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llvm-project/llvm/lib/Target/AArch64/AArch64InstructionSelector.cpp

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//===- AArch64InstructionSelector.cpp ----------------------------*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
/// \file
/// This file implements the targeting of the InstructionSelector class for
/// AArch64.
/// \todo This should be generated by TableGen.
//===----------------------------------------------------------------------===//
#include "AArch64InstructionSelector.h"
#include "AArch64InstrInfo.h"
#include "AArch64RegisterBankInfo.h"
#include "AArch64RegisterInfo.h"
#include "AArch64Subtarget.h"
#include "AArch64TargetMachine.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrBuilder.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/IR/Type.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/raw_ostream.h"
#define DEBUG_TYPE "aarch64-isel"
using namespace llvm;
#ifndef LLVM_BUILD_GLOBAL_ISEL
#error "You shouldn't build this"
#endif
AArch64InstructionSelector::AArch64InstructionSelector(
const AArch64TargetMachine &TM, const AArch64Subtarget &STI,
const AArch64RegisterBankInfo &RBI)
: InstructionSelector(), TM(TM), STI(STI), TII(*STI.getInstrInfo()),
TRI(*STI.getRegisterInfo()), RBI(RBI) {}
/// Check whether \p I is a currently unsupported binary operation:
/// - it has an unsized type
/// - an operand is not a vreg
/// - all operands are not in the same bank
/// These are checks that should someday live in the verifier, but right now,
/// these are mostly limitations of the aarch64 selector.
static bool unsupportedBinOp(const MachineInstr &I,
const AArch64RegisterBankInfo &RBI,
const MachineRegisterInfo &MRI,
const AArch64RegisterInfo &TRI) {
LLT Ty = MRI.getType(I.getOperand(0).getReg());
if (!Ty.isValid()) {
DEBUG(dbgs() << "Generic binop register should be typed\n");
return true;
}
const RegisterBank *PrevOpBank = nullptr;
for (auto &MO : I.operands()) {
// FIXME: Support non-register operands.
if (!MO.isReg()) {
DEBUG(dbgs() << "Generic inst non-reg operands are unsupported\n");
return true;
}
// FIXME: Can generic operations have physical registers operands? If
// so, this will need to be taught about that, and we'll need to get the
// bank out of the minimal class for the register.
// Either way, this needs to be documented (and possibly verified).
if (!TargetRegisterInfo::isVirtualRegister(MO.getReg())) {
DEBUG(dbgs() << "Generic inst has physical register operand\n");
return true;
}
const RegisterBank *OpBank = RBI.getRegBank(MO.getReg(), MRI, TRI);
if (!OpBank) {
DEBUG(dbgs() << "Generic register has no bank or class\n");
return true;
}
if (PrevOpBank && OpBank != PrevOpBank) {
DEBUG(dbgs() << "Generic inst operands have different banks\n");
return true;
}
PrevOpBank = OpBank;
}
return false;
}
/// Select the AArch64 opcode for the basic binary operation \p GenericOpc
/// (such as G_OR or G_ADD), appropriate for the register bank \p RegBankID
/// and of size \p OpSize.
/// \returns \p GenericOpc if the combination is unsupported.
