallerF.getFunction().hasFnAttribute("branch-target-enforcement")) + return AArch64::TCRETURNriBTI; + + return AArch64::TCRETURNri; +} + +bool AArch64CallLowering::lowerTailCall( + MachineIRBuilder &MIRBuilder, CallLoweringInfo &Info, + SmallVectorImpl<ArgInfo> &OutArgs) const { + MachineFunction &MF = MIRBuilder.getMF(); + const Function &F = MF.getFunction(); + MachineRegisterInfo &MRI = MF.getRegInfo(); + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + AArch64FunctionInfo *FuncInfo = MF.getInfo<AArch64FunctionInfo>(); + + // True when we're tail calling, but without -tailcallopt. + bool IsSibCall = !MF.getTarget().Options.GuaranteedTailCallOpt; + + // TODO: Right now, regbankselect doesn't know how to handle the rtcGPR64 + // register class. Until we can do that, we should fall back here. + if (F.hasFnAttribute("branch-target-enforcement")) { + LLVM_DEBUG( + dbgs() << "Cannot lower indirect tail calls with BTI enabled yet.\n"); + return false; + } + + // 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(AArch64::ADJCALLSTACKDOWN); + + unsigned Opc = getCallOpcode(MF, Info.Callee.isReg(), true); + auto MIB = MIRBuilder.buildInstrNoInsert(Opc); + MIB.add(Info.Callee); + + // 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. + auto TRI = MF.getSubtarget<AArch64Subtarget>().getRegisterInfo(); + const uint32_t *Mask = TRI->getCallPreservedMask(MF, CalleeCC); + if (MF.getSubtarget<AArch64Subtarget>().hasCustomCallingConv()) + TRI->UpdateCustomCallPreservedMask(MF, &Mask); + MIB.addRegMask(Mask); + + if (TRI->isAnyArgRegReserved(MF)) + TRI->emitReservedArgRegCallError(MF); + + // 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()); + analyzeArgInfo(OutInfo, OutArgs, *AssignFnFixed, *AssignFnVarArg); + + // The callee will pop the argument stack as a tail call. Thus, we must + // keep it 16-byte aligned. + NumBytes = alignTo(OutInfo.getNextStackOffset(), 16); + + // 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(FPDiff % 16 == 0 && "unaligned stack on tail call"); + } + + const auto &Forwards = FuncInfo->getForwardedMustTailRegParms(); + + // Do the actual argument marshalling. + OutgoingArgHandler Handler(MIRBuilder, MRI, MIB, AssignFnFixed, + AssignFnVarArg, true, FPDiff); + if (!handleAssignments(MIRBuilder, OutArgs, Handler)) + return false; + + if (Info.IsVarArg && Info.IsMustTailCall) { + // Now we know what's being passed to the function. Add uses to the call for + // the forwarded registers that we *aren't* passing as parameters. This will + // preserve the copies we build earlier. + for (const auto &F : Forwards) { + Register ForwardedReg = F.PReg; + // If the register is already passed, or aliases a register which is + // already being passed, then skip it. + if (any_of(MIB->uses(), [&ForwardedReg, &TRI](const MachineOperand &Use) { + if (!Use.isReg()) + return false; + return TRI->regsOverlap(Use.getReg(), ForwardedReg); + })) + continue; + + // We aren't passing it already, so we should add it to the call. + MIRBuilder.buildCopy(ForwardedReg, Register(F.VReg)); + MIB.addReg(ForwardedReg, RegState::Implicit); + } + } + + // 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(AArch64::ADJCALLSTACKUP).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. + if (Info.Callee.isReg()) + MIB->getOperand(0).setReg(constrainOperandRegClass( + MF, *TRI, MRI, *MF.getSubtarget().getInstrInfo(), + *MF.getSubtarget().getRegBankInfo(), *MIB, MIB->getDesc(), Info.Callee, + 0)); + + MF.getFrameInfo().setHasTailCall(); + Info.LoweredTailCall = true; + return true; +} + +bool AArch64CallLowering::lowerCall(MachineIRBuilder &MIRBuilder, + CallLoweringInfo &Info) const { + MachineFunction &MF = MIRBuilder.getMF(); + const Function &F = MF.getFunction(); + MachineRegisterInfo &MRI = MF.getRegInfo(); + auto &DL = F.getParent()->getDataLayout(); + const AArch64TargetLowering &TLI = *getTLI<AArch64TargetLowering>(); + + SmallVector<ArgInfo, 8> OutArgs; + for (auto &OrigArg : Info.OrigArgs) { + splitToValueTypes(OrigArg, OutArgs, DL, MRI, Info.CallConv); + // AAPCS requires that we zero-extend i1 to 8 bits by the caller. + if (OrigArg.Ty->isIntegerTy(1)) + OutArgs.back().Flags[0].setZExt(); + } + + SmallVector<ArgInfo, 8> InArgs; + if (!Info.OrigRet.Ty->isVoidTy()) + splitToValueTypes(Info.OrigRet, InArgs, DL, MRI, F.getCallingConv()); + + // 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) { + // There are types of incoming/outgoing arguments we can't handle yet, so + // it doesn't make sense to actually die here like in ISelLowering. Instead, + // fall back to SelectionDAG and let it try to handle this. + 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); + + MachineInstrBuilder CallSeqStart; + CallSeqStart = MIRBuilder.buildInstr(AArch64::ADJCALLSTACKDOWN); + + // 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.add(Info.Callee); + + // Tell the call which registers are clobbered. + auto TRI = MF.getSubtarget<AArch64Subtarget>().getRegisterInfo(); + const uint32_t *Mask = TRI->getCallPreservedMask(MF, Info.CallConv); + if (MF.getSubtarget<AArch64Subtarget>().hasCustomCallingConv()) + TRI->UpdateCustomCallPreservedMask(MF, &Mask); + MIB.addRegMask(Mask); + + if (TRI->isAnyArgRegReserved(MF)) + TRI->emitReservedArgRegCallError(MF); + + // Do the actual argument marshalling. + OutgoingArgHandler Handler(MIRBuilder, MRI, MIB, AssignFnFixed, + AssignFnVarArg, false); + if (!handleAssignments(MIRBuilder, OutArgs, Handler)) + return false; + + // 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. + if (Info.Callee.isReg()) + MIB->getOperand(0).setReg(constrainOperandRegClass( + MF, *TRI, MRI, *MF.getSubtarget().getInstrInfo(), + *MF.getSubtarget().getRegBankInfo(), *MIB, MIB->getDesc(), Info.Callee, + 0)); + + // 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.OrigRet.Ty->isVoidTy()) { + CCAssignFn *RetAssignFn = TLI.CCAssignFnForReturn(Info.CallConv); + CallReturnHandler Handler(MIRBuilder, MRI, MIB, RetAssignFn); + if (!handleAssignments(MIRBuilder, InArgs, Handler)) + return false; + } + + if (Info.SwiftErrorVReg) { + MIB.addDef(AArch64::X21, RegState::Implicit); + MIRBuilder.buildCopy(Info.SwiftErrorVReg, Register(AArch64::X21)); + } + + uint64_t CalleePopBytes = + doesCalleeRestoreStack(Info.CallConv, + MF.getTarget().Options.GuaranteedTailCallOpt) + ? alignTo(Handler.StackSize, 16) + : 0; + + CallSeqStart.addImm(Handler.StackSize).addImm(0); + MIRBuilder.buildInstr(AArch64::ADJCALLSTACKUP) + .addImm(Handler.StackSize) + .addImm(CalleePopBytes); + + return true; +} |