LLVM  8.0.0svn
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 
16 #include "llvm/IR/Function.h"
17 #include "llvm/IR/GlobalAlias.h"
18 #include "llvm/IR/GlobalValue.h"
19 #include "llvm/IR/GlobalVariable.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"
27 #include "llvm/MC/SectionKind.h"
29 using namespace llvm;
30 
31 //---------------------------------------------------------------------------
32 // TargetMachine Class
33 //
34 
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 
44  delete AsmInfo;
45  delete MRI;
46  delete MII;
47  delete STI;
48 }
49 
51  return getRelocationModel() == Reloc::PIC_;
52 }
53 
54 /// Reset the target options based on the function's attributes.
55 // 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.
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")
78  else if (Denormal == "preserve-sign")
80  else if (Denormal == "positive-zero")
82  else
84 }
85 
86 /// Returns the code generation relocation model. The choices are static, PIC,
87 /// and dynamic-no-pic.
89 
90 /// Returns the code model. The choices are small, kernel, medium, large, and
91 /// target default.
93 
94 /// Get the IR-specified TLS model for Var.
96  switch (GV->getThreadLocalMode()) {
98  llvm_unreachable("getSelectedTLSModel for non-TLS variable");
99  break;
103  return TLSModel::LocalDynamic;
105  return TLSModel::InitialExec;
107  return TLSModel::LocalExec;
108  }
109  llvm_unreachable("invalid TLS model");
110 }
111 
113  const GlobalValue *GV) const {
114  // If the IR producer requested that this GV be treated as dso local, obey.
115  if (GV && GV->isDSOLocal())
116  return true;
117 
118  // 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.
136 
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.
145  // Make an exception for windows OS in the triple: Some firmware builds use
146  // *-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 
151  // 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.
155  if (GV && isPositionIndependent() && GV->hasExternalWeakLinkage())
156  return false;
157 
158  if (GV && !GV->hasDefaultVisibility())
159  return true;
160 
161  if (TT.isOSBinFormatMachO()) {
162  if (RM == Reloc::Static)
163  return true;
164  return GV && GV->isStrongDefinitionForLinker();
165  }
166 
167  assert(TT.isOSBinFormatELF());
169 
170  bool IsExecutable =
172  if (IsExecutable) {
173  // If the symbol is defined, it cannot be preempted.
174  if (GV && !GV->isDeclarationForLinker())
175  return true;
176 
177  // 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.
180  const Function *F = dyn_cast_or_null<Function>(GV);
181  if (F && F->hasFnAttribute(Attribute::NonLazyBind))
182  return false;
183 
184  bool IsTLS = GV && GV->isThreadLocal();
185  bool IsAccessViaCopyRelocs =
186  GV && Options.MCOptions.MCPIECopyRelocations && isa<GlobalVariable>(GV);
187  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 
200  // Returns Options.EmulatedTLS if the -emulated-tls or -no-emulated-tls
201  // was specified explicitly; otherwise uses target triple to decide default.
203  return Options.EmulatedTLS;
205 }
206 
208  bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
210  bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
211  bool IsLocal = shouldAssumeDSOLocal(*GV->getParent(), GV);
212 
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.
236 
238 
241 }
242 
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  }
253  TLOF->getNameWithPrefix(Name, GV, *this);
254 }
255 
258  SmallString<128> NameStr;
259  getNameWithPrefix(NameStr, GV, TLOF->getMangler());
260  return TLOF->getContext().getOrCreateSymbol(NameStr);
261 }
262 
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 }
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:307
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
bool hasDefaultEmulatedTLS() const
Tests whether the target uses emulated TLS as default.
Definition: Triple.h:684
#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 useEmulatedTLS() const
Returns true if this target uses emulated TLS.
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:494
unsigned ExplicitEmulatedTLS
Whether -emulated-tls or -no-emulated-tls is set.
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.
unsigned EmulatedTLS
EmulatedTLS - This flag enables emulated TLS model, using emutls function in the runtime library...
const MCRegisterInfo * MRI
Definition: TargetMachine.h:89
bool getRtLibUseGOT() const
Returns true if PLT should be avoided for RTLib calls.
Definition: Module.cpp:520
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:123
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
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:317
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:112
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.