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Matthias Braunbb8507e2017-10-12 22:57:28 +00001//===-- 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"
Matthias Braunbb8507e2017-10-12 22:57:28 +000016#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"
David Blaikie6054e652018-03-23 23:58:19 +000028#include "llvm/Target/TargetLoweringObjectFile.h"
Matthias Braunbb8507e2017-10-12 22:57:28 +000029using namespace llvm;
30
31//---------------------------------------------------------------------------
32// TargetMachine Class
33//
34
35TargetMachine::TargetMachine(const Target &T, StringRef DataLayoutString,
36 const Triple &TT, StringRef CPU, StringRef FS,
37 const TargetOptions &Options)
38 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
39 TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
40 RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
41}
42
43TargetMachine::~TargetMachine() {
44 delete AsmInfo;
45 delete MRI;
46 delete MII;
47 delete STI;
48}
49
50bool TargetMachine::isPositionIndependent() const {
51 return getRelocationModel() == Reloc::PIC_;
52}
53
Adrian Prantl5f8f34e42018-05-01 15:54:18 +000054/// Reset the target options based on the function's attributes.
Matthias Braunbb8507e2017-10-12 22:57:28 +000055// FIXME: This function needs to go away for a number of reasons:
56// a) global state on the TargetMachine is terrible in general,
57// b) these target options should be passed only on the function
58// and not on the TargetMachine (via TargetOptions) at all.
59void TargetMachine::resetTargetOptions(const Function &F) const {
60#define RESET_OPTION(X, Y) \
61 do { \
62 if (F.hasFnAttribute(Y)) \
63 Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
64 else \
65 Options.X = DefaultOptions.X; \
66 } while (0)
67
68 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
69 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
70 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
71 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
72 RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
73
74 StringRef Denormal =
75 F.getFnAttribute("denormal-fp-math").getValueAsString();
76 if (Denormal == "ieee")
77 Options.FPDenormalMode = FPDenormal::IEEE;
78 else if (Denormal == "preserve-sign")
79 Options.FPDenormalMode = FPDenormal::PreserveSign;
80 else if (Denormal == "positive-zero")
81 Options.FPDenormalMode = FPDenormal::PositiveZero;
82 else
83 Options.FPDenormalMode = DefaultOptions.FPDenormalMode;
84}
85
86/// Returns the code generation relocation model. The choices are static, PIC,
87/// and dynamic-no-pic.
88Reloc::Model TargetMachine::getRelocationModel() const { return RM; }
89
90/// Returns the code model. The choices are small, kernel, medium, large, and
91/// target default.
92CodeModel::Model TargetMachine::getCodeModel() const { return CMModel; }
93
94/// Get the IR-specified TLS model for Var.
95static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV) {
96 switch (GV->getThreadLocalMode()) {
97 case GlobalVariable::NotThreadLocal:
98 llvm_unreachable("getSelectedTLSModel for non-TLS variable");
99 break;
100 case GlobalVariable::GeneralDynamicTLSModel:
101 return TLSModel::GeneralDynamic;
102 case GlobalVariable::LocalDynamicTLSModel:
103 return TLSModel::LocalDynamic;
104 case GlobalVariable::InitialExecTLSModel:
105 return TLSModel::InitialExec;
106 case GlobalVariable::LocalExecTLSModel:
107 return TLSModel::LocalExec;
108 }
109 llvm_unreachable("invalid TLS model");
110}
111
112bool TargetMachine::shouldAssumeDSOLocal(const Module &M,
113 const GlobalValue *GV) const {
Rafael Espindola6f366372017-10-30 16:32:31 +0000114 // If the IR producer requested that this GV be treated as dso local, obey.
115 if (GV && GV->isDSOLocal())
116 return true;
117
Rafael Espindola63c378d2018-03-10 02:42:14 +0000118 // If we are not supossed to use a PLT, we cannot assume that intrinsics are
119 // local since the linker can convert some direct access to access via plt.
120 if (M.getRtLibUseGOT() && !GV)
121 return false;
122
123 // According to the llvm language reference, we should be able to
124 // just return false in here if we have a GV, as we know it is
125 // dso_preemptable. At this point in time, the various IR producers
126 // have not been transitioned to always produce a dso_local when it
127 // is possible to do so.
128 // In the case of intrinsics, GV is null and there is nowhere to put
129 // dso_local. Returning false for those will produce worse code in some
130 // architectures. For example, on x86 the caller has to set ebx before calling
131 // a plt.
132 // As a result we still have some logic in here to improve the quality of the
133 // generated code.
134 // FIXME: Add a module level metadata for whether intrinsics should be assumed
135 // local.
Rafael Espindola6f366372017-10-30 16:32:31 +0000136
Matthias Braunbb8507e2017-10-12 22:57:28 +0000137 Reloc::Model RM = getRelocationModel();
138 const Triple &TT = getTargetTriple();
139
140 // DLLImport explicitly marks the GV as external.
141 if (GV && GV->hasDLLImportStorageClass())
142 return false;
143
144 // Every other GV is local on COFF.
Rafael Espindolaba02f3f2018-02-22 23:59:46 +0000145 // Make an exception for windows OS in the triple: Some firmware builds use
Matthias Braunbb8507e2017-10-12 22:57:28 +0000146 // *-win32-macho triples. This (accidentally?) produced windows relocations
147 // without GOT tables in older clang versions; Keep this behaviour.
148 if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
149 return true;
150
Rafael Espindola2393c3b2017-10-27 21:18:48 +0000151 // Most PIC code sequences that assume that a symbol is local cannot
152 // produce a 0 if it turns out the symbol is undefined. While this
153 // is ABI and relocation depended, it seems worth it to handle it
154 // here.
