1 //===-- CGCleanup.h - Classes for cleanups IR generation --------*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 // These classes support the generation of LLVM IR for cleanups.
11 //===----------------------------------------------------------------------===//
13 #ifndef LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
14 #define LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
16 #include "EHScopeStack.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include "llvm/ADT/SmallVector.h"
33 class CodeGenFunction;
35 /// The MS C++ ABI needs a pointer to RTTI data plus some flags to describe the
36 /// type of a catch handler, so we use this wrapper.
37 struct CatchTypeInfo {
42 /// A protected scope for zero-cost EH handling.
44 llvm::BasicBlock *CachedLandingPad;
45 llvm::BasicBlock *CachedEHDispatchBlock;
47 EHScopeStack::stable_iterator EnclosingEHScope;
49 class CommonBitFields {
53 enum { NumCommonBits = 3 };
56 class CatchBitFields {
57 friend class EHCatchScope;
58 unsigned : NumCommonBits;
60 unsigned NumHandlers : 32 - NumCommonBits;
63 class CleanupBitFields {
64 friend class EHCleanupScope;
65 unsigned : NumCommonBits;
67 /// Whether this cleanup needs to be run along normal edges.
68 unsigned IsNormalCleanup : 1;
70 /// Whether this cleanup needs to be run along exception edges.
71 unsigned IsEHCleanup : 1;
73 /// Whether this cleanup is currently active.
74 unsigned IsActive : 1;
76 /// Whether this cleanup is a lifetime marker
77 unsigned IsLifetimeMarker : 1;
79 /// Whether the normal cleanup should test the activation flag.
80 unsigned TestFlagInNormalCleanup : 1;
82 /// Whether the EH cleanup should test the activation flag.
83 unsigned TestFlagInEHCleanup : 1;
85 /// The amount of extra storage needed by the Cleanup.
86 /// Always a multiple of the scope-stack alignment.
87 unsigned CleanupSize : 12;
90 class FilterBitFields {
91 friend class EHFilterScope;
92 unsigned : NumCommonBits;
94 unsigned NumFilters : 32 - NumCommonBits;
98 CommonBitFields CommonBits;
99 CatchBitFields CatchBits;
100 CleanupBitFields CleanupBits;
101 FilterBitFields FilterBits;
105 enum Kind { Cleanup, Catch, Terminate, Filter, PadEnd };
107 EHScope(Kind kind, EHScopeStack::stable_iterator enclosingEHScope)
108 : CachedLandingPad(nullptr), CachedEHDispatchBlock(nullptr),
109 EnclosingEHScope(enclosingEHScope) {
110 CommonBits.Kind = kind;
113 Kind getKind() const { return static_cast<Kind>(CommonBits.Kind); }
115 llvm::BasicBlock *getCachedLandingPad() const {
116 return CachedLandingPad;
119 void setCachedLandingPad(llvm::BasicBlock *block) {
120 CachedLandingPad = block;
123 llvm::BasicBlock *getCachedEHDispatchBlock() const {
124 return CachedEHDispatchBlock;
127 void setCachedEHDispatchBlock(llvm::BasicBlock *block) {
128 CachedEHDispatchBlock = block;
131 bool hasEHBranches() const {
132 if (llvm::BasicBlock *block = getCachedEHDispatchBlock())
133 return !block->use_empty();
137 EHScopeStack::stable_iterator getEnclosingEHScope() const {
138 return EnclosingEHScope;
142 /// A scope which attempts to handle some, possibly all, types of
145 /// Objective C \@finally blocks are represented using a cleanup scope
146 /// after the catch scope.
147 class EHCatchScope : public EHScope {
148 // In effect, we have a flexible array member
149 // Handler Handlers[0];
150 // But that's only standard in C99, not C++, so we have to do
151 // annoying pointer arithmetic instead.
155 /// A type info value, or null (C++ null, not an LLVM null pointer)
159 /// The catch handler for this type.
