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//===-- ARMMCInstLower.cpp - Convert ARM MachineInstr to an MCInst --------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains code to lower ARM MachineInstrs to their corresponding
// MCInst records.
//
//===----------------------------------------------------------------------===//
#include "ARM.h"
#include "ARMAsmPrinter.h"
#include "ARMBaseInstrInfo.h"
#include "ARMMachineFunctionInfo.h"
#include "ARMSubtarget.h"
#include "MCTargetDesc/ARMAddressingModes.h"
#include "MCTargetDesc/ARMBaseInfo.h"
#include "MCTargetDesc/ARMMCExpr.h"
#include "llvm/ADT/APFloat.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/IR/Constants.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCInst.h"
#include "llvm/MC/MCInstBuilder.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/Support/ErrorHandling.h"
#include <cassert>
#include <cstdint>
using namespace llvm;
MCOperand ARMAsmPrinter::GetSymbolRef(const MachineOperand &MO,
const MCSymbol *Symbol) {
MCSymbolRefExpr::VariantKind SymbolVariant = MCSymbolRefExpr::VK_None;
if (MO.getTargetFlags() & ARMII::MO_SBREL)
SymbolVariant = MCSymbolRefExpr::VK_ARM_SBREL;
const MCExpr *Expr =
MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
switch (MO.getTargetFlags() & ARMII::MO_OPTION_MASK) {
default:
llvm_unreachable("Unknown target flag on symbol operand");
case ARMII::MO_NO_FLAG:
break;
case ARMII::MO_LO16:
Expr =
MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
Expr = ARMMCExpr::createLower16(Expr, OutContext);
break;
case ARMII::MO_HI16:
Expr =
MCSymbolRefExpr::create(Symbol, SymbolVariant, OutContext);
Expr = ARMMCExpr::createUpper16(Expr, OutContext);
break;
}
if (!MO.isJTI() && MO.getOffset())
Expr = MCBinaryExpr::createAdd(Expr,
MCConstantExpr::create(MO.getOffset(),
OutContext),
OutContext);
return MCOperand::createExpr(Expr);
}
bool ARMAsmPrinter::lowerOperand(const MachineOperand &MO,
MCOperand &MCOp) {
switch (MO.getType()) {
default: llvm_unreachable("unknown operand type");
case MachineOperand::MO_Register:
// Ignore all implicit register operands.
if (MO.isImplicit())
return false;
assert(!MO.getSubReg() && "Subregs should be eliminated!");
MCOp = MCOperand::createReg(MO.getReg());
break;
case MachineOperand::MO_Immediate:
MCOp = MCOperand::createImm(MO.getImm());
break;
case MachineOperand::MO_MachineBasicBlock:
MCOp = MCOperand::createExpr(MCSymbolRefExpr::create(
MO.getMBB()->getSymbol(), OutContext));
break;
case MachineOperand::MO_GlobalAddress:
MCOp = GetSymbolRef(MO,
GetARMGVSymbol(MO.getGlobal(), MO.getTargetFlags()));
break;
case MachineOperand::MO_ExternalSymbol:
MCOp = GetSymbolRef(MO,
GetExternalSymbolSymbol(MO.getSymbolName()));
break;
case MachineOperand::MO_JumpTableIndex:
MCOp = GetSymbolRef(MO, GetJTISymbol(MO.getIndex()));
break;
case MachineOperand::MO_ConstantPoolIndex:
if (Subtarget->genExecuteOnly())
llvm_unreachable("execute-only should not generate constant pools");
MCOp = GetSymbolRef(MO, GetCPISymbol(MO.getIndex()));
break;
case MachineOperand::MO_BlockAddress:
MCOp = GetSymbolRef(MO, GetBlockAddressSymbol(MO.getBlockAddress()));
break;
case MachineOperand::MO_FPImmediate: {
APFloat Val = MO.getFPImm()->getValueAPF();
bool ignored;
Val.convert(APFloat::IEEEdouble(), APFloat::rmTowardZero, &ignored);
MCOp = MCOperand::createDFPImm(bit_cast<uint64_t>(Val.convertToDouble()));
break;
}
case MachineOperand::MO_RegisterMask:
// Ignore call clobbers.
