CGDecl.cpp revision ddfc8a1e68ac67d748ca918acac8f1c78a51395c 
1//===--- CGDecl.cpp - Emit LLVM Code for declarations ---------------------===//
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 contains code to emit Decl nodes as LLVM code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CGDebugInfo.h"
15#include "CodeGenFunction.h"
16#include "CodeGenModule.h"
17#include "CGOpenCLRuntime.h"
18#include "clang/AST/ASTContext.h"
19#include "clang/AST/CharUnits.h"
20#include "clang/AST/Decl.h"
21#include "clang/AST/DeclObjC.h"
22#include "clang/Basic/SourceManager.h"
23#include "clang/Basic/TargetInfo.h"
24#include "clang/Frontend/CodeGenOptions.h"
25#include "llvm/GlobalVariable.h"
26#include "llvm/Intrinsics.h"
27#include "llvm/Target/TargetData.h"
28#include "llvm/Type.h"
29using namespace clang;
30using namespace CodeGen;
31
32
33void CodeGenFunction::EmitDecl(const Decl &D) {
34  switch (D.getKind()) {
35  case Decl::TranslationUnit:
36  case Decl::Namespace:
37  case Decl::UnresolvedUsingTypename:
38  case Decl::ClassTemplateSpecialization:
39  case Decl::ClassTemplatePartialSpecialization:
40  case Decl::TemplateTypeParm:
41  case Decl::UnresolvedUsingValue:
42  case Decl::NonTypeTemplateParm:
43  case Decl::CXXMethod:
44  case Decl::CXXConstructor:
45  case Decl::CXXDestructor:
46  case Decl::CXXConversion:
47  case Decl::Field:
48  case Decl::IndirectField:
49  case Decl::ObjCIvar:
50  case Decl::ObjCAtDefsField:
51  case Decl::ParmVar:
52  case Decl::ImplicitParam:
53  case Decl::ClassTemplate:
54  case Decl::FunctionTemplate:
55  case Decl::TypeAliasTemplate:
56  case Decl::TemplateTemplateParm:
57  case Decl::ObjCMethod:
58  case Decl::ObjCCategory:
59  case Decl::ObjCProtocol:
60  case Decl::ObjCInterface:
61  case Decl::ObjCCategoryImpl:
62  case Decl::ObjCImplementation:
63  case Decl::ObjCProperty:
64  case Decl::ObjCCompatibleAlias:
65  case Decl::AccessSpec:
66  case Decl::LinkageSpec:
67  case Decl::ObjCPropertyImpl:
68  case Decl::FileScopeAsm:
69  case Decl::Friend:
70  case Decl::FriendTemplate:
71  case Decl::Block:
72  case Decl::ClassScopeFunctionSpecialization:
73    llvm_unreachable("Declaration should not be in declstmts!");
74  case Decl::Function:  // void X();
75  case Decl::Record:    // struct/union/class X;
76  case Decl::Enum:      // enum X;
77  case Decl::EnumConstant: // enum ? { X = ? }
78  case Decl::CXXRecord: // struct/union/class X; [C++]
79  case Decl::Using:          // using X; [C++]
80  case Decl::UsingShadow:
81  case Decl::UsingDirective: // using namespace X; [C++]
82  case Decl::NamespaceAlias:
83  case Decl::StaticAssert: // static_assert(X, ""); [C++0x]
84  case Decl::Label:        // __label__ x;
85  case Decl::Import:
86    // None of these decls require codegen support.
87    return;
88
89  case Decl::Var: {
90    const VarDecl &VD = cast<VarDecl>(D);
91    assert(VD.isLocalVarDecl() &&
92           "Should not see file-scope variables inside a function!");
93    return EmitVarDecl(VD);
94  }
95
96  case Decl::Typedef:      // typedef int X;
97  case Decl::TypeAlias: {  // using X = int; [C++0x]
98    const TypedefNameDecl &TD = cast<TypedefNameDecl>(D);
99    QualType Ty = TD.getUnderlyingType();
100
101    if (Ty->isVariablyModifiedType())
102      EmitVariablyModifiedType(Ty);
103  }
104  }
105}
106
107/// EmitVarDecl - This method handles emission of any variable declaration
108/// inside a function, including static vars etc.
109void CodeGenFunction::EmitVarDecl(const VarDecl &D) {
110  switch (D.getStorageClass()) {
111  case SC_None:
112  case SC_Auto:
113  case SC_Register:
114    return EmitAutoVarDecl(D);
115  case SC_Static: {
116    llvm::GlobalValue::LinkageTypes Linkage =
117      llvm::GlobalValue::InternalLinkage;
118
119    // If the function definition has some sort of weak linkage, its
120    // static variables should also be weak so that they get properly
121    // uniqued.  We can't do this in C, though, because there's no
122    // standard way to agree on which variables are the same (i.e.
123    // there's no mangling).
124    if (getContext().getLangOpts().CPlusPlus)
125      if (llvm::GlobalValue::isWeakForLinker(CurFn->getLinkage()))
126        Linkage = CurFn->getLinkage();
127
128    return EmitStaticVarDecl(D, Linkage);
129  }
130  case SC_Extern:
131  case SC_PrivateExtern:
132    // Don't emit it now, allow it to be emitted lazily on its first use.
133    return;
134  case SC_OpenCLWorkGroupLocal:
135    return CGM.getOpenCLRuntime().EmitWorkGroupLocalVarDecl(*this, D);
136  }
137
138  llvm_unreachable("Unknown storage class");
139}
140
141static std::string GetStaticDeclName(CodeGenFunction &CGF, const VarDecl &D,
142                                     const char *Separator) {
143  CodeGenModule &CGM = CGF.CGM;
144  if (CGF.getContext().getLangOpts().CPlusPlus) {
145    StringRef Name = CGM.getMangledName(&D);
146    return Name.str();
147  }
148
149  std::string ContextName;
150  if (!CGF.CurFuncDecl) {
151    // Better be in a block declared in global scope.
152    const NamedDecl *ND = cast<NamedDecl>(&D);
153    const DeclContext *DC = ND->getDeclContext();
154    if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) {
155      MangleBuffer Name;
156      CGM.getBlockMangledName(GlobalDecl(), Name, BD);
157      ContextName = Name.getString();
158    }
159    else
160      llvm_unreachable("Unknown context for block static var decl");
161  } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CGF.CurFuncDecl)) {
162    StringRef Name = CGM.getMangledName(FD);
163    ContextName = Name.str();
164  } else if (isa<ObjCMethodDecl>(CGF.CurFuncDecl))
165    ContextName = CGF.CurFn->getName();
166  else
167    llvm_unreachable("Unknown context for static var decl");
168
169  return ContextName + Separator + D.getNameAsString();
170}
171
172llvm::GlobalVariable *
173CodeGenFunction::CreateStaticVarDecl(const VarDecl &D,
174                                     const char *Separator,
175                                     llvm::GlobalValue::LinkageTypes Linkage) {
176  QualType Ty = D.getType();
177  assert(Ty->isConstantSizeType() && "VLAs can't be static");
178
179  // Use the label if the variable is renamed with the asm-label extension.
