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      1 //===-- TargetMachine.cpp - General Target Information ---------------------==//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file describes the general parts of a Target machine.
     11 //
     12 //===----------------------------------------------------------------------===//
     13 
     14 #include "llvm/Target/TargetMachine.h"
     15 #include "llvm/CodeGen/MachineFunction.h"
     16 #include "llvm/IR/Function.h"
     17 #include "llvm/IR/GlobalAlias.h"
     18 #include "llvm/IR/GlobalValue.h"
     19 #include "llvm/IR/GlobalVariable.h"
     20 #include "llvm/IR/Mangler.h"
     21 #include "llvm/MC/MCAsmInfo.h"
     22 #include "llvm/MC/MCCodeGenInfo.h"
     23 #include "llvm/MC/MCContext.h"
     24 #include "llvm/MC/MCTargetOptions.h"
     25 #include "llvm/MC/SectionKind.h"
     26 #include "llvm/Support/CommandLine.h"
     27 #include "llvm/Target/TargetLowering.h"
     28 #include "llvm/Target/TargetLoweringObjectFile.h"
     29 using namespace llvm;
     30 
     31 //---------------------------------------------------------------------------
     32 // TargetMachine Class
     33 //
     34 
     35 TargetMachine::TargetMachine(const Target &T,
     36                              StringRef TT, StringRef CPU, StringRef FS,
     37                              const TargetOptions &Options)
     38   : TheTarget(T), TargetTriple(TT), TargetCPU(CPU), TargetFS(FS),
     39     CodeGenInfo(nullptr), AsmInfo(nullptr),
     40     RequireStructuredCFG(false),
     41     Options(Options) {
     42 }
     43 
     44 TargetMachine::~TargetMachine() {
     45   delete CodeGenInfo;
     46   delete AsmInfo;
     47 }
     48 
     49 /// \brief Reset the target options based on the function's attributes.
     50 void TargetMachine::resetTargetOptions(const MachineFunction *MF) const {
     51   const Function *F = MF->getFunction();
     52   TargetOptions &TO = MF->getTarget().Options;
     53 
     54 #define RESET_OPTION(X, Y)                                              \
     55   do {                                                                  \
     56     if (F->hasFnAttribute(Y))                                           \
     57       TO.X =                                                            \
     58         (F->getAttributes().                                            \
     59            getAttribute(AttributeSet::FunctionIndex,                    \
     60                         Y).getValueAsString() == "true");               \
     61   } while (0)
     62 
     63   RESET_OPTION(NoFramePointerElim, "no-frame-pointer-elim");
     64   RESET_OPTION(LessPreciseFPMADOption, "less-precise-fpmad");
     65   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
     66   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
     67   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
     68   RESET_OPTION(UseSoftFloat, "use-soft-float");
     69   RESET_OPTION(DisableTailCalls, "disable-tail-calls");
     70 
     71   TO.MCOptions.SanitizeAddress = F->hasFnAttribute(Attribute::SanitizeAddress);
     72 }
     73 
     74 /// getRelocationModel - Returns the code generation relocation model. The
     75 /// choices are static, PIC, and dynamic-no-pic, and target default.
     76 Reloc::Model TargetMachine::getRelocationModel() const {
     77   if (!CodeGenInfo)
     78     return Reloc::Default;
     79   return CodeGenInfo->getRelocationModel();
     80 }
     81 
     82 /// getCodeModel - Returns the code model. The choices are small, kernel,
     83 /// medium, large, and target default.
     84 CodeModel::Model TargetMachine::getCodeModel() const {
     85   if (!CodeGenInfo)
     86     return CodeModel::Default;
     87   return CodeGenInfo->getCodeModel();
     88 }
     89 
     90 /// Get the IR-specified TLS model for Var.
