1//===-- llvm/GlobalValue.h - Class to represent a global value --*- C++ -*-===//
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 is a common base class of all globally definable objects. As such,
10// it is subclassed by GlobalVariable, GlobalAlias and by Function. This is
11// used because you can do certain things with these global objects that you
12// can't do to anything else. For example, use the address of one as a
13// constant.
14//
15//===----------------------------------------------------------------------===//
16
17#ifndef LLVM_IR_GLOBALVALUE_H
18#define LLVM_IR_GLOBALVALUE_H
19
20#include "llvm/ADT/StringRef.h"
21#include "llvm/ADT/Twine.h"
22#include "llvm/IR/Constant.h"
23#include "llvm/IR/DerivedTypes.h"
24#include "llvm/IR/Value.h"
25#include "llvm/Support/Casting.h"
26#include "llvm/Support/ErrorHandling.h"
27#include "llvm/Support/MD5.h"
28#include <cassert>
29#include <cstdint>
30#include <string>
31
32namespace llvm {
33
34class Comdat;
35class ConstantRange;
36class Error;
37class GlobalObject;
38class Module;
39
40namespace Intrinsic {
41typedef unsigned ID;
42} // end namespace Intrinsic
43
44// Choose ';' as the delimiter. ':' was used once but it doesn't work well for
45// Objective-C functions which commonly have :'s in their names.
46inline constexpr char kGlobalIdentifierDelimiter = ';';
47
48class GlobalValue : public Constant {
49public:
50 /// An enumeration for the kinds of linkage for global values.
51 enum LinkageTypes {
52 ExternalLinkage = 0,///< Externally visible function
53 AvailableExternallyLinkage, ///< Available for inspection, not emission.
54 LinkOnceAnyLinkage, ///< Keep one copy of function when linking (inline)
55 LinkOnceODRLinkage, ///< Same, but only replaced by something equivalent.
56 WeakAnyLinkage, ///< Keep one copy of named function when linking (weak)
57 WeakODRLinkage, ///< Same, but only replaced by something equivalent.
58 AppendingLinkage, ///< Special purpose, only applies to global arrays
59 InternalLinkage, ///< Rename collisions when linking (static functions).
60 PrivateLinkage, ///< Like Internal, but omit from symbol table.
61 ExternalWeakLinkage,///< ExternalWeak linkage description.
62 CommonLinkage ///< Tentative definitions.
63 };
64
65 /// An enumeration for the kinds of visibility of global values.
66 enum VisibilityTypes {
67 DefaultVisibility = 0, ///< The GV is visible
68 HiddenVisibility, ///< The GV is hidden
69 ProtectedVisibility ///< The GV is protected
70 };
71
72 /// Storage classes of global values for PE targets.
73 enum DLLStorageClassTypes {
74 DefaultStorageClass = 0,
75 DLLImportStorageClass = 1, ///< Function to be imported from DLL
76 DLLExportStorageClass = 2 ///< Function to be accessible from DLL.
77 };
78
79protected:
80 GlobalValue(Type *Ty, ValueTy VTy, Use *Ops, unsigned NumOps,
81 LinkageTypes Linkage, const Twine &Name, unsigned AddressSpace)
82 : Constant(PointerType::get(ElementType: Ty, AddressSpace), VTy, Ops, NumOps),
83 ValueType(Ty), Visibility(DefaultVisibility),
84 UnnamedAddrVal(unsigned(UnnamedAddr::None)),
85 DllStorageClass(DefaultStorageClass), ThreadLocal(NotThreadLocal),
86 HasLLVMReservedName(false), IsDSOLocal(false), HasPartition(false),
87 HasSanitizerMetadata(false) {
88 setLinkage(Linkage);
89 setName(Name);
90 }
91
92 Type *ValueType;
93
94 static const unsigned GlobalValueSubClassDataBits = 15;
95
96 // All bitfields use unsigned as the underlying type so that MSVC will pack
97 // them.
