LLVM 19.0.0git
TargetMachine.cpp
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1//===-- TargetMachine.cpp - General Target Information ---------------------==//
2//
3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4// See https://llvm.org/LICENSE.txt for license information.
5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6//
7//===----------------------------------------------------------------------===//
8//
9// This file describes the general parts of a Target machine.
10//
11//===----------------------------------------------------------------------===//
12
15#include "llvm/IR/Function.h"
16#include "llvm/IR/GlobalValue.h"
18#include "llvm/IR/Mangler.h"
19#include "llvm/MC/MCAsmInfo.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCInstrInfo.h"
26using namespace llvm;
27
28//---------------------------------------------------------------------------
29// TargetMachine Class
30//
31
33 const Triple &TT, StringRef CPU, StringRef FS,
35 : TheTarget(T), DL(DataLayoutString), TargetTriple(TT),
36 TargetCPU(std::string(CPU)), TargetFS(std::string(FS)), AsmInfo(nullptr),
37 MRI(nullptr), MII(nullptr), STI(nullptr), RequireStructuredCFG(false),
38 O0WantsFastISel(false), Options(Options) {}
39
41
43 if (getTargetTriple().getArch() != Triple::x86_64)
44 return false;
45
46 // Remaining logic below is ELF-specific. For other object file formats where
47 // the large code model is mostly used for JIT compilation, just look at the
48 // code model.
49 if (!getTargetTriple().isOSBinFormatELF())
51
52 auto *GO = GVal->getAliaseeObject();
53
54 // Be conservative if we can't find an underlying GlobalObject.
55 if (!GO)
56 return true;
57
58 auto *GV = dyn_cast<GlobalVariable>(GO);
59
60 auto IsPrefix = [](StringRef Name, StringRef Prefix) {
61 return Name.consume_front(Prefix) && (Name.empty() || Name[0] == '.');
62 };
63
64 // Functions/GlobalIFuncs are only large under the large code model.
65 if (!GV) {
66 // Handle explicit sections as we do for GlobalVariables with an explicit
67 // section, see comments below.
68 if (GO->hasSection()) {
69 StringRef Name = GO->getSection();
70 return IsPrefix(Name, ".ltext");
71 }
73 }
74
75 if (GV->isThreadLocal())
76 return false;
77
78 // For x86-64, we treat an explicit GlobalVariable small code model to mean
79 // that the global should be placed in a small section, and ditto for large.
80 if (auto CM = GV->getCodeModel()) {
81 if (*CM == CodeModel::Small)
82 return false;
83 if (*CM == CodeModel::Large)
84 return true;
85 }
86
87 // Treat all globals in explicit sections as small, except for the standard
88 // large sections of .lbss, .ldata, .lrodata. This reduces the risk of linking
89 // together small and large sections, resulting in small references to large
90 // data sections. The code model attribute overrides this above.
91 if (GV->hasSection()) {
92 StringRef Name = GV->getSection();
93 return IsPrefix(Name, ".lbss") || IsPrefix(Name, ".ldata") ||
94 IsPrefix(Name, ".lrodata");
95 }
96
97 // Respect large data threshold for medium and large code models.
100 if (!GV->getValueType()->isSized())
101 return true;
102 // Linker defined start/stop symbols can point to arbitrary points in the
103 // binary, so treat them as large.
104 if (GV->isDeclaration() && (GV->getName() == "__ehdr_start" ||
105 GV->getName().starts_with("__start_") ||
106 GV->getName().starts_with("__stop_")))
107 return true;
108 const DataLayout &DL = GV->getParent()->getDataLayout();
109 uint64_t Size = DL.getTypeAllocSize(GV->getValueType());
110 return Size == 0 || Size > LargeDataThreshold;
111 }
112
113 return false;
114}
115
118}
119
120/// Reset the target options based on the function's attributes.
121/// setFunctionAttributes should have made the raw attribute value consistent
122/// with the command line flag if used.
123//
124// FIXME: This function needs to go away for a number of reasons:
125// a) global state on the TargetMachine is terrible in general,
126// b) these target options should be passed only on the function
127// and not on the TargetMachine (via TargetOptions) at all.
129#define RESET_OPTION(X, Y) \
130 do { \
131 Options.X = F.getFnAttribute(Y).getValueAsBool(); \
132 } while (0)
133
134 RESET_OPTION(UnsafeFPMath, "unsafe-fp-math");
135 RESET_OPTION(NoInfsFPMath, "no-infs-fp-math");
136 RESET_OPTION(NoNaNsFPMath, "no-nans-fp-math");
137 RESET_OPTION(NoSignedZerosFPMath, "no-signed-zeros-fp-math");
138 RESET_OPTION(ApproxFuncFPMath, "approx-func-fp-math");
139}
140
141/// Returns the code generation relocation model. The choices are static, PIC,
142/// and dynamic-no-pic.
144
146 switch (getCodeModel()) {
147 case CodeModel::Tiny:
148 return llvm::maxUIntN(10);
149 case CodeModel::Small:
152 return llvm::maxUIntN(31);
153 case CodeModel::Large:
154 return llvm::maxUIntN(64);
155 }
156 llvm_unreachable("Unhandled CodeModel enum");
157}
158
159/// Get the IR-specified TLS model for Var.