     91 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
     92   switch (GV->getThreadLocalMode()) {
     93   case GlobalVariable::NotThreadLocal:
     94     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
     95     break;
     96   case GlobalVariable::GeneralDynamicTLSModel:
     97     return TLSModel::GeneralDynamic;
     98   case GlobalVariable::LocalDynamicTLSModel:
     99     return TLSModel::LocalDynamic;
    100   case GlobalVariable::InitialExecTLSModel:
    101     return TLSModel::InitialExec;
    102   case GlobalVariable::LocalExecTLSModel:
    103     return TLSModel::LocalExec;
    104   }
    105   llvm_unreachable("invalid TLS model");
    106 }
    107 
    108 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
    109   bool isLocal = GV->hasLocalLinkage();
    110   bool isDeclaration = GV->isDeclaration();
    111   bool isPIC = getRelocationModel() == Reloc::PIC_;
    112   bool isPIE = Options.PositionIndependentExecutable;
    113   // FIXME: what should we do for protected and internal visibility?
    114   // For variables, is internal different from hidden?
    115   bool isHidden = GV->hasHiddenVisibility();
    116 
    117   TLSModel::Model Model;
    118   if (isPIC && !isPIE) {
    119     if (isLocal || isHidden)
    120       Model = TLSModel::LocalDynamic;
    121     else
    122       Model = TLSModel::GeneralDynamic;
    123   } else {
    124     if (!isDeclaration || isHidden)
    125       Model = TLSModel::LocalExec;
    126     else
    127       Model = TLSModel::InitialExec;
    128   }
    129 
    130   // If the user specified a more specific model, use that.
    131   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
    132   if (SelectedModel > Model)
    133     return SelectedModel;
    134 
    135   return Model;
    136 }
    137 
    138 /// getOptLevel - Returns the optimization level: None, Less,
    139 /// Default, or Aggressive.
    140 CodeGenOpt::Level TargetMachine::getOptLevel() const {
    141   if (!CodeGenInfo)
    142     return CodeGenOpt::Default;
    143   return CodeGenInfo->getOptLevel();
    144 }
    145 
    146 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
    147   if (CodeGenInfo)
    148     CodeGenInfo->setOptLevel(Level);
    149 }
    150 
    151 bool TargetMachine::getAsmVerbosityDefault() const {
    152   return Options.MCOptions.AsmVerbose;
    153 }
    154 
    155 void TargetMachine::setAsmVerbosityDefault(bool V) {
    156   Options.MCOptions.AsmVerbose = V;
    157 }
    158 
    159 bool TargetMachine::getFunctionSections() const {
    160   return Options.FunctionSections;
    161 }
    162 
    163 bool TargetMachine::getDataSections() const {
    164   return Options.DataSections;
    165 }
    166 
    167 void TargetMachine::setFunctionSections(bool V) {
    168   Options.FunctionSections = V;
    169 }
    170 
    171 void TargetMachine::setDataSections(bool V) {
    172   Options.DataSections = V;
    173 }
    174 
    175 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
    176                                       const GlobalValue *GV, Mangler &Mang,
    177                                       bool MayAlwaysUsePrivate) const {
    178   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
    179     // Simple case: If GV is not private, it is not important to find out if
    180     // private labels are legal in this case or not.
    181     Mang.getNameWithPrefix(Name, GV, false);
    182     return;
    183   }
    184   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, *this);
    185   const TargetLoweringObjectFile &TLOF =
    186       getTargetLowering()->getObjFileLowering();
    187   const MCSection *TheSection = TLOF.SectionForGlobal(GV, GVKind, Mang, *this);
    188   bool CannotUsePrivateLabel = TLOF.isSectionAtomizableBySymbols(*TheSection);
    189   Mang.getNameWithPrefix(Name, GV, CannotUsePrivateLabel);
    190 }
    191 
    192 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
    193   SmallString<60> NameStr;
    194   getNameWithPrefix(NameStr, GV, Mang);
    195   const TargetLoweringObjectFile &TLOF =
    196       getTargetLowering()->getObjFileLowering();
    197   return TLOF.getContext().GetOrCreateSymbol(NameStr.str());
    198 }
    199