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