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//===-- ARMTargetMachine.cpp - Define TargetMachine for ARM ---------------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "ARMTargetMachine.h"
#include "ARM.h"
#include "ARMMacroFusion.h"
#include "ARMSubtarget.h"
#include "ARMTargetObjectFile.h"
#include "ARMTargetTransformInfo.h"
#include "MCTargetDesc/ARMMCTargetDesc.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/ExecutionDomainFix.h"
#include "llvm/CodeGen/GlobalISel/CallLowering.h"
#include "llvm/CodeGen/GlobalISel/IRTranslator.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelect.h"
#include "llvm/CodeGen/GlobalISel/InstructionSelector.h"
#include "llvm/CodeGen/GlobalISel/Legalizer.h"
#include "llvm/CodeGen/GlobalISel/LegalizerInfo.h"
#include "llvm/CodeGen/GlobalISel/RegBankSelect.h"
#include "llvm/CodeGen/GlobalISel/RegisterBankInfo.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineScheduler.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/CodeGen/TargetPassConfig.h"
#include "llvm/IR/Attributes.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/Function.h"
#include "llvm/Pass.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetParser.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Transforms/Scalar.h"
#include <cassert>
#include <memory>
#include <string>
using namespace llvm;
static cl::opt<bool>
DisableA15SDOptimization("disable-a15-sd-optimization", cl::Hidden,
cl::desc("Inhibit optimization of S->D register accesses on A15"),
static cl::opt<bool>
EnableAtomicTidy("arm-atomic-cfg-tidy", cl::Hidden,
cl::desc("Run SimplifyCFG after expanding atomic operations"
" to make use of cmpxchg flow-based information"),
static cl::opt<bool>
EnableARMLoadStoreOpt("arm-load-store-opt", cl::Hidden,
cl::desc("Enable ARM load/store optimization pass"),
// FIXME: Unify control over GlobalMerge.
static cl::opt<cl::boolOrDefault>
EnableGlobalMerge("arm-global-merge", cl::Hidden,
cl::desc("Enable the global merge pass"));
namespace llvm {
void initializeARMExecutionDomainFixPass(PassRegistry&);
extern "C" void LLVMInitializeARMTarget() {
// Register the target.
RegisterTargetMachine<ARMLETargetMachine> X(getTheARMLETarget());
RegisterTargetMachine<ARMLETargetMachine> A(getTheThumbLETarget());
RegisterTargetMachine<ARMBETargetMachine> Y(getTheARMBETarget());
RegisterTargetMachine<ARMBETargetMachine> B(getTheThumbBETarget());
PassRegistry &Registry = *PassRegistry::getPassRegistry();
static std::unique_ptr<TargetLoweringObjectFile> createTLOF(const Triple &TT) {
if (TT.isOSBinFormatMachO())
return llvm::make_unique<TargetLoweringObjectFileMachO>();
if (TT.isOSWindows())
return llvm::make_unique<TargetLoweringObjectFileCOFF>();
return llvm::make_unique<ARMElfTargetObjectFile>();
static ARMBaseTargetMachine::ARMABI
computeTargetABI(const Triple &TT, StringRef CPU,
const TargetOptions &Options) {
StringRef ABIName = Options.MCOptions.getABIName();
if (ABIName.empty())
ABIName = ARM::computeDefaultTargetABI(TT, CPU);
if (ABIName == "aapcs16")
return ARMBaseTargetMachine::ARM_ABI_AAPCS16;
else if (ABIName.startswith("aapcs"))
return ARMBaseTargetMachine::ARM_ABI_AAPCS;
else if (ABIName.startswith("apcs"))
return ARMBaseTargetMachine::ARM_ABI_APCS;
llvm_unreachable("Unhandled/unknown ABI Name!");
return ARMBaseTargetMachine::ARM_ABI_UNKNOWN;
static std::string computeDataLayout(const Triple &TT, StringRef CPU,
const TargetOptions &Options,
bool isLittle) {
auto ABI = computeTargetABI(TT, CPU, Options);
std::string Ret;
if (isLittle)
// Little endian.
Ret += "e";
// Big endian.