static unsigned selectBinaryOp(unsigned GenericOpc, unsigned RegBankID,
unsigned OpSize) {
switch (RegBankID) {
case AArch64::GPRRegBankID:
switch (OpSize) {
case 32:
switch (GenericOpc) {
case TargetOpcode::G_OR:
return AArch64::ORRWrr;
case TargetOpcode::G_XOR:
return AArch64::EORWrr;
case TargetOpcode::G_AND:
return AArch64::ANDWrr;
case TargetOpcode::G_ADD:
return AArch64::ADDWrr;
case TargetOpcode::G_SUB:
return AArch64::SUBWrr;
case TargetOpcode::G_SHL:
return AArch64::LSLVWr;
case TargetOpcode::G_LSHR:
return AArch64::LSRVWr;
case TargetOpcode::G_ASHR:
return AArch64::ASRVWr;
case TargetOpcode::G_SDIV:
return AArch64::SDIVWr;
case TargetOpcode::G_UDIV:
return AArch64::UDIVWr;
default:
return GenericOpc;
}
case 64:
switch (GenericOpc) {
case TargetOpcode::G_OR:
return AArch64::ORRXrr;
case TargetOpcode::G_XOR:
return AArch64::EORXrr;
case TargetOpcode::G_AND:
return AArch64::ANDXrr;
case TargetOpcode::G_ADD:
case TargetOpcode::G_GEP:
return AArch64::ADDXrr;
case TargetOpcode::G_SUB:
return AArch64::SUBXrr;
case TargetOpcode::G_SHL:
return AArch64::LSLVXr;
case TargetOpcode::G_LSHR:
return AArch64::LSRVXr;
case TargetOpcode::G_ASHR:
return AArch64::ASRVXr;
case TargetOpcode::G_SDIV:
return AArch64::SDIVXr;
case TargetOpcode::G_UDIV:
return AArch64::UDIVXr;
default:
return GenericOpc;
}
}
case AArch64::FPRRegBankID:
switch (OpSize) {
case 32:
switch (GenericOpc) {
case TargetOpcode::G_FADD:
return AArch64::FADDSrr;
case TargetOpcode::G_FSUB:
return AArch64::FSUBSrr;
case TargetOpcode::G_FMUL:
return AArch64::FMULSrr;
case TargetOpcode::G_FDIV:
return AArch64::FDIVSrr;
default:
return GenericOpc;
}
case 64:
switch (GenericOpc) {
case TargetOpcode::G_FADD:
return AArch64::FADDDrr;
case TargetOpcode::G_FSUB:
return AArch64::FSUBDrr;
case TargetOpcode::G_FMUL:
return AArch64::FMULDrr;
case TargetOpcode::G_FDIV:
return AArch64::FDIVDrr;
case TargetOpcode::G_OR:
return AArch64::ORRv8i8;
default:
return GenericOpc;
}
}
};
return GenericOpc;
}
/// Select the AArch64 opcode for the G_LOAD or G_STORE operation \p GenericOpc,
/// appropriate for the (value) register bank \p RegBankID and of memory access
/// size \p OpSize. This returns the variant with the base+unsigned-immediate
/// addressing mode (e.g., LDRXui).
/// \returns \p GenericOpc if the combination is unsupported.
static unsigned selectLoadStoreUIOp(unsigned GenericOpc, unsigned RegBankID,
unsigned OpSize) {
const bool isStore = GenericOpc == TargetOpcode::G_STORE;
switch (RegBankID) {
case AArch64::GPRRegBankID:
switch (OpSize) {
case 32:
return isStore ? AArch64::STRWui : AArch64::LDRWui;
case 64:
return isStore ? AArch64::STRXui : AArch64::LDRXui;
}
case AArch64::FPRRegBankID:
switch (OpSize) {
case 32:
return isStore ? AArch64::STRSui : AArch64::LDRSui;
case 64:
return isStore ? AArch64::STRDui : AArch64::LDRDui;
}
};
return GenericOpc;
}
static bool selectCopy(MachineInstr &I, const TargetInstrInfo &TII,
MachineRegisterInfo &MRI, const TargetRegisterInfo &TRI,
const RegisterBankInfo &RBI) {
unsigned DstReg = I.getOperand(0).getReg();
if (TargetRegisterInfo::isPhysicalRegister(DstReg)) {
assert(I.isCopy() && "Generic operators do not allow physical registers");
return true;
}
const RegisterBank &RegBank = *RBI.getRegBank(DstReg, MRI, TRI);
const unsigned DstSize = MRI.getType(DstReg).getSizeInBits();
unsigned SrcReg = I.getOperand(1).getReg();
const unsigned SrcSize = RBI.getSizeInBits(SrcReg, MRI, TRI);
(void)SrcSize;
assert((!TargetRegisterInfo::isPhysicalRegister(SrcReg) || I.isCopy()) &&
"No phys reg on generic operators");
assert(
(DstSize == SrcSize ||
// Copies are a mean to setup initial types, the number of
// bits may not exactly match.
