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/SectionKind.h"
25 #include "llvm/Support/CommandLine.h"
26 #include "llvm/Target/TargetLowering.h"
27 #include "llvm/Target/TargetLoweringObjectFile.h"
28 using namespace llvm;
29 
30 //---------------------------------------------------------------------------
31 // Command-line options that tend to be useful on more than one back-end.
32 //
33 
34 namespace llvm {
35   bool HasDivModLibcall;
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(0), AsmInfo(0),
57     MCRelaxAll(false),
58     MCNoExecStack(false),
59     MCSaveTempLabels(false),
60     MCUseCFI(true),
61     MCUseDwarfDirectory(false),
62     RequireStructuredCFG(false),
63     Options(Options) {
64 }
65 
66 TargetMachine::~TargetMachine() {
67   delete CodeGenInfo;
68   delete AsmInfo;
69 }
70 
71 /// \brief Reset the target options based on the function's attributes.
72 void TargetMachine::resetTargetOptions(const MachineFunction *MF) const {
73   const Function *F = MF->getFunction();
74   TargetOptions &TO = MF->getTarget().Options;
75 
76 #define RESET_OPTION(X, Y)                                              \
77   do {                                                                  \
78     if (F->hasFnAttribute(Y))                                           \
79       TO.X =                                                            \
80         (F->getAttributes().                                            \
81            getAttribute(AttributeSet::FunctionIndex,                    \
82                         Y).getValueAsString() == "true");               \
83   } while (0)
84 
85   RESET_OPTION(NoFramePointerElim, "no-frame-pointer-elim");
86   RESET_OPTION(LessPreciseFPMADOption, "less-precise-fpmad");
87   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
88   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
89   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
90   RESET_OPTION(UseSoftFloat, "use-soft-float");
91   RESET_OPTION(DisableTailCalls, "disable-tail-calls");
92 }
93 
94 /// getRelocationModel - Returns the code generation relocation model. The
95 /// choices are static, PIC, and dynamic-no-pic, and target default.
96 Reloc::Model TargetMachine::getRelocationModel() const {
97   if (!CodeGenInfo)
98     return Reloc::Default;
99   return CodeGenInfo->getRelocationModel();
100 }
101 
102 /// getCodeModel - Returns the code model. The choices are small, kernel,
103 /// medium, large, and target default.
104 CodeModel::Model TargetMachine::getCodeModel() const {
105   if (!CodeGenInfo)
106     return CodeModel::Default;
107   return CodeGenInfo->getCodeModel();
108 }
109 
110 /// Get the IR-specified TLS model for Var.
111 static TLSModel::Model getSelectedTLSModel(const GlobalVariable *Var) {
112   switch (Var->getThreadLocalMode()) {
113   case GlobalVariable::NotThreadLocal:
114     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
115     break;
116   case GlobalVariable::GeneralDynamicTLSModel:
117     return TLSModel::GeneralDynamic;
118   case GlobalVariable::LocalDynamicTLSModel:
119     return TLSModel::LocalDynamic;
120   case GlobalVariable::InitialExecTLSModel:
121     return TLSModel::InitialExec;
122   case GlobalVariable::LocalExecTLSModel:
123     return TLSModel::LocalExec;
124   }
125   llvm_unreachable("invalid TLS model");
126 }
127 
128 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
129   // If GV is an alias then use the aliasee for determining
130   // thread-localness.
131   if (const GlobalAlias *GA = dyn_cast<GlobalAlias>(GV))
132     GV = GA->resolveAliasedGlobal(false);
133   const GlobalVariable *Var = cast<GlobalVariable>(GV);
134 
135   bool isLocal = Var->hasLocalLinkage();
136   bool isDeclaration = Var->isDeclaration();
137   bool isPIC = getRelocationModel() == Reloc::PIC_;
138   bool isPIE = Options.PositionIndependentExecutable;
139   // FIXME: what should we do for protected and internal visibility?
140   // For variables, is internal different from hidden?
141   bool isHidden = Var->hasHiddenVisibility();
142 
143   TLSModel::Model Model;
144   if (isPIC && !isPIE) {
145     if (isLocal || isHidden)
146       Model = TLSModel::LocalDynamic;
147     else
148       Model = TLSModel::GeneralDynamic;
149   } else {
150     if (!isDeclaration || isHidden)
151       Model = TLSModel::LocalExec;
152     else
153       Model = TLSModel::InitialExec;
154   }
155 
156   // If the user specified a more specific model, use that.
157   TLSModel::Model SelectedModel = getSelectedTLSModel(Var);
158   if (SelectedModel > Model)
159     return SelectedModel;
160 
161   return Model;
162 }
163 
164 /// getOptLevel - Returns the optimization level: None, Less,
165 /// Default, or Aggressive.
166 CodeGenOpt::Level TargetMachine::getOptLevel() const {
167   if (!CodeGenInfo)
168     return CodeGenOpt::Default;
169   return CodeGenInfo->getOptLevel();
170 }
171 
172 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
173   if (CodeGenInfo)
174     CodeGenInfo->setOptLevel(Level);
175 }
176 
177 bool TargetMachine::getAsmVerbosityDefault() {
178   return AsmVerbosityDefault;
179 }
180 
181 void TargetMachine::setAsmVerbosityDefault(bool V) {
182   AsmVerbosityDefault = V;
183 }
184 
185 bool TargetMachine::getFunctionSections() {
186   return FunctionSections;
187 }
188 
189 bool TargetMachine::getDataSections() {
190   return DataSections;
191 }
192 
193 void TargetMachine::setFunctionSections(bool V) {
194   FunctionSections = V;
195 }
196 
197 void TargetMachine::setDataSections(bool V) {
198   DataSections = V;
199 }
200 
201 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
202                                       const GlobalValue *GV, Mangler &Mang,
203                                       bool MayAlwaysUsePrivate) const {
204   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
205     // Simple case: If GV is not private, it is not important to find out if
206     // private labels are legal in this case or not.
207     Mang.getNameWithPrefix(Name, GV, false);
208     return;
209   }
210   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, *this);
211   const TargetLoweringObjectFile &TLOF =
212       getTargetLowering()->getObjFileLowering();
213   const MCSection *TheSection = TLOF.SectionForGlobal(GV, GVKind, Mang, *this);
214   bool CannotUsePrivateLabel = TLOF.isSectionAtomizableBySymbols(*TheSection);
215   Mang.getNameWithPrefix(Name, GV, CannotUsePrivateLabel);
216 }
217 
218 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
219   SmallString<60> NameStr;
220   getNameWithPrefix(NameStr, GV, Mang);
221   const TargetLoweringObjectFile &TLOF =
222       getTargetLowering()->getObjFileLowering();
223   return TLOF.getContext().GetOrCreateSymbol(NameStr.str());
224 }
225