1//===-- CGCleanup.h - Classes for cleanups IR generation --------*- 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// These classes support the generation of LLVM IR for cleanups.
10//
11//===----------------------------------------------------------------------===//
12
13#ifndef LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
14#define LLVM_CLANG_LIB_CODEGEN_CGCLEANUP_H
15
16#include "EHScopeStack.h"
17
18#include "Address.h"
19#include "llvm/ADT/SmallPtrSet.h"
20#include "llvm/ADT/SmallVector.h"
21
22namespace llvm {
23class BasicBlock;
24class Value;
25class ConstantInt;
26class AllocaInst;
27}
28
29namespace clang {
30class FunctionDecl;
31namespace CodeGen {
32class CodeGenModule;
33class CodeGenFunction;
34
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.
37struct CatchTypeInfo {
38 llvm::Constant *RTTI;
39 unsigned Flags;
40};
41
42/// A protected scope for zero-cost EH handling.
43class EHScope {
44 llvm::BasicBlock *CachedLandingPad;
45 llvm::BasicBlock *CachedEHDispatchBlock;
46
47 EHScopeStack::stable_iterator EnclosingEHScope;
48
49 class CommonBitFields {
50 friend class EHScope;
51 unsigned Kind : 3;
52 };
53 enum { NumCommonBits = 3 };
54
55protected:
56 class CatchBitFields {
57 friend class EHCatchScope;
58 unsigned : NumCommonBits;
59
60 unsigned NumHandlers : 32 - NumCommonBits;
61 };
62
63 class CleanupBitFields {
64 friend class EHCleanupScope;
65 unsigned : NumCommonBits;
66
67 /// Whether this cleanup needs to be run along normal edges.
68 unsigned IsNormalCleanup : 1;
69
70 /// Whether this cleanup needs to be run along exception edges.
71 unsigned IsEHCleanup : 1;
72
73 /// Whether this cleanup is currently active.
74 unsigned IsActive : 1;
75
76 /// Whether this cleanup is a lifetime marker
77 unsigned IsLifetimeMarker : 1;
78
79 /// Whether the normal cleanup should test the activation flag.
80 unsigned TestFlagInNormalCleanup : 1;
81
82 /// Whether the EH cleanup should test the activation flag.
83 unsigned TestFlagInEHCleanup : 1;
84
85 /// The amount of extra storage needed by the Cleanup.
86 /// Always a multiple of the scope-stack alignment.
87 unsigned CleanupSize : 12;
88 };
89
90 class FilterBitFields {
91 friend class EHFilterScope;
92 unsigned : NumCommonBits;
93
94 unsigned NumFilters : 32 - NumCommonBits;
95 };
96
97 union {
98 CommonBitFields CommonBits;
99 CatchBitFields CatchBits;
100 CleanupBitFields CleanupBits;
101 FilterBitFields FilterBits;
102 };
103
104public:
105 enum Kind { Cleanup, Catch, Terminate, Filter };
106
107 EHScope(Kind kind, EHScopeStack::stable_iterator enclosingEHScope)
108 : CachedLandingPad(nullptr), CachedEHDispatchBlock(nullptr),
109 EnclosingEHScope(enclosingEHScope) {
110 CommonBits.Kind = kind;
111 }
112
113 Kind getKind() const { return static_cast<Kind>(CommonBits.Kind); }
114
115 llvm::BasicBlock *getCachedLandingPad() const {
116 return CachedLandingPad;
117 }
118
119 void setCachedLandingPad(llvm::BasicBlock *block) {
120 CachedLandingPad = block;
121 }
122
123 llvm::BasicBlock *getCachedEHDispatchBlock() const {
124 return CachedEHDispatchBlock;
125 }
126
127 void setCachedEHDispatchBlock(llvm::BasicBlock *block) {
128 CachedEHDispatchBlock = block;
129 }
130
131 bool hasEHBranches() const {
132 if (llvm::BasicBlock *block = getCachedEHDispatchBlock())
133 return !block->use_empty();
134 return false;
135 }
136
137 EHScopeStack::stable_iterator getEnclosingEHScope() const {
138 return EnclosingEHScope;
139 }
140};
141
142/// A scope which attempts to handle some, possibly all, types of
143/// exceptions.