return false;
}
return true;
}
void llvm::LowerARMMachineInstrToMCInst(const MachineInstr *MI, MCInst &OutMI,
ARMAsmPrinter &AP) {
OutMI.setOpcode(MI->getOpcode());
// In the MC layer, we keep modified immediates in their encoded form
bool EncodeImms = false;
switch (MI->getOpcode()) {
default: break;
case ARM::MOVi:
case ARM::MVNi:
case ARM::CMPri:
case ARM::CMNri:
case ARM::TSTri:
case ARM::TEQri:
case ARM::MSRi:
case ARM::ADCri:
case ARM::ADDri:
case ARM::ADDSri:
case ARM::SBCri:
case ARM::SUBri:
case ARM::SUBSri:
case ARM::ANDri:
case ARM::ORRri:
case ARM::EORri:
case ARM::BICri:
case ARM::RSBri:
case ARM::RSBSri:
case ARM::RSCri:
EncodeImms = true;
break;
}
for (const MachineOperand &MO : MI->operands()) {
MCOperand MCOp;
if (AP.lowerOperand(MO, MCOp)) {
if (MCOp.isImm() && EncodeImms) {
int32_t Enc = ARM_AM::getSOImmVal(MCOp.getImm());
if (Enc != -1)
MCOp.setImm(Enc);
}
OutMI.addOperand(MCOp);
}
}
}
void ARMAsmPrinter::EmitSled(const MachineInstr &MI, SledKind Kind)
{
if (MI.getParent()->getParent()->getInfo<ARMFunctionInfo>()
->isThumbFunction())
{
MI.emitError("An attempt to perform XRay instrumentation for a"
" Thumb function (not supported). Detected when emitting a sled.");
return;
}
static const int8_t NoopsInSledCount = 6;
// We want to emit the following pattern:
//
// .Lxray_sled_N:
// ALIGN
// B #20
// ; 6 NOP instructions (24 bytes)
// .tmpN
//
// We need the 24 bytes (6 instructions) because at runtime, we'd be patching
// over the full 28 bytes (7 instructions) with the following pattern:
//
// PUSH{ r0, lr }
// MOVW r0, #<lower 16 bits of function ID>
// MOVT r0, #<higher 16 bits of function ID>
// MOVW ip, #<lower 16 bits of address of __xray_FunctionEntry/Exit>
// MOVT ip, #<higher 16 bits of address of __xray_FunctionEntry/Exit>
// BLX ip
// POP{ r0, lr }
//
OutStreamer->emitCodeAlignment(Align(4), &getSubtargetInfo());
auto CurSled = OutContext.createTempSymbol("xray_sled_", true);
OutStreamer->emitLabel(CurSled);
auto Target = OutContext.createTempSymbol();
// Emit "B #20" instruction, which jumps over the next 24 bytes (because
// register pc is 8 bytes ahead of the jump instruction by the moment CPU
// is executing it).
// By analogy to ARMAsmPrinter::emitPseudoExpansionLowering() |case ARM::B|.
// It is not clear why |addReg(0)| is needed (the last operand).
EmitToStreamer(*OutStreamer, MCInstBuilder(ARM::Bcc).addImm(20)
.addImm(ARMCC::AL).addReg(0));
emitNops(NoopsInSledCount);
OutStreamer->emitLabel(Target);
recordSled(CurSled, MI, Kind, 2);
}
void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_ENTER(const MachineInstr &MI)
{
EmitSled(MI, SledKind::FUNCTION_ENTER);
}
void ARMAsmPrinter::LowerPATCHABLE_FUNCTION_EXIT(const MachineInstr &MI)
{
EmitSled(MI, SledKind::FUNCTION_EXIT);
}
void ARMAsmPrinter::LowerPATCHABLE_TAIL_CALL(const MachineInstr &MI)
{
EmitSled(MI, SledKind::TAIL_CALL);
}
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