Ret += "E";
Ret += DataLayout::getManglingComponent(TT);
// Pointers are 32 bits and aligned to 32 bits.
Ret += "-p:32:32";
// ABIs other than APCS have 64 bit integers with natural alignment.
if (ABI != ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-i64:64";
// We have 64 bits floats. The APCS ABI requires them to be aligned to 32
// bits, others to 64 bits. We always try to align to 64 bits.
if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-f64:32:64";
// We have 128 and 64 bit vectors. The APCS ABI aligns them to 32 bits, others
// to 64. We always ty to give them natural alignment.
if (ABI == ARMBaseTargetMachine::ARM_ABI_APCS)
Ret += "-v64:32:64-v128:32:128";
else if (ABI != ARMBaseTargetMachine::ARM_ABI_AAPCS16)
Ret += "-v128:64:128";
// Try to align aggregates to 32 bits (the default is 64 bits, which has no
// particular hardware support on 32-bit ARM).
Ret += "-a:0:32";
// Integer registers are 32 bits.
Ret += "-n32";
// The stack is 128 bit aligned on NaCl, 64 bit aligned on AAPCS and 32 bit
// aligned everywhere else.
if (TT.isOSNaCl() || ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS16)
Ret += "-S128";
else if (ABI == ARMBaseTargetMachine::ARM_ABI_AAPCS)
Ret += "-S64";
Ret += "-S32";
return Ret;
static Reloc::Model getEffectiveRelocModel(const Triple &TT,
Optional<Reloc::Model> RM) {
if (!RM.hasValue())
// Default relocation model on Darwin is PIC.
return TT.isOSBinFormatMachO() ? Reloc::PIC_ : Reloc::Static;
if (*RM == Reloc::ROPI || *RM == Reloc::RWPI || *RM == Reloc::ROPI_RWPI)
assert(TT.isOSBinFormatELF() &&
"ROPI/RWPI currently only supported for ELF");
// DynamicNoPIC is only used on darwin.
if (*RM == Reloc::DynamicNoPIC && !TT.isOSDarwin())
return Reloc::Static;
return *RM;
/// Create an ARM architecture model.
ARMBaseTargetMachine::ARMBaseTargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool isLittle)
: LLVMTargetMachine(T, computeDataLayout(TT, CPU, Options, isLittle), TT,
CPU, FS, Options, getEffectiveRelocModel(TT, RM),
getEffectiveCodeModel(CM, CodeModel::Small), OL),
TargetABI(computeTargetABI(TT, CPU, Options)),
TLOF(createTLOF(getTargetTriple())), isLittle(isLittle) {
// Default to triple-appropriate float ABI
if (Options.FloatABIType == FloatABI::Default) {
if (isTargetHardFloat())
this->Options.FloatABIType = FloatABI::Hard;
this->Options.FloatABIType = FloatABI::Soft;
// Default to triple-appropriate EABI
if (Options.EABIVersion == EABI::Default ||
Options.EABIVersion == EABI::Unknown) {
// musl is compatible with glibc with regard to EABI version
if ((TargetTriple.getEnvironment() == Triple::GNUEABI ||
TargetTriple.getEnvironment() == Triple::GNUEABIHF ||
TargetTriple.getEnvironment() == Triple::MuslEABI ||
TargetTriple.getEnvironment() == Triple::MuslEABIHF) &&
!(TargetTriple.isOSWindows() || TargetTriple.isOSDarwin()))
this->Options.EABIVersion = EABI::GNU;
this->Options.EABIVersion = EABI::EABI5;
if (TT.isOSBinFormatMachO()) {
this->Options.TrapUnreachable = true;
this->Options.NoTrapAfterNoreturn = true;
ARMBaseTargetMachine::~ARMBaseTargetMachine() = default;
const ARMSubtarget *
ARMBaseTargetMachine::getSubtargetImpl(const Function &F) const {
Attribute CPUAttr = F.getFnAttribute("target-cpu");
Attribute FSAttr = F.getFnAttribute("target-features");
std::string CPU = !CPUAttr.hasAttribute(Attribute::None)
? CPUAttr.getValueAsString().str()
: TargetCPU;
std::string FS = !FSAttr.hasAttribute(Attribute::None)
? FSAttr.getValueAsString().str()
: TargetFS;
// FIXME: This is related to the code below to reset the target options,
// we need to know whether or not the soft float flag is set on the
// function before we can generate a subtarget. We also need to use
// it as a key for the subtarget since that can be the only difference
// between two functions.