98 unsigned Linkage : 4; // The linkage of this global
99 unsigned Visibility : 2; // The visibility style of this global
100 unsigned UnnamedAddrVal : 2; // This value's address is not significant
101 unsigned DllStorageClass : 2; // DLL storage class
102
103 unsigned ThreadLocal : 3; // Is this symbol "Thread Local", if so, what is
104 // the desired model?
105
106 /// True if the function's name starts with "llvm.". This corresponds to the
107 /// value of Function::isIntrinsic(), which may be true even if
108 /// Function::intrinsicID() returns Intrinsic::not_intrinsic.
109 unsigned HasLLVMReservedName : 1;
110
111 /// If true then there is a definition within the same linkage unit and that
112 /// definition cannot be runtime preempted.
113 unsigned IsDSOLocal : 1;
114
115 /// True if this symbol has a partition name assigned (see
116 /// https://lld.llvm.org/Partitions.html).
117 unsigned HasPartition : 1;
118
119 /// True if this symbol has sanitizer metadata available. Should only happen
120 /// if sanitizers were enabled when building the translation unit which
121 /// contains this GV.
122 unsigned HasSanitizerMetadata : 1;
123
124private:
125 // Give subclasses access to what otherwise would be wasted padding.
126 // (15 + 4 + 2 + 2 + 2 + 3 + 1 + 1 + 1 + 1) == 32.
127 unsigned SubClassData : GlobalValueSubClassDataBits;
128
129 friend class Constant;
130
131 void destroyConstantImpl();
132 Value *handleOperandChangeImpl(Value *From, Value *To);
133
134 /// Returns true if the definition of this global may be replaced by a
135 /// differently optimized variant of the same source level function at link
136 /// time.
137 bool mayBeDerefined() const {
138 switch (getLinkage()) {
139 case WeakODRLinkage:
140 case LinkOnceODRLinkage:
141 case AvailableExternallyLinkage:
142 return true;
143
144 case WeakAnyLinkage:
145 case LinkOnceAnyLinkage:
146 case CommonLinkage:
147 case ExternalWeakLinkage:
148 case ExternalLinkage:
149 case AppendingLinkage:
150 case InternalLinkage:
151 case PrivateLinkage:
152 // Optimizations may assume builtin semantics for functions defined as
153 // nobuiltin due to attributes at call-sites. To avoid applying IPO based
154 // on nobuiltin semantics, treat such function definitions as maybe
155 // derefined.
156 return isInterposable() || isNobuiltinFnDef();
157 }
158
159 llvm_unreachable("Fully covered switch above!");
160 }
161
162 /// Returns true if the global is a function definition with the nobuiltin
163 /// attribute.
164 bool isNobuiltinFnDef() const;
165
166protected:
167 /// The intrinsic ID for this subclass (which must be a Function).
168 ///
169 /// This member is defined by this class, but not used for anything.
170 /// Subclasses can use it to store their intrinsic ID, if they have one.
171 ///
172 /// This is stored here to save space in Function on 64-bit hosts.
173 Intrinsic::ID IntID = (Intrinsic::ID)0U;
174
175 unsigned getGlobalValueSubClassData() const {
176 return SubClassData;
177 }
178 void setGlobalValueSubClassData(unsigned V) {
179 assert(V < (1 << GlobalValueSubClassDataBits) && "It will not fit");
180 SubClassData = V;
181 }
182
183 Module *Parent = nullptr; // The containing module.
184
185 // Used by SymbolTableListTraits.
186 void setParent(Module *parent) {
187 Parent = parent;
188 }
189
190 ~GlobalValue() {
191 removeDeadConstantUsers(); // remove any dead constants using this.
192 }
193
194public:
195 enum ThreadLocalMode {
196 NotThreadLocal = 0,
197 GeneralDynamicTLSModel,
198 LocalDynamicTLSModel,
199 InitialExecTLSModel,
200 LocalExecTLSModel
201 };
202
203 GlobalValue(const GlobalValue &) = delete;
204
205 unsigned getAddressSpace() const {
206 return getType()->getAddressSpace();
207 }
208
209 enum class UnnamedAddr {
210 None,
211 Local,
212 Global,
213 };
214
215 bool hasGlobalUnnamedAddr() const {
216 return getUnnamedAddr() == UnnamedAddr::Global;
217 }
218
219 /// Returns true if this value's address is not significant in this module.