144///
145/// Objective C \@finally blocks are represented using a cleanup scope
146/// after the catch scope.
147class 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.
152
153public:
154 struct Handler {
155 /// A type info value, or null (C++ null, not an LLVM null pointer)
156 /// for a catch-all.
157 CatchTypeInfo Type;
158
159 /// The catch handler for this type.
160 llvm::BasicBlock *Block;
161
162 bool isCatchAll() const { return Type.RTTI == nullptr; }
163 };
164
165private:
166 friend class EHScopeStack;
167
168 Handler *getHandlers() {
169 return reinterpret_cast<Handler*>(this+1);
170 }
171
172 const Handler *getHandlers() const {
173 return reinterpret_cast<const Handler*>(this+1);
174 }
175
176public:
177 static size_t getSizeForNumHandlers(unsigned N) {
178 return sizeof(EHCatchScope) + N * sizeof(Handler);
179 }
180
181 EHCatchScope(unsigned numHandlers,
182 EHScopeStack::stable_iterator enclosingEHScope)
183 : EHScope(Catch, enclosingEHScope) {
184 CatchBits.NumHandlers = numHandlers;
185 assert(CatchBits.NumHandlers == numHandlers && "NumHandlers overflow?");
186 }
187
188 unsigned getNumHandlers() const {
189 return CatchBits.NumHandlers;
190 }
191
192 void setCatchAllHandler(unsigned I, llvm::BasicBlock *Block) {
193 setHandler(I, CatchTypeInfo{nullptr, 0}, Block);
194 }
195
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;
200 }
201
202 void setHandler(unsigned I, CatchTypeInfo Type, llvm::BasicBlock *Block) {
203 assert(I < getNumHandlers());
204 getHandlers()[I].Type = Type;
205 getHandlers()[I].Block = Block;
206 }
207
208 const Handler &getHandler(unsigned I) const {
209 assert(I < getNumHandlers());
210 return getHandlers()[I];
211 }
212
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;
220 }
221
222 typedef const Handler *iterator;
223 iterator begin() const { return getHandlers(); }
224 iterator end() const { return getHandlers() + getNumHandlers(); }
225
226 static bool classof(const EHScope *Scope) {
227 return Scope->getKind() == Catch;
228 }
229};
230
231/// A cleanup scope which generates the cleanup blocks lazily.
232class alignas(8) EHCleanupScope : public EHScope {
233 /// The nearest normal cleanup scope enclosing this one.
234 EHScopeStack::stable_iterator EnclosingNormal;
235
236 /// The nearest EH scope enclosing this one.
237 EHScopeStack::stable_iterator EnclosingEH;
238
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;
242
243 /// An optional i1 variable indicating whether this cleanup has been
244 /// activated yet.
245 llvm::AllocaInst *ActiveFlag;
246
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
250 /// movable.
251 struct ExtInfo {
252 /// The destinations of normal branch-afters and branch-throughs.
253 llvm::SmallPtrSet<llvm::BasicBlock*, 4> Branches;
254
255 /// Normal branch-afters.
256 SmallVector<std::pair<llvm::BasicBlock*,llvm::ConstantInt*>, 4>
257 BranchAfters;
258 };
259 mutable struct ExtInfo *ExtInfo;
260
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.