bool SoftFloat =
F.getFnAttribute("use-soft-float").getValueAsString() == "true";
// If the soft float attribute is set on the function turn on the soft float
// subtarget feature.
if (SoftFloat)
FS += FS.empty() ? "+soft-float" : ",+soft-float";
// Use the optminsize to identify the subtarget, but don't use it in the
// feature string.
std::string Key = CPU + FS;
if (F.optForMinSize())
Key += "+minsize";
auto &I = SubtargetMap[Key];
if (!I) {
// This needs to be done before we create a new subtarget since any
// creation will depend on the TM and the code generation flags on the
// function that reside in TargetOptions.
I = llvm::make_unique<ARMSubtarget>(TargetTriple, CPU, FS, *this, isLittle,
if (!I->isThumb() && !I->hasARMOps())
F.getContext().emitError("Function '" + F.getName() + "' uses ARM "
"instructions, but the target does not support ARM mode execution.");
return I.get();
ARMBaseTargetMachine::getTargetTransformInfo(const Function &F) {
return TargetTransformInfo(ARMTTIImpl(this, F));
ARMLETargetMachine::ARMLETargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool JIT)
: ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, true) {}
ARMBETargetMachine::ARMBETargetMachine(const Target &T, const Triple &TT,
StringRef CPU, StringRef FS,
const TargetOptions &Options,
Optional<Reloc::Model> RM,
Optional<CodeModel::Model> CM,
CodeGenOpt::Level OL, bool JIT)
: ARMBaseTargetMachine(T, TT, CPU, FS, Options, RM, CM, OL, false) {}
namespace {
/// ARM Code Generator Pass Configuration Options.
class ARMPassConfig : public TargetPassConfig {
ARMPassConfig(ARMBaseTargetMachine &TM, PassManagerBase &PM)
: TargetPassConfig(TM, PM) {
if (TM.getOptLevel() != CodeGenOpt::None) {
ARMGenSubtargetInfo STI(TM.getTargetTriple(), TM.getTargetCPU(),
if (STI.hasFeature(ARM::FeatureUseMISched))
substitutePass(&PostRASchedulerID, &PostMachineSchedulerID);
ARMBaseTargetMachine &getARMTargetMachine() const {
return getTM<ARMBaseTargetMachine>();
ScheduleDAGInstrs *
createMachineScheduler(MachineSchedContext *C) const override {
ScheduleDAGMILive *DAG = createGenericSchedLive(C);
// add DAG Mutations here.
const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
if (ST.hasFusion())
return DAG;
ScheduleDAGInstrs *
createPostMachineScheduler(MachineSchedContext *C) const override {
ScheduleDAGMI *DAG = createGenericSchedPostRA(C);
// add DAG Mutations here.
const ARMSubtarget &ST = C->MF->getSubtarget<ARMSubtarget>();
if (ST.hasFusion())
return DAG;
void addIRPasses() override;
void addCodeGenPrepare() override;
bool addPreISel() override;
bool addInstSelector() override;
bool addIRTranslator() override;
bool addLegalizeMachineIR() override;
bool addRegBankSelect() override;
bool addGlobalInstructionSelect() override;
void addPreRegAlloc() override;
void addPreSched2() override;
void addPreEmitPass() override;
class ARMExecutionDomainFix : public ExecutionDomainFix {
static char ID;
ARMExecutionDomainFix() : ExecutionDomainFix(ID, ARM::DPRRegClass) {}
StringRef getPassName() const override {
return "ARM Execution Domain Fix";
char ARMExecutionDomainFix::ID;
} // end anonymous namespace
INITIALIZE_PASS_BEGIN(ARMExecutionDomainFix, "arm-execution-domain-fix",
"ARM Execution Domain Fix", false, false)
INITIALIZE_PASS_END(ARMExecutionDomainFix, "arm-execution-domain-fix",
"ARM Execution Domain Fix", false, false)
TargetPassConfig *ARMBaseTargetMachine::createPassConfig(PassManagerBase &PM) {
return new ARMPassConfig(*this, PM);
void ARMPassConfig::addIRPasses() {
if (TM->Options.ThreadModel == ThreadModel::Single)
// Cmpxchg instructions are often used with a subsequent comparison to
// determine whether it succeeded. We can exploit existing control-flow in
// ldrex/strex loops to simplify this, but it needs tidying up.