220 /// This attribute is intended to be used only by the code generator and LTO
221 /// to allow the linker to decide whether the global needs to be in the symbol
222 /// table. It should probably not be used in optimizations, as the value may
223 /// have uses outside the module; use hasGlobalUnnamedAddr() instead.
224 bool hasAtLeastLocalUnnamedAddr() const {
225 return getUnnamedAddr() != UnnamedAddr::None;
226 }
227
228 UnnamedAddr getUnnamedAddr() const {
229 return UnnamedAddr(UnnamedAddrVal);
230 }
231 void setUnnamedAddr(UnnamedAddr Val) { UnnamedAddrVal = unsigned(Val); }
232
233 static UnnamedAddr getMinUnnamedAddr(UnnamedAddr A, UnnamedAddr B) {
234 if (A == UnnamedAddr::None || B == UnnamedAddr::None)
235 return UnnamedAddr::None;
236 if (A == UnnamedAddr::Local || B == UnnamedAddr::Local)
237 return UnnamedAddr::Local;
238 return UnnamedAddr::Global;
239 }
240
241 bool hasComdat() const { return getComdat() != nullptr; }
242 const Comdat *getComdat() const;
243 Comdat *getComdat() {
244 return const_cast<Comdat *>(
245 static_cast<const GlobalValue *>(this)->getComdat());
246 }
247
248 VisibilityTypes getVisibility() const { return VisibilityTypes(Visibility); }
249 bool hasDefaultVisibility() const { return Visibility == DefaultVisibility; }
250 bool hasHiddenVisibility() const { return Visibility == HiddenVisibility; }
251 bool hasProtectedVisibility() const {
252 return Visibility == ProtectedVisibility;
253 }
254 void setVisibility(VisibilityTypes V) {
255 assert((!hasLocalLinkage() || V == DefaultVisibility) &&
256 "local linkage requires default visibility");
257 Visibility = V;
258 if (isImplicitDSOLocal())
259 setDSOLocal(true);
260 }
261
262 /// If the value is "Thread Local", its value isn't shared by the threads.
263 bool isThreadLocal() const { return getThreadLocalMode() != NotThreadLocal; }
264 void setThreadLocal(bool Val) {
265 setThreadLocalMode(Val ? GeneralDynamicTLSModel : NotThreadLocal);
266 }
267 void setThreadLocalMode(ThreadLocalMode Val) {
268 assert(Val == NotThreadLocal || getValueID() != Value::FunctionVal);
269 ThreadLocal = Val;
270 }
271 ThreadLocalMode getThreadLocalMode() const {
272 return static_cast<ThreadLocalMode>(ThreadLocal);
273 }
274
275 DLLStorageClassTypes getDLLStorageClass() const {
276 return DLLStorageClassTypes(DllStorageClass);
277 }
278 bool hasDLLImportStorageClass() const {
279 return DllStorageClass == DLLImportStorageClass;
280 }
281 bool hasDLLExportStorageClass() const {
282 return DllStorageClass == DLLExportStorageClass;
283 }
284 void setDLLStorageClass(DLLStorageClassTypes C) {
285 assert((!hasLocalLinkage() || C == DefaultStorageClass) &&
286 "local linkage requires DefaultStorageClass");
287 DllStorageClass = C;
288 }
289
290 bool hasSection() const { return !getSection().empty(); }
291 StringRef getSection() const;
292
293 /// Global values are always pointers.
294 PointerType *getType() const { return cast<PointerType>(Val: User::getType()); }
295
296 Type *getValueType() const { return ValueType; }
297
298 bool isImplicitDSOLocal() const {
299 return hasLocalLinkage() ||
300 (!hasDefaultVisibility() && !hasExternalWeakLinkage());
301 }
302
303 void setDSOLocal(bool Local) { IsDSOLocal = Local; }
304
305 bool isDSOLocal() const {
306 return IsDSOLocal;
307 }
308
309 bool hasPartition() const {
310 return HasPartition;
311 }
312 StringRef getPartition() const;
313 void setPartition(StringRef Part);
314
315 // ASan, HWASan and Memtag sanitizers have some instrumentation that applies
316 // specifically to global variables.
