LLVM  6.0.0svn
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 
20 #include "llvm/IR/Function.h"
21 #include "llvm/IR/GlobalAlias.h"
22 #include "llvm/IR/GlobalValue.h"
23 #include "llvm/IR/GlobalVariable.h"
25 #include "llvm/IR/Mangler.h"
26 #include "llvm/MC/MCAsmInfo.h"
27 #include "llvm/MC/MCContext.h"
28 #include "llvm/MC/MCInstrInfo.h"
29 #include "llvm/MC/MCSectionMachO.h"
31 #include "llvm/MC/SectionKind.h"
32 using namespace llvm;
33 
34 //---------------------------------------------------------------------------
35 // TargetMachine Class
36 //
37 
39  const Triple &TT, StringRef CPU, StringRef FS,
40  const TargetOptions &Options)
41  : TheTarget(T), DL(DataLayoutString), TargetTriple(TT), TargetCPU(CPU),
42  TargetFS(FS), AsmInfo(nullptr), MRI(nullptr), MII(nullptr), STI(nullptr),
43  RequireStructuredCFG(false), DefaultOptions(Options), Options(Options) {
44 }
45 
47  delete AsmInfo;
48  delete MRI;
49  delete MII;
50  delete STI;
51 }
52 
54  return getRelocationModel() == Reloc::PIC_;
55 }
56 
57 /// \brief Reset the target options based on the function's attributes.
58 // FIXME: This function needs to go away for a number of reasons:
59 // a) global state on the TargetMachine is terrible in general,
60 // b) these target options should be passed only on the function
61 // and not on the TargetMachine (via TargetOptions) at all.
63 #define RESET_OPTION(X, Y) \
64  do { \
65  if (F.hasFnAttribute(Y)) \
66  Options.X = (F.getFnAttribute(Y).getValueAsString() == "true"); \
67  else \
68  Options.X = DefaultOptions.X; \
69  } while (0)
70 
71  RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
72  RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
73  RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
74  RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
75  RESET_OPTION(NoTrappingFPMath, "no-trapping-math");
76 
77  StringRef Denormal =
78  F.getFnAttribute("denormal-fp-math").getValueAsString();
79  if (Denormal == "ieee")
81  else if (Denormal == "preserve-sign")
83  else if (Denormal == "positive-zero")
85  else
87 }
88 
89 /// Returns the code generation relocation model. The choices are static, PIC,
90 /// and dynamic-no-pic.
92 
93 /// Returns the code model. The choices are small, kernel, medium, large, and
94 /// target default.
96 
97 /// Get the IR-specified TLS model for Var.
99  switch (GV->getThreadLocalMode()) {
101  llvm_unreachable("getSelectedTLSModel for non-TLS variable");
102  break;
106  return TLSModel::LocalDynamic;
108  return TLSModel::InitialExec;
110  return TLSModel::LocalExec;
111  }
112  llvm_unreachable("invalid TLS model");
113 }
114 
116  const GlobalValue *GV) const {
117  // If the IR producer requested that this GV be treated as dso local, obey.
118  if (GV && GV->isDSOLocal())
119  return true;
120 
121  // According to the llvm language reference, we should be able to just return
122  // false in here if we have a GV, as we know it is dso_preemptable.
123  // At this point in time, the various IR producers have not been transitioned
124  // to always produce a dso_local when it is possible to do so. As a result we
125  // still have some pre-dso_local logic in here to improve the quality of the
126  // generated code:
127 
129  const Triple &TT = getTargetTriple();
130 
131  // DLLImport explicitly marks the GV as external.
132  if (GV && GV->hasDLLImportStorageClass())
133  return false;
134 
135  // Every other GV is local on COFF.
136  // Make an exception for windows OS in the triple: Some firmwares builds use
137  // *-win32-macho triples. This (accidentally?) produced windows relocations
138  // without GOT tables in older clang versions; Keep this behaviour.
139  if (TT.isOSBinFormatCOFF() || (TT.isOSWindows() && TT.isOSBinFormatMachO()))
140  return true;
141 
142  // Most PIC code sequences that assume that a symbol is local cannot
143  // produce a 0 if it turns out the symbol is undefined. While this
144  // is ABI and relocation depended, it seems worth it to handle it
145  // here.
146  // FIXME: this is probably not ELF specific.
