LLVM  7.0.0svn
TargetMachine.cpp
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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 
18 #include "llvm/IR/Function.h"
19 #include "llvm/IR/GlobalAlias.h"
20 #include "llvm/IR/GlobalValue.h"
21 #include "llvm/IR/GlobalVariable.h"
23 #include "llvm/IR/Mangler.h"
24 #include "llvm/MC/MCAsmInfo.h"
25 #include "llvm/MC/MCContext.h"
26 #include "llvm/MC/MCInstrInfo.h"
27 #include "llvm/MC/MCSectionMachO.h"
29 #include "llvm/MC/SectionKind.h"
30 using namespace llvm;
31 
32 //---------------------------------------------------------------------------
33 // TargetMachine Class
34 //
35 
37  const Triple &TT, StringRef CPU, StringRef FS,
38  const TargetOptions &Options)
39  : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
40  TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
41  RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
42 }
43 
45  delete AsmInfo;
46  delete MRI;
47  delete MII;
48  delete STI;
49 }
50 
52  return getRelocationModel() == Reloc::PIC_;
53 }
54 
55 /// \brief Reset the target options based on the function's attributes.
56 // FIXME: This function needs to go away for a number of reasons:
57 // a) global state on the TargetMachine is terrible in general,
58 // b) these target options should be passed only on the function
59 // and not on the TargetMachine (via TargetOptions) at all.
61 #define RESET_OPTION(X, Y) \
62  do { \
63  if (F.hasFnAttribute(Y)) \
64  Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
65  else \
66  Options.X = DefaultOptions.X; \
67  } while (0)
68 
69  RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
70  RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
71  RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
72  RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
73  RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
74 
75  StringRef Denormal =
76  F.getFnAttribute("denormal-fp-math").getValueAsString();
77  if (Denormal == "ieee")
79  else if (Denormal == "preserve-sign")
81  else if (Denormal == "positive-zero")
83  else
85 }
86 
87 /// Returns the code generation relocation model. The choices are static, PIC,
88 /// and dynamic-no-pic.
90 
91 /// Returns the code model. The choices are small, kernel, medium, large, and
92 /// target default.
94 
95 /// Get the IR-specified TLS model for Var.
97  switch (GV->getThreadLocalMode()) {
99  llvm_unreachable("getSelectedTLSModel for non-TLS variable");
100  break;
104  return TLSModel::LocalDynamic;
106  return TLSModel::InitialExec;
108  return TLSModel::LocalExec;
109  }
110  llvm_unreachable("invalid TLS model");
111 }
112 
114  const GlobalValue *GV) const {
115  // If the IR producer requested that this GV be treated as dso local, obey.
116  if (GV && GV->isDSOLocal())
117  return true;
118 
119  // According to the llvm language reference, we should be able to just return
120  // false in here if we have a GV, as we know it is dso_preemptable.
121  // At this point in time, the various IR producers have not been transitioned
122  // to always produce a dso_local when it is possible to do so. As a result we
123  // still have some pre-dso_local logic in here to improve the quality of the
124  // generated code:
125 
127  const Triple &TT = getTargetTriple();
128 
129  // DLLImport explicitly marks the GV as external.
130  if (GV && GV->hasDLLImportStorageClass())
131  return false;
132 
133  // Every other GV is local on COFF.
134  // Make an exception for windows OS in the triple: Some firmwares builds use
135  // *-win32-macho triples. This (accidentally?) produced windows relocations
136  // without GOT tables in older clang versions; Keep this behaviour.
137  if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
138  return true;
139 
140  // If GV is null we know that this is a call to an intrinsic. For ELF and
141  // MachO we don't need to assume those are local since the liker can trivially
142  // convert a call to a PLT to a direct call if the target (in the runtime
143  // library) turns out to be local.
144  if (!GV)
145  return false;
146 
147  // Most PIC code sequences that assume that a symbol is local cannot
148  // produce a 0 if it turns out the symbol is undefined. While this
149  // is ABI and relocation depended, it seems worth it to handle it
150  // here.
