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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/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/LegacyPassManager.h"
21 : #include "llvm/IR/Mangler.h"
22 : #include "llvm/MC/MCAsmInfo.h"
23 : #include "llvm/MC/MCContext.h"
24 : #include "llvm/MC/MCInstrInfo.h"
25 : #include "llvm/MC/MCSectionMachO.h"
26 : #include "llvm/MC/MCTargetOptions.h"
27 : #include "llvm/MC/SectionKind.h"
28 : #include "llvm/Target/TargetLoweringObjectFile.h"
29 : using namespace llvm;
30 :
31 : //---------------------------------------------------------------------------
32 : // TargetMachine Class
33 : //
34 :
35 40979 : TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
36 : const Triple &TT, StringRef CPU, StringRef FS,
37 40979 : const TargetOptions &Options)
38 : : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
39 : TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
40 122937 : RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
41 40979 : }
42 :
43 : TargetMachine::~TargetMachine() = default;
44 :
45 6843164 : bool TargetMachine::isPositionIndependent() const {
46 6843164 : return getRelocationModel() == Reloc::PIC_;
47 : }
48 :
49 : /// Reset the target options based on the function's attributes.
50 : // FIXME: This function needs to go away for a number of reasons:
51 : // a) global state on the TargetMachine is terrible in general,
52 : // b) these target options should be passed only on the function
53 : // and not on the TargetMachine (via TargetOptions) at all.
54 434128 : void TargetMachine::resetTargetOptions(const Function &F) const {
55 : #define RESET_OPTION(X, Y) \
56 : do { \
57 : if (F.hasFnAttribute(Y)) \
58 : Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
59 : else \
60 : Options.X = DefaultOptions.X; \
61 : } while (0)
62 :
63 867328 : RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
64 865134 : RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
65 865632 : RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
66 861864 : RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
67 861242 : RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
68 :
69 : StringRef Denormal =
70 434128 : F.getFnAttribute("denormal-fp-math").getValueAsString();
71 : if (Denormal == "ieee")
72 12 : Options.FPDenormalMode = FPDenormal::IEEE;
73 : else if (Denormal == "preserve-sign")
74 10 : Options.FPDenormalMode = FPDenormal::PreserveSign;
75 : else if (Denormal == "positive-zero")
76 3 : Options.FPDenormalMode = FPDenormal::PositiveZero;
77 : else
78 434103 : Options.FPDenormalMode = DefaultOptions.FPDenormalMode;
79 434128 : }
80 :
81 : /// Returns the code generation relocation model. The choices are static, PIC,
82 : /// and dynamic-no-pic.
83 7637468 : Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
84 :
85 : /// Returns the code model. The choices are small, kernel, medium, large, and
86 : /// target default.
87 20239974 : CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
88 :
89 : /// Get the IR-specified TLS model for Var.
90 : static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
91 653 : switch (GV->getThreadLocalMode()) {
92 : case GlobalVariable::NotThreadLocal:
93 : llvm_unreachable("getSelectedTLSModel for non-TLS variable");
94 : break;
95 : case GlobalVariable::GeneralDynamicTLSModel:
96 : return TLSModel::GeneralDynamic;
97 : case GlobalVariable::LocalDynamicTLSModel:
98 : return TLSModel::LocalDynamic;
99 : case GlobalVariable::InitialExecTLSModel:
100 : return TLSModel::InitialExec;
101 : case GlobalVariable::LocalExecTLSModel:
102 : return TLSModel::LocalExec;
103 : }
104 0 : llvm_unreachable("invalid TLS model");
105 : }
106 :
107 5724599 : bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
108 : const GlobalValue *GV) const {
109 : // If the IR producer requested that this GV be treated as dso local, obey.
110 5724599 : if (GV && GV->isDSOLocal())
111 : return true;
112 :
113 : // If we are not supossed to use a PLT, we cannot assume that intrinsics are
114 : // local since the linker can convert some direct access to access via plt.
115 241404 : if (M.getRtLibUseGOT() && !GV)
116 : return false;
117 :
118 : // According to the llvm language reference, we should be able to
119 : // just return false in here if we have a GV, as we know it is
120 : // dso_preemptable. At this point in time, the various IR producers
121 : // have not been transitioned to always produce a dso_local when it
122 : // is possible to do so.
123 : // In the case of intrinsics, GV is null and there is nowhere to put
124 : // dso_local. Returning false for those will produce worse code in some
125 : // architectures. For example, on x86 the caller has to set ebx before calling
126 : // a plt.
127 : // As a result we still have some logic in here to improve the quality of the
128 : // generated code.
129 : // FIXME: Add a module level metadata for whether intrinsics should be assumed
130 : // local.
131 :
132 241400 : Reloc::Model RM = getRelocationModel();
133 : const Triple &TT = getTargetTriple();
134 :
135 : // DLLImport explicitly marks the GV as external.
136 241400 : if (GV && GV->hasDLLImportStorageClass())
137 : return false;
138 :
139 : // On MinGW, variables that haven't been declared with DLLImport may still
140 : // end up automatically imported by the linker. To make this feasible,
141 : // don't assume the variables to be DSO local unless we actually know
142 : // that for sure. This only has to be done for variables; for functions
143 : // the linker can insert thunks for calling functions from another DLL.
