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556d8103ca
Reviewers: pcc, dblaikie Reviewed By: dblaikie Subscribers: llvm-commits Differential Revision: https://reviews.llvm.org/D52389 llvm-svn: 342945
273 lines
11 KiB
C++
273 lines
11 KiB
C++
//===-- TargetMachine.cpp - General Target Information ---------------------==//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file describes the general parts of a Target machine.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Analysis/TargetTransformInfo.h"
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#include "llvm/IR/Function.h"
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#include "llvm/IR/GlobalAlias.h"
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#include "llvm/IR/GlobalValue.h"
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#include "llvm/IR/GlobalVariable.h"
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#include "llvm/IR/LegacyPassManager.h"
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#include "llvm/IR/Mangler.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCInstrInfo.h"
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#include "llvm/MC/MCSectionMachO.h"
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#include "llvm/MC/MCTargetOptions.h"
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#include "llvm/MC/SectionKind.h"
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#include "llvm/Target/TargetLoweringObjectFile.h"
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using namespace llvm;
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//---------------------------------------------------------------------------
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// TargetMachine Class
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//
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TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
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const Triple &TT, StringRef CPU, StringRef FS,
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const TargetOptions &Options)
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: TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
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TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
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RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
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}
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TargetMachine::~TargetMachine() = default;
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bool TargetMachine::isPositionIndependent() const {
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return getRelocationModel() == Reloc::PIC_;
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}
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/// Reset the target options based on the function's attributes.
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// FIXME: This function needs to go away for a number of reasons:
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// a) global state on the TargetMachine is terrible in general,
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// b) these target options should be passed only on the function
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// and not on the TargetMachine (via TargetOptions) at all.
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void TargetMachine::resetTargetOptions(const Function &F) const {
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#define RESET_OPTION(X, Y) \
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do { \
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if (F.hasFnAttribute(Y)) \
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Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
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else \
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Options.X = DefaultOptions.X; \
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} while (0)
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RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
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RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
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RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
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RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
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RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
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StringRef Denormal =
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F.getFnAttribute("denormal-fp-math").getValueAsString();
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if (Denormal == "ieee")
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Options.FPDenormalMode = FPDenormal::IEEE;
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else if (Denormal == "preserve-sign")
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Options.FPDenormalMode = FPDenormal::PreserveSign;
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else if (Denormal == "positive-zero")
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Options.FPDenormalMode = FPDenormal::PositiveZero;
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else
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Options.FPDenormalMode = DefaultOptions.FPDenormalMode;
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}
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/// Returns the code generation relocation model. The choices are static, PIC,
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/// and dynamic-no-pic.
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Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
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/// Returns the code model. The choices are small, kernel, medium, large, and
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/// target default.
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CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
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/// Get the IR-specified TLS model for Var.
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static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
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switch (GV->getThreadLocalMode()) {
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case GlobalVariable::NotThreadLocal:
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llvm_unreachable("getSelectedTLSModel for non-TLS variable");
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break;
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case GlobalVariable::GeneralDynamicTLSModel:
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return TLSModel::GeneralDynamic;
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case GlobalVariable::LocalDynamicTLSModel:
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return TLSModel::LocalDynamic;
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case GlobalVariable::InitialExecTLSModel:
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return TLSModel::InitialExec;
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case GlobalVariable::LocalExecTLSModel:
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return TLSModel::LocalExec;
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}
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llvm_unreachable("invalid TLS model");
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}
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bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
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const GlobalValue *GV) const {
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// If the IR producer requested that this GV be treated as dso local, obey.
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if (GV && GV->isDSOLocal())
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return true;
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// If we are not supossed to use a PLT, we cannot assume that intrinsics are
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// local since the linker can convert some direct access to access via plt.
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if (M.getRtLibUseGOT() && !GV)
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return false;
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// According to the llvm language reference, we should be able to
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// just return false in here if we have a GV, as we know it is
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// dso_preemptable. At this point in time, the various IR producers
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// have not been transitioned to always produce a dso_local when it
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// is possible to do so.
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// In the case of intrinsics, GV is null and there is nowhere to put
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// dso_local. Returning false for those will produce worse code in some
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// architectures. For example, on x86 the caller has to set ebx before calling
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// a plt.
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// As a result we still have some logic in here to improve the quality of the
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// generated code.
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// FIXME: Add a module level metadata for whether intrinsics should be assumed
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// local.