317 struct SanitizerMetadata {
318 SanitizerMetadata()
319 : NoAddress(false), NoHWAddress(false),
320 Memtag(false), IsDynInit(false) {}
321 // For ASan and HWASan, this instrumentation is implicitly applied to all
322 // global variables when built with -fsanitize=*. What we need is a way to
323 // persist the information that a certain global variable should *not* have
324 // sanitizers applied, which occurs if:
325 // 1. The global variable is in the sanitizer ignore list, or
326 // 2. The global variable is created by the sanitizers itself for internal
327 // usage, or
328 // 3. The global variable has __attribute__((no_sanitize("..."))) or
329 // __attribute__((disable_sanitizer_instrumentation)).
330 //
331 // This is important, a some IR passes like GlobalMerge can delete global
332 // variables and replace them with new ones. If the old variables were
333 // marked to be unsanitized, then the new ones should also be.
334 unsigned NoAddress : 1;
335 unsigned NoHWAddress : 1;
336
337 // Memtag sanitization works differently: sanitization is requested by clang
338 // when `-fsanitize=memtag-globals` is provided, and the request can be
339 // denied (and the attribute removed) by the AArch64 global tagging pass if
340 // it can't be fulfilled (e.g. the global variable is a TLS variable).
341 // Memtag sanitization has to interact with other parts of LLVM (like
342 // supressing certain optimisations, emitting assembly directives, or
343 // creating special relocation sections).
344 //
345 // Use `GlobalValue::isTagged()` to check whether tagging should be enabled
346 // for a global variable.
347 unsigned Memtag : 1;
348
349 // ASan-specific metadata. Is this global variable dynamically initialized
350 // (from a C++ language perspective), and should therefore be checked for
351 // ODR violations.
352 unsigned IsDynInit : 1;
353 };
354
355 bool hasSanitizerMetadata() const { return HasSanitizerMetadata; }
356 const SanitizerMetadata &getSanitizerMetadata() const;
357 // Note: Not byref as it's a POD and otherwise it's too easy to call
358 // G.setSanitizerMetadata(G2.getSanitizerMetadata()), and the argument becomes
359 // dangling when the backing storage allocates the metadata for `G`, as the
360 // storage is shared between `G1` and `G2`.
361 void setSanitizerMetadata(SanitizerMetadata Meta);
362 void removeSanitizerMetadata();
363 void setNoSanitizeMetadata();
364
365 bool isTagged() const {
366 return hasSanitizerMetadata() && getSanitizerMetadata().Memtag;
367 }
368
369 static LinkageTypes getLinkOnceLinkage(bool ODR) {
370 return ODR ? LinkOnceODRLinkage : LinkOnceAnyLinkage;
371 }
372 static LinkageTypes getWeakLinkage(bool ODR) {
373 return ODR ? WeakODRLinkage : WeakAnyLinkage;
374 }
375
376 static bool isExternalLinkage(LinkageTypes Linkage) {
377 return Linkage == ExternalLinkage;
378 }
379 static bool isAvailableExternallyLinkage(LinkageTypes Linkage) {
380 return Linkage == AvailableExternallyLinkage;
381 }
382 static bool isLinkOnceAnyLinkage(LinkageTypes Linkage) {
383 return Linkage == LinkOnceAnyLinkage;
384 }
385 static bool isLinkOnceODRLinkage(LinkageTypes Linkage) {
386 return Linkage == LinkOnceODRLinkage;
387 }
388 static bool isLinkOnceLinkage(LinkageTypes Linkage) {
389 return isLinkOnceAnyLinkage(Linkage) || isLinkOnceODRLinkage(Linkage);
390 }
391 static bool isWeakAnyLinkage(LinkageTypes Linkage) {
392 return Linkage == WeakAnyLinkage;
393 }
394 static bool isWeakODRLinkage(LinkageTypes Linkage) {
395 return Linkage == WeakODRLinkage;
396 }
397 static bool isWeakLinkage(LinkageTypes Linkage) {
398 return isWeakAnyLinkage(Linkage) || isWeakODRLinkage(Linkage);
399 }
400 static bool isAppendingLinkage(LinkageTypes Linkage) {
