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//===-- TargetMachine.cpp - General Target Information ---------------------==//
// 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
// This file describes the general parts of a Target machine.
#include "llvm/Target/TargetMachine.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Mangler.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCInstrInfo.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
using namespace llvm;
// TargetMachine Class
TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
const Triple &TT, StringRef CPU, StringRef FS,
const TargetOptions &Options)
: TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
RequireStructuredCFG(false), O0WantsFastISel(false),
DefaultOptions(Options), Options(Options) {}
TargetMachine::~TargetMachine() = default;
bool TargetMachine::isPositionIndependent() const {
return getRelocationModel() == Reloc::PIC_;
/// Reset the target options based on the function's attributes.
// FIXME: This function needs to go away for a number of reasons:
// a) global state on the TargetMachine is terrible in general,
// b) these target options should be passed only on the function
// and not on the TargetMachine (via TargetOptions) at all.
void TargetMachine::resetTargetOptions(const Function &F) const {
#define RESET_OPTION(X, Y) \
do { \
if (F.hasFnAttribute(Y)) \
Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
else \
Options.X = DefaultOptions.X; \
} while (0)
RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
/// Returns the code generation relocation model. The choices are static, PIC,
/// and dynamic-no-pic.
Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
/// Returns the code model. The choices are small, kernel, medium, large, and
/// target default.
CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
/// Get the IR-specified TLS model for Var.
static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
switch (GV->getThreadLocalMode()) {
case GlobalVariable::NotThreadLocal:
llvm_unreachable("getSelectedTLSModel for non-TLS variable");
case GlobalVariable::GeneralDynamicTLSModel:
return TLSModel::GeneralDynamic;
case GlobalVariable::LocalDynamicTLSModel:
return TLSModel::LocalDynamic;
case GlobalVariable::InitialExecTLSModel:
return TLSModel::InitialExec;
case GlobalVariable::LocalExecTLSModel:
return TLSModel::LocalExec;
llvm_unreachable("invalid TLS model");
bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
const GlobalValue *GV) const {
// If the IR producer requested that this GV be treated as dso local, obey.
if (GV && GV->isDSOLocal())
return true;
// If we are not supossed to use a PLT, we cannot assume that intrinsics are
// local since the linker can convert some direct access to access via plt.
if (M.getRtLibUseGOT() && !GV)
return false;
// According to the llvm language reference, we should be able to
// just return false in here if we have a GV, as we know it is
// dso_preemptable. At this point in time, the various IR producers
// have not been transitioned to always produce a dso_local when it
// is possible to do so.
// In the case of intrinsics, GV is null and there is nowhere to put
// dso_local. Returning false for those will produce worse code in some
// architectures. For example, on x86 the caller has to set ebx before calling
// a plt.
// As a result we still have some logic in here to improve the quality of the
// generated code.
// FIXME: Add a module level metadata for whether intrinsics should be assumed
// local.
Reloc::Model RM = getRelocationModel();
const Triple &TT = getTargetTriple();
// DLLImport explicitly marks the GV as external.
if (GV && GV->hasDLLImportStorageClass())
return false;
// On MinGW, variables that haven't been declared with DLLImport may still
// end up automatically imported by the linker. To make this feasible,
// don't assume the variables to be DSO local unless we actually know
// that for sure. This only has to be done for variables; for functions
// the linker can insert thunks for calling functions from another DLL.
if (TT.isWindowsGNUEnvironment() && TT.isOSBinFormatCOFF() && GV &&
GV->isDeclarationForLinker() && isa<GlobalVariable>(GV))
return false;
// On COFF, don't mark 'extern_weak' symbols as DSO local. If these symbols
// remain unresolved in the link, they can be resolved to zero, which is
// outside the current DSO.
if (TT.isOSBinFormatCOFF() && GV && GV->hasExternalWeakLinkage())
return false;
// Every other GV is local on COFF.
// Make an exception for windows OS in the triple: Some firmware builds use
// *-win32-macho triples. This (accidentally?) produced windows relocations
// without GOT tables in older clang versions; Keep this behaviour.
// Some JIT users use *-win32-elf triples; these shouldn't use GOT tables
// either.
if (TT.isOSBinFormatCOFF() || TT.isOSWindows())
return true;
// Most PIC code sequences that assume that a symbol is local cannot
// produce a 0 if it turns out the symbol is undefined. While this
// is ABI and relocation depended, it seems worth it to handle it
// here.
if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
return false;
if (GV && !GV->hasDefaultVisibility())
return true;
if (TT.isOSBinFormatMachO()) {
if (RM == Reloc::Static)
return true;
return GV && GV->isStrongDefinitionForLinker();
// Due to the AIX linkage model, any global with default visibility is
// considered non-local.
if (TT.isOSBinFormatXCOFF())
return false;
assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm());
assert(RM != Reloc::DynamicNoPIC);
bool IsExecutable =
RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
if (IsExecutable) {
// If the symbol is defined, it cannot be preempted.
if (GV && !GV->isDeclarationForLinker())
return true;
// A symbol marked nonlazybind should not be accessed with a plt. If the
// symbol turns out to be external, the linker will convert a direct
// access to an access via the plt, so don't assume it is local.
const Function *F = dyn_cast_or_null<Function>(GV);
if (F && F->hasFnAttribute(Attribute::NonLazyBind))
return false;
Triple::ArchType Arch = TT.getArch();
// PowerPC prefers avoiding copy relocations.
if (Arch == Triple::ppc || TT.isPPC64())
return false;
// Check if we can use copy relocations.
if (!(GV && GV->isThreadLocal()) && RM == Reloc::Static)
return true;
// ELF & wasm support preemption of other symbols.
return false;
bool TargetMachine::useEmulatedTLS() const {
// Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
// was specified explicitly; otherwise uses target triple to decide default.
if (Options.ExplicitEmulatedTLS)
return Options.EmulatedTLS;
return getTargetTriple().hasDefaultEmulatedTLS();
TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
Reloc::Model RM = getRelocationModel();
bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
TLSModel::Model Model;
if (IsSharedLibrary) {
if (IsLocal)
Model = TLSModel::LocalDynamic;
Model = TLSModel::GeneralDynamic;
} else {
if (IsLocal)
Model = TLSModel::LocalExec;
Model = TLSModel::InitialExec;
// If the user specified a more specific model, use that.
TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
if (SelectedModel > Model)
return SelectedModel;
return Model;
/// Returns the optimization level: None, Less, Default, or Aggressive.
CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {
return TargetTransformInfo(F.getParent()->getDataLayout());
void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
const GlobalValue *GV, Mangler &Mang,
bool MayAlwaysUsePrivate) const {
if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
// Simple case: If GV is not private, it is not important to find out if
// private labels are legal in this case or not.
Mang.getNameWithPrefix(Name, GV, false);
const TargetLoweringObjectFile *TLOF = getObjFileLowering();
TLOF->getNameWithPrefix(Name, GV, *this);
MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
const TargetLoweringObjectFile *TLOF = getObjFileLowering();
SmallString<128> NameStr;
getNameWithPrefix(NameStr, GV, TLOF->getMangler());
return TLOF->getContext().getOrCreateSymbol(NameStr);
TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
// Since Analysis can't depend on Target, use a std::function to invert the
// dependency.
return TargetIRAnalysis(
[this](const Function &F) { return this->getTargetTransformInfo(F); });