180  std::string Name;
181  if (D.hasAttr<AsmLabelAttr>())
182    Name = CGM.getMangledName(&D);
183  else
184    Name = GetStaticDeclName(*this, D, Separator);
185
186  llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
187  llvm::GlobalVariable *GV =
188    new llvm::GlobalVariable(CGM.getModule(), LTy,
189                             Ty.isConstant(getContext()), Linkage,
190                             CGM.EmitNullConstant(D.getType()), Name, 0,
191                             D.isThreadSpecified(),
192                             CGM.getContext().getTargetAddressSpace(Ty));
193  GV->setAlignment(getContext().getDeclAlign(&D).getQuantity());
194  if (Linkage != llvm::GlobalValue::InternalLinkage)
195    GV->setVisibility(CurFn->getVisibility());
196  return GV;
197}
198
199/// hasNontrivialDestruction - Determine whether a type's destruction is
200/// non-trivial. If so, and the variable uses static initialization, we must
201/// register its destructor to run on exit.
202static bool hasNontrivialDestruction(QualType T) {
203  CXXRecordDecl *RD = T->getBaseElementTypeUnsafe()->getAsCXXRecordDecl();
204  return RD && !RD->hasTrivialDestructor();
205}
206
207/// AddInitializerToStaticVarDecl - Add the initializer for 'D' to the
208/// global variable that has already been created for it.  If the initializer
209/// has a different type than GV does, this may free GV and return a different
210/// one.  Otherwise it just returns GV.
211llvm::GlobalVariable *
212CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D,
213                                               llvm::GlobalVariable *GV) {
214  llvm::Constant *Init = CGM.EmitConstantInit(D, this);
215
216  // If constant emission failed, then this should be a C++ static
217  // initializer.
218  if (!Init) {
219    if (!getContext().getLangOpts().CPlusPlus)
220      CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
221    else if (Builder.GetInsertBlock()) {
222      // Since we have a static initializer, this global variable can't
223      // be constant.
224      GV->setConstant(false);
225
226      EmitCXXGuardedInit(D, GV, /*PerformInit*/true);
227    }
228    return GV;
229  }
230
231  // The initializer may differ in type from the global. Rewrite
232  // the global to match the initializer.  (We have to do this
233  // because some types, like unions, can't be completely represented
234  // in the LLVM type system.)
235  if (GV->getType()->getElementType() != Init->getType()) {
236    llvm::GlobalVariable *OldGV = GV;
237
238    GV = new llvm::GlobalVariable(CGM.getModule(), Init->getType(),
239                                  OldGV->isConstant(),
240                                  OldGV->getLinkage(), Init, "",
241                                  /*InsertBefore*/ OldGV,
242                                  D.isThreadSpecified(),
243                           CGM.getContext().getTargetAddressSpace(D.getType()));
244    GV->setVisibility(OldGV->getVisibility());
245
246    // Steal the name of the old global
247    GV->takeName(OldGV);
248
249    // Replace all uses of the old global with the new global
250    llvm::Constant *NewPtrForOldDecl =
251    llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
252    OldGV->replaceAllUsesWith(NewPtrForOldDecl);
253
254    // Erase the old global, since it is no longer used.
255    OldGV->eraseFromParent();
256  }
257
258  GV->setConstant(CGM.isTypeConstant(D.getType(), true));
259  GV->setInitializer(Init);
260
261  if (hasNontrivialDestruction(D.getType())) {
262    // We have a constant initializer, but a nontrivial destructor. We still
263    // need to perform a guarded "initialization" in order to register the
264    // destructor.
265    EmitCXXGuardedInit(D, GV, /*PerformInit*/false);
266  }
267
268  return GV;
269}
270
271void CodeGenFunction::EmitStaticVarDecl(const VarDecl &D,
272                                      llvm::GlobalValue::LinkageTypes Linkage) {
273  llvm::Value *&DMEntry = LocalDeclMap[&D];
274  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
275
276  // Check to see if we already have a global variable for this
277  // declaration.  This can happen when double-emitting function
278  // bodies, e.g. with complete and base constructors.
279  llvm::Constant *addr =
280    CGM.getStaticLocalDeclAddress(&D);
281
282  llvm::GlobalVariable *var;
283  if (addr) {
284    var = cast<llvm::GlobalVariable>(addr->stripPointerCasts());
285  } else {
286    addr = var = CreateStaticVarDecl(D, ".", Linkage);
287  }
288
289  // Store into LocalDeclMap before generating initializer to handle
290  // circular references.
291  DMEntry = addr;
292  CGM.setStaticLocalDeclAddress(&D, addr);
293
294  // We can't have a VLA here, but we can have a pointer to a VLA,
295  // even though that doesn't really make any sense.
296  // Make sure to evaluate VLA bounds now so that we have them for later.
297  if (D.getType()->isVariablyModifiedType())
298    EmitVariablyModifiedType(D.getType());
299
300  // Save the type in case adding the initializer forces a type change.
301  llvm::Type *expectedType = addr->getType();
302
303  // If this value has an initializer, emit it.
304  if (D.getInit())
305    var = AddInitializerToStaticVarDecl(D, var);
306
307  var->setAlignment(getContext().getDeclAlign(&D).getQuantity());
308
309  if (D.hasAttr<AnnotateAttr>())
310    CGM.AddGlobalAnnotations(&D, var);
311
312  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
313    var->setSection(SA->getName());
314
315  if (D.hasAttr<UsedAttr>())
316    CGM.AddUsedGlobal(var);
317
318  // We may have to cast the constant because of the initializer
319  // mismatch above.
320  //
321  // FIXME: It is really dangerous to store this in the map; if anyone
322  // RAUW's the GV uses of this constant will be invalid.
323  llvm::Constant *castedAddr = llvm::ConstantExpr::getBitCast(var, expectedType);
324  DMEntry = castedAddr;
325  CGM.setStaticLocalDeclAddress(&D, castedAddr);
326
327  // Emit global variable debug descriptor for static vars.
328  CGDebugInfo *DI = getDebugInfo();
329  if (DI &&
330      CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
331    DI->setLocation(D.getLocation());
332    DI->EmitGlobalVariable(var, &D);
333  }
334}
335
336namespace {
337  struct DestroyObject : EHScopeStack::Cleanup {
338    DestroyObject(llvm::Value *addr, QualType type,
339                  CodeGenFunction::Destroyer *destroyer,
340                  bool useEHCleanupForArray)
341      : addr(addr), type(type), destroyer(destroyer),
342        useEHCleanupForArray(useEHCleanupForArray) {}
343
344    llvm::Value *addr;
345    QualType type;
346    CodeGenFunction::Destroyer *destroyer;
347    bool useEHCleanupForArray;
348
349    void Emit(CodeGenFunction &CGF, Flags flags) {
350      // Don't use an EH cleanup recursively from an EH cleanup.
