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