160 llvm::BasicBlock *Block;
162 bool isCatchAll() const { return Type.RTTI == nullptr; }
166 friend class EHScopeStack;
168 Handler *getHandlers() {
169 return reinterpret_cast<Handler*>(this+1);
172 const Handler *getHandlers() const {
173 return reinterpret_cast<const Handler*>(this+1);
177 static size_t getSizeForNumHandlers(unsigned N) {
178 return sizeof(EHCatchScope) + N * sizeof(Handler);
181 EHCatchScope(unsigned numHandlers,
182 EHScopeStack::stable_iterator enclosingEHScope)
183 : EHScope(Catch, enclosingEHScope) {
184 CatchBits.NumHandlers = numHandlers;
185 assert(CatchBits.NumHandlers == numHandlers && "NumHandlers overflow?");
188 unsigned getNumHandlers() const {
189 return CatchBits.NumHandlers;
192 void setCatchAllHandler(unsigned I, llvm::BasicBlock *Block) {
193 setHandler(I, CatchTypeInfo{nullptr, 0}, Block);
196 void setHandler(unsigned I, llvm::Constant *Type, llvm::BasicBlock *Block) {
197 assert(I < getNumHandlers());
198 getHandlers()[I].Type = CatchTypeInfo{Type, 0};
199 getHandlers()[I].Block = Block;
202 void setHandler(unsigned I, CatchTypeInfo Type, llvm::BasicBlock *Block) {
203 assert(I < getNumHandlers());
204 getHandlers()[I].Type = Type;
205 getHandlers()[I].Block = Block;
208 const Handler &getHandler(unsigned I) const {
209 assert(I < getNumHandlers());
210 return getHandlers()[I];
213 // Clear all handler blocks.
214 // FIXME: it's better to always call clearHandlerBlocks in DTOR and have a
215 // 'takeHandler' or some such function which removes ownership from the
216 // EHCatchScope object if the handlers should live longer than EHCatchScope.
217 void clearHandlerBlocks() {
218 for (unsigned I = 0, N = getNumHandlers(); I != N; ++I)
219 delete getHandler(I).Block;
222 typedef const Handler *iterator;
223 iterator begin() const { return getHandlers(); }
224 iterator end() const { return getHandlers() + getNumHandlers(); }
226 static bool classof(const EHScope *Scope) {
227 return Scope->getKind() == Catch;
231 /// A cleanup scope which generates the cleanup blocks lazily.
232 class alignas(8) EHCleanupScope : public EHScope {
233 /// The nearest normal cleanup scope enclosing this one.
234 EHScopeStack::stable_iterator EnclosingNormal;
236 /// The nearest EH scope enclosing this one.
237 EHScopeStack::stable_iterator EnclosingEH;
239 /// The dual entry/exit block along the normal edge. This is lazily
240 /// created if needed before the cleanup is popped.
241 llvm::BasicBlock *NormalBlock;
243 /// An optional i1 variable indicating whether this cleanup has been
245 llvm::AllocaInst *ActiveFlag;
247 /// Extra information required for cleanups that have resolved
248 /// branches through them. This has to be allocated on the side
249 /// because everything on the cleanup stack has be trivially
252 /// The destinations of normal branch-afters and branch-throughs.
253 llvm::SmallPtrSet<llvm::BasicBlock*, 4> Branches;
255 /// Normal branch-afters.
256 SmallVector<std::pair<llvm::BasicBlock*,llvm::ConstantInt*>, 4>
259 mutable struct ExtInfo *ExtInfo;
261 /// The number of fixups required by enclosing scopes (not including
262 /// this one). If this is the top cleanup scope, all the fixups
263 /// from this index onwards belong to this scope.
266 struct ExtInfo &getExtInfo() {
267 if (!ExtInfo) ExtInfo = new struct ExtInfo();
271 const struct ExtInfo &getExtInfo() const {
272 if (!ExtInfo) ExtInfo = new struct ExtInfo();
277 /// Gets the size required for a lazy cleanup scope with the given
278 /// cleanup-data requirements.
279 static size_t getSizeForCleanupSize(size_t Size) {
280 return sizeof(EHCleanupScope) + Size;
283 size_t getAllocatedSize() const {
284 return sizeof(EHCleanupScope) + CleanupBits.CleanupSize;
287 EHCleanupScope(bool isNormal, bool isEH, bool isActive,
288 unsigned cleanupSize, unsigned fixupDepth,
289 EHScopeStack::stable_iterator enclosingNormal,
290 EHScopeStack::stable_iterator enclosingEH)
291 : EHScope(EHScope::Cleanup, enclosingEH),
292 EnclosingNormal(enclosingNormal), NormalBlock(nullptr),
293 ActiveFlag(nullptr), ExtInfo(nullptr), FixupDepth(fixupDepth) {
294 CleanupBits.IsNormalCleanup = isNormal;
295 CleanupBits.IsEHCleanup = isEH;
296 CleanupBits.IsActive = isActive;
297 CleanupBits.IsLifetimeMarker = false;
298 CleanupBits.TestFlagInNormalCleanup = false;
299 CleanupBits.TestFlagInEHCleanup = false;
300 CleanupBits.CleanupSize = cleanupSize;
302 assert(CleanupBits.CleanupSize == cleanupSize && "cleanup size overflow");
308 // Objects of EHCleanupScope are not destructed. Use Destroy().