351      bool useEHCleanupForArray =
352        flags.isForNormalCleanup() && this->useEHCleanupForArray;
353
354      CGF.emitDestroy(addr, type, destroyer, useEHCleanupForArray);
355    }
356  };
357
358  struct DestroyNRVOVariable : EHScopeStack::Cleanup {
359    DestroyNRVOVariable(llvm::Value *addr,
360                        const CXXDestructorDecl *Dtor,
361                        llvm::Value *NRVOFlag)
362      : Dtor(Dtor), NRVOFlag(NRVOFlag), Loc(addr) {}
363
364    const CXXDestructorDecl *Dtor;
365    llvm::Value *NRVOFlag;
366    llvm::Value *Loc;
367
368    void Emit(CodeGenFunction &CGF, Flags flags) {
369      // Along the exceptions path we always execute the dtor.
370      bool NRVO = flags.isForNormalCleanup() && NRVOFlag;
371
372      llvm::BasicBlock *SkipDtorBB = 0;
373      if (NRVO) {
374        // If we exited via NRVO, we skip the destructor call.
375        llvm::BasicBlock *RunDtorBB = CGF.createBasicBlock("nrvo.unused");
376        SkipDtorBB = CGF.createBasicBlock("nrvo.skipdtor");
377        llvm::Value *DidNRVO = CGF.Builder.CreateLoad(NRVOFlag, "nrvo.val");
378        CGF.Builder.CreateCondBr(DidNRVO, SkipDtorBB, RunDtorBB);
379        CGF.EmitBlock(RunDtorBB);
380      }
381
382      CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete,
383                                /*ForVirtualBase=*/false, Loc);
384
385      if (NRVO) CGF.EmitBlock(SkipDtorBB);
386    }
387  };
388
389  struct CallStackRestore : EHScopeStack::Cleanup {
390    llvm::Value *Stack;
391    CallStackRestore(llvm::Value *Stack) : Stack(Stack) {}
392    void Emit(CodeGenFunction &CGF, Flags flags) {
393      llvm::Value *V = CGF.Builder.CreateLoad(Stack);
394      llvm::Value *F = CGF.CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
395      CGF.Builder.CreateCall(F, V);
396    }
397  };
398
399  struct ExtendGCLifetime : EHScopeStack::Cleanup {
400    const VarDecl &Var;
401    ExtendGCLifetime(const VarDecl *var) : Var(*var) {}
402
403    void Emit(CodeGenFunction &CGF, Flags flags) {
404      // Compute the address of the local variable, in case it's a
405      // byref or something.
406      DeclRefExpr DRE(const_cast<VarDecl*>(&Var), false,
407                      Var.getType(), VK_LValue, SourceLocation());
408      llvm::Value *value = CGF.EmitLoadOfScalar(CGF.EmitDeclRefLValue(&DRE));
409      CGF.EmitExtendGCLifetime(value);
410    }
411  };
412
413  struct CallCleanupFunction : EHScopeStack::Cleanup {
414    llvm::Constant *CleanupFn;
415    const CGFunctionInfo &FnInfo;
416    const VarDecl &Var;
417
418    CallCleanupFunction(llvm::Constant *CleanupFn, const CGFunctionInfo *Info,
419                        const VarDecl *Var)
420      : CleanupFn(CleanupFn), FnInfo(*Info), Var(*Var) {}
421
422    void Emit(CodeGenFunction &CGF, Flags flags) {
423      DeclRefExpr DRE(const_cast<VarDecl*>(&Var), false,
424                      Var.getType(), VK_LValue, SourceLocation());
425      // Compute the address of the local variable, in case it's a byref
426      // or something.
427      llvm::Value *Addr = CGF.EmitDeclRefLValue(&DRE).getAddress();
428
429      // In some cases, the type of the function argument will be different from
430      // the type of the pointer. An example of this is
431      // void f(void* arg);
432      // __attribute__((cleanup(f))) void *g;
433      //
434      // To fix this we insert a bitcast here.
435      QualType ArgTy = FnInfo.arg_begin()->type;
436      llvm::Value *Arg =
437        CGF.Builder.CreateBitCast(Addr, CGF.ConvertType(ArgTy));
438
439      CallArgList Args;
440      Args.add(RValue::get(Arg),
441               CGF.getContext().getPointerType(Var.getType()));
442      CGF.EmitCall(FnInfo, CleanupFn, ReturnValueSlot(), Args);
443    }
444  };
445}
446
447/// EmitAutoVarWithLifetime - Does the setup required for an automatic
448/// variable with lifetime.
449static void EmitAutoVarWithLifetime(CodeGenFunction &CGF, const VarDecl &var,
450                                    llvm::Value *addr,
451                                    Qualifiers::ObjCLifetime lifetime) {
452  switch (lifetime) {
453  case Qualifiers::OCL_None:
454    llvm_unreachable("present but none");
455
456  case Qualifiers::OCL_ExplicitNone:
457    // nothing to do
458    break;
459
460  case Qualifiers::OCL_Strong: {
461    CodeGenFunction::Destroyer *destroyer =
462      (var.hasAttr<ObjCPreciseLifetimeAttr>()
463       ? CodeGenFunction::destroyARCStrongPrecise
464       : CodeGenFunction::destroyARCStrongImprecise);
465
466    CleanupKind cleanupKind = CGF.getARCCleanupKind();
467    CGF.pushDestroy(cleanupKind, addr, var.getType(), destroyer,
468                    cleanupKind & EHCleanup);
469    break;
470  }
471  case Qualifiers::OCL_Autoreleasing:
472    // nothing to do
473    break;
474
475  case Qualifiers::OCL_Weak:
476    // __weak objects always get EH cleanups; otherwise, exceptions
477    // could cause really nasty crashes instead of mere leaks.
478    CGF.pushDestroy(NormalAndEHCleanup, addr, var.getType(),
479                    CodeGenFunction::destroyARCWeak,
480                    /*useEHCleanup*/ true);
481    break;
482  }
483}
484
485static bool isAccessedBy(const VarDecl &var, const Stmt *s) {
486  if (const Expr *e = dyn_cast<Expr>(s)) {
487    // Skip the most common kinds of expressions that make
488    // hierarchy-walking expensive.
489    s = e = e->IgnoreParenCasts();
490
491    if (const DeclRefExpr *ref = dyn_cast<DeclRefExpr>(e))
492      return (ref->getDecl() == &var);
493    if (const BlockExpr *be = dyn_cast<BlockExpr>(e)) {
494      const BlockDecl *block = be->getBlockDecl();
495      for (BlockDecl::capture_const_iterator i = block->capture_begin(),
496           e = block->capture_end(); i != e; ++i) {
497        if (i->getVariable() == &var)
498          return true;
499      }
500    }
501  }
502
503  for (Stmt::const_child_range children = s->children(); children; ++children)
504    // children might be null; as in missing decl or conditional of an if-stmt.
