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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/Analysis/TargetTransformInfo.h"
16 #include "llvm/CodeGen/MachineFunction.h"
17 #include "llvm/IR/Function.h"
18 #include "llvm/IR/GlobalAlias.h"
19 #include "llvm/IR/GlobalValue.h"
20 #include "llvm/IR/GlobalVariable.h"
21 #include "llvm/IR/LegacyPassManager.h"
22 #include "llvm/IR/Mangler.h"
23 #include "llvm/MC/MCAsmInfo.h"
24 #include "llvm/MC/MCContext.h"
25 #include "llvm/MC/MCInstrInfo.h"
26 #include "llvm/MC/MCSectionMachO.h"
27 #include "llvm/MC/MCTargetOptions.h"
28 #include "llvm/MC/SectionKind.h"
29 #include "llvm/Target/TargetLowering.h"
30 #include "llvm/Target/TargetLoweringObjectFile.h"
31 #include "llvm/Target/TargetSubtargetInfo.h"
32 using namespace llvm;
33 
34 cl::opt<bool> EnableIPRA("enable-ipra", cl::init(false), cl::Hidden,
35                          cl::desc("Enable interprocedural register allocation "
36                                   "to reduce load/store at procedure calls."));
37 
38 //---------------------------------------------------------------------------
39 // TargetMachine Class
40 //
41 
TargetMachine(const Target & T,StringRef DataLayoutString,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options)42 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
43                              const Triple &TT, StringRef CPU, StringRef FS,
44                              const TargetOptions &Options)
45     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
46       TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
47       RequireStructuredCFG(false), Options(Options) {
48   if (EnableIPRA.getNumOccurrences())
49     this->Options.EnableIPRA = EnableIPRA;
50 }
51 
~TargetMachine()52 TargetMachine::~TargetMachine() {
53   delete AsmInfo;
54   delete MRI;
55   delete MII;
56   delete STI;
57 }
58 
isPositionIndependent() const59 bool TargetMachine::isPositionIndependent() const {
60   return getRelocationModel() == Reloc::PIC_;
61 }
62 
63 /// \brief Reset the target options based on the function's attributes.
64 // FIXME: This function needs to go away for a number of reasons:
65 // a) global state on the TargetMachine is terrible in general,
66 // b) there's no default state here to keep,
67 // c) these target options should be passed only on the function
68 //    and not on the TargetMachine (via TargetOptions) at all.
resetTargetOptions(const Function & F) const69 void TargetMachine::resetTargetOptions(const Function &F) const {
70 #define RESET_OPTION(X, Y)                                                     \
71   do {                                                                         \
72     if (F.hasFnAttribute(Y))                                                   \
73       Options.X = (F.getFnAttribute(Y).getValueAsString() == "true");          \
74   } while (0)
75 
76   RESET_OPTION(LessPreciseFPMADOption, "less-precise-fpmad");
77   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
78   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
79   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
80 }
81 
82 /// Returns the code generation relocation model. The choices are static, PIC,
83 /// and dynamic-no-pic.
getRelocationModel() const84 Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
85 
86 /// Returns the code model. The choices are small, kernel, medium, large, and
87 /// target default.
getCodeModel() const88 CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
89 
90 /// Get the IR-specified TLS model for Var.
getSelectedTLSModel(const GlobalValue * GV)91 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
92   switch (GV->getThreadLocalMode()) {
93   case GlobalVariable::NotThreadLocal:
94     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
95     break;
96   case GlobalVariable::GeneralDynamicTLSModel:
97     return TLSModel::GeneralDynamic;
98   case GlobalVariable::LocalDynamicTLSModel:
99     return TLSModel::LocalDynamic;
100   case GlobalVariable::InitialExecTLSModel:
101     return TLSModel::InitialExec;
102   case GlobalVariable::LocalExecTLSModel:
103     return TLSModel::LocalExec;
104   }
105   llvm_unreachable("invalid TLS model");
106 }
107 
108 // FIXME: make this a proper option
109 static bool CanUseCopyRelocWithPIE = false;
110 
shouldAssumeDSOLocal(const Module & M,const GlobalValue * GV) const111 bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
112                                          const GlobalValue *GV) const {
113   Reloc::Model RM = getRelocationModel();
114   const Triple &TT = getTargetTriple();
115 
116   // DLLImport explicitly marks the GV as external.
117   if (GV && GV->hasDLLImportStorageClass())
118     return false;
119 
120   // Every other GV is local on COFF
121   if (TT.isOSBinFormatCOFF())
122     return true;
123 
124   if (GV && (GV->hasLocalLinkage() || !GV->hasDefaultVisibility()))
125     return true;
126 
127   if (TT.isOSBinFormatMachO()) {
128     if (RM == Reloc::Static)
129       return true;
130     return GV && GV->isStrongDefinitionForLinker();
131   }
132 
133   assert(TT.isOSBinFormatELF());
134   assert(RM != Reloc::DynamicNoPIC);
135 
136   bool IsExecutable =
137       RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
138   if (IsExecutable) {
139     // If the symbol is defined, it cannot be preempted.
140     if (GV && !GV->isDeclarationForLinker())
141       return true;
142 
143     bool IsTLS = GV && GV->isThreadLocal();
144     // Check if we can use copy relocations.
145     if (!IsTLS && (RM == Reloc::Static || CanUseCopyRelocWithPIE))
146       return true;
147   }
148 
149   // ELF supports preemption of other symbols.
150   return false;
151 }
152 
getTLSModel(const GlobalValue * GV) const153 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
154   bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
155   Reloc::Model RM = getRelocationModel();
156   bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
157   bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
158 
159   TLSModel::Model Model;
160   if (IsSharedLibrary) {
161     if (IsLocal)
162       Model = TLSModel::LocalDynamic;
163     else
164       Model = TLSModel::GeneralDynamic;
165   } else {
166     if (IsLocal)
167       Model = TLSModel::LocalExec;
168     else
169       Model = TLSModel::InitialExec;
170   }
171 
172   // If the user specified a more specific model, use that.
173   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
174   if (SelectedModel > Model)
175     return SelectedModel;
176 
177   return Model;
178 }
179 
180 /// Returns the optimization level: None, Less, Default, or Aggressive.
getOptLevel() const181 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
182 
setOptLevel(CodeGenOpt::Level Level)183 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
184 
getTargetIRAnalysis()185 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
186   return TargetIRAnalysis([this](const Function &F) {
187     return TargetTransformInfo(F.getParent()->getDataLayout());
188   });
189 }
190 
getNameWithPrefix(SmallVectorImpl<char> & Name,const GlobalValue * GV,Mangler & Mang,bool MayAlwaysUsePrivate) const191 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
192                                       const GlobalValue *GV, Mangler &Mang,
193                                       bool MayAlwaysUsePrivate) const {
194   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
195     // Simple case: If GV is not private, it is not important to find out if
196     // private labels are legal in this case or not.
197     Mang.getNameWithPrefix(Name, GV, false);
198     return;
199   }
200   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
201   TLOF->getNameWithPrefix(Name, GV, Mang, *this);
202 }
203 
getSymbol(const GlobalValue * GV,Mangler & Mang) const204 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
205   SmallString<128> NameStr;
206   getNameWithPrefix(NameStr, GV, Mang);
207   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
208   return TLOF->getContext().getOrCreateSymbol(NameStr);
209 }
210