161 switch (GV->getThreadLocalMode()) {
163 llvm_unreachable("getSelectedTLSModel for non-TLS variable");
164 break;
172 return TLSModel::LocalExec;
173 }
174 llvm_unreachable("invalid TLS model");
175}
176
178 const Triple &TT = getTargetTriple();
180
181 // According to the llvm language reference, we should be able to
182 // just return false in here if we have a GV, as we know it is
183 // dso_preemptable. At this point in time, the various IR producers
184 // have not been transitioned to always produce a dso_local when it
185 // is possible to do so.
186 //
187 // As a result we still have some logic in here to improve the quality of the
188 // generated code.
189 if (!GV)
190 return false;
191
192 // If the IR producer requested that this GV be treated as dso local, obey.
193 if (GV->isDSOLocal())
194 return true;
195
196 if (TT.isOSBinFormatCOFF()) {
197 // DLLImport explicitly marks the GV as external.
198 if (GV->hasDLLImportStorageClass())
199 return false;
200
201 // On MinGW, variables that haven't been declared with DLLImport may still
202 // end up automatically imported by the linker. To make this feasible,
203 // don't assume the variables to be DSO local unless we actually know
204 // that for sure. This only has to be done for variables; for functions
205 // the linker can insert thunks for calling functions from another DLL.
206 if (TT.isWindowsGNUEnvironment() && GV->isDeclarationForLinker() &&
207 isa<GlobalVariable>(GV))
208 return false;
209
210 // Don't mark 'extern_weak' symbols as DSO local. If these symbols remain
211 // unresolved in the link, they can be resolved to zero, which is outside
212 // the current DSO.
213 if (GV->hasExternalWeakLinkage())
214 return false;
215
216 // Every other GV is local on COFF.
217 return true;
218 }
219
220 if (TT.isOSBinFormatGOFF())
221 return true;
222
223 if (TT.isOSBinFormatMachO()) {
224 if (RM == Reloc::Static)
225 return true;
226 return GV->isStrongDefinitionForLinker();
227 }
228
229 assert(TT.isOSBinFormatELF() || TT.isOSBinFormatWasm() ||
230 TT.isOSBinFormatXCOFF());
231 return false;
232}
233
236
238 bool IsPIE = GV->getParent()->getPIELevel() != PIELevel::Default;
240 bool IsSharedLibrary = RM == Reloc::PIC_ && !IsPIE;
241 bool IsLocal = shouldAssumeDSOLocal(GV);
242
243 TLSModel::Model Model;
244 if (IsSharedLibrary) {
245 if (IsLocal)
247 else
249 } else {
250 if (IsLocal)
251 Model = TLSModel::LocalExec;
252 else
253 Model = TLSModel::InitialExec;
254 }
255
256 // If the user specified a more specific model, use that.
257 TLSModel::Model SelectedModel = getSelectedTLSModel(GV);
258 if (SelectedModel > Model)
259 return SelectedModel;
260
261 return Model;
262}
263
264/// Returns the optimization level: None, Less, Default, or Aggressive.
266
268
271 return TargetTransformInfo(F.getParent()->getDataLayout());
272}
273
275 const GlobalValue *GV, Mangler &Mang,
276 bool MayAlwaysUsePrivate) const {
277 if (MayAlwaysUsePrivate || !GV->hasPrivateLinkage()) {
278 // Simple case: If GV is not private, it is not important to find out if
279 // private labels are legal in this case or not.
280 Mang.getNameWithPrefix(Name, GV, false);
281 return;
282 }
284 TLOF->getNameWithPrefix(Name, GV, *this);
285}
286
289 // XCOFF symbols could have special naming convention.
290 if (MCSymbol *TargetSymbol = TLOF->getTargetSymbol(GV, *this))
291 return TargetSymbol;
292
293 SmallString<128> NameStr;
294 getNameWithPrefix(NameStr, GV, TLOF->getMangler());
295 return TLOF->getContext().getOrCreateSymbol(NameStr);
296}
297
299 // Since Analysis can't depend on Target, use a std::function to invert the
300 // dependency.
301 return TargetIRAnalysis(
302 [this](const Function &F) { return this->getTargetTransformInfo(F); });
303}
304
306 if (Version == "none")
307 return {INT_MAX, INT_MAX}; // Make binutilsIsAtLeast() return true.
308 std::pair<int, int> Ret;
309 if (!Version.consumeInteger(10, Ret.first) && Version.consume_front("."))
310 Version.consumeInteger(10, Ret.second);
311 return Ret;
312}
unsigned const MachineRegisterInfo * MRI
MachineBasicBlock MachineBasicBlock::iterator DebugLoc DL
std::string Name
uint64_t Size
static LVOptions Options
Definition: LVOptions.cpp:25
#define F(x, y, z)
Definition: MD5.cpp:55
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
static TLSModel::Model getSelectedTLSModel(const GlobalValue *GV)
Get the IR-specified TLS model for Var.
#define RESET_OPTION(X, Y)
This pass exposes codegen information to IR-level passes.