309 ~EHCleanupScope() = delete;
311 bool isNormalCleanup() const { return CleanupBits.IsNormalCleanup; }
312 llvm::BasicBlock *getNormalBlock() const { return NormalBlock; }
313 void setNormalBlock(llvm::BasicBlock *BB) { NormalBlock = BB; }
315 bool isEHCleanup() const { return CleanupBits.IsEHCleanup; }
317 bool isActive() const { return CleanupBits.IsActive; }
318 void setActive(bool A) { CleanupBits.IsActive = A; }
320 bool isLifetimeMarker() const { return CleanupBits.IsLifetimeMarker; }
321 void setLifetimeMarker() { CleanupBits.IsLifetimeMarker = true; }
323 bool hasActiveFlag() const { return ActiveFlag != nullptr; }
324 Address getActiveFlag() const {
325 return Address(ActiveFlag, CharUnits::One());
327 void setActiveFlag(Address Var) {
328 assert(Var.getAlignment().isOne());
329 ActiveFlag = cast<llvm::AllocaInst>(Var.getPointer());
332 void setTestFlagInNormalCleanup() {
333 CleanupBits.TestFlagInNormalCleanup = true;
335 bool shouldTestFlagInNormalCleanup() const {
336 return CleanupBits.TestFlagInNormalCleanup;
339 void setTestFlagInEHCleanup() {
340 CleanupBits.TestFlagInEHCleanup = true;
342 bool shouldTestFlagInEHCleanup() const {
343 return CleanupBits.TestFlagInEHCleanup;
346 unsigned getFixupDepth() const { return FixupDepth; }
347 EHScopeStack::stable_iterator getEnclosingNormalCleanup() const {
348 return EnclosingNormal;
351 size_t getCleanupSize() const { return CleanupBits.CleanupSize; }
352 void *getCleanupBuffer() { return this + 1; }
354 EHScopeStack::Cleanup *getCleanup() {
355 return reinterpret_cast<EHScopeStack::Cleanup*>(getCleanupBuffer());
358 /// True if this cleanup scope has any branch-afters or branch-throughs.
359 bool hasBranches() const { return ExtInfo && !ExtInfo->Branches.empty(); }
361 /// Add a branch-after to this cleanup scope. A branch-after is a
362 /// branch from a point protected by this (normal) cleanup to a
363 /// point in the normal cleanup scope immediately containing it.
365 /// for (;;) { A a; break; }
366 /// contains a branch-after.
368 /// Branch-afters each have their own destination out of the
369 /// cleanup, guaranteed distinct from anything else threaded through
370 /// it. Therefore branch-afters usually force a switch after the
372 void addBranchAfter(llvm::ConstantInt *Index,
373 llvm::BasicBlock *Block) {
374 struct ExtInfo &ExtInfo = getExtInfo();
375 if (ExtInfo.Branches.insert(Block).second)
376 ExtInfo.BranchAfters.push_back(std::make_pair(Block, Index));
379 /// Return the number of unique branch-afters on this scope.
380 unsigned getNumBranchAfters() const {
381 return ExtInfo ? ExtInfo->BranchAfters.size() : 0;
384 llvm::BasicBlock *getBranchAfterBlock(unsigned I) const {
385 assert(I < getNumBranchAfters());
386 return ExtInfo->BranchAfters[I].first;
389 llvm::ConstantInt *getBranchAfterIndex(unsigned I) const {
390 assert(I < getNumBranchAfters());
391 return ExtInfo->BranchAfters[I].second;
394 /// Add a branch-through to this cleanup scope. A branch-through is
395 /// a branch from a scope protected by this (normal) cleanup to an
396 /// enclosing scope other than the immediately-enclosing normal
399 /// In the following example, the branch through B's scope is a
400 /// branch-through, while the branch through A's scope is a
402 /// for (;;) { A a; B b; break; }
404 /// All branch-throughs have a common destination out of the
405 /// cleanup, one possibly shared with the fall-through. Therefore
406 /// branch-throughs usually don't force a switch after the cleanup.
