1 //===-- TargetMachine.cpp - General Target Information ---------------------==//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file describes the general parts of a Target machine.
10 //
11 //===----------------------------------------------------------------------===//
12
13 #include "llvm/Target/TargetMachine.h"
14 #include "llvm/Analysis/TargetTransformInfo.h"
15 #include "llvm/IR/Function.h"
16 #include "llvm/IR/GlobalValue.h"
17 #include "llvm/IR/GlobalVariable.h"
18 #include "llvm/IR/Mangler.h"
19 #include "llvm/MC/MCAsmInfo.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCInstrInfo.h"
22 #include "llvm/MC/MCRegisterInfo.h"
23 #include "llvm/MC/MCSubtargetInfo.h"
24 #include "llvm/Target/TargetLoweringObjectFile.h"
25 using namespace llvm;
26
27 //---------------------------------------------------------------------------
28 // TargetMachine Class
29 //
30
TargetMachine(const Target & T,StringRef DataLayoutString,const Triple & TT,StringRef CPU,StringRef FS,const TargetOptions & Options)31 TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
32 const Triple &TT, StringRef CPU, StringRef FS,
33 const TargetOptions &Options)
34 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT),
35 TargetCPU(std::string(CPU)), TargetFS(std::string(FS)), AsmInfo(nullptr),
36 MRI(nullptr), MII(nullptr), STI(nullptr), RequireStructuredCFG(false),
37 O0WantsFastISel(false), DefaultOptions(Options), Options(Options) {}
38
39 TargetMachine::~TargetMachine() = default;
40
isPositionIndependent() const41 bool TargetMachine::isPositionIndependent() const {
42 return getRelocationModel() == Reloc::PIC_;
43 }
44
45 /// Reset the target options based on the function's attributes.
46 /// setFunctionAttributes should have made the raw attribute value consistent
47 /// with the command line flag if used.
48 //
49 // FIXME: This function needs to go away for a number of reasons:
50 // a) global state on the TargetMachine is terrible in general,
51 // b) these target options should be passed only on the function
52 // and not on the TargetMachine (via TargetOptions) at all.
resetTargetOptions(const Function & F) const53 void TargetMachine::resetTargetOptions(const Function &F) const {
54 #define RESET_OPTION(X, Y) \
55 do { \
56 Options.X = F.getFnAttribute(Y).getValueAsBool(); \
57 } while (0)
58
59 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
60 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
61 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
62 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
63 RESET_OPTION(ApproxFuncFPMath, "approx-func-fp-math");
64 }
65
66 /// Returns the code generation relocation model. The choices are static, PIC,
67 /// and dynamic-no-pic.
getRelocationModel() const68 Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
69
70 /// Get the IR-specified TLS model for Var.
getSelectedTLSModel(const GlobalValue * GV)71 static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
72 switch (GV->getThreadLocalMode()) {
73 case GlobalVariable::NotThreadLocal:
74 llvm_unreachable("getSelectedTLSModel for non-TLS variable");
75 break;
76 case GlobalVariable::GeneralDynamicTLSModel:
77 return TLSModel::GeneralDynamic;
78 case GlobalVariable::LocalDynamicTLSModel:
79 return TLSModel::LocalDynamic;
80 case GlobalVariable::InitialExecTLSModel:
81 return TLSModel::InitialExec;
82 case GlobalVariable::LocalExecTLSModel:
83 return TLSModel::LocalExec;
84 }
85 llvm_unreachable("invalid TLS model");
86 }
87
shouldAssumeDSOLocal(const Module & M,const GlobalValue * GV) const88 bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
89 const GlobalValue *GV) const {
90 const Triple &TT = getTargetTriple();
91 Reloc::Model RM = getRelocationModel();
92
93 // According to the llvm language reference, we should be able to
94 // just return false in here if we have a GV, as we know it is
95 // dso_preemptable. At this point in time, the various IR producers
96 // have not been transitioned to always produce a dso_local when it
97 // is possible to do so.
98 //
99 // As a result we still have some logic in here to improve the quality of the
100 // generated code.
101 if (!GV)
102 return false;
103
104 // If the IR producer requested that this GV be treated as dso local, obey.