505    if ((*children) && isAccessedBy(var, *children))
506      return true;
507
508  return false;
509}
510
511static bool isAccessedBy(const ValueDecl *decl, const Expr *e) {
512  if (!decl) return false;
513  if (!isa<VarDecl>(decl)) return false;
514  const VarDecl *var = cast<VarDecl>(decl);
515  return isAccessedBy(*var, e);
516}
517
518static void drillIntoBlockVariable(CodeGenFunction &CGF,
519                                   LValue &lvalue,
520                                   const VarDecl *var) {
521  lvalue.setAddress(CGF.BuildBlockByrefAddress(lvalue.getAddress(), var));
522}
523
524void CodeGenFunction::EmitScalarInit(const Expr *init,
525                                     const ValueDecl *D,
526                                     LValue lvalue,
527                                     bool capturedByInit) {
528  Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime();
529  if (!lifetime) {
530    llvm::Value *value = EmitScalarExpr(init);
531    if (capturedByInit)
532      drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
533    EmitStoreThroughLValue(RValue::get(value), lvalue, true);
534    return;
535  }
536
537  // If we're emitting a value with lifetime, we have to do the
538  // initialization *before* we leave the cleanup scopes.
539  if (const ExprWithCleanups *ewc = dyn_cast<ExprWithCleanups>(init)) {
540    enterFullExpression(ewc);
541    init = ewc->getSubExpr();
542  }
543  CodeGenFunction::RunCleanupsScope Scope(*this);
544
545  // We have to maintain the illusion that the variable is
546  // zero-initialized.  If the variable might be accessed in its
547  // initializer, zero-initialize before running the initializer, then
548  // actually perform the initialization with an assign.
549  bool accessedByInit = false;
550  if (lifetime != Qualifiers::OCL_ExplicitNone)
551    accessedByInit = (capturedByInit || isAccessedBy(D, init));
552  if (accessedByInit) {
553    LValue tempLV = lvalue;
554    // Drill down to the __block object if necessary.
555    if (capturedByInit) {
556      // We can use a simple GEP for this because it can't have been
557      // moved yet.
558      tempLV.setAddress(Builder.CreateStructGEP(tempLV.getAddress(),
559                                   getByRefValueLLVMField(cast<VarDecl>(D))));
560    }
561
562    llvm::PointerType *ty
563      = cast<llvm::PointerType>(tempLV.getAddress()->getType());
564    ty = cast<llvm::PointerType>(ty->getElementType());
565
566    llvm::Value *zero = llvm::ConstantPointerNull::get(ty);
567
568    // If __weak, we want to use a barrier under certain conditions.
569    if (lifetime == Qualifiers::OCL_Weak)
570      EmitARCInitWeak(tempLV.getAddress(), zero);
571
572    // Otherwise just do a simple store.
573    else
574      EmitStoreOfScalar(zero, tempLV, /* isInitialization */ true);
575  }
576
577  // Emit the initializer.
578  llvm::Value *value = 0;
579
580  switch (lifetime) {
581  case Qualifiers::OCL_None:
582    llvm_unreachable("present but none");
583
584  case Qualifiers::OCL_ExplicitNone:
585    // nothing to do
586    value = EmitScalarExpr(init);
587    break;
588
589  case Qualifiers::OCL_Strong: {
590    value = EmitARCRetainScalarExpr(init);
591    break;
592  }
593
594  case Qualifiers::OCL_Weak: {
595    // No way to optimize a producing initializer into this.  It's not
596    // worth optimizing for, because the value will immediately
597    // disappear in the common case.
598    value = EmitScalarExpr(init);
599
600    if (capturedByInit) drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
601    if (accessedByInit)
602      EmitARCStoreWeak(lvalue.getAddress(), value, /*ignored*/ true);
603    else
604      EmitARCInitWeak(lvalue.getAddress(), value);
605    return;
606  }
607
608  case Qualifiers::OCL_Autoreleasing:
609    value = EmitARCRetainAutoreleaseScalarExpr(init);
610    break;
611  }
612
613  if (capturedByInit) drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
614
615  // If the variable might have been accessed by its initializer, we
616  // might have to initialize with a barrier.  We have to do this for
617  // both __weak and __strong, but __weak got filtered out above.
618  if (accessedByInit && lifetime == Qualifiers::OCL_Strong) {
619    llvm::Value *oldValue = EmitLoadOfScalar(lvalue);
620    EmitStoreOfScalar(value, lvalue, /* isInitialization */ true);
621    EmitARCRelease(oldValue, /*precise*/ false);
622    return;
623  }
624
625  EmitStoreOfScalar(value, lvalue, /* isInitialization */ true);
626}
627
628/// EmitScalarInit - Initialize the given lvalue with the given object.
629void CodeGenFunction::EmitScalarInit(llvm::Value *init, LValue lvalue) {
630  Qualifiers::ObjCLifetime lifetime = lvalue.getObjCLifetime();
631  if (!lifetime)
632    return EmitStoreThroughLValue(RValue::get(init), lvalue, true);
633
634  switch (lifetime) {
635  case Qualifiers::OCL_None:
636    llvm_unreachable("present but none");
637
638  case Qualifiers::OCL_ExplicitNone:
639    // nothing to do
640    break;
641
642  case Qualifiers::OCL_Strong:
643    init = EmitARCRetain(lvalue.getType(), init);
644    break;
645
646  case Qualifiers::OCL_Weak:
647    // Initialize and then skip the primitive store.
648    EmitARCInitWeak(lvalue.getAddress(), init);
649    return;
650
651  case Qualifiers::OCL_Autoreleasing:
652    init = EmitARCRetainAutorelease(lvalue.getType(), init);
653    break;
654  }
655
656  EmitStoreOfScalar(init, lvalue, /* isInitialization */ true);
657}
658
659/// canEmitInitWithFewStoresAfterMemset - Decide whether we can emit the
660/// non-zero parts of the specified initializer with equal or fewer than
661/// NumStores scalar stores.
662static bool canEmitInitWithFewStoresAfterMemset(llvm::Constant *Init,
663                                                unsigned &NumStores) {
664  // Zero and Undef never requires any extra stores.
665  if (isa<llvm::ConstantAggregateZero>(Init) ||
666      isa<llvm::ConstantPointerNull>(Init) ||
667      isa<llvm::UndefValue>(Init))
668    return true;
669  if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) ||
670      isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) ||
671      isa<llvm::ConstantExpr>(Init))
672    return Init->isNullValue() || NumStores--;
673
674  // See if we can emit each element.
675  if (isa<llvm::ConstantArray>(Init) || isa<llvm::ConstantStruct>(Init)) {
676    for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) {
677      llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i));
678      if (!canEmitInitWithFewStoresAfterMemset(Elt, NumStores))
679        return false;
680    }
681    return true;
682  }
683
684  if (llvm::ConstantDataSequential *CDS =
685        dyn_cast<llvm::ConstantDataSequential>(Init)) {
686    for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
687      llvm::Constant *Elt = CDS->getElementAsConstant(i);
688      if (!canEmitInitWithFewStoresAfterMemset(Elt, NumStores))
689        return false;
690    }
691    return true;
692  }
693
694  // Anything else is hard and scary.
695  return false;
696}
697
698/// emitStoresForInitAfterMemset - For inits that
699/// canEmitInitWithFewStoresAfterMemset returned true for, emit the scalar
700/// stores that would be required.
701static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc,
702                                         bool isVolatile, CGBuilderTy &Builder) {
703  // Zero doesn't require a store.