144 1007 : if (TT.isWindowsGNUEnvironment() && GV && GV->isDeclarationForLinker() &&
145 : isa<GlobalVariable>(GV))
146 : return false;
147 :
148 : // Every other GV is local on COFF.
149 : // Make an exception for windows OS in the triple: Some firmware builds use
150 : // *-win32-macho triples. This (accidentally?) produced windows relocations
151 : // without GOT tables in older clang versions; Keep this behaviour.
152 241154 : if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
153 : return true;
154 :
155 : // Most PIC code sequences that assume that a symbol is local cannot
156 : // produce a 0 if it turns out the symbol is undefined. While this
157 : // is ABI and relocation depended, it seems worth it to handle it
158 : // here.
159 238117 : if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
160 : return false;
161 :
162 238078 : if (GV && !GV->hasDefaultVisibility())
163 : return true;
164 :
165 238070 : if (TT.isOSBinFormatMachO()) {
166 15721 : if (RM == Reloc::Static)
167 : return true;
168 14793 : return GV && GV->isStrongDefinitionForLinker();
169 : }
170 :
171 : assert(TT.isOSBinFormatELF());
172 : assert(RM != Reloc::DynamicNoPIC);
173 :
174 : bool IsExecutable =
175 222349 : RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
176 : if (IsExecutable) {
177 : // If the symbol is defined, it cannot be preempted.
178 240523 : if (GV && !GV->isDeclarationForLinker())
179 : return true;
180 :
181 : // A symbol marked nonlazybind should not be accessed with a plt. If the
182 : // symbol turns out to be external, the linker will convert a direct
183 : // access to an access via the plt, so don't assume it is local.
184 : const Function *F = dyn_cast_or_null<Function>(GV);
185 85732 : if (F && F->hasFnAttribute(Attribute::NonLazyBind))
186 : return false;
187 :
188 108500 : bool IsTLS = GV && GV->isThreadLocal();
189 : bool IsAccessViaCopyRelocs =
190 108500 : GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
191 108500 : Triple::ArchType Arch = TT.getArch();
192 : bool IsPPC =
193 108500 : Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
194 : // Check if we can use copy relocations. PowerPC has no copy relocations.
195 108500 : if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
196 107842 : return true;
197 : }
198 :
199 : // ELF supports preemption of other symbols.
200 : return false;
201 : }
202 :
203 320174 : bool TargetMachine::useEmulatedTLS() const {
204 : // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
205 : // was specified explicitly; otherwise uses target triple to decide default.
206 320174 : if (Options.ExplicitEmulatedTLS)
207 1491 : return Options.EmulatedTLS;
208 : return getTargetTriple().hasDefaultEmulatedTLS();
209 : }
210 :
211 653 : TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
212 653 : bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
213 653 : Reloc::Model RM = getRelocationModel();
214 653 : bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
215 653 : bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
216 :
217 : TLSModel::Model Model;
218 653 : if (IsSharedLibrary) {
219 289 : if (IsLocal)
220 : Model = TLSModel::LocalDynamic;
221 : else
222 : Model = TLSModel::GeneralDynamic;
223 : } else {
224 364 : if (IsLocal)
225 : Model = TLSModel::LocalExec;
226 : else
227 : Model = TLSModel::InitialExec;
228 : }
229 :
230 : // If the user specified a more specific model, use that.
231 : TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
232 653 : if (SelectedModel > Model)
233 102 : return SelectedModel;
234 :
235 : return Model;
236 : }
237 :
238 : /// Returns the optimization level: None, Less, Default, or Aggressive.
239 10078704 : CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
240 :
241 372 : void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
242 :
243 0 : TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {
244 0 : return TargetTransformInfo(F.getParent()->getDataLayout());
245 : }
246 :
247 5216125 : void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
248 : const GlobalValue *GV, Mangler &Mang,
249 : bool MayAlwaysUsePrivate) const {
250 5216125 : if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
251 : // Simple case: If GV is not private, it is not important to find out if
252 : // private labels are legal in this case or not.
253 4055081 : Mang.getNameWithPrefix(Name, GV, false);
254 4055081 : return;
255 : }
256 1161044 : const TargetLoweringObjectFile *TLOF = getObjFileLowering();
257 1161044 : TLOF->getNameWithPrefix(Name, GV, *this);
258 : }
259 :
260 1505388 : MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
261 1505388 : const TargetLoweringObjectFile *TLOF = getObjFileLowering();
262 : SmallString<128> NameStr;
263 1505389 : getNameWithPrefix(NameStr, GV, TLOF->getMangler());
264 3010778 : return TLOF->getContext().getOrCreateSymbol(NameStr);
265 : }
266 :
267 75817 : TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
268 : // Since Analysis can't depend on Target, use a std::function to invert the
269 : // dependency.
270 : return TargetIRAnalysis(
271 3135973 : [this](const Function &F) { return this->getTargetTransformInfo(F); });
272 : }
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