401 return Linkage == AppendingLinkage;
402 }
403 static bool isInternalLinkage(LinkageTypes Linkage) {
404 return Linkage == InternalLinkage;
405 }
406 static bool isPrivateLinkage(LinkageTypes Linkage) {
407 return Linkage == PrivateLinkage;
408 }
409 static bool isLocalLinkage(LinkageTypes Linkage) {
410 return isInternalLinkage(Linkage) || isPrivateLinkage(Linkage);
411 }
412 static bool isExternalWeakLinkage(LinkageTypes Linkage) {
413 return Linkage == ExternalWeakLinkage;
414 }
415 static bool isCommonLinkage(LinkageTypes Linkage) {
416 return Linkage == CommonLinkage;
417 }
418 static bool isValidDeclarationLinkage(LinkageTypes Linkage) {
419 return isExternalWeakLinkage(Linkage) || isExternalLinkage(Linkage);
420 }
421
422 /// Whether the definition of this global may be replaced by something
423 /// non-equivalent at link time. For example, if a function has weak linkage
424 /// then the code defining it may be replaced by different code.
425 static bool isInterposableLinkage(LinkageTypes Linkage) {
426 switch (Linkage) {
427 case WeakAnyLinkage:
428 case LinkOnceAnyLinkage:
429 case CommonLinkage:
430 case ExternalWeakLinkage:
431 return true;
432
433 case AvailableExternallyLinkage:
434 case LinkOnceODRLinkage:
435 case WeakODRLinkage:
436 // The above three cannot be overridden but can be de-refined.
437
438 case ExternalLinkage:
439 case AppendingLinkage:
440 case InternalLinkage:
441 case PrivateLinkage:
442 return false;
443 }
444 llvm_unreachable("Fully covered switch above!");
445 }
446
447 /// Whether the definition of this global may be discarded if it is not used
448 /// in its compilation unit.
449 static bool isDiscardableIfUnused(LinkageTypes Linkage) {
450 return isLinkOnceLinkage(Linkage) || isLocalLinkage(Linkage) ||
451 isAvailableExternallyLinkage(Linkage);
452 }
453
454 /// Whether the definition of this global may be replaced at link time. NB:
455 /// Using this method outside of the code generators is almost always a
456 /// mistake: when working at the IR level use isInterposable instead as it
457 /// knows about ODR semantics.
458 static bool isWeakForLinker(LinkageTypes Linkage) {
459 return Linkage == WeakAnyLinkage || Linkage == WeakODRLinkage ||
460 Linkage == LinkOnceAnyLinkage || Linkage == LinkOnceODRLinkage ||
461 Linkage == CommonLinkage || Linkage == ExternalWeakLinkage;
462 }
463
464 /// Return true if the currently visible definition of this global (if any) is
465 /// exactly the definition we will see at runtime.
466 ///
467 /// Non-exact linkage types inhibits most non-inlining IPO, since a
468 /// differently optimized variant of the same function can have different
469 /// observable or undefined behavior than in the variant currently visible.
470 /// For instance, we could have started with
471 ///
472 /// void foo(int *v) {
473 /// int t = 5 / v[0];
474 /// (void) t;
475 /// }
476 ///
477 /// and "refined" it to
478 ///
479 /// void foo(int *v) { }
480 ///
481 /// However, we cannot infer readnone for `foo`, since that would justify
482 /// DSE'ing a store to `v[0]` across a call to `foo`, which can cause
483 /// undefined behavior if the linker replaces the actual call destination with
484 /// the unoptimized `foo`.
485 ///
486 /// Inlining is okay across non-exact linkage types as long as they're not
487 /// interposable (see \c isInterposable), since in such cases the currently
488 /// visible variant is *a* correct implementation of the original source
489 /// function; it just isn't the *only* correct implementation.
490 bool isDefinitionExact() const {
491 return !mayBeDerefined();
492 }
493
494 /// Return true if this global has an exact defintion.
