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(LessPreciseFPMADOption, "less-precise-fpmad");
70   RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
71   RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
72   RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
73   RESET_OPTION(DisableTailCalls, "disable-tail-calls");
74 }
75 
76 /// getRelocationModel - Returns the code generation relocation model. The
77 /// choices are static, PIC, and dynamic-no-pic, and target default.
78 Reloc::Model TargetMachine::getRelocationModel() const {
79   if (!CodeGenInfo)
80     return Reloc::Default;
81   return CodeGenInfo->getRelocationModel();
82 }
83 
84 /// getCodeModel - Returns the code model. The choices are small, kernel,
85 /// medium, large, and target default.
86 CodeModel::Model TargetMachine::getCodeModel() const {
87   if (!CodeGenInfo)
88     return CodeModel::Default;
89   return CodeGenInfo->getCodeModel();
90 }
91 
92 /// Get the IR-specified TLS model for Var.
93 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
94   switch (GV->getThreadLocalMode()) {
95   case GlobalVariable::NotThreadLocal:
96     llvm_unreachable("getSelectedTLSModel for non-TLS variable");
97     break;
98   case GlobalVariable::GeneralDynamicTLSModel:
99     return TLSModel::GeneralDynamic;
100   case GlobalVariable::LocalDynamicTLSModel:
101     return TLSModel::LocalDynamic;
102   case GlobalVariable::InitialExecTLSModel:
103     return TLSModel::InitialExec;
104   case GlobalVariable::LocalExecTLSModel:
105     return TLSModel::LocalExec;
106   }
107   llvm_unreachable("invalid TLS model");
108 }
109 
110 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
111   bool isLocal = GV->hasLocalLinkage();
112   bool isDeclaration = GV->isDeclaration();
113   bool isPIC = getRelocationModel() == Reloc::PIC_;
114   bool isPIE = Options.PositionIndependentExecutable;
115   // FIXME: what should we do for protected and internal visibility?
116   // For variables, is internal different from hidden?
117   bool isHidden = GV->hasHiddenVisibility();
118 
119   TLSModel::Model Model;
120   if (isPIC && !isPIE) {
121     if (isLocal || isHidden)
122       Model = TLSModel::LocalDynamic;
123     else
124       Model = TLSModel::GeneralDynamic;
125   } else {
126     if (!isDeclaration || isHidden)
127       Model = TLSModel::LocalExec;
128     else
129       Model = TLSModel::InitialExec;
130   }
131 
132   // If the user specified a more specific model, use that.
133   TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
134   if (SelectedModel > Model)
135     return SelectedModel;
136 
137   return Model;
138 }
139 
140 /// getOptLevel - Returns the optimization level: None, Less,
141 /// Default, or Aggressive.
142 CodeGenOpt::Level TargetMachine::getOptLevel() const {
143   if (!CodeGenInfo)
144     return CodeGenOpt::Default;
145   return CodeGenInfo->getOptLevel();
146 }
147 
148 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) const {
149   if (CodeGenInfo)
150     CodeGenInfo->setOptLevel(Level);
151 }
152 
153 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
154   return TargetIRAnalysis(
155       [this](Function &) { return TargetTransformInfo(getDataLayout()); });
156 }
157 
158 static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
159                                const MCSection &Section) {
160   if (!AsmInfo.isSectionAtomizableBySymbols(Section))
161     return true;
162 
163   // If it is not dead stripped, it is safe to use private labels.
164   const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
165   if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
166     return true;
167 
168   return false;
169 }
170 
171 void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
172                                       const GlobalValue *GV, Mangler &Mang,
173                                       bool MayAlwaysUsePrivate) const {
174   if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
175     // Simple case: If GV is not private, it is not important to find out if
176     // private labels are legal in this case or not.
177     Mang.getNameWithPrefix(Name, GV, false);
178     return;
179   }
180   SectionKind GVKind = TargetLoweringObjectFile::getKindForGlobal(GV, *this);
181   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
182   const MCSection *TheSection = TLOF->SectionForGlobal(GV, GVKind, Mang, *this);
183   bool CannotUsePrivateLabel = !canUsePrivateLabel(*AsmInfo, *TheSection);
184   TLOF->getNameWithPrefix(Name, GV, CannotUsePrivateLabel, Mang, *this);
185 }
186 
187 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV, Mangler &Mang) const {
188   SmallString<128> NameStr;
189   getNameWithPrefix(NameStr, GV, Mang);
190   const TargetLoweringObjectFile *TLOF = getObjFileLowering();
191   return TLOF->getContext().getOrCreateSymbol(NameStr);
192 }
193