152  return false;
153 
154  if (!GV->hasDefaultVisibility())
155  return true;
156 
157  if (TT.isOSBinFormatMachO()) {
158  if (RM == Reloc::Static)
159  return true;
160  return GV->isStrongDefinitionForLinker();
161  }
162 
163  assert(TT.isOSBinFormatELF());
165 
166  bool IsExecutable =
168  if (IsExecutable) {
169  // If the symbol is defined, it cannot be preempted.
170  if (!GV->isDeclarationForLinker())
171  return true;
172 
173  // A symbol marked nonlazybind should not be accessed with a plt. If the
174  // symbol turns out to be external, the linker will convert a direct
175  // access to an access via the plt, so don't assume it is local.
176  const Function *F = dyn_cast<Function>(GV);
177  if (F && F->hasFnAttribute(Attribute::NonLazyBind))
178  return false;
179 
180  bool IsTLS = GV->isThreadLocal();
181  bool IsAccessViaCopyRelocs =
182  Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
183  Triple::ArchType Arch = TT.getArch();
184  bool IsPPC =
185  Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
186  // Check if we can use copy relocations. PowerPC has no copy relocations.
187  if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
188  return true;
189  }
190 
191  // ELF supports preemption of other symbols.
192  return false;
193 }
194 
196  bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
198  bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
199  bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
200 
202  if (IsSharedLibrary) {
203  if (IsLocal)
204  Model = TLSModel::LocalDynamic;
205  else
206  Model = TLSModel::GeneralDynamic;
207  } else {
208  if (IsLocal)
209  Model = TLSModel::LocalExec;
210  else
211  Model = TLSModel::InitialExec;
212  }
213 
214  // If the user specified a more specific model, use that.
215  TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
216  if (SelectedModel > Model)
217  return SelectedModel;
218 
219  return Model;
220 }
221 
222 /// Returns the optimization level: None, Less, Default, or Aggressive.
224 
226 
229 }
230 
232  const GlobalValue *GV, Mangler &Mang,
233  bool MayAlwaysUsePrivate) const {
234  if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
235  // Simple case: If GV is not private, it is not important to find out if
236  // private labels are legal in this case or not.
237  Mang.getNameWithPrefix(Name, GV, false);
238  return;
239  }
241  TLOF->getNameWithPrefix(Name, GV, *this);
242 }
243 
246  SmallString<128> NameStr;
247  getNameWithPrefix(NameStr, GV, TLOF->getMangler());
248  return TLOF->getContext().getOrCreateSymbol(NameStr);
249 }
250 
252  // Since Analysis can't depend on Target, use a std::function to invert the
253  // dependency.
254  return TargetIRAnalysis(
255  [this](const Function &F) { return this->getTargetTransformInfo(F); });
256 }
bool isDeclarationForLinker() const
Definition: GlobalValue.h:523
TargetMachine(const Target &T, StringRef DataLayoutString, const Triple &TargetTriple, StringRef CPU, StringRef FS, const TargetOptions &Options)
ThreadLocalMode getThreadLocalMode() const
Definition: GlobalValue.h:254
MCTargetOptions MCOptions
Machine level options.
bool hasPrivateLinkage() const
Definition: GlobalValue.h:434
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:42
A Module instance is used to store all the information related to an LLVM module. ...
Definition: Module.h:63
bool isOSBinFormatELF() const
Tests whether the OS uses the ELF binary format.
Definition: Triple.h:588
static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV)
Get the IR-specified TLS model for Var.
Analysis pass providing the TargetTransformInfo.
bool hasFnAttribute(Attribute::AttrKind Kind) const
Return true if the function has the attribute.
Definition: Function.h:302
bool hasDLLImportStorageClass() const
Definition: GlobalValue.h:261
F(f)
bool hasExternalWeakLinkage() const
Definition: GlobalValue.h:436
CodeGenOpt::Level OptLevel
Definition: TargetMachine.h:84
void resetTargetOptions(const Function &F) const
Reset the target options based on the function&#39;s attributes.
const DataLayout & getDataLayout() const
Get the data layout for the module&#39;s target platform.
