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/Mangler.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCCodeGenInfo.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/IR/LegacyPassManager.h"
30 #include "llvm/Support/CommandLine.h"
31 #include "llvm/Target/TargetLowering.h"
32 #include "llvm/Target/TargetLoweringObjectFile.h"
33 #include "llvm/Target/TargetSubtargetInfo.h"
34 using namespace llvm;
35 
36 //---------------------------------------------------------------------------
37 // TargetMachine Class
38 //
39 
40 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
41                              StringRef TT, StringRef CPU, StringRef FS,
42                              const TargetOptions &Options)
43     : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
44       TargetFS(FS), CodeGenInfo(nullptr), AsmInfo(nullptr), MRI(nullptr),
45       MII(nullptr), STI(nullptr), RequireStructuredCFG(false),
46       Options(Options) {}
47 
48 TargetMachine::~TargetMachine() {
49   delete CodeGenInfo;
50   delete AsmInfo;
51   delete MRI;
52   delete MII;
53   delete STI;
54 }
55 
56 /// \brief Reset the target options based on the function's attributes.
57 // FIXME: This function needs to go away for a number of reasons:
58 // a) global state on the TargetMachine is terrible in general,
59 // b) there's no default state here to keep,
60 // c) these target options should be passed only on the function
61 //    and not on the TargetMachine (via TargetOptions) at all.
62 void TargetMachine::resetTargetOptions(const Function &F) const {
63 #define RESET_OPTION(X, Y)                                                     \
64   do {                                                                         \
65     if (F.hasFnAttribute(Y))                                                   \
66       Options.X = (F.getFnAttribute(Y).getValueAsString() == "true");          \
67   } while (0)
68 
69   RESET_OPTION(NoFramePointerElim, "no-frame-pointer-elim");
70   RESET_OPTION(LessPreciseFPMADOption, "less-precise-fpmad");
71   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
72   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
73   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
74   RESET_OPTION(UseSoftFloat, "use-soft-float");
75   RESET_OPTION(DisableTailCalls, "disable-tail-calls");
76 
77   Options.MCOptions.SanitizeAddress = F.hasFnAttribute(Attribute::SanitizeAddress);
78 }
79 
80 /// getRelocationModel - Returns the code generation relocation model. The
81 /// choices are static, PIC, and dynamic-no-pic, and target default.
82 Reloc::Model TargetMachine::getRelocationModel() const {
83   if (!CodeGenInfo)
84     return Reloc::Default;
85   return CodeGenInfo->getRelocationModel();
86 }
87 
88 /// getCodeModel - Returns the code model. The choices are small, kernel,
89 /// medium, large, and target default.
90 CodeModel::Model TargetMachine::getCodeModel() const {
91   if (!CodeGenInfo)
92     return CodeModel::Default;
93   return CodeGenInfo->getCodeModel();
94 }
95 
96 /// Get the IR-specified TLS model for Var.
97 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
98   switch (GV->getThreadLocalMode()) {
99   case GlobalVariable::NotThreadLocal:
100     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
101     break;
102   case GlobalVariable::GeneralDynamicTLSModel:
103     return TLSModel::GeneralDynamic;
104   case GlobalVariable::LocalDynamicTLSModel:
105     return TLSModel::LocalDynamic;
106   case GlobalVariable::InitialExecTLSModel:
107     return TLSModel::InitialExec;
108   case GlobalVariable::LocalExecTLSModel:
109     return TLSModel::LocalExec;
110   }
111   llvm_unreachable("invalid TLS model");
112 }
113 
114 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
115   bool isLocal = GV->hasLocalLinkage();
116   bool isDeclaration = GV->isDeclaration();
117   bool isPIC = getRelocationModel() == Reloc::PIC_;
118   bool isPIE = Options.PositionIndependentExecutable;
119   // FIXME: what should we do for protected and internal visibility?
120   // For variables, is internal different from hidden?
121   bool isHidden = GV->hasHiddenVisibility();
122 
123   TLSModel::Model Model;
124   if (isPIC && !isPIE) {
125     if (isLocal || isHidden)
126       Model = TLSModel::LocalDynamic;
127     else
128       Model = TLSModel::GeneralDynamic;
129   } else {
130     if (!isDeclaration || isHidden)
131       Model = TLSModel::LocalExec;
132     else
133       Model = TLSModel::InitialExec;
134   }
135 
136   // If the user specified a more specific model, use that.
137   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
138   if (SelectedModel > Model)
139     return SelectedModel;
140 
141   return Model;
142 }
143 
144 /// getOptLevel - Returns the optimization level: None, Less,
145 /// Default, or Aggressive.
146 CodeGenOpt::Level TargetMachine::getOptLevel() const {
147   if (!CodeGenInfo)
148     return CodeGenOpt::Default;
149   return CodeGenInfo->getOptLevel();
150 }
151 
152 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
153   if (CodeGenInfo)
154     CodeGenInfo->setOptLevel(Level);
155 }
156 
157 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
158   return TargetIRAnalysis(
159       [this](Function &) { return TargetTransformInfo(getDataLayout()); });
160 }
161 
162 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
163                                const MCSection &Section) {
164   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
165     return true;
166 
167   // If it is not dead stripped, it is safe to use private labels.
168   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
169   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
170     return true;
171 
172   return false;
173 }
174 
175 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
176                                       const GlobalValue *GV, Mangler &Mang,
177                                       bool MayAlwaysUsePrivate) const {
178   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
179     // Simple case: If GV is not private, it is not important to find out if
180     // private labels are legal in this case or not.
181     Mang.getNameWithPrefix(Name, GV, false);
182     return;
183   }
184   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, *this);
185   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
186   const MCSection *TheSection = TLOF->SectionForGlobal(GV, GVKind, Mang, *this);
187   bool CannotUsePrivateLabel = !canUsePrivateLabel(*AsmInfo, *TheSection);
188   TLOF->getNameWithPrefix(Name, GV, CannotUsePrivateLabel, Mang, *this);
189 }
190 
191 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
192   SmallString<60> NameStr;
193   getNameWithPrefix(NameStr, GV, Mang);
194   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
195   return TLOF->getContext().GetOrCreateSymbol(NameStr);
196 }
197