147  if (GV && isPositionIndependent() && TT.isOSBinFormatELF() &&
149  return false;
150 
151  if (GV && (GV->hasLocalLinkage() || !GV->hasDefaultVisibility()))
152  return true;
153 
154  if (TT.isOSBinFormatMachO()) {
155  if (RM == Reloc::Static)
156  return true;
157  return GV && GV->isStrongDefinitionForLinker();
158  }
159 
160  assert(TT.isOSBinFormatELF());
162 
163  bool IsExecutable =
165  if (IsExecutable) {
166  // If the symbol is defined, it cannot be preempted.
167  if (GV && !GV->isDeclarationForLinker())
168  return true;
169 
170  // A symbol marked nonlazybind should not be accessed with a plt. If the
171  // symbol turns out to be external, the linker will convert a direct
172  // access to an access via the plt, so don't assume it is local.
173  const Function *F = dyn_cast_or_null<Function>(GV);
174  if (F && F->hasFnAttribute(Attribute::NonLazyBind))
175  return false;
176 
177  bool IsTLS = GV && GV->isThreadLocal();
178  bool IsAccessViaCopyRelocs =
179  Options.MCOptions.MCPIECopyRelocations && GV && isa<GlobalVariable>(GV);
180  Triple::ArchType Arch = TT.getArch();
181  bool IsPPC =
182  Arch == Triple::ppc || Arch == Triple::ppc64 || Arch == Triple::ppc64le;
183  // Check if we can use copy relocations. PowerPC has no copy relocations.
184  if (!IsTLS && !IsPPC && (RM == Reloc::Static || IsAccessViaCopyRelocs))
185  return true;
186  }
187 
188  // ELF supports preemption of other symbols.
189  return false;
190 }
191 
193  bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
195  bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
196  bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
197 
199  if (IsSharedLibrary) {
200  if (IsLocal)
201  Model = TLSModel::LocalDynamic;
202  else
203  Model = TLSModel::GeneralDynamic;
204  } else {
205  if (IsLocal)
206  Model = TLSModel::LocalExec;
207  else
208  Model = TLSModel::InitialExec;
209  }
210 
211  // If the user specified a more specific model, use that.
212  TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
213  if (SelectedModel > Model)
214  return SelectedModel;
215 
216  return Model;
217 }
218 
219 /// Returns the optimization level: None, Less, Default, or Aggressive.
221 
223 
225  return TargetIRAnalysis([](const Function &F) {
227  });
228 }
229 
231  const GlobalValue *GV, Mangler &Mang,
232  bool MayAlwaysUsePrivate) const {
233  if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
234  // Simple case: If GV is not private, it is not important to find out if
235  // private labels are legal in this case or not.
236  Mang.getNameWithPrefix(Name, GV, false);
237  return;
238  }
240  TLOF->getNameWithPrefix(Name, GV, *this);
241 }
242 
245  SmallString<128> NameStr;
246  getNameWithPrefix(NameStr, GV, TLOF->getMangler());
247  return TLOF->getContext().getOrCreateSymbol(NameStr);
248 }
bool isDeclarationForLinker() const
Definition: GlobalValue.h:514
TargetMachine(const Target &T, StringRef DataLayoutString, const Triple &TargetTriple, StringRef CPU, StringRef FS, const TargetOptions &Options)
ThreadLocalMode getThreadLocalMode() const
Definition: GlobalValue.h:246
bool hasLocalLinkage() const
Definition: GlobalValue.h:427
MCTargetOptions MCOptions
Machine level options.
bool hasPrivateLinkage() const
Definition: GlobalValue.h:426
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:262
bool hasDLLImportStorageClass() const
Definition: GlobalValue.h:253
F(f)
bool hasExternalWeakLinkage() const
Definition: GlobalValue.h:428
CodeGenOpt::Level OptLevel
Definition: TargetMachine.h:82
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:271
#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:85
const MCSubtargetInfo * STI
Definition: TargetMachine.h:89
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.
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:81
virtual 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:88
#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:95
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:87
bool isStrongDefinitionForLinker() const
Returns true if this global&#39;s definition will be the one chosen by the linker.
Definition: GlobalValue.h:527
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:96
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:556
Attribute getFnAttribute(Attribute::AttrKind Kind) const
Return the attribute for the given attribute kind.
Definition: Function.h:270
bool hasDefaultVisibility() const
Definition: GlobalValue.h:226
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:238
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:49
This pass exposes codegen information to IR-level passes.
This file describes how to lower LLVM code to machine code.