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Reloc::Model RM = getRelocationModel();
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const Triple &TT = getTargetTriple();
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// DLLImport explicitly marks the GV as external.
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if (GV && GV->hasDLLImportStorageClass())
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return false;
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// On MinGW, variables that haven't been declared with DLLImport may still
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// end up automatically imported by the linker. To make this feasible,
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// don't assume the variables to be DSO local unless we actually know
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// that for sure. This only has to be done for variables; for functions
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// the linker can insert thunks for calling functions from another DLL.
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if (TT.isWindowsGNUEnvironment() && GV && GV->isDeclarationForLinker() &&
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isa<GlobalVariable>(GV))
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return false;
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// Every other GV is local on COFF.
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// Make an exception for windows OS in the triple: Some firmware builds use
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// *-win32-macho triples. This (accidentally?) produced windows relocations
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// without GOT tables in older clang versions; Keep this behaviour.
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if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
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return true;
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// Most PIC code sequences that assume that a symbol is local cannot
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// produce a 0 if it turns out the symbol is undefined. While this
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// is ABI and relocation depended, it seems worth it to handle it
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// here.
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if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
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return false;
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if (GV && !GV->hasDefaultVisibility())
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return true;
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if (TT.isOSBinFormatMachO()) {
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if (RM == Reloc::Static)
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return true;
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return GV && GV->isStrongDefinitionForLinker();
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}
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assert(TT.isOSBinFormatELF());
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assert(RM != Reloc::DynamicNoPIC);
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bool IsExecutable =
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RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
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if (IsExecutable) {
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// If the symbol is defined, it cannot be preempted.
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if (GV && !GV->isDeclarationForLinker())
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return true;
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// A symbol marked nonlazybind should not be accessed with a plt. If the
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// symbol turns out to be external, the linker will convert a direct
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// access to an access via the plt, so don't assume it is local.
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const Function *F = dyn_cast_or_null<Function>(GV);
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if (F && F->hasFnAttribute(Attribute::NonLazyBind))
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return false;
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bool IsTLS = GV && GV->isThreadLocal();
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bool IsAccessViaCopyRelocs =
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GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
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Triple::ArchType Arch = TT.getArch();
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bool IsPPC =
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Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
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// Check if we can use copy relocations. PowerPC has no copy relocations.
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if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
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return true;
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}
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// ELF supports preemption of other symbols.
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return false;
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}
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bool TargetMachine::useEmulatedTLS() const {
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// Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
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// was specified explicitly; otherwise uses target triple to decide default.
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if (Options.ExplicitEmulatedTLS)
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return Options.EmulatedTLS;
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return getTargetTriple().hasDefaultEmulatedTLS();
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}
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TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
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bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
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Reloc::Model RM = getRelocationModel();
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bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
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bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
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TLSModel::Model Model;
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if (IsSharedLibrary) {
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if (IsLocal)
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Model = TLSModel::LocalDynamic;
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else
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Model = TLSModel::GeneralDynamic;
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} else {
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if (IsLocal)
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Model = TLSModel::LocalExec;
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else
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Model = TLSModel::InitialExec;
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}
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// If the user specified a more specific model, use that.
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TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
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if (SelectedModel > Model)
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return SelectedModel;
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return Model;
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}
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/// Returns the optimization level: None, Less, Default, or Aggressive.
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CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
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void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
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TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {
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return TargetTransformInfo(F.getParent()->getDataLayout());
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}
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void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
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const GlobalValue *GV, Mangler &Mang,
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bool MayAlwaysUsePrivate) const {
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if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
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// Simple case: If GV is not private, it is not important to find out if
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// private labels are legal in this case or not.
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Mang.getNameWithPrefix(Name, GV, false);
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return;
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}
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const TargetLoweringObjectFile *TLOF = getObjFileLowering();
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TLOF->getNameWithPrefix(Name, GV, *this);
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}
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MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
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const TargetLoweringObjectFile *TLOF = getObjFileLowering();
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SmallString<128> NameStr;
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getNameWithPrefix(NameStr, GV, TLOF->getMangler());
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return TLOF->getContext().getOrCreateSymbol(NameStr);
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}
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TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
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// Since Analysis can't depend on Target, use a std::function to invert the
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// dependency.
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return TargetIRAnalysis(
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[this](const Function &F) { return this->getTargetTransformInfo(F); });
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}
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