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//===-- TargetMachine.cpp - General Target Information ---------------------==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file describes the general parts of a Target machine.
//
//===----------------------------------------------------------------------===//
#include "llvm/Target/TargetMachine.h"
#include "llvm/Analysis/TargetTransformInfo.h"
#include "llvm/CodeGen/MachineFunction.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/TargetLowering.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetSubtargetInfo.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), DefaultOptions(Options), Options(Options) {
}
TargetMachine::~TargetMachine() {
delete AsmInfo;
delete MRI;
delete MII;
delete STI;
}
bool TargetMachine::isPositionIndependent() const {
return getRelocationModel() == Reloc::PIC_;
}
/// \brief 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");
RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
StringRef Denormal =
F.getFnAttribute("denormal-fp-math").getValueAsString();
if (Denormal == "ieee")
Options.FPDenormalMode = FPDenormal::IEEE;
else if (Denormal == "preserve-sign")
Options.FPDenormalMode = FPDenormal::PreserveSign;
else if (Denormal == "positive-zero")
Options.FPDenormalMode = FPDenormal::PositiveZero;
else
Options.FPDenormalMode = DefaultOptions.FPDenormalMode;
}
/// 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");
break;
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;
// 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. As a result we
// still have some pre-dso_local logic in here to improve the quality of the
// generated code:
Reloc::Model RM = getRelocationModel();
const Triple &TT = getTargetTriple();
// DLLImport explicitly marks the GV as external.
if (GV && GV->hasDLLImportStorageClass())
return false;
// Every other GV is local on COFF.
// Make an exception for windows OS in the triple: Some firmwares builds use
// *-win32-macho triples. This (accidentally?) produced windows relocations
// without GOT tables in older clang versions; Keep this behaviour.
if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
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.
// FIXME: this is probably not ELF specific.
if (GV && isPositionIndependent() && TT.isOSBinFormatELF() &&
GV->hasExternalWeakLinkage())
return false;
if (GV && (GV->hasLocalLinkage() || !GV->hasDefaultVisibility()))
return true;
if (TT.isOSBinFormatMachO()) {
if (RM == Reloc::Static)
return true;
return GV && GV->isStrongDefinitionForLinker();
}
assert(TT.isOSBinFormatELF());
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;
bool IsTLS = GV && GV->isThreadLocal();
bool IsAccessViaCopyRelocs =
Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
Triple::ArchType Arch = TT.getArch();
bool IsPPC =
Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
// Check if we can use copy relocations. PowerPC has no copy relocations.
if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
return true;
}
// ELF supports preemption of other symbols.
return false;
}
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;
else
Model = TLSModel::GeneralDynamic;
} else {
if (IsLocal)
Model = TLSModel::LocalExec;
else
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; }
TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
return TargetIRAnalysis([](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);
return;
}
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);
}
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