(TargetRegisterInfo::isPhysicalRegister(SrcReg) &&
DstSize <= RBI.getSizeInBits(SrcReg, MRI, TRI)) ||
// Copies are a mean to copy bits around, as long as we are
// on the same register class, that's fine. Otherwise, that
// means we need some SUBREG_TO_REG or AND & co.
(((DstSize + 31) / 32 == (SrcSize + 31) / 32) && DstSize > SrcSize)) &&
"Copy with different width?!");
assert((DstSize <= 64 || RegBank.getID() == AArch64::FPRRegBankID) &&
"GPRs cannot get more than 64-bit width values");
const TargetRegisterClass *RC = nullptr;
if (RegBank.getID() == AArch64::FPRRegBankID) {
if (DstSize <= 32)
RC = &AArch64::FPR32RegClass;
else if (DstSize <= 64)
RC = &AArch64::FPR64RegClass;
else if (DstSize <= 128)
RC = &AArch64::FPR128RegClass;
else {
DEBUG(dbgs() << "Unexpected bitcast size " << DstSize << '\n');
return false;
}
} else {
assert(RegBank.getID() == AArch64::GPRRegBankID &&
"Bitcast for the flags?");
RC =
DstSize <= 32 ? &AArch64::GPR32allRegClass : &AArch64::GPR64allRegClass;
}
// No need to constrain SrcReg. It will get constrained when
// we hit another of its use or its defs.
// Copies do not have constraints.
if (!RBI.constrainGenericRegister(DstReg, *RC, MRI)) {
DEBUG(dbgs() << "Failed to constrain " << TII.getName(I.getOpcode())
<< " operand\n");
return false;
}
I.setDesc(TII.get(AArch64::COPY));
return true;
}
static AArch64CC::CondCode changeICMPPredToAArch64CC(CmpInst::Predicate P) {
switch (P) {
default:
llvm_unreachable("Unknown condition code!");
case CmpInst::ICMP_NE:
return AArch64CC::NE;
case CmpInst::ICMP_EQ:
return AArch64CC::EQ;
case CmpInst::ICMP_SGT:
return AArch64CC::GT;
case CmpInst::ICMP_SGE:
return AArch64CC::GE;
case CmpInst::ICMP_SLT:
return AArch64CC::LT;
case CmpInst::ICMP_SLE:
return AArch64CC::LE;
case CmpInst::ICMP_UGT:
return AArch64CC::HI;
case CmpInst::ICMP_UGE:
return AArch64CC::HS;
case CmpInst::ICMP_ULT:
return AArch64CC::LO;
case CmpInst::ICMP_ULE:
return AArch64CC::LS;
}
}
bool AArch64InstructionSelector::select(MachineInstr &I) const {
assert(I.getParent() && "Instruction should be in a basic block!");
assert(I.getParent()->getParent() && "Instruction should be in a function!");
MachineBasicBlock &MBB = *I.getParent();
MachineFunction &MF = *MBB.getParent();
MachineRegisterInfo &MRI = MF.getRegInfo();
if (!isPreISelGenericOpcode(I.getOpcode()))
return !I.isCopy() || selectCopy(I, TII, MRI, TRI, RBI);
if (I.getNumOperands() != I.getNumExplicitOperands()) {
DEBUG(dbgs() << "Generic instruction has unexpected implicit operands\n");
return false;
}
LLT Ty =
I.getOperand(0).isReg() ? MRI.getType(I.getOperand(0).getReg()) : LLT{};
switch (I.getOpcode()) {
case TargetOpcode::G_BR: {
I.setDesc(TII.get(AArch64::B));
return true;
}
case TargetOpcode::G_BRCOND: {
if (Ty.getSizeInBits() > 32) {
// We shouldn't need this on AArch64, but it would be implemented as an
// EXTRACT_SUBREG followed by a TBNZW because TBNZX has no encoding if the
// bit being tested is < 32.