495 bool hasExactDefinition() const {
496 // While this computes exactly the same thing as
497 // isStrongDefinitionForLinker, the intended uses are different. This
498 // function is intended to help decide if specific inter-procedural
499 // transforms are correct, while isStrongDefinitionForLinker's intended use
500 // is in low level code generation.
501 return !isDeclaration() && isDefinitionExact();
502 }
503
504 /// Return true if this global's definition can be substituted with an
505 /// *arbitrary* definition at link time or load time. We cannot do any IPO or
506 /// inlining across interposable call edges, since the callee can be
507 /// replaced with something arbitrary.
508 bool isInterposable() const;
509 bool canBenefitFromLocalAlias() const;
510
511 bool hasExternalLinkage() const { return isExternalLinkage(Linkage: getLinkage()); }
512 bool hasAvailableExternallyLinkage() const {
513 return isAvailableExternallyLinkage(Linkage: getLinkage());
514 }
515 bool hasLinkOnceLinkage() const { return isLinkOnceLinkage(Linkage: getLinkage()); }
516 bool hasLinkOnceAnyLinkage() const {
517 return isLinkOnceAnyLinkage(Linkage: getLinkage());
518 }
519 bool hasLinkOnceODRLinkage() const {
520 return isLinkOnceODRLinkage(Linkage: getLinkage());
521 }
522 bool hasWeakLinkage() const { return isWeakLinkage(Linkage: getLinkage()); }
523 bool hasWeakAnyLinkage() const { return isWeakAnyLinkage(Linkage: getLinkage()); }
524 bool hasWeakODRLinkage() const { return isWeakODRLinkage(Linkage: getLinkage()); }
525 bool hasAppendingLinkage() const { return isAppendingLinkage(Linkage: getLinkage()); }
526 bool hasInternalLinkage() const { return isInternalLinkage(Linkage: getLinkage()); }
527 bool hasPrivateLinkage() const { return isPrivateLinkage(Linkage: getLinkage()); }
528 bool hasLocalLinkage() const { return isLocalLinkage(Linkage: getLinkage()); }
529 bool hasExternalWeakLinkage() const {
530 return isExternalWeakLinkage(Linkage: getLinkage());
531 }
532 bool hasCommonLinkage() const { return isCommonLinkage(Linkage: getLinkage()); }
533 bool hasValidDeclarationLinkage() const {
534 return isValidDeclarationLinkage(Linkage: getLinkage());
535 }
536
537 void setLinkage(LinkageTypes LT) {
538 if (isLocalLinkage(Linkage: LT)) {
539 Visibility = DefaultVisibility;
540 DllStorageClass = DefaultStorageClass;
541 }
542 Linkage = LT;
543 if (isImplicitDSOLocal())
544 setDSOLocal(true);
545 }
546 LinkageTypes getLinkage() const { return LinkageTypes(Linkage); }
547
548 bool isDiscardableIfUnused() const {
549 return isDiscardableIfUnused(Linkage: getLinkage());
550 }
551
552 bool isWeakForLinker() const { return isWeakForLinker(Linkage: getLinkage()); }
553
554protected:
555 /// Copy all additional attributes (those not needed to create a GlobalValue)
556 /// from the GlobalValue Src to this one.
557 void copyAttributesFrom(const GlobalValue *Src);
558
559public:
560 /// If the given string begins with the GlobalValue name mangling escape
561 /// character '\1', drop it.
562 ///
563 /// This function applies a specific mangling that is used in PGO profiles,
564 /// among other things. If you're trying to get a symbol name for an
565 /// arbitrary GlobalValue, this is not the function you're looking for; see
566 /// Mangler.h.
567 static StringRef dropLLVMManglingEscape(StringRef Name) {
568 Name.consume_front(Prefix: "\1");
569 return Name;
570 }
571
572 /// Return the modified name for a global value suitable to be
573 /// used as the key for a global lookup (e.g. profile or ThinLTO).
574 /// The value's original name is \c Name and has linkage of type
575 /// \c Linkage. The value is defined in module \c FileName.
