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 // Command-line options that tend to be useful on more than one back-end.
33 //
34 
35 namespace llvm {
36   bool HasDivModLibcall;
37   bool AsmVerbosityDefault(false);
38 }
39 
40 static cl::opt<bool>
41 DataSections("fdata-sections",
42   cl::desc("Emit data into separate sections"),
43   cl::init(false));
44 static cl::opt<bool>
45 FunctionSections("ffunction-sections",
46   cl::desc("Emit functions into separate sections"),
47   cl::init(false));
48 
49 //---------------------------------------------------------------------------
50 // TargetMachine Class
51 //
52 
53 TargetMachine::TargetMachine(const Target &T,
54                              StringRef TT, StringRef CPU, StringRef FS,
55                              const TargetOptions &Options)
56   : TheTarget(T), TargetTriple(TT), TargetCPU(CPU), TargetFS(FS),
57     CodeGenInfo(nullptr), AsmInfo(nullptr),
58     MCRelaxAll(false),
59     MCNoExecStack(false),
60     MCSaveTempLabels(false),
61     MCUseCFI(true),
62     MCUseDwarfDirectory(false),
63     RequireStructuredCFG(false),
64     Options(Options) {
65 }
66 
67 TargetMachine::~TargetMachine() {
68   delete CodeGenInfo;
69   delete AsmInfo;
70 }
71 
72 /// \brief Reset the target options based on the function's attributes.
73 void TargetMachine::resetTargetOptions(const MachineFunction *MF) const {
74   const Function *F = MF->getFunction();
75   TargetOptions &TO = MF->getTarget().Options;
76 
77 #define RESET_OPTION(X, Y)                                              \
78   do {                                                                  \
79     if (F->hasFnAttribute(Y))                                           \
80       TO.X =                                                            \
81         (F->getAttributes().                                            \
82            getAttribute(AttributeSet::FunctionIndex,                    \
83                         Y).getValueAsString() == "true");               \
84   } while (0)
85 
86   RESET_OPTION(NoFramePointerElim, "no-frame-pointer-elim");
87   RESET_OPTION(LessPreciseFPMADOption, "less-precise-fpmad");
88   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
89   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
90   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
91   RESET_OPTION(UseSoftFloat, "use-soft-float");
92   RESET_OPTION(DisableTailCalls, "disable-tail-calls");
93 
94   TO.MCOptions.SanitizeAddress = F->hasFnAttribute(Attribute::SanitizeAddress);
95 }
96 
97 /// getRelocationModel - Returns the code generation relocation model. The
98 /// choices are static, PIC, and dynamic-no-pic, and target default.
99 Reloc::Model TargetMachine::getRelocationModel() const {
100   if (!CodeGenInfo)
101     return Reloc::Default;
102   return CodeGenInfo->getRelocationModel();
103 }
104 
105 /// getCodeModel - Returns the code model. The choices are small, kernel,
106 /// medium, large, and target default.
107 CodeModel::Model TargetMachine::getCodeModel() const {
108   if (!CodeGenInfo)
109     return CodeModel::Default;
110   return CodeGenInfo->getCodeModel();
111 }
112 
113 /// Get the IR-specified TLS model for Var.
114 static TLSModel::Model getSelectedTLSModel(const GlobalVariable *Var) {
115   switch (Var->getThreadLocalMode()) {
116   case GlobalVariable::NotThreadLocal:
117     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
118     break;
119   case GlobalVariable::GeneralDynamicTLSModel:
120     return TLSModel::GeneralDynamic;
121   case GlobalVariable::LocalDynamicTLSModel:
122     return TLSModel::LocalDynamic;
123   case GlobalVariable::InitialExecTLSModel:
124     return TLSModel::InitialExec;
125   case GlobalVariable::LocalExecTLSModel:
126     return TLSModel::LocalExec;
127   }
128   llvm_unreachable("invalid TLS model");
129 }
130 
131 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
132   // If GV is an alias then use the aliasee for determining
133   // thread-localness.
134   if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
135     GV = GA->getAliasedGlobal();
136   const GlobalVariable *Var = cast<GlobalVariable>(GV);
137 
138   bool isLocal = Var->hasLocalLinkage();
139   bool isDeclaration = Var->isDeclaration();
140   bool isPIC = getRelocationModel() == Reloc::PIC_;
141   bool isPIE = Options.PositionIndependentExecutable;
142   // FIXME: what should we do for protected and internal visibility?
143   // For variables, is internal different from hidden?
144   bool isHidden = Var->hasHiddenVisibility();
145 
146   TLSModel::Model Model;
147   if (isPIC && !isPIE) {
148     if (isLocal || isHidden)
149       Model = TLSModel::LocalDynamic;
150     else
151       Model = TLSModel::GeneralDynamic;
152   } else {
153     if (!isDeclaration || isHidden)
154       Model = TLSModel::LocalExec;
155     else
156       Model = TLSModel::InitialExec;
157   }
158 
159   // If the user specified a more specific model, use that.
160   TLSModel::Model SelectedModel = getSelectedTLSModel(Var);
161   if (SelectedModel > Model)
162     return SelectedModel;
163 
164   return Model;
165 }
166 
167 /// getOptLevel - Returns the optimization level: None, Less,
168 /// Default, or Aggressive.
169 CodeGenOpt::Level TargetMachine::getOptLevel() const {
170   if (!CodeGenInfo)
171     return CodeGenOpt::Default;
172   return CodeGenInfo->getOptLevel();
173 }
174 
175 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
176   if (CodeGenInfo)
177     CodeGenInfo->setOptLevel(Level);
178 }
179 
180 bool TargetMachine::getAsmVerbosityDefault() {
181   return AsmVerbosityDefault;
182 }
183 
184 void TargetMachine::setAsmVerbosityDefault(bool V) {
185   AsmVerbosityDefault = V;
186 }
187 
188 bool TargetMachine::getFunctionSections() {
189   return FunctionSections;
190 }
191 
192 bool TargetMachine::getDataSections() {
193   return DataSections;
194 }
195 
196 void TargetMachine::setFunctionSections(bool V) {
197   FunctionSections = V;
198 }
199 
200 void TargetMachine::setDataSections(bool V) {
201   DataSections = V;
202 }
203 
204 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
205                                       const GlobalValue *GV, Mangler &Mang,
206                                       bool MayAlwaysUsePrivate) const {
207   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
208     // Simple case: If GV is not private, it is not important to find out if
209     // private labels are legal in this case or not.
210     Mang.getNameWithPrefix(Name, GV, false);
211     return;
212   }
213   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, *this);
214   const TargetLoweringObjectFile &TLOF =
215       getTargetLowering()->getObjFileLowering();
216   const MCSection *TheSection = TLOF.SectionForGlobal(GV, GVKind, Mang, *this);
217   bool CannotUsePrivateLabel = TLOF.isSectionAtomizableBySymbols(*TheSection);
218   Mang.getNameWithPrefix(Name, GV, CannotUsePrivateLabel);
219 }
220 
221 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
222   SmallString<60> NameStr;
223   getNameWithPrefix(NameStr, GV, Mang);
224   const TargetLoweringObjectFile &TLOF =
225       getTargetLowering()->getObjFileLowering();
226   return TLOF.getContext().GetOrCreateSymbol(NameStr.str());
227 }
228