704  if (Init->isNullValue() || isa<llvm::UndefValue>(Init))
705    return;
706
707  if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) ||
708      isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) ||
709      isa<llvm::ConstantExpr>(Init)) {
710    Builder.CreateStore(Init, Loc, isVolatile);
711    return;
712  }
713
714  if (llvm::ConstantDataSequential *CDS =
715        dyn_cast<llvm::ConstantDataSequential>(Init)) {
716    for (unsigned i = 0, e = CDS->getNumElements(); i != e; ++i) {
717      llvm::Constant *Elt = CDS->getElementAsConstant(i);
718
719      // Get a pointer to the element and emit it.
720      emitStoresForInitAfterMemset(Elt, Builder.CreateConstGEP2_32(Loc, 0, i),
721                                   isVolatile, Builder);
722    }
723    return;
724  }
725
726  assert((isa<llvm::ConstantStruct>(Init) || isa<llvm::ConstantArray>(Init)) &&
727         "Unknown value type!");
728
729  for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) {
730    llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i));
731    // Get a pointer to the element and emit it.
732    emitStoresForInitAfterMemset(Elt, Builder.CreateConstGEP2_32(Loc, 0, i),
733                                 isVolatile, Builder);
734  }
735}
736
737
738/// shouldUseMemSetPlusStoresToInitialize - Decide whether we should use memset
739/// plus some stores to initialize a local variable instead of using a memcpy
740/// from a constant global.  It is beneficial to use memset if the global is all
741/// zeros, or mostly zeros and large.
742static bool shouldUseMemSetPlusStoresToInitialize(llvm::Constant *Init,
743                                                  uint64_t GlobalSize) {
744  // If a global is all zeros, always use a memset.
745  if (isa<llvm::ConstantAggregateZero>(Init)) return true;
746
747
748  // If a non-zero global is <= 32 bytes, always use a memcpy.  If it is large,
749  // do it if it will require 6 or fewer scalar stores.
750  // TODO: Should budget depends on the size?  Avoiding a large global warrants
751  // plopping in more stores.
752  unsigned StoreBudget = 6;
753  uint64_t SizeLimit = 32;
754
755  return GlobalSize > SizeLimit &&
756         canEmitInitWithFewStoresAfterMemset(Init, StoreBudget);
757}
758
759
760/// EmitAutoVarDecl - Emit code and set up an entry in LocalDeclMap for a
761/// variable declaration with auto, register, or no storage class specifier.
762/// These turn into simple stack objects, or GlobalValues depending on target.
763void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D) {
764  AutoVarEmission emission = EmitAutoVarAlloca(D);
765  EmitAutoVarInit(emission);
766  EmitAutoVarCleanups(emission);
767}
768
769/// EmitAutoVarAlloca - Emit the alloca and debug information for a
770/// local variable.  Does not emit initalization or destruction.
771CodeGenFunction::AutoVarEmission
772CodeGenFunction::EmitAutoVarAlloca(const VarDecl &D) {
773  QualType Ty = D.getType();
774
775  AutoVarEmission emission(D);
776
777  bool isByRef = D.hasAttr<BlocksAttr>();
778  emission.IsByRef = isByRef;
779
780  CharUnits alignment = getContext().getDeclAlign(&D);
781  emission.Alignment = alignment;
782
783  // If the type is variably-modified, emit all the VLA sizes for it.
784  if (Ty->isVariablyModifiedType())
785    EmitVariablyModifiedType(Ty);
786
787  llvm::Value *DeclPtr;
788  if (Ty->isConstantSizeType()) {
789    if (!Target.useGlobalsForAutomaticVariables()) {
790      bool NRVO = getContext().getLangOpts().ElideConstructors &&
791                  D.isNRVOVariable();
792
793      // If this value is a POD array or struct with a statically
794      // determinable constant initializer, there are optimizations we can do.
795      //
796      // TODO: We should constant-evaluate the initializer of any variable,
797      // as long as it is initialized by a constant expression. Currently,
798      // isConstantInitializer produces wrong answers for structs with
799      // reference or bitfield members, and a few other cases, and checking
800      // for POD-ness protects us from some of these.
801      if (D.getInit() &&
802          (Ty->isArrayType() || Ty->isRecordType()) &&
803          (Ty.isPODType(getContext()) ||
804           getContext().getBaseElementType(Ty)->isObjCObjectPointerType()) &&
805          D.getInit()->isConstantInitializer(getContext(), false)) {
806
807        // If the variable's a const type, and it's neither an NRVO
808        // candidate nor a __block variable and has no mutable members,
809        // emit it as a global instead.
810        if (CGM.getCodeGenOpts().MergeAllConstants && !NRVO && !isByRef &&
811            CGM.isTypeConstant(Ty, true)) {
812          EmitStaticVarDecl(D, llvm::GlobalValue::InternalLinkage);
813
814          emission.Address = 0; // signal this condition to later callbacks
815          assert(emission.wasEmittedAsGlobal());
816          return emission;
817        }
818
819        // Otherwise, tell the initialization code that we're in this case.
820        emission.IsConstantAggregate = true;
821      }
822
823      // A normal fixed sized variable becomes an alloca in the entry block,
824      // unless it's an NRVO variable.
825      llvm::Type *LTy = ConvertTypeForMem(Ty);
826
827      if (NRVO) {
828        // The named return value optimization: allocate this variable in the
829        // return slot, so that we can elide the copy when returning this
830        // variable (C++0x [class.copy]p34).
831        DeclPtr = ReturnValue;
832
833        if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
834          if (!cast<CXXRecordDecl>(RecordTy->getDecl())->hasTrivialDestructor()) {
835            // Create a flag that is used to indicate when the NRVO was applied
836            // to this variable. Set it to zero to indicate that NRVO was not
837            // applied.
838            llvm::Value *Zero = Builder.getFalse();
839            llvm::Value *NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo");
840            EnsureInsertPoint();
841            Builder.CreateStore(Zero, NRVOFlag);
842
843            // Record the NRVO flag for this variable.
844            NRVOFlags[&D] = NRVOFlag;
845            emission.NRVOFlag = NRVOFlag;
846          }
847        }
848      } else {
849        if (isByRef)
850          LTy = BuildByRefType(&D);
851
852        llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
853        Alloc->setName(D.getName());
854
855        CharUnits allocaAlignment = alignment;
856        if (isByRef)
857          allocaAlignment = std::max(allocaAlignment,
858              getContext().toCharUnitsFromBits(Target.getPointerAlign(0)));
859        Alloc->setAlignment(allocaAlignment.getQuantity());
860        DeclPtr = Alloc;
861      }
862    } else {
863      // Targets that don't support recursion emit locals as globals.
864      const char *Class =
865        D.getStorageClass() == SC_Register ? ".reg." : ".auto.";
866      DeclPtr = CreateStaticVarDecl(D, Class,
867                                    llvm::GlobalValue::InternalLinkage);
868    }
869  } else {
870    EnsureInsertPoint();
871
872    if (!DidCallStackSave) {
873      // Save the stack.
874      llvm::Value *Stack = CreateTempAlloca(Int8PtrTy, "saved_stack");
875
876      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
877      llvm::Value *V = Builder.CreateCall(F);
878
879      Builder.CreateStore(V, Stack);
880
881      DidCallStackSave = true;
882
883      // Push a cleanup block and restore the stack there.