576 static std::string getGlobalIdentifier(StringRef Name,
577 GlobalValue::LinkageTypes Linkage,
578 StringRef FileName);
579
580 /// Return the modified name for this global value suitable to be
581 /// used as the key for a global lookup (e.g. profile or ThinLTO).
582 std::string getGlobalIdentifier() const;
583
584 /// Declare a type to represent a global unique identifier for a global value.
585 /// This is a 64 bits hash that is used by PGO and ThinLTO to have a compact
586 /// unique way to identify a symbol.
587 using GUID = uint64_t;
588
589 /// Return a 64-bit global unique ID constructed from global value name
590 /// (i.e. returned by getGlobalIdentifier()).
591 static GUID getGUID(StringRef GlobalName) { return MD5Hash(Str: GlobalName); }
592
593 /// Return a 64-bit global unique ID constructed from global value name
594 /// (i.e. returned by getGlobalIdentifier()).
595 GUID getGUID() const { return getGUID(GlobalName: getGlobalIdentifier()); }
596
597 /// @name Materialization
598 /// Materialization is used to construct functions only as they're needed.
599 /// This
600 /// is useful to reduce memory usage in LLVM or parsing work done by the
601 /// BitcodeReader to load the Module.
602 /// @{
603
604 /// If this function's Module is being lazily streamed in functions from disk
605 /// or some other source, this method can be used to check to see if the
606 /// function has been read in yet or not.
607 bool isMaterializable() const;
608
609 /// Make sure this GlobalValue is fully read.
610 Error materialize();
611
612/// @}
613
614 /// Return true if the primary definition of this global value is outside of
615 /// the current translation unit.
616 bool isDeclaration() const;
617
618 bool isDeclarationForLinker() const {
619 if (hasAvailableExternallyLinkage())
620 return true;
621
622 return isDeclaration();
623 }
624
625 /// Returns true if this global's definition will be the one chosen by the
626 /// linker.
627 ///
628 /// NB! Ideally this should not be used at the IR level at all. If you're
629 /// interested in optimization constraints implied by the linker's ability to
630 /// choose an implementation, prefer using \c hasExactDefinition.
631 bool isStrongDefinitionForLinker() const {
632 return !(isDeclarationForLinker() || isWeakForLinker());
633 }
634
635 const GlobalObject *getAliaseeObject() const;
636 GlobalObject *getAliaseeObject() {
637 return const_cast<GlobalObject *>(
638 static_cast<const GlobalValue *>(this)->getAliaseeObject());
639 }
640
641 /// Returns whether this is a reference to an absolute symbol.
642 bool isAbsoluteSymbolRef() const;
643
644 /// If this is an absolute symbol reference, returns the range of the symbol,
645 /// otherwise returns std::nullopt.
646 std::optional<ConstantRange> getAbsoluteSymbolRange() const;
647
648 /// This method unlinks 'this' from the containing module, but does not delete
649 /// it.
650 void removeFromParent();
651
652 /// This method unlinks 'this' from the containing module and deletes it.
653 void eraseFromParent();
654
655 /// Get the module that this global value is contained inside of...
656 Module *getParent() { return Parent; }
657 const Module *getParent() const { return Parent; }
658
659 // Methods for support type inquiry through isa, cast, and dyn_cast:
660 static bool classof(const Value *V) {
661 return V->getValueID() == Value::FunctionVal ||
662 V->getValueID() == Value::GlobalVariableVal ||
663 V->getValueID() == Value::GlobalAliasVal ||
664 V->getValueID() == Value::GlobalIFuncVal;
665 }
666
667 /// True if GV can be left out of the object symbol table. This is the case
668 /// for linkonce_odr values whose address is not significant. While legal, it
669 /// is not normally profitable to omit them from the .o symbol table. Using
670 /// this analysis makes sense when the information can be passed down to the
671 /// linker or we are in LTO.
672 bool canBeOmittedFromSymbolTable() const;
673};
674
675} // end namespace llvm
676
677#endif // LLVM_IR_GLOBALVALUE_H
678

source code of llvm/include/llvm/IR/GlobalValue.h