DEBUG(dbgs() << "G_BRCOND has type: " << Ty
<< ", expected at most 32-bits");
return false;
}
const unsigned CondReg = I.getOperand(0).getReg();
MachineBasicBlock *DestMBB = I.getOperand(1).getMBB();
auto MIB = BuildMI(MBB, I, I.getDebugLoc(), TII.get(AArch64::TBNZW))
.addUse(CondReg)
.addImm(/*bit offset=*/0)
.addMBB(DestMBB);
I.eraseFromParent();
return constrainSelectedInstRegOperands(*MIB.getInstr(), TII, TRI, RBI);
}
case TargetOpcode::G_CONSTANT: {
if (Ty.getSizeInBits() <= 32)
I.setDesc(TII.get(AArch64::MOVi32imm));
else if (Ty.getSizeInBits() <= 64)
I.setDesc(TII.get(AArch64::MOVi64imm));
else
return false;
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_FRAME_INDEX: {
// allocas and G_FRAME_INDEX are only supported in addrspace(0).
if (Ty != LLT::pointer(0, 64)) {
DEBUG(dbgs() << "G_FRAME_INDEX pointer has type: " << Ty
<< ", expected: " << LLT::pointer(0, 64) << '\n');
return false;
}
I.setDesc(TII.get(AArch64::ADDXri));
// MOs for a #0 shifted immediate.
I.addOperand(MachineOperand::CreateImm(0));
I.addOperand(MachineOperand::CreateImm(0));
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_GLOBAL_VALUE: {
auto GV = I.getOperand(1).getGlobal();
if (GV->isThreadLocal()) {
// FIXME: we don't support TLS yet.
return false;
}
unsigned char OpFlags = STI.ClassifyGlobalReference(GV, TM);
if (OpFlags & AArch64II::MO_GOT)
I.setDesc(TII.get(AArch64::LOADgot));
else {
I.setDesc(TII.get(AArch64::MOVaddr));
I.getOperand(1).setTargetFlags(OpFlags | AArch64II::MO_PAGE);
MachineInstrBuilder MIB(MF, I);
MIB.addGlobalAddress(GV, I.getOperand(1).getOffset(),
OpFlags | AArch64II::MO_PAGEOFF | AArch64II::MO_NC);
}
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_LOAD:
case TargetOpcode::G_STORE: {
LLT MemTy = Ty;
LLT PtrTy = MRI.getType(I.getOperand(1).getReg());
if (PtrTy != LLT::pointer(0, 64)) {
DEBUG(dbgs() << "Load/Store pointer has type: " << PtrTy
<< ", expected: " << LLT::pointer(0, 64) << '\n');
return false;
}
#ifndef NDEBUG
// Sanity-check the pointer register.
const unsigned PtrReg = I.getOperand(1).getReg();
const RegisterBank &PtrRB = *RBI.getRegBank(PtrReg, MRI, TRI);
assert(PtrRB.getID() == AArch64::GPRRegBankID &&
"Load/Store pointer operand isn't a GPR");
assert(MRI.getType(PtrReg).isPointer() &&
"Load/Store pointer operand isn't a pointer");
#endif
const unsigned ValReg = I.getOperand(0).getReg();
const RegisterBank &RB = *RBI.getRegBank(ValReg, MRI, TRI);
const unsigned NewOpc =
selectLoadStoreUIOp(I.getOpcode(), RB.getID(), MemTy.getSizeInBits());
if (NewOpc == I.getOpcode())
return false;
I.setDesc(TII.get(NewOpc));
I.addOperand(MachineOperand::CreateImm(0));
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_MUL: {
// Reject the various things we don't support yet.