884      // FIXME: in general circumstances, this should be an EH cleanup.
885      EHStack.pushCleanup<CallStackRestore>(NormalCleanup, Stack);
886    }
887
888    llvm::Value *elementCount;
889    QualType elementType;
890    llvm::tie(elementCount, elementType) = getVLASize(Ty);
891
892    llvm::Type *llvmTy = ConvertTypeForMem(elementType);
893
894    // Allocate memory for the array.
895    llvm::AllocaInst *vla = Builder.CreateAlloca(llvmTy, elementCount, "vla");
896    vla->setAlignment(alignment.getQuantity());
897
898    DeclPtr = vla;
899  }
900
901  llvm::Value *&DMEntry = LocalDeclMap[&D];
902  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
903  DMEntry = DeclPtr;
904  emission.Address = DeclPtr;
905
906  // Emit debug info for local var declaration.
907  if (HaveInsertPoint())
908    if (CGDebugInfo *DI = getDebugInfo()) {
909      if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
910        DI->setLocation(D.getLocation());
911        if (Target.useGlobalsForAutomaticVariables()) {
912          DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr),
913                                 &D);
914        } else
915          DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
916      }
917    }
918
919  if (D.hasAttr<AnnotateAttr>())
920      EmitVarAnnotations(&D, emission.Address);
921
922  return emission;
923}
924
925/// Determines whether the given __block variable is potentially
926/// captured by the given expression.
927static bool isCapturedBy(const VarDecl &var, const Expr *e) {
928  // Skip the most common kinds of expressions that make
929  // hierarchy-walking expensive.
930  e = e->IgnoreParenCasts();
931
932  if (const BlockExpr *be = dyn_cast<BlockExpr>(e)) {
933    const BlockDecl *block = be->getBlockDecl();
934    for (BlockDecl::capture_const_iterator i = block->capture_begin(),
935           e = block->capture_end(); i != e; ++i) {
936      if (i->getVariable() == &var)
937        return true;
938    }
939
940    // No need to walk into the subexpressions.
941    return false;
942  }
943
944  if (const StmtExpr *SE = dyn_cast<StmtExpr>(e)) {
945    const CompoundStmt *CS = SE->getSubStmt();
946    for (CompoundStmt::const_body_iterator BI = CS->body_begin(),
947	   BE = CS->body_end(); BI != BE; ++BI)
948      if (Expr *E = dyn_cast<Expr>((*BI))) {
949        if (isCapturedBy(var, E))
950            return true;
951      }
952      else if (DeclStmt *DS = dyn_cast<DeclStmt>((*BI))) {
953          // special case declarations
954          for (DeclStmt::decl_iterator I = DS->decl_begin(), E = DS->decl_end();
955               I != E; ++I) {
956              if (VarDecl *VD = dyn_cast<VarDecl>((*I))) {
957                Expr *Init = VD->getInit();
958                if (Init && isCapturedBy(var, Init))
959                  return true;
960              }
961          }
962      }
963      else
964        // FIXME. Make safe assumption assuming arbitrary statements cause capturing.
965        // Later, provide code to poke into statements for capture analysis.
966        return true;
967    return false;
968  }
969
970  for (Stmt::const_child_range children = e->children(); children; ++children)
971    if (isCapturedBy(var, cast<Expr>(*children)))
972      return true;
973
974  return false;
975}
976
977/// \brief Determine whether the given initializer is trivial in the sense
978/// that it requires no code to be generated.
979static bool isTrivialInitializer(const Expr *Init) {
980  if (!Init)
981    return true;
982
983  if (const CXXConstructExpr *Construct = dyn_cast<CXXConstructExpr>(Init))
984    if (CXXConstructorDecl *Constructor = Construct->getConstructor())
985      if (Constructor->isTrivial() &&
986          Constructor->isDefaultConstructor() &&
987          !Construct->requiresZeroInitialization())
988        return true;
989
990  return false;
991}
992void CodeGenFunction::EmitAutoVarInit(const AutoVarEmission &emission) {
993  assert(emission.Variable && "emission was not valid!");
994
995  // If this was emitted as a global constant, we're done.
996  if (emission.wasEmittedAsGlobal()) return;
997
998  const VarDecl &D = *emission.Variable;
999  QualType type = D.getType();
1000
1001  // If this local has an initializer, emit it now.
1002  const Expr *Init = D.getInit();
1003
1004  // If we are at an unreachable point, we don't need to emit the initializer
1005  // unless it contains a label.
1006  if (!HaveInsertPoint()) {
1007    if (!Init || !ContainsLabel(Init)) return;
1008    EnsureInsertPoint();
1009  }
1010
1011  // Initialize the structure of a __block variable.
1012  if (emission.IsByRef)
1013    emitByrefStructureInit(emission);
1014
1015  if (isTrivialInitializer(Init))
1016    return;
1017
1018  CharUnits alignment = emission.Alignment;
1019
1020  // Check whether this is a byref variable that's potentially
1021  // captured and moved by its own initializer.  If so, we'll need to
1022  // emit the initializer first, then copy into the variable.
1023  bool capturedByInit = emission.IsByRef && isCapturedBy(D, Init);
1024
1025  llvm::Value *Loc =
1026    capturedByInit ? emission.Address : emission.getObjectAddress(*this);
1027
1028  llvm::Constant *constant = 0;
1029  if (emission.IsConstantAggregate) {
1030    assert(!capturedByInit && "constant init contains a capturing block?");
1031    constant = CGM.EmitConstantInit(D, this);
1032  }
1033
1034  if (!constant) {
1035    LValue lv = MakeAddrLValue(Loc, type, alignment);
1036    lv.setNonGC(true);
1037    return EmitExprAsInit(Init, &D, lv, capturedByInit);
1038  }
1039
1040  // If this is a simple aggregate initialization, we can optimize it
1041  // in various ways.
1042  bool isVolatile = type.isVolatileQualified();
1043
1044  llvm::Value *SizeVal =
1045    llvm::ConstantInt::get(IntPtrTy,
1046                           getContext().getTypeSizeInChars(type).getQuantity());
1047
1048  llvm::Type *BP = Int8PtrTy;
1049  if (Loc->getType() != BP)
1050    Loc = Builder.CreateBitCast(Loc, BP);
1051
1052  // If the initializer is all or mostly zeros, codegen with memset then do
1053  // a few stores afterward.
1054  if (shouldUseMemSetPlusStoresToInitialize(constant,
1055                CGM.getTargetData().getTypeAllocSize(constant->getType()))) {
1056    Builder.CreateMemSet(Loc, llvm::ConstantInt::get(Int8Ty, 0), SizeVal,
1057                         alignment.getQuantity(), isVolatile);
1058    if (!constant->isNullValue()) {
1059      Loc = Builder.CreateBitCast(Loc, constant->getType()->getPointerTo());
1060      emitStoresForInitAfterMemset(constant, Loc, isVolatile, Builder);
1061    }
1062  } else {
1063    // Otherwise, create a temporary global with the initializer then
1064    // memcpy from the global to the alloca.