if (TM->getOptLevel() != CodeGenOpt::None && EnableAtomicTidy)
1, false, false, true, true, [this](const Function &F) {
const auto &ST = this->TM->getSubtarget<ARMSubtarget>(F);
return ST.hasAnyDataBarrier() && !ST.isThumb1Only();
// Match interleaved memory accesses to ldN/stN intrinsics.
if (TM->getOptLevel() != CodeGenOpt::None)
void ARMPassConfig::addCodeGenPrepare() {
if (getOptLevel() != CodeGenOpt::None)
bool ARMPassConfig::addPreISel() {
if (getOptLevel() != CodeGenOpt::None)
if ((TM->getOptLevel() != CodeGenOpt::None &&
EnableGlobalMerge == cl::BOU_UNSET) ||
EnableGlobalMerge == cl::BOU_TRUE) {
// FIXME: This is using the thumb1 only constant value for
// maximal global offset for merging globals. We may want
// to look into using the old value for non-thumb1 code of
// 4095 based on the TargetMachine, but this starts to become
// tricky when doing code gen per function.
bool OnlyOptimizeForSize = (TM->getOptLevel() < CodeGenOpt::Aggressive) &&
(EnableGlobalMerge == cl::BOU_UNSET);
// Merging of extern globals is enabled by default on non-Mach-O as we
// expect it to be generally either beneficial or harmless. On Mach-O it
// is disabled as we emit the .subsections_via_symbols directive which
// means that merging extern globals is not safe.
bool MergeExternalByDefault = !TM->getTargetTriple().isOSBinFormatMachO();
addPass(createGlobalMergePass(TM, 127, OnlyOptimizeForSize,
return false;
bool ARMPassConfig::addInstSelector() {
addPass(createARMISelDag(getARMTargetMachine(), getOptLevel()));
return false;
bool ARMPassConfig::addIRTranslator() {
addPass(new IRTranslator());
return false;
bool ARMPassConfig::addLegalizeMachineIR() {
addPass(new Legalizer());
return false;
bool ARMPassConfig::addRegBankSelect() {
addPass(new RegBankSelect());
return false;
bool ARMPassConfig::addGlobalInstructionSelect() {
addPass(new InstructionSelect());
return false;
void ARMPassConfig::addPreRegAlloc() {
if (getOptLevel() != CodeGenOpt::None) {
if (EnableARMLoadStoreOpt)
addPass(createARMLoadStoreOptimizationPass(/* pre-register alloc */ true));
if (!DisableA15SDOptimization)
void ARMPassConfig::addPreSched2() {
if (getOptLevel() != CodeGenOpt::None) {
if (EnableARMLoadStoreOpt)
addPass(new ARMExecutionDomainFix());
// Expand some pseudo instructions into multiple instructions to allow
// proper scheduling.
if (getOptLevel() != CodeGenOpt::None) {
// in v8, IfConversion depends on Thumb instruction widths
addPass(createThumb2SizeReductionPass([this](const Function &F) {
return this->TM->getSubtarget<ARMSubtarget>(F).restrictIT();
addPass(createIfConverter([](const MachineFunction &MF) {
return !MF.getSubtarget<ARMSubtarget>().isThumb1Only();
void ARMPassConfig::addPreEmitPass() {
// Constant island pass work on unbundled instructions.
addPass(createUnpackMachineBundles([](const MachineFunction &MF) {
return MF.getSubtarget<ARMSubtarget>().isThumb2();
// Don't optimize barriers at -O0.
if (getOptLevel() != CodeGenOpt::None)