Rafael Espindola63c378d2018-03-10 02:42:14 +0000155 if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
Rafael Espindola2393c3b2017-10-27 21:18:48 +0000156 return false;
157
Rafael Espindola63c378d2018-03-10 02:42:14 +0000158 if (GV && !GV->hasDefaultVisibility())
Matthias Braunbb8507e2017-10-12 22:57:28 +0000159 return true;
160
161 if (TT.isOSBinFormatMachO()) {
162 if (RM == Reloc::Static)
163 return true;
Rafael Espindola63c378d2018-03-10 02:42:14 +0000164 return GV && GV->isStrongDefinitionForLinker();
Matthias Braunbb8507e2017-10-12 22:57:28 +0000165 }
166
167 assert(TT.isOSBinFormatELF());
168 assert(RM != Reloc::DynamicNoPIC);
169
170 bool IsExecutable =
171 RM == Reloc::Static || M.getPIELevel() != PIELevel::Default;
172 if (IsExecutable) {
173 // If the symbol is defined, it cannot be preempted.
Rafael Espindola63c378d2018-03-10 02:42:14 +0000174 if (GV && !GV->isDeclarationForLinker())
Matthias Braunbb8507e2017-10-12 22:57:28 +0000175 return true;
176
Sriraman Tallam056b3fd2017-11-08 00:01:05 +0000177 // A symbol marked nonlazybind should not be accessed with a plt. If the
178 // symbol turns out to be external, the linker will convert a direct
179 // access to an access via the plt, so don't assume it is local.
Rafael Espindola63c378d2018-03-10 02:42:14 +0000180 const Function *F = dyn_cast_or_null<Function>(GV);
Sriraman Tallam056b3fd2017-11-08 00:01:05 +0000181 if (F && F->hasFnAttribute(Attribute::NonLazyBind))
182 return false;
183
Rafael Espindola63c378d2018-03-10 02:42:14 +0000184 bool IsTLS = GV && GV->isThreadLocal();
Rafael Espindola2393c3b2017-10-27 21:18:48 +0000185 bool IsAccessViaCopyRelocs =
Rafael Espindola63c378d2018-03-10 02:42:14 +0000186 GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
Matthias Braunbb8507e2017-10-12 22:57:28 +0000187 Triple::ArchType Arch = TT.getArch();
188 bool IsPPC =
189 Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
190 // Check if we can use copy relocations. PowerPC has no copy relocations.
191 if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
192 return true;
193 }
194
195 // ELF supports preemption of other symbols.
196 return false;
197}
198
Chih-Hung Hsieh9f9e4682018-02-28 17:48:55 +0000199bool TargetMachine::useEmulatedTLS() const {
200 // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
201 // was specified explicitly; otherwise uses target triple to decide default.
202 if (Options.ExplicitEmulatedTLS)
203 return Options.EmulatedTLS;
204 return getTargetTriple().hasDefaultEmulatedTLS();
205}
206
Matthias Braunbb8507e2017-10-12 22:57:28 +0000207TLSModel::Model TargetMachine::getTLSModel(const GlobalValue *GV) const {
208 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
209 Reloc::Model RM = getRelocationModel();
210 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
211 bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
212
213 TLSModel::Model Model;
214 if (IsSharedLibrary) {
215 if (IsLocal)
216 Model = TLSModel::LocalDynamic;
217 else
218 Model = TLSModel::GeneralDynamic;
219 } else {
220 if (IsLocal)
221 Model = TLSModel::LocalExec;
222 else
223 Model = TLSModel::InitialExec;
224 }
225
226 // If the user specified a more specific model, use that.
227 TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
228 if (SelectedModel > Model)
229 return SelectedModel;
230
231 return Model;
232}
233
234/// Returns the optimization level: None, Less, Default, or Aggressive.
235CodeGenOpt::Level TargetMachine::getOptLevel() const { return OptLevel; }
236
237void TargetMachine::setOptLevel(CodeGenOpt::Level Level) { OptLevel = Level; }
238
Sanjoy Das26d11ca2017-12-22 18:21:59 +0000239TargetTransformInfo TargetMachine::getTargetTransformInfo(const Function &F) {
240 return TargetTransformInfo(F.getParent()->getDataLayout());
Matthias Braunbb8507e2017-10-12 22:57:28 +0000241}
242
243void TargetMachine::getNameWithPrefix(SmallVectorImpl<char> &Name,
244 const GlobalValue *GV, Mangler &Mang,
245 bool MayAlwaysUsePrivate) const {
246 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
247 // Simple case: If GV is not private, it is not important to find out if
248 // private labels are legal in this case or not.
249 Mang.getNameWithPrefix(Name, GV, false);
250 return;
251 }
252 const TargetLoweringObjectFile *TLOF = getObjFileLowering();
253 TLOF->getNameWithPrefix(Name, GV, *this);
254}
255
256MCSymbol *TargetMachine::getSymbol(const GlobalValue *GV) const {
257 const TargetLoweringObjectFile *TLOF = getObjFileLowering();
258 SmallString<128> NameStr;
259 getNameWithPrefix(NameStr, GV, TLOF->getMangler());
260 return TLOF->getContext().getOrCreateSymbol(NameStr);
261}
Sanjoy Das26d11ca2017-12-22 18:21:59 +0000262
263TargetIRAnalysis TargetMachine::getTargetIRAnalysis() {
264 // Since Analysis can't depend on Target, use a std::function to invert the
265 // dependency.
266 return TargetIRAnalysis(
267 [this](const Function &F) { return this->getTargetTransformInfo(F); });
268}