if (unsupportedBinOp(I, RBI, MRI, TRI))
return false;
const unsigned DefReg = I.getOperand(0).getReg();
const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
if (RB.getID() != AArch64::GPRRegBankID) {
DEBUG(dbgs() << "G_MUL on bank: " << RB << ", expected: GPR\n");
return false;
}
unsigned ZeroReg;
unsigned NewOpc;
if (Ty == LLT::scalar(32)) {
NewOpc = AArch64::MADDWrrr;
ZeroReg = AArch64::WZR;
} else if (Ty == LLT::scalar(64)) {
NewOpc = AArch64::MADDXrrr;
ZeroReg = AArch64::XZR;
} else {
DEBUG(dbgs() << "G_MUL has type: " << Ty << ", expected: "
<< LLT::scalar(32) << " or " << LLT::scalar(64) << '\n');
return false;
}
I.setDesc(TII.get(NewOpc));
I.addOperand(MachineOperand::CreateReg(ZeroReg, /*isDef=*/false));
// Now that we selected an opcode, we need to constrain the register
// operands to use appropriate classes.
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_FADD:
case TargetOpcode::G_FSUB:
case TargetOpcode::G_FMUL:
case TargetOpcode::G_FDIV:
case TargetOpcode::G_OR:
case TargetOpcode::G_XOR:
case TargetOpcode::G_AND:
case TargetOpcode::G_SHL:
case TargetOpcode::G_LSHR:
case TargetOpcode::G_ASHR:
case TargetOpcode::G_SDIV:
case TargetOpcode::G_UDIV:
case TargetOpcode::G_ADD:
case TargetOpcode::G_SUB:
case TargetOpcode::G_GEP: {
// Reject the various things we don't support yet.
if (unsupportedBinOp(I, RBI, MRI, TRI))
return false;
const unsigned OpSize = Ty.getSizeInBits();
const unsigned DefReg = I.getOperand(0).getReg();
const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
const unsigned NewOpc = selectBinaryOp(I.getOpcode(), RB.getID(), OpSize);
if (NewOpc == I.getOpcode())
return false;
I.setDesc(TII.get(NewOpc));
// FIXME: Should the type be always reset in setDesc?
// Now that we selected an opcode, we need to constrain the register
// operands to use appropriate classes.
return constrainSelectedInstRegOperands(I, TII, TRI, RBI);
}
case TargetOpcode::G_ANYEXT: {
const unsigned DstReg = I.getOperand(0).getReg();
const unsigned SrcReg = I.getOperand(1).getReg();
const RegisterBank &RBDst = *RBI.getRegBank(DstReg, MRI, TRI);
if (RBDst.getID() != AArch64::GPRRegBankID) {
DEBUG(dbgs() << "G_ANYEXT on bank: " << RBDst << ", expected: GPR\n");
return false;
}
const RegisterBank &RBSrc = *RBI.getRegBank(SrcReg, MRI, TRI);
if (RBSrc.getID() != AArch64::GPRRegBankID) {
DEBUG(dbgs() << "G_ANYEXT on bank: " << RBSrc << ", expected: GPR\n");
return false;
}
const unsigned DstSize = MRI.getType(DstReg).getSizeInBits();
if (DstSize == 0) {
DEBUG(dbgs() << "G_ANYEXT operand has no size, not a gvreg?\n");
return false;
}
if (DstSize != 64 && DstSize > 32) {
DEBUG(dbgs() << "G_ANYEXT to size: " << DstSize
<< ", expected: 32 or 64\n");
return false;
}
// At this point G_ANYEXT is just like a plain COPY, but we need
// to explicitly form the 64-bit value if any.
if (DstSize > 32) {
unsigned ExtSrc = MRI.createVirtualRegister(&AArch64::GPR64allRegClass);
BuildMI(MBB, I, I.getDebugLoc(), TII.get(AArch64::SUBREG_TO_REG))
.addDef(ExtSrc)
.addImm(0)
.addUse(SrcReg)
.addImm(AArch64::sub_32);
I.getOperand(1).setReg(ExtSrc);
}
return selectCopy(I, TII, MRI, TRI, RBI);
}
case TargetOpcode::G_ZEXT:
case TargetOpcode::G_SEXT: {
unsigned Opcode = I.getOpcode();
const LLT DstTy = MRI.getType(I.getOperand(0).getReg()),
SrcTy = MRI.getType(I.getOperand(1).getReg());
const bool isSigned = Opcode == TargetOpcode::G_SEXT;
const unsigned DefReg = I.getOperand(0).getReg();
const unsigned SrcReg = I.getOperand(1).getReg();
const RegisterBank &RB = *RBI.getRegBank(DefReg, MRI, TRI);
if (RB.getID() != AArch64::GPRRegBankID) {
DEBUG(dbgs() << TII.getName(I.getOpcode()) << " on bank: " << RB
<< ", expected: GPR\n");
return false;
}
MachineInstr *ExtI;
if (DstTy == LLT::scalar(64)) {
// FIXME: Can we avoid manually doing this?
