1 //===-- TargetMachine.cpp - General Target Information ---------------------==//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file describes the general parts of a Target machine.
12 //===----------------------------------------------------------------------===//
14 #include "llvm/Target/TargetMachine.h"
15 #include "llvm/Analysis/TargetTransformInfo.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/LegacyPassManager.h"
21 #include "llvm/IR/Mangler.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCContext.h"
24 #include "llvm/MC/MCInstrInfo.h"
25 #include "llvm/MC/MCSectionMachO.h"
26 #include "llvm/MC/MCTargetOptions.h"
27 #include "llvm/MC/SectionKind.h"
28 #include "llvm/Target/TargetLoweringObjectFile.h"
31 //---------------------------------------------------------------------------
32 // TargetMachine Class
35 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
36 const Triple &TT, StringRef CPU, StringRef FS,
37 const TargetOptions &Options)
38 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
39 TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
40 RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
43 TargetMachine::~TargetMachine() {
50 bool TargetMachine::isPositionIndependent() const {
51 return getRelocationModel() == Reloc::PIC_;
54 /// Reset the target options based on the function's attributes.
55 // FIXME: This function needs to go away for a number of reasons:
56 // a) global state on the TargetMachine is terrible in general,
57 // b) these target options should be passed only on the function
58 // and not on the TargetMachine (via TargetOptions) at all.
59 void TargetMachine::resetTargetOptions(const Function &F) const {
60 #define RESET_OPTION(X, Y) \
62 if (F.hasFnAttribute(Y)) \
63 Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
65 Options.X = DefaultOptions.X; \
68 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
69 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
70 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
71 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
72 RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
75 F.getFnAttribute("denormal-fp-math").getValueAsString();
76 if (Denormal == "ieee")
77 Options.FPDenormalMode = FPDenormal::IEEE;
78 else if (Denormal == "preserve-sign")
79 Options.FPDenormalMode = FPDenormal::PreserveSign;
80 else if (Denormal == "positive-zero")
81 Options.FPDenormalMode = FPDenormal::PositiveZero;
83 Options.FPDenormalMode = DefaultOptions.FPDenormalMode;
86 /// Returns the code generation relocation model. The choices are static, PIC,
87 /// and dynamic-no-pic.
88 Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
90 /// Returns the code model. The choices are small, kernel, medium, large, and
92 CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
94 /// Get the IR-specified TLS model for Var.
95 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
96 switch (GV->getThreadLocalMode()) {
97 case GlobalVariable::NotThreadLocal:
98 llvm_unreachable("getSelectedTLSModel for non-TLS variable");
100 case GlobalVariable::GeneralDynamicTLSModel:
101 return TLSModel::GeneralDynamic;
102 case GlobalVariable::LocalDynamicTLSModel:
103 return TLSModel::LocalDynamic;
104 case GlobalVariable::InitialExecTLSModel:
105 return TLSModel::InitialExec;
106 case GlobalVariable::LocalExecTLSModel:
107 return TLSModel::LocalExec;
109 llvm_unreachable("invalid TLS model");
112 bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
113 const GlobalValue *GV) const {
114 // If the IR producer requested that this GV be treated as dso local, obey.
115 if (GV && GV->isDSOLocal())
118 // If we are not supossed to use a PLT, we cannot assume that intrinsics are
119 // local since the linker can convert some direct access to access via plt.
120 if (M.getRtLibUseGOT() && !GV)
123 // According to the llvm language reference, we should be able to
124 // just return false in here if we have a GV, as we know it is
125 // dso_preemptable. At this point in time, the various IR producers
126 // have not been transitioned to always produce a dso_local when it
127 // is possible to do so.
128 // In the case of intrinsics, GV is null and there is nowhere to put
129 // dso_local. Returning false for those will produce worse code in some
130 // architectures. For example, on x86 the caller has to set ebx before calling
132 // As a result we still have some logic in here to improve the quality of the
134 // FIXME: Add a module level metadata for whether intrinsics should be assumed
137 Reloc::Model RM = getRelocationModel();
138 const Triple &TT = getTargetTriple();
140 // DLLImport explicitly marks the GV as external.
141 if (GV && GV->hasDLLImportStorageClass())
144 // Every other GV is local on COFF.
145 // Make an exception for windows OS in the triple: Some firmware builds use
146 // *-win32-macho triples. This (accidentally?) produced windows relocations
147 // without GOT tables in older clang versions; Keep this behaviour.
148 if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
151 // Most PIC code sequences that assume that a symbol is local cannot
152 // produce a 0 if it turns out the symbol is undefined. While this
153 // is ABI and relocation depended, it seems worth it to handle it
155 if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
158 if (GV && !GV->hasDefaultVisibility())
161 if (TT.isOSBinFormatMachO()) {
162 if (RM == Reloc::Static)
164 return GV && GV->isStrongDefinitionForLinker();
167 assert(TT.isOSBinFormatELF());
168 assert(RM != Reloc::DynamicNoPIC);
171 RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
173 // If the symbol is defined, it cannot be preempted.
174 if (GV && !GV->isDeclarationForLinker())
177 // A symbol marked nonlazybind should not be accessed with a plt. If the
178 // symbol turns out to be external, the linker will convert a direct
179 // access to an access via the plt, so don't assume it is local.
180 const Function *F = dyn_cast_or_null<Function>(GV);
181 if (F && F->hasFnAttribute(Attribute::NonLazyBind))
184 bool IsTLS = GV && GV->isThreadLocal();
185 bool IsAccessViaCopyRelocs =
186 GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
187 Triple::ArchType Arch = TT.getArch();
189 Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
190 // Check if we can use copy relocations. PowerPC has no copy relocations.
191 if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
195 // ELF supports preemption of other symbols.
199 bool TargetMachine::useEmulatedTLS() const {
200 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
201 // was specified explicitly; otherwise uses target triple to decide default.
202 if (Options.ExplicitEmulatedTLS)
203 return Options.EmulatedTLS;
204 return getTargetTriple().hasDefaultEmulatedTLS();
207 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
208 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
209 Reloc::Model RM = getRelocationModel();
210 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
211 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
213 TLSModel::Model Model;
214 if (IsSharedLibrary) {
216 Model = TLSModel::LocalDynamic;
218 Model = TLSModel::GeneralDynamic;
221 Model = TLSModel::LocalExec;
223 Model = TLSModel::InitialExec;
226 // If the user specified a more specific model, use that.
227 TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
228 if (SelectedModel > Model)
229 return SelectedModel;
234 /// Returns the optimization level: None, Less, Default, or Aggressive.
235 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
237 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
239 TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {
240 return TargetTransformInfo(F.getParent()->getDataLayout());
243 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
244 const GlobalValue *GV, Mangler &Mang,
245 bool MayAlwaysUsePrivate) const {
246 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
247 // Simple case: If GV is not private, it is not important to find out if
248 // private labels are legal in this case or not.
249 Mang.getNameWithPrefix(Name, GV, false);
252 const TargetLoweringObjectFile *TLOF = getObjFileLowering();
253 TLOF->getNameWithPrefix(Name, GV, *this);
256 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
257 const TargetLoweringObjectFile *TLOF = getObjFileLowering();
258 SmallString<128> NameStr;
259 getNameWithPrefix(NameStr, GV, TLOF->getMangler());
260 return TLOF->getContext().getOrCreateSymbol(NameStr);
263 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
264 // Since Analysis can't depend on Target, use a std::function to invert the
266 return TargetIRAnalysis(
267 [this](const Function &F) { return this->getTargetTransformInfo(F); });