105 if (GV->isDSOLocal())
106 return true;
107
108 if (TT.isOSBinFormatCOFF()) {
109 // DLLImport explicitly marks the GV as external.
110 if (GV->hasDLLImportStorageClass())
111 return false;
112
113 // On MinGW, variables that haven't been declared with DLLImport may still
114 // end up automatically imported by the linker. To make this feasible,
115 // don't assume the variables to be DSO local unless we actually know
116 // that for sure. This only has to be done for variables; for functions
117 // the linker can insert thunks for calling functions from another DLL.
118 if (TT.isWindowsGNUEnvironment() && GV->isDeclarationForLinker() &&
119 isa<GlobalVariable>(GV))
120 return false;
121
122 // Don't mark 'extern_weak' symbols as DSO local. If these symbols remain
123 // unresolved in the link, they can be resolved to zero, which is outside
124 // the current DSO.
125 if (GV->hasExternalWeakLinkage())
126 return false;
127
128 // Every other GV is local on COFF.
129 return true;
130 }
131
132 if (TT.isOSBinFormatGOFF())
133 return true;
134
135 if (TT.isOSBinFormatMachO()) {
136 if (RM == Reloc::Static)
137 return true;
138 return GV->isStrongDefinitionForLinker();
139 }
140
141 assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm() ||
142 TT.isOSBinFormatXCOFF());
143 return false;
144 }
145
useEmulatedTLS() const146 bool TargetMachine::useEmulatedTLS() const {
147 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
148 // was specified explicitly; otherwise uses target triple to decide default.
149 if (Options.ExplicitEmulatedTLS)
150 return Options.EmulatedTLS;
151 return getTargetTriple().hasDefaultEmulatedTLS();
152 }
153
getTLSModel(const GlobalValue * GV) const154 TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
155 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
156 Reloc::Model RM = getRelocationModel();
157 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
158 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
159
160 TLSModel::Model Model;
161 if (IsSharedLibrary) {
162 if (IsLocal)
163 Model = TLSModel::LocalDynamic;
164 else
165 Model = TLSModel::GeneralDynamic;
166 } else {
167 if (IsLocal)
168 Model = TLSModel::LocalExec;
169 else
170 Model = TLSModel::InitialExec;
171 }
172
173 // If the user specified a more specific model, use that.
174 TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
175 if (SelectedModel > Model)
176 return SelectedModel;
177
178 return Model;
179 }
180
181 /// Returns the optimization level: None, Less, Default, or Aggressive.
getOptLevel() const182 CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
183
setOptLevel(CodeGenOpt::Level Level)184 void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
185
186 TargetTransformInfo
getTargetTransformInfo(const Function & F) const187 TargetMachine::getTargetTransformInfo(const Function &F) const {
188 return TargetTransformInfo(F.getParent()->getDataLayout());
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, *this);
202 }
203
getSymbol(const GlobalValue * GV) const204 MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
205 const TargetLoweringObjectFile *TLOF = getObjFileLowering();
206 // XCOFF symbols could have special naming convention.
207 if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this))
208 return TargetSymbol;
209
210 SmallString<128> NameStr;
211 getNameWithPrefix(NameStr, GV, TLOF->getMangler());
212 return TLOF->getContext().getOrCreateSymbol(NameStr);
213 }
214
getTargetIRAnalysis() const215 TargetIRAnalysis TargetMachine::getTargetIRAnalysis() const {
216 // Since Analysis can't depend on Target, use a std::function to invert the
217 // dependency.
218 return TargetIRAnalysis(
219 [this](const Function &F) { return this->getTargetTransformInfo(F); });
220 }
221
parseBinutilsVersion(StringRef Version)222 std::pair<int, int> TargetMachine::parseBinutilsVersion(StringRef Version) {
223 if (Version == "none")
224 return {INT_MAX, INT_MAX}; // Make binutilsIsAtLeast() return true.
225 std::pair<int, int> Ret;
226 if (!Version.consumeInteger(10, Ret.first) && Version.consume_front("."))
227 Version.consumeInteger(10, Ret.second);
228 return Ret;
229 }
230