264 unsigned FixupDepth;
265
266 struct ExtInfo &getExtInfo() {
267 if (!ExtInfo) ExtInfo = new struct ExtInfo();
268 return *ExtInfo;
269 }
270
271 const struct ExtInfo &getExtInfo() const {
272 if (!ExtInfo) ExtInfo = new struct ExtInfo();
273 return *ExtInfo;
274 }
275
276public:
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;
281 }
282
283 size_t getAllocatedSize() const {
284 return sizeof(EHCleanupScope) + CleanupBits.CleanupSize;
285 }
286
287 EHCleanupScope(bool isNormal, bool isEH, unsigned cleanupSize,
288 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 = true;
297 CleanupBits.IsLifetimeMarker = false;
298 CleanupBits.TestFlagInNormalCleanup = false;
299 CleanupBits.TestFlagInEHCleanup = false;
300 CleanupBits.CleanupSize = cleanupSize;
301
302 assert(CleanupBits.CleanupSize == cleanupSize && "cleanup size overflow");
303 }
304
305 void Destroy() {
306 delete ExtInfo;
307 }
308 // Objects of EHCleanupScope are not destructed. Use Destroy().
309 ~EHCleanupScope() = delete;
310
311 bool isNormalCleanup() const { return CleanupBits.IsNormalCleanup; }
312 llvm::BasicBlock *getNormalBlock() const { return NormalBlock; }
313 void setNormalBlock(llvm::BasicBlock *BB) { NormalBlock = BB; }
314
315 bool isEHCleanup() const { return CleanupBits.IsEHCleanup; }
316
317 bool isActive() const { return CleanupBits.IsActive; }
318 void setActive(bool A) { CleanupBits.IsActive = A; }
319
320 bool isLifetimeMarker() const { return CleanupBits.IsLifetimeMarker; }
321 void setLifetimeMarker() { CleanupBits.IsLifetimeMarker = true; }
322
323 bool hasActiveFlag() const { return ActiveFlag != nullptr; }
324 Address getActiveFlag() const {
325 return Address(ActiveFlag, CharUnits::One());
326 }
327 void setActiveFlag(Address Var) {
328 assert(Var.getAlignment().isOne());
329 ActiveFlag = cast<llvm::AllocaInst>(Var.getPointer());
330 }
331
332 void setTestFlagInNormalCleanup() {
333 CleanupBits.TestFlagInNormalCleanup = true;
334 }
335 bool shouldTestFlagInNormalCleanup() const {
336 return CleanupBits.TestFlagInNormalCleanup;
337 }
338
339 void setTestFlagInEHCleanup() {
340 CleanupBits.TestFlagInEHCleanup = true;
341 }
342 bool shouldTestFlagInEHCleanup() const {
343 return CleanupBits.TestFlagInEHCleanup;
344 }
345
346 unsigned getFixupDepth() const { return FixupDepth; }
347 EHScopeStack::stable_iterator getEnclosingNormalCleanup() const {
348 return EnclosingNormal;
349 }
350
351 size_t getCleanupSize() const { return CleanupBits.CleanupSize; }
352 void *getCleanupBuffer() { return this + 1; }
353
354 EHScopeStack::Cleanup *getCleanup() {
355 return reinterpret_cast<EHScopeStack::Cleanup*>(getCleanupBuffer());
356 }
357
358 /// True if this cleanup scope has any branch-afters or branch-throughs.
359 bool hasBranches() const { return ExtInfo && !ExtInfo->Branches.empty(); }
360
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.
364 /// For example,
365 /// for (;;) { A a; break; }
366 /// contains a branch-after.
367 ///
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
371 /// cleanup.
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));
377 }
378
379 /// Return the number of unique branch-afters on this scope.
380 unsigned getNumBranchAfters() const {
381 return ExtInfo ? ExtInfo->BranchAfters.size() : 0;
382 }
383
384 llvm::BasicBlock *getBranchAfterBlock(unsigned I) const {
385 assert(I < getNumBranchAfters());
386 return ExtInfo->BranchAfters[I].first;
387 }
388
389 llvm::ConstantInt *getBranchAfterIndex(unsigned I) const {
390 assert(I < getNumBranchAfters());
391 return ExtInfo->BranchAfters[I].second;
392 }
393
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
397 /// cleanup scope.
398 ///
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
401 /// branch-after:
402 /// for (;;) { A a; B b; break; }
403 ///
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.