if (!RBI.constrainGenericRegister(SrcReg, AArch64::GPR32RegClass, MRI)) {
DEBUG(dbgs() << "Failed to constrain " << TII.getName(Opcode)
<< " operand\n");
return false;
}
const unsigned SrcXReg =
MRI.createVirtualRegister(&AArch64::GPR64RegClass);
BuildMI(MBB, I, I.getDebugLoc(), TII.get(AArch64::SUBREG_TO_REG))
.addDef(SrcXReg)
.addImm(0)
.addUse(SrcReg)
.addImm(AArch64::sub_32);
const unsigned NewOpc = isSigned ? AArch64::SBFMXri : AArch64::UBFMXri;
ExtI = BuildMI(MBB, I, I.getDebugLoc(), TII.get(NewOpc))
.addDef(DefReg)
.addUse(SrcXReg)
.addImm(0)
.addImm(SrcTy.getSizeInBits() - 1);
} else if (DstTy == LLT::scalar(32)) {
const unsigned NewOpc = isSigned ? AArch64::SBFMWri : AArch64::UBFMWri;
ExtI = BuildMI(MBB, I, I.getDebugLoc(), TII.get(NewOpc))
.addDef(DefReg)
.addUse(SrcReg)
.addImm(0)
.addImm(SrcTy.getSizeInBits() - 1);
} else {
return false;
}
constrainSelectedInstRegOperands(*ExtI, TII, TRI, RBI);
I.eraseFromParent();
return true;
}
case TargetOpcode::G_INTTOPTR:
case TargetOpcode::G_PTRTOINT:
case TargetOpcode::G_BITCAST:
return selectCopy(I, TII, MRI, TRI, RBI);
case TargetOpcode::G_ICMP: {
if (Ty != LLT::scalar(1)) {
DEBUG(dbgs() << "G_ICMP result has type: " << Ty
<< ", expected: " << LLT::scalar(1) << '\n');
return false;
}
unsigned CmpOpc = 0;
unsigned ZReg = 0;
LLT CmpTy = MRI.getType(I.getOperand(2).getReg());
if (CmpTy == LLT::scalar(32)) {
CmpOpc = AArch64::SUBSWrr;
ZReg = AArch64::WZR;
} else if (CmpTy == LLT::scalar(64) || CmpTy.isPointer()) {
CmpOpc = AArch64::SUBSXrr;
ZReg = AArch64::XZR;
} else {
return false;
}
const AArch64CC::CondCode CC = changeICMPPredToAArch64CC(
(CmpInst::Predicate)I.getOperand(1).getPredicate());
MachineInstr &CmpMI = *BuildMI(MBB, I, I.getDebugLoc(), TII.get(CmpOpc))
.addDef(ZReg)
.addUse(I.getOperand(2).getReg())
.addUse(I.getOperand(3).getReg());
MachineInstr &CSetMI =
*BuildMI(MBB, I, I.getDebugLoc(), TII.get(AArch64::CSINCWr))
.addDef(I.getOperand(0).getReg())
.addUse(AArch64::WZR)
.addUse(AArch64::WZR)
.addImm(CC);
constrainSelectedInstRegOperands(CmpMI, TII, TRI, RBI);
constrainSelectedInstRegOperands(CSetMI, TII, TRI, RBI);
I.eraseFromParent();
return true;
}
}
return false;
}
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