408 /// \return true if the branch-through was new to this scope
409 bool addBranchThrough(llvm::BasicBlock *Block) {
410 return getExtInfo().Branches.insert(Block).second;
413 /// Determines if this cleanup scope has any branch throughs.
414 bool hasBranchThroughs() const {
415 if (!ExtInfo) return false;
416 return (ExtInfo->BranchAfters.size() != ExtInfo->Branches.size());
419 static bool classof(const EHScope *Scope) {
420 return (Scope->getKind() == Cleanup);
423 // NOTE: there's a bunch of different data classes tacked on after an
424 // EHCleanupScope. It is asserted (in EHScopeStack::pushCleanup*) that
425 // they don't require greater alignment than ScopeStackAlignment. So,
426 // EHCleanupScope ought to have alignment equal to that -- not more
427 // (would be misaligned by the stack allocator), and not less (would
428 // break the appended classes).
429 static_assert(alignof(EHCleanupScope) == EHScopeStack::ScopeStackAlignment,
430 "EHCleanupScope expected alignment");
432 /// An exceptions scope which filters exceptions thrown through it.
433 /// Only exceptions matching the filter types will be permitted to be
436 /// This is used to implement C++ exception specifications.
437 class EHFilterScope : public EHScope {
438 // Essentially ends in a flexible array member:
439 // llvm::Value *FilterTypes[0];
441 llvm::Value **getFilters() {
442 return reinterpret_cast<llvm::Value**>(this+1);
445 llvm::Value * const *getFilters() const {
446 return reinterpret_cast<llvm::Value* const *>(this+1);
450 EHFilterScope(unsigned numFilters)
451 : EHScope(Filter, EHScopeStack::stable_end()) {
452 FilterBits.NumFilters = numFilters;
453 assert(FilterBits.NumFilters == numFilters && "NumFilters overflow");
456 static size_t getSizeForNumFilters(unsigned numFilters) {
457 return sizeof(EHFilterScope) + numFilters * sizeof(llvm::Value*);
460 unsigned getNumFilters() const { return FilterBits.NumFilters; }
462 void setFilter(unsigned i, llvm::Value *filterValue) {
463 assert(i < getNumFilters());
464 getFilters()[i] = filterValue;
467 llvm::Value *getFilter(unsigned i) const {
468 assert(i < getNumFilters());
469 return getFilters()[i];
472 static bool classof(const EHScope *scope) {
473 return scope->getKind() == Filter;
477 /// An exceptions scope which calls std::terminate if any exception
479 class EHTerminateScope : public EHScope {
481 EHTerminateScope(EHScopeStack::stable_iterator enclosingEHScope)
482 : EHScope(Terminate, enclosingEHScope) {}
483 static size_t getSize() { return sizeof(EHTerminateScope); }
485 static bool classof(const EHScope *scope) {
486 return scope->getKind() == Terminate;
490 class EHPadEndScope : public EHScope {
492 EHPadEndScope(EHScopeStack::stable_iterator enclosingEHScope)
493 : EHScope(PadEnd, enclosingEHScope) {}
494 static size_t getSize() { return sizeof(EHPadEndScope); }
496 static bool classof(const EHScope *scope) {
497 return scope->getKind() == PadEnd;
501 /// A non-stable pointer into the scope stack.