Definition: Module.cpp:361
bool isDSOLocal() const
Definition: GlobalValue.h:279
#define RESET_OPTION(X, Y)
void getNameWithPrefix(SmallVectorImpl< char > &Name, const GlobalValue *GV, Mangler &Mang, bool MayAlwaysUsePrivate=false) const
const MCAsmInfo * AsmInfo
Contains target specific asm information.
Definition: TargetMachine.h:87
const MCSubtargetInfo * STI
Definition: TargetMachine.h:91
ArchType getArch() const
getArch - Get the parsed architecture type of this triple.
Definition: Triple.h:285
Reloc::Model getRelocationModel() const
Returns the code generation relocation model.
TLSModel::Model getTLSModel(const GlobalValue *GV) const
Returns the TLS model which should be used for the given global variable.
virtual TargetTransformInfo getTargetTransformInfo(const Function &F)
Return a TargetTransformInfo for a given function.
bool isOSWindows() const
Tests whether the OS is Windows.
Definition: Triple.h:562
CodeGenOpt::Level getOptLevel() const
Returns the optimization level: None, Less, Default, or Aggressive.
unsigned const MachineRegisterInfo * MRI
bool shouldAssumeDSOLocal(const Module &M, const GlobalValue *GV) const
PIELevel::Level getPIELevel() const
Returns the PIE level (small or large model)
Definition: Module.cpp:487
bool isOSBinFormatCOFF() const
Tests whether the OS uses the COFF binary format.
Definition: Triple.h:593
CodeModel::Model CMModel
Definition: TargetMachine.h:83
TargetIRAnalysis getTargetIRAnalysis()
Get a TargetIRAnalysis appropriate for the target.
MCSymbol * getSymbol(const GlobalValue *GV) const
const Triple & getTargetTriple() const
bool isOSBinFormatMachO() const
Tests whether the environment is MachO.
Definition: Triple.h:598
FPDenormal::DenormalMode FPDenormalMode
FPDenormalMode - This flags specificies which denormal numbers the code is permitted to require...
const MCInstrInfo * MII
Definition: TargetMachine.h:90
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
const TargetOptions DefaultOptions
Definition: TargetMachine.h:97
virtual TargetLoweringObjectFile * getObjFileLowering() const
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
Target - Wrapper for Target specific information.
CodeModel::Model getCodeModel() const
Returns the code model.
const MCRegisterInfo * MRI
Definition: TargetMachine.h:89
bool isStrongDefinitionForLinker() const
Returns true if this global&#39;s definition will be the one chosen by the linker.
Definition: GlobalValue.h:536
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:121
StringRef getValueAsString() const
Return the attribute&#39;s value as a string.
Definition: Attributes.cpp:195
bool isPositionIndependent() const
TargetOptions Options
Definition: TargetMachine.h:98
LLVM_NODISCARD std::enable_if<!is_simple_type< Y >::value, typename cast_retty< X, const Y >::ret_type >::type dyn_cast(const Y &Val)
Definition: Casting.h:323
void setOptLevel(CodeGenOpt::Level Level)
Overrides the optimization level.
virtual void getNameWithPrefix(SmallVectorImpl< char > &OutName, const GlobalValue *GV, const TargetMachine &TM) const
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:565
Attribute getFnAttribute(Attribute::AttrKind Kind) const
Return the attribute for the given attribute kind.
Definition: Function.h:312
bool hasDefaultVisibility() const
Definition: GlobalValue.h:233
void getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV, bool CannotUsePrivateLabel) const
Print the appropriate prefix and the specified global variable&#39;s name.
Definition: Mangler.cpp:109
bool isThreadLocal() const
If the value is "Thread Local", its value isn&#39;t shared by the threads.
Definition: GlobalValue.h:246
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
This pass exposes codegen information to IR-level passes.