A parsed version of the target data layout string in and methods for querying it.
Definition: DataLayout.h:110
TypeSize getTypeAllocSize(Type *Ty) const
Returns the offset in bytes between successive objects of the specified type, including alignment pad...
Definition: DataLayout.h:504
bool isDSOLocal() const
Definition: GlobalValue.h:304
bool hasPrivateLinkage() const
Definition: GlobalValue.h:526
bool hasExternalWeakLinkage() const
Definition: GlobalValue.h:528
ThreadLocalMode getThreadLocalMode() const
Definition: GlobalValue.h:270
bool hasDLLImportStorageClass() const
Definition: GlobalValue.h:277
bool isDeclarationForLinker() const
Definition: GlobalValue.h:617
Module * getParent()
Get the module that this global value is contained inside of...
Definition: GlobalValue.h:655
const GlobalObject * getAliaseeObject() const
Definition: Globals.cpp:380
bool isStrongDefinitionForLinker() const
Returns true if this global's definition will be the one chosen by the linker.
Definition: GlobalValue.h:630
MCSymbol * getOrCreateSymbol(const Twine &Name)
Lookup the symbol inside with the specified Name.
Definition: MCContext.cpp:202
MCContext & getContext() const
MCSymbol - Instances of this class represent a symbol name in the MC file, and MCSymbols are created ...
Definition: MCSymbol.h:40
void getNameWithPrefix(raw_ostream &OS, const GlobalValue *GV, bool CannotUsePrivateLabel) const
Print the appropriate prefix and the specified global variable's name.
Definition: Mangler.cpp:120
PIELevel::Level getPIELevel() const
Returns the PIE level (small or large model)
Definition: Module.cpp:611
SmallString - A SmallString is just a SmallVector with methods and accessors that make it work better...
Definition: SmallString.h:26
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition: SmallVector.h:586
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:50
Analysis pass providing the TargetTransformInfo.
virtual void getNameWithPrefix(SmallVectorImpl< char > &OutName, const GlobalValue *GV, const TargetMachine &TM) const
virtual MCSymbol * getTargetSymbol(const GlobalValue *GV, const TargetMachine &TM) const
Targets that have a special convention for their symbols could use this hook to return a specialized ...
TLSModel::Model getTLSModel(const GlobalValue *GV) const
Returns the TLS model which should be used for the given global variable.
bool isPositionIndependent() const
uint64_t getMaxCodeSize() const
Returns the maximum code size possible under the code model.
const Triple & getTargetTriple() const
bool useTLSDESC() const
Returns true if this target uses TLS Descriptors.
uint64_t LargeDataThreshold
bool useEmulatedTLS() const
Returns true if this target uses emulated TLS.
virtual TargetLoweringObjectFile * getObjFileLowering() const
Reloc::Model getRelocationModel() const
Returns the code generation relocation model.
virtual TargetTransformInfo getTargetTransformInfo(const Function &F) const
Return a TargetTransformInfo for a given function.
const DataLayout DL
DataLayout for the target: keep ABI type size and alignment.
Definition: TargetMachine.h:91
bool shouldAssumeDSOLocal(const GlobalValue *GV) const
static std::pair< int, int > parseBinutilsVersion(StringRef Version)
TargetIRAnalysis getTargetIRAnalysis() const
Get a TargetIRAnalysis appropriate for the target.
TargetOptions Options
virtual ~TargetMachine()
MCSymbol * getSymbol(const GlobalValue *GV) const
CodeModel::Model getCodeModel() const
Returns the code model.
bool isLargeGlobalValue(const GlobalValue *GV) const
void resetTargetOptions(const Function &F) const
Reset the target options based on the function's attributes.
TargetMachine(const Target &T, StringRef DataLayoutString, const Triple &TargetTriple, StringRef CPU, StringRef FS, const TargetOptions &Options)
void getNameWithPrefix(SmallVectorImpl< char > &Name, const GlobalValue *GV, Mangler &Mang, bool MayAlwaysUsePrivate=false) const
CodeGenOptLevel getOptLevel() const
Returns the optimization level: None, Less, Default, or Aggressive.
CodeGenOptLevel OptLevel
void setOptLevel(CodeGenOptLevel Level)
Overrides the optimization level.
unsigned EnableTLSDESC
EnableTLSDESC - This flag enables TLS Descriptors.
unsigned EmulatedTLS
EmulatedTLS - This flag enables emulated TLS model, using emutls function in the runtime library.
This pass provides access to the codegen interfaces that are needed for IR-level transformations.
Target - Wrapper for Target specific information.
Triple - Helper class for working with autoconf configuration names.
Definition: Triple.h:44
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
@ GeneralDynamic
Definition: CodeGen.h:46
This is an optimization pass for GlobalISel generic memory operations.
Definition: AddressRanges.h:18
CodeGenOptLevel
Code generation optimization level.
Definition: CodeGen.h:54
uint64_t maxUIntN(uint64_t N)
Gets the maximum value for a N-bit unsigned integer.
Definition: MathExtras.h:203
Implement std::hash so that hash_code can be used in STL containers.
Definition: BitVector.h:858