502 class EHScopeStack::iterator {
505 friend class EHScopeStack;
506 explicit iterator(char *Ptr) : Ptr(Ptr) {}
509 iterator() : Ptr(nullptr) {}
511 EHScope *get() const {
512 return reinterpret_cast<EHScope*>(Ptr);
515 EHScope *operator->() const { return get(); }
516 EHScope &operator*() const { return *get(); }
518 iterator &operator++() {
520 switch (get()->getKind()) {
522 Size = EHCatchScope::getSizeForNumHandlers(
523 static_cast<const EHCatchScope *>(get())->getNumHandlers());
526 case EHScope::Filter:
527 Size = EHFilterScope::getSizeForNumFilters(
528 static_cast<const EHFilterScope *>(get())->getNumFilters());
531 case EHScope::Cleanup:
532 Size = static_cast<const EHCleanupScope *>(get())->getAllocatedSize();
535 case EHScope::Terminate:
536 Size = EHTerminateScope::getSize();
539 case EHScope::PadEnd:
540 Size = EHPadEndScope::getSize();
543 Ptr += llvm::alignTo(Size, ScopeStackAlignment);
548 iterator copy = *this;
553 iterator operator++(int) {
554 iterator copy = *this;
559 bool encloses(iterator other) const { return Ptr >= other.Ptr; }
560 bool strictlyEncloses(iterator other) const { return Ptr > other.Ptr; }
562 bool operator==(iterator other) const { return Ptr == other.Ptr; }
563 bool operator!=(iterator other) const { return Ptr != other.Ptr; }
566 inline EHScopeStack::iterator EHScopeStack::begin() const {
567 return iterator(StartOfData);
570 inline EHScopeStack::iterator EHScopeStack::end() const {
571 return iterator(EndOfBuffer);
574 inline void EHScopeStack::popCatch() {
575 assert(!empty() && "popping exception stack when not empty");
577 EHCatchScope &scope = cast<EHCatchScope>(*begin());
578 InnermostEHScope = scope.getEnclosingEHScope();
579 deallocate(EHCatchScope::getSizeForNumHandlers(scope.getNumHandlers()));
582 inline void EHScopeStack::popTerminate() {
583 assert(!empty() && "popping exception stack when not empty");
585 EHTerminateScope &scope = cast<EHTerminateScope>(*begin());
586 InnermostEHScope = scope.getEnclosingEHScope();
587 deallocate(EHTerminateScope::getSize());
590 inline EHScopeStack::iterator EHScopeStack::find(stable_iterator sp) const {
591 assert(sp.isValid() && "finding invalid savepoint");
592 assert(sp.Size <= stable_begin().Size && "finding savepoint after pop");
593 return iterator(EndOfBuffer - sp.Size);
596 inline EHScopeStack::stable_iterator
597 EHScopeStack::stabilize(iterator ir) const {
598 assert(StartOfData <= ir.Ptr && ir.Ptr <= EndOfBuffer);
599 return stable_iterator(EndOfBuffer - ir.Ptr);
602 /// The exceptions personality for a function.
603 struct EHPersonality {
604 const char *PersonalityFn;
606 // If this is non-null, this personality requires a non-standard
607 // function for rethrowing an exception after a catchall cleanup.
608 // This function must have prototype void(void*).
609 const char *CatchallRethrowFn;
611 static const EHPersonality &get(CodeGenModule &CGM, const FunctionDecl *FD);
612 static const EHPersonality &get(CodeGenFunction &CGF);
614 static const EHPersonality GNU_C;
615 static const EHPersonality GNU_C_SJLJ;
616 static const EHPersonality GNU_C_SEH;
617 static const EHPersonality GNU_ObjC;
618 static const EHPersonality GNU_ObjC_SJLJ;
619 static const EHPersonality GNU_ObjC_SEH;
620 static const EHPersonality GNUstep_ObjC;
621 static const EHPersonality GNU_ObjCXX;
622 static const EHPersonality NeXT_ObjC;
623 static const EHPersonality GNU_CPlusPlus;
624 static const EHPersonality GNU_CPlusPlus_SJLJ;
625 static const EHPersonality GNU_CPlusPlus_SEH;
626 static const EHPersonality MSVC_except_handler;
627 static const EHPersonality MSVC_C_specific_handler;
628 static const EHPersonality MSVC_CxxFrameHandler3;
629 static const EHPersonality GNU_Wasm_CPlusPlus;
631 /// Does this personality use landingpads or the family of pad instructions
632 /// designed to form funclets?
633 bool usesFuncletPads() const {
634 return isMSVCPersonality() || isWasmPersonality();
637 bool isMSVCPersonality() const {
638 return this == &MSVC_except_handler || this == &MSVC_C_specific_handler ||
639 this == &MSVC_CxxFrameHandler3;
642 bool isWasmPersonality() const { return this == &GNU_Wasm_CPlusPlus; }
644 bool isMSVCXXPersonality() const { return this == &MSVC_CxxFrameHandler3; }