407 ///
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;
411 }
412
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());
417 }
418
419 static bool classof(const EHScope *Scope) {
420 return (Scope->getKind() == Cleanup);
421 }
422};
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).
429static_assert(alignof(EHCleanupScope) == EHScopeStack::ScopeStackAlignment,
430 "EHCleanupScope expected alignment");
431
432/// An exceptions scope which filters exceptions thrown through it.
433/// Only exceptions matching the filter types will be permitted to be
434/// thrown.
435///
436/// This is used to implement C++ exception specifications.
437class EHFilterScope : public EHScope {
438 // Essentially ends in a flexible array member:
439 // llvm::Value *FilterTypes[0];
440
441 llvm::Value **getFilters() {
442 return reinterpret_cast<llvm::Value**>(this+1);
443 }
444
445 llvm::Value * const *getFilters() const {
446 return reinterpret_cast<llvm::Value* const *>(this+1);
447 }
448
449public:
450 EHFilterScope(unsigned numFilters)
451 : EHScope(Filter, EHScopeStack::stable_end()) {
452 FilterBits.NumFilters = numFilters;
453 assert(FilterBits.NumFilters == numFilters && "NumFilters overflow");
454 }
455
456 static size_t getSizeForNumFilters(unsigned numFilters) {
457 return sizeof(EHFilterScope) + numFilters * sizeof(llvm::Value*);
458 }
459
460 unsigned getNumFilters() const { return FilterBits.NumFilters; }
461
462 void setFilter(unsigned i, llvm::Value *filterValue) {
463 assert(i < getNumFilters());
464 getFilters()[i] = filterValue;
465 }
466
467 llvm::Value *getFilter(unsigned i) const {
468 assert(i < getNumFilters());
469 return getFilters()[i];
470 }
471
472 static bool classof(const EHScope *scope) {
473 return scope->getKind() == Filter;
474 }
475};
476
477/// An exceptions scope which calls std::terminate if any exception
478/// reaches it.
479class EHTerminateScope : public EHScope {
480public:
481 EHTerminateScope(EHScopeStack::stable_iterator enclosingEHScope)
482 : EHScope(Terminate, enclosingEHScope) {}
483 static size_t getSize() { return sizeof(EHTerminateScope); }
484
485 static bool classof(const EHScope *scope) {
486 return scope->getKind() == Terminate;
487 }
488};
489
490/// A non-stable pointer into the scope stack.
491class EHScopeStack::iterator {
492 char *Ptr;
493
494 friend class EHScopeStack;
495 explicit iterator(char *Ptr) : Ptr(Ptr) {}
496
497public:
498 iterator() : Ptr(nullptr) {}
499
500 EHScope *get() const {
501 return reinterpret_cast<EHScope*>(Ptr);
502 }
503
504 EHScope *operator->() const { return get(); }
505 EHScope &operator*() const { return *get(); }
506
507 iterator &operator++() {
508 size_t Size;
509 switch (get()->getKind()) {
510 case EHScope::Catch:
511 Size = EHCatchScope::getSizeForNumHandlers(
512 static_cast<const EHCatchScope *>(get())->getNumHandlers());
513 break;
514
515 case EHScope::Filter:
516 Size = EHFilterScope::getSizeForNumFilters(
517 static_cast<const EHFilterScope *>(get())->getNumFilters());
518 break;
519
520 case EHScope::Cleanup:
521 Size = static_cast<const EHCleanupScope *>(get())->getAllocatedSize();
522 break;
523
524 case EHScope::Terminate:
525 Size = EHTerminateScope::getSize();
526 break;
527 }
528 Ptr += llvm::alignTo(Size, ScopeStackAlignment);
529 return *this;
530 }
531
532 iterator next() {
533 iterator copy = *this;
534 ++copy;
535 return copy;
536 }
537
538 iterator operator++(int) {
539 iterator copy = *this;
540 operator++();
541 return copy;
542 }
543
544 bool encloses(iterator other) const { return Ptr >= other.Ptr; }
545 bool strictlyEncloses(iterator other) const { return Ptr > other.Ptr; }
546
547 bool operator==(iterator other) const { return Ptr == other.Ptr; }
548 bool operator!=(iterator other) const { return Ptr != other.Ptr; }
549};
550
551inline EHScopeStack::iterator EHScopeStack::begin() const {
552 return iterator(StartOfData);
553}
554
555inline EHScopeStack::iterator EHScopeStack::end() const {
556 return iterator(EndOfBuffer);
557}
558
559inline void EHScopeStack::popCatch() {
560 assert(!empty() && "popping exception stack when not empty");
561
562 EHCatchScope &scope = cast<EHCatchScope>(*begin());
563 InnermostEHScope = scope.getEnclosingEHScope();
564 deallocate(EHCatchScope::getSizeForNumHandlers(scope.getNumHandlers()));
565}
566
567inline void EHScopeStack::popTerminate() {
568 assert(!empty() && "popping exception stack when not empty");
569
570 EHTerminateScope &scope = cast<EHTerminateScope>(*begin());
571 InnermostEHScope = scope.getEnclosingEHScope();
572 deallocate(EHTerminateScope::getSize());
573}
574
575inline EHScopeStack::iterator EHScopeStack::find(stable_iterator sp) const {
576 assert(sp.isValid() && "finding invalid savepoint");
577 assert(sp.Size <= stable_begin().Size && "finding savepoint after pop");
578 return iterator(EndOfBuffer - sp.Size);
579}
580
581inline EHScopeStack::stable_iterator
582EHScopeStack::stabilize(iterator ir) const {
583 assert(StartOfData <= ir.Ptr && ir.Ptr <= EndOfBuffer);
584 return stable_iterator(EndOfBuffer - ir.Ptr);
585}
586
587/// The exceptions personality for a function.
588struct EHPersonality {
589 const char *PersonalityFn;
590
591 // If this is non-null, this personality requires a non-standard
592 // function for rethrowing an exception after a catchall cleanup.
593 // This function must have prototype void(void*).
594 const char *CatchallRethrowFn;
595
596 static const EHPersonality &get(CodeGenModule &CGM, const FunctionDecl *FD);
597 static const EHPersonality &get(CodeGenFunction &CGF);
598
599 static const EHPersonality GNU_C;
600 static const EHPersonality GNU_C_SJLJ;
601 static const EHPersonality GNU_C_SEH;
602 static const EHPersonality GNU_ObjC;
603 static const EHPersonality GNU_ObjC_SJLJ;
604 static const EHPersonality GNU_ObjC_SEH;
605 static const EHPersonality GNUstep_ObjC;
606 static const EHPersonality GNU_ObjCXX;
607 static const EHPersonality NeXT_ObjC;
608 static const EHPersonality GNU_CPlusPlus;
609 static const EHPersonality GNU_CPlusPlus_SJLJ;
610 static const EHPersonality GNU_CPlusPlus_SEH;
611 static const EHPersonality MSVC_except_handler;
612 static const EHPersonality MSVC_C_specific_handler;
613 static const EHPersonality MSVC_CxxFrameHandler3;
614 static const EHPersonality GNU_Wasm_CPlusPlus;
615 static const EHPersonality XL_CPlusPlus;
616
617 /// Does this personality use landingpads or the family of pad instructions
618 /// designed to form funclets?
619 bool usesFuncletPads() const {
620 return isMSVCPersonality() || isWasmPersonality();
621 }
622
623 bool isMSVCPersonality() const {
624 return this == &MSVC_except_handler || this == &MSVC_C_specific_handler ||
625 this == &MSVC_CxxFrameHandler3;
626 }
627
628 bool isWasmPersonality() const { return this == &GNU_Wasm_CPlusPlus; }
629
630 bool isMSVCXXPersonality() const { return this == &MSVC_CxxFrameHandler3; }
631};
632}
633}
634
635#endif
636