1065    std::string Name = GetStaticDeclName(*this, D, ".");
1066    llvm::GlobalVariable *GV =
1067      new llvm::GlobalVariable(CGM.getModule(), constant->getType(), true,
1068                               llvm::GlobalValue::PrivateLinkage,
1069                               constant, Name, 0, false, 0);
1070    GV->setAlignment(alignment.getQuantity());
1071    GV->setUnnamedAddr(true);
1072
1073    llvm::Value *SrcPtr = GV;
1074    if (SrcPtr->getType() != BP)
1075      SrcPtr = Builder.CreateBitCast(SrcPtr, BP);
1076
1077    Builder.CreateMemCpy(Loc, SrcPtr, SizeVal, alignment.getQuantity(),
1078                         isVolatile);
1079  }
1080}
1081
1082/// Emit an expression as an initializer for a variable at the given
1083/// location.  The expression is not necessarily the normal
1084/// initializer for the variable, and the address is not necessarily
1085/// its normal location.
1086///
1087/// \param init the initializing expression
1088/// \param var the variable to act as if we're initializing
1089/// \param loc the address to initialize; its type is a pointer
1090///   to the LLVM mapping of the variable's type
1091/// \param alignment the alignment of the address
1092/// \param capturedByInit true if the variable is a __block variable
1093///   whose address is potentially changed by the initializer
1094void CodeGenFunction::EmitExprAsInit(const Expr *init,
1095                                     const ValueDecl *D,
1096                                     LValue lvalue,
1097                                     bool capturedByInit) {
1098  QualType type = D->getType();
1099
1100  if (type->isReferenceType()) {
1101    RValue rvalue = EmitReferenceBindingToExpr(init, D);
1102    if (capturedByInit)
1103      drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
1104    EmitStoreThroughLValue(rvalue, lvalue, true);
1105  } else if (!hasAggregateLLVMType(type)) {
1106    EmitScalarInit(init, D, lvalue, capturedByInit);
1107  } else if (type->isAnyComplexType()) {
1108    ComplexPairTy complex = EmitComplexExpr(init);
1109    if (capturedByInit)
1110      drillIntoBlockVariable(*this, lvalue, cast<VarDecl>(D));
1111    StoreComplexToAddr(complex, lvalue.getAddress(), lvalue.isVolatile());
1112  } else {
1113    // TODO: how can we delay here if D is captured by its initializer?
1114    EmitAggExpr(init, AggValueSlot::forLValue(lvalue,
1115                                              AggValueSlot::IsDestructed,
1116                                         AggValueSlot::DoesNotNeedGCBarriers,
1117                                              AggValueSlot::IsNotAliased));
1118    MaybeEmitStdInitializerListCleanup(lvalue.getAddress(), init);
1119  }
1120}
1121
1122/// Enter a destroy cleanup for the given local variable.
1123void CodeGenFunction::emitAutoVarTypeCleanup(
1124                            const CodeGenFunction::AutoVarEmission &emission,
1125                            QualType::DestructionKind dtorKind) {
1126  assert(dtorKind != QualType::DK_none);
1127
1128  // Note that for __block variables, we want to destroy the
1129  // original stack object, not the possibly forwarded object.
1130  llvm::Value *addr = emission.getObjectAddress(*this);
1131
1132  const VarDecl *var = emission.Variable;
1133  QualType type = var->getType();
1134
1135  CleanupKind cleanupKind = NormalAndEHCleanup;
1136  CodeGenFunction::Destroyer *destroyer = 0;
1137
1138  switch (dtorKind) {
1139  case QualType::DK_none:
1140    llvm_unreachable("no cleanup for trivially-destructible variable");
1141
1142  case QualType::DK_cxx_destructor:
1143    // If there's an NRVO flag on the emission, we need a different
1144    // cleanup.
1145    if (emission.NRVOFlag) {
1146      assert(!type->isArrayType());
1147      CXXDestructorDecl *dtor = type->getAsCXXRecordDecl()->getDestructor();
1148      EHStack.pushCleanup<DestroyNRVOVariable>(cleanupKind, addr, dtor,
1149                                               emission.NRVOFlag);
1150      return;
1151    }
1152    break;
1153
1154  case QualType::DK_objc_strong_lifetime:
1155    // Suppress cleanups for pseudo-strong variables.
1156    if (var->isARCPseudoStrong()) return;
1157
1158    // Otherwise, consider whether to use an EH cleanup or not.
1159    cleanupKind = getARCCleanupKind();
1160
1161    // Use the imprecise destroyer by default.
1162    if (!var->hasAttr<ObjCPreciseLifetimeAttr>())
1163      destroyer = CodeGenFunction::destroyARCStrongImprecise;
1164    break;
1165
1166  case QualType::DK_objc_weak_lifetime:
1167    break;
1168  }
1169
1170  // If we haven't chosen a more specific destroyer, use the default.
1171  if (!destroyer) destroyer = getDestroyer(dtorKind);
1172
1173  // Use an EH cleanup in array destructors iff the destructor itself
1174  // is being pushed as an EH cleanup.
1175  bool useEHCleanup = (cleanupKind & EHCleanup);
1176  EHStack.pushCleanup<DestroyObject>(cleanupKind, addr, type, destroyer,
1177                                     useEHCleanup);
1178}
1179
1180void CodeGenFunction::EmitAutoVarCleanups(const AutoVarEmission &emission) {
1181  assert(emission.Variable && "emission was not valid!");
1182
1183  // If this was emitted as a global constant, we're done.
1184  if (emission.wasEmittedAsGlobal()) return;
1185
1186  // If we don't have an insertion point, we're done.  Sema prevents
1187  // us from jumping into any of these scopes anyway.
1188  if (!HaveInsertPoint()) return;
1189
1190  const VarDecl &D = *emission.Variable;
1191
1192  // Check the type for a cleanup.
1193  if (QualType::DestructionKind dtorKind = D.getType().isDestructedType())
1194    emitAutoVarTypeCleanup(emission, dtorKind);
1195
1196  // In GC mode, honor objc_precise_lifetime.
1197  if (getLangOpts().getGC() != LangOptions::NonGC &&
1198      D.hasAttr<ObjCPreciseLifetimeAttr>()) {
1199    EHStack.pushCleanup<ExtendGCLifetime>(NormalCleanup, &D);
1200  }
1201
1202  // Handle the cleanup attribute.
1203  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
1204    const FunctionDecl *FD = CA->getFunctionDecl();
1205
1206    llvm::Constant *F = CGM.GetAddrOfFunction(FD);
1207    assert(F && "Could not find function!");
1208
1209    const CGFunctionInfo &Info = CGM.getTypes().arrangeFunctionDeclaration(FD);
1210    EHStack.pushCleanup<CallCleanupFunction>(NormalAndEHCleanup, F, &Info, &D);
1211  }
1212
1213  // If this is a block variable, call _Block_object_destroy
1214  // (on the unforwarded address).
