llvm/lib/Target/TargetMachine.cpp

   1 //===-- TargetMachine.cpp - General Target Information ---------------------==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file describes the general parts of a Target machine.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "llvm/Target/TargetMachine.h"
  14 #include "llvm/Analysis/TargetTransformInfo.h"
  15 #include "llvm/IR/Function.h"
  16 #include "llvm/IR/GlobalAlias.h"
  17 #include "llvm/IR/GlobalValue.h"
  18 #include "llvm/IR/GlobalVariable.h"
  19 #include "llvm/IR/LegacyPassManager.h"
  20 #include "llvm/IR/Mangler.h"
  21 #include "llvm/MC/MCAsmInfo.h"
  22 #include "llvm/MC/MCContext.h"
  23 #include "llvm/MC/MCInstrInfo.h"
  24 #include "llvm/MC/MCRegisterInfo.h"
  25 #include "llvm/MC/MCSectionMachO.h"
  26 #include "llvm/MC/MCSubtargetInfo.h"
  27 #include "llvm/MC/MCTargetOptions.h"
  28 #include "llvm/MC/SectionKind.h"
  29 #include "llvm/Target/TargetLoweringObjectFile.h"
  30 using namespace llvm;
  31
  32 //---------------------------------------------------------------------------
  33 // TargetMachine Class
  34 //
  35
  36 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
  37                              const Triple &TT, StringRef CPU, StringRef FS,
  38                              const TargetOptions &Options)
  39     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT),
  40       TargetCPU(std::string(CPU)), TargetFS(std::string(FS)), AsmInfo(nullptr),
  41       MRI(nullptr), MII(nullptr), STI(nullptr), RequireStructuredCFG(false),
  42       O0WantsFastISel(false), DefaultOptions(Options), Options(Options) {}
  43
  44 TargetMachine::~TargetMachine() = default;
  45
  46 bool TargetMachine::isPositionIndependent() const {
  47   return getRelocationModel() == Reloc::PIC_;
  48 }
  49
  50 /// Reset the target options based on the function's attributes.
  51 /// setFunctionAttributes should have made the raw attribute value consistent
  52 /// with the command line flag if used.
  53 //
  54 // FIXME: This function needs to go away for a number of reasons:
  55 // a) global state on the TargetMachine is terrible in general,
  56 // b) these target options should be passed only on the function
  57 //    and not on the TargetMachine (via TargetOptions) at all.
  58 void TargetMachine::resetTargetOptions(const Function &F) const {
  59 #define RESET_OPTION(X, Y)                                              \
  60   do {                                                                  \
  61     Options.X = F.getFnAttribute(Y).getValueAsBool();     \
  62   } while (0)
  63
  64   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
  65   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
  66   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
  67   RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
  68   RESET_OPTION(ApproxFuncFPMath, "approx-func-fp-math");
  69 }
  70
  71 /// Returns the code generation relocation model. The choices are static, PIC,
  72 /// and dynamic-no-pic.
  73 Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
  74
  75 /// Returns the code model. The choices are small, kernel, medium, large, and
  76 /// target default.
  77 CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
  78
  79 /// Get the IR-specified TLS model for Var.
  80 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
  81   switch (GV->getThreadLocalMode()) {
  82   case GlobalVariable::NotThreadLocal:
  83     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
  84     break;
  85   case GlobalVariable::GeneralDynamicTLSModel:
  86     return TLSModel::GeneralDynamic;
  87   case GlobalVariable::LocalDynamicTLSModel:
  88     return TLSModel::LocalDynamic;
  89   case GlobalVariable::InitialExecTLSModel:
  90     return TLSModel::InitialExec;
  91   case GlobalVariable::LocalExecTLSModel:
  92     return TLSModel::LocalExec;
  93   }
  94   llvm_unreachable("invalid TLS model");
  95 }
  96
  97 bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
  98                                          const GlobalValue *GV) const {
  99   const Triple &TT = getTargetTriple();
 100   Reloc::Model RM = getRelocationModel();
 101
 102   // According to the llvm language reference, we should be able to
 103   // just return false in here if we have a GV, as we know it is
 104   // dso_preemptable.  At this point in time, the various IR producers
 105   // have not been transitioned to always produce a dso_local when it
 106   // is possible to do so.
 107   //
 108   // As a result we still have some logic in here to improve the quality of the
 109   // generated code.
 110   if (!GV)
 111     return false;
 112
 113   // If the IR producer requested that this GV be treated as dso local, obey.
 114   if (GV->isDSOLocal())
 115     return true;
 116
 117   if (TT.isOSBinFormatCOFF()) {
 118     // DLLImport explicitly marks the GV as external.
 119     if (GV->hasDLLImportStorageClass())
 120       return false;
 121
 122     // On MinGW, variables that haven't been declared with DLLImport may still
 123     // end up automatically imported by the linker. To make this feasible,
 124     // don't assume the variables to be DSO local unless we actually know
 125     // that for sure. This only has to be done for variables; for functions
 126     // the linker can insert thunks for calling functions from another DLL.
 127     if (TT.isWindowsGNUEnvironment() && GV->isDeclarationForLinker() &&
 128         isa<GlobalVariable>(GV))
 129       return false;
 130
 131     // Don't mark 'extern_weak' symbols as DSO local. If these symbols remain
 132     // unresolved in the link, they can be resolved to zero, which is outside
 133     // the current DSO.
 134     if (GV->hasExternalWeakLinkage())
 135       return false;
 136
 137     // Every other GV is local on COFF.
 138     return true;
 139   }
 140
 141   if (TT.isOSBinFormatGOFF())
 142     return true;
 143
 144   if (TT.isOSBinFormatMachO()) {
 145     if (RM == Reloc::Static)
 146       return true;
 147     return GV->isStrongDefinitionForLinker();
 148   }
 149
 150   assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm() ||
 151          TT.isOSBinFormatXCOFF());
 152   return false;
 153 }
 154
 155 bool TargetMachine::useEmulatedTLS() const {
 156   // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
 157   // was specified explicitly; otherwise uses target triple to decide default.
 158   if (Options.ExplicitEmulatedTLS)
 159     return Options.EmulatedTLS;
 160   return getTargetTriple().hasDefaultEmulatedTLS();
 161 }
 162
 163 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
 164   bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
 165   Reloc::Model RM = getRelocationModel();
 166   bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
 167   bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
 168
 169   TLSModel::Model Model;
 170   if (IsSharedLibrary) {
 171     if (IsLocal)
 172       Model = TLSModel::LocalDynamic;
 173     else
 174       Model = TLSModel::GeneralDynamic;
 175   } else {
 176     if (IsLocal)
 177       Model = TLSModel::LocalExec;
 178     else
 179       Model = TLSModel::InitialExec;
 180   }
 181
 182   // If the user specified a more specific model, use that.
 183   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
 184   if (SelectedModel > Model)
 185     return SelectedModel;
 186
 187   return Model;
 188 }
 189
 190 /// Returns the optimization level: None, Less, Default, or Aggressive.
 191 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
 192
 193 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
 194
 195 TargetTransformInfo
 196 TargetMachine::getTargetTransformInfo(const Function &F) const {
 197   return TargetTransformInfo(F.getParent()->getDataLayout());
 198 }
 199
 200 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
 201                                       const GlobalValue *GV, Mangler &Mang,
 202                                       bool MayAlwaysUsePrivate) const {
 203   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
 204     // Simple case: If GV is not private, it is not important to find out if
 205     // private labels are legal in this case or not.
 206     Mang.getNameWithPrefix(Name, GV, false);
 207     return;
 208   }
 209   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
 210   TLOF->getNameWithPrefix(Name, GV, *this);
 211 }
 212
 213 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
 214   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
 215   // XCOFF symbols could have special naming convention.
 216   if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this))
 217     return TargetSymbol;
 218
 219   SmallString<128> NameStr;
 220   getNameWithPrefix(NameStr, GV, TLOF->getMangler());
 221   return TLOF->getContext().getOrCreateSymbol(NameStr);
 222 }
 223
 224 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() const {
 225   // Since Analysis can't depend on Target, use a std::function to invert the
 226   // dependency.
 227   return TargetIRAnalysis(
 228       [this](const Function &F) { return this->getTargetTransformInfo(F); });
 229 }
 230
 231 std::pair<int, int> TargetMachine::parseBinutilsVersion(StringRef Version) {
 232   if (Version == "none")
 233     return {INT_MAX, INT_MAX}; // Make binutilsIsAtLeast() return true.
 234   std::pair<int, int> Ret;
 235   if (!Version.consumeInteger(10, Ret.first) && Version.consume_front("."))
 236     Version.consumeInteger(10, Ret.second);
 237   return Ret;
 238 }