1215  if (emission.IsByRef)
1216    enterByrefCleanup(emission);
1217}
1218
1219CodeGenFunction::Destroyer *
1220CodeGenFunction::getDestroyer(QualType::DestructionKind kind) {
1221  switch (kind) {
1222  case QualType::DK_none: llvm_unreachable("no destroyer for trivial dtor");
1223  case QualType::DK_cxx_destructor:
1224    return destroyCXXObject;
1225  case QualType::DK_objc_strong_lifetime:
1226    return destroyARCStrongPrecise;
1227  case QualType::DK_objc_weak_lifetime:
1228    return destroyARCWeak;
1229  }
1230  llvm_unreachable("Unknown DestructionKind");
1231}
1232
1233/// pushDestroy - Push the standard destructor for the given type.
1234void CodeGenFunction::pushDestroy(QualType::DestructionKind dtorKind,
1235                                  llvm::Value *addr, QualType type) {
1236  assert(dtorKind && "cannot push destructor for trivial type");
1237
1238  CleanupKind cleanupKind = getCleanupKind(dtorKind);
1239  pushDestroy(cleanupKind, addr, type, getDestroyer(dtorKind),
1240              cleanupKind & EHCleanup);
1241}
1242
1243void CodeGenFunction::pushDestroy(CleanupKind cleanupKind, llvm::Value *addr,
1244                                  QualType type, Destroyer *destroyer,
1245                                  bool useEHCleanupForArray) {
1246  pushFullExprCleanup<DestroyObject>(cleanupKind, addr, type,
1247                                     destroyer, useEHCleanupForArray);
1248}
1249
1250/// emitDestroy - Immediately perform the destruction of the given
1251/// object.
1252///
1253/// \param addr - the address of the object; a type*
1254/// \param type - the type of the object; if an array type, all
1255///   objects are destroyed in reverse order
1256/// \param destroyer - the function to call to destroy individual
1257///   elements
1258/// \param useEHCleanupForArray - whether an EH cleanup should be
1259///   used when destroying array elements, in case one of the
1260///   destructions throws an exception
1261void CodeGenFunction::emitDestroy(llvm::Value *addr, QualType type,
1262                                  Destroyer *destroyer,
1263                                  bool useEHCleanupForArray) {
1264  const ArrayType *arrayType = getContext().getAsArrayType(type);
1265  if (!arrayType)
1266    return destroyer(*this, addr, type);
1267
1268  llvm::Value *begin = addr;
1269  llvm::Value *length = emitArrayLength(arrayType, type, begin);
1270
1271  // Normally we have to check whether the array is zero-length.
1272  bool checkZeroLength = true;
1273
1274  // But if the array length is constant, we can suppress that.
1275  if (llvm::ConstantInt *constLength = dyn_cast<llvm::ConstantInt>(length)) {
1276    // ...and if it's constant zero, we can just skip the entire thing.
1277    if (constLength->isZero()) return;
1278    checkZeroLength = false;
1279  }
1280
1281  llvm::Value *end = Builder.CreateInBoundsGEP(begin, length);
1282  emitArrayDestroy(begin, end, type, destroyer,
1283                   checkZeroLength, useEHCleanupForArray);
1284}
1285
1286/// emitArrayDestroy - Destroys all the elements of the given array,
1287/// beginning from last to first.  The array cannot be zero-length.
1288///
1289/// \param begin - a type* denoting the first element of the array
1290/// \param end - a type* denoting one past the end of the array
1291/// \param type - the element type of the array
1292/// \param destroyer - the function to call to destroy elements
1293/// \param useEHCleanup - whether to push an EH cleanup to destroy
1294///   the remaining elements in case the destruction of a single
1295///   element throws
1296void CodeGenFunction::emitArrayDestroy(llvm::Value *begin,
1297                                       llvm::Value *end,
1298                                       QualType type,
1299                                       Destroyer *destroyer,
1300                                       bool checkZeroLength,
1301                                       bool useEHCleanup) {
1302  assert(!type->isArrayType());
1303
1304  // The basic structure here is a do-while loop, because we don't
1305  // need to check for the zero-element case.
1306  llvm::BasicBlock *bodyBB = createBasicBlock("arraydestroy.body");
1307  llvm::BasicBlock *doneBB = createBasicBlock("arraydestroy.done");
1308
1309  if (checkZeroLength) {
1310    llvm::Value *isEmpty = Builder.CreateICmpEQ(begin, end,
1311                                                "arraydestroy.isempty");
1312    Builder.CreateCondBr(isEmpty, doneBB, bodyBB);
1313  }
1314
1315  // Enter the loop body, making that address the current address.
1316  llvm::BasicBlock *entryBB = Builder.GetInsertBlock();
1317  EmitBlock(bodyBB);
1318  llvm::PHINode *elementPast =
1319    Builder.CreatePHI(begin->getType(), 2, "arraydestroy.elementPast");
1320  elementPast->addIncoming(end, entryBB);
1321
1322  // Shift the address back by one element.
1323  llvm::Value *negativeOne = llvm::ConstantInt::get(SizeTy, -1, true);
1324  llvm::Value *element = Builder.CreateInBoundsGEP(elementPast, negativeOne,
1325                                                   "arraydestroy.element");
1326
1327  if (useEHCleanup)
1328    pushRegularPartialArrayCleanup(begin, element, type, destroyer);
1329
1330  // Perform the actual destruction there.
1331  destroyer(*this, element, type);
1332
1333  if (useEHCleanup)
1334    PopCleanupBlock();
1335
1336  // Check whether we've reached the end.
1337  llvm::Value *done = Builder.CreateICmpEQ(element, begin, "arraydestroy.done");
1338  Builder.CreateCondBr(done, doneBB, bodyBB);
1339  elementPast->addIncoming(element, Builder.GetInsertBlock());
1340
1341  // Done.
1342  EmitBlock(doneBB);
1343}
1344
1345/// Perform partial array destruction as if in an EH cleanup.  Unlike
1346/// emitArrayDestroy, the element type here may still be an array type.
1347static void emitPartialArrayDestroy(CodeGenFunction &CGF,
1348                                    llvm::Value *begin, llvm::Value *end,
1349                                    QualType type,
1350                                    CodeGenFunction::Destroyer *destroyer) {
1351  // If the element type is itself an array, drill down.
1352  unsigned arrayDepth = 0;
1353  while (const ArrayType *arrayType = CGF.getContext().getAsArrayType(type)) {
1354    // VLAs don't require a GEP index to walk into.
1355    if (!isa<VariableArrayType>(arrayType))
1356      arrayDepth++;
1357    type = arrayType->getElementType();
1358  }
1359
1360  if (arrayDepth) {
1361    llvm::Value *zero = llvm::ConstantInt::get(CGF.SizeTy, arrayDepth+1);
1362
1363    SmallVector<llvm::Value*,4> gepIndices(arrayDepth, zero);
1364    begin = CGF.Builder.CreateInBoundsGEP(begin, gepIndices, "pad.arraybegin");
1365    end = CGF.Builder.CreateInBoundsGEP(end, gepIndices, "pad.arrayend");
1366  }
1367
1368  // Destroy the array.  We don't ever need an EH cleanup because we
1369  // assume that we're in an EH cleanup ourselves, so a throwing
1370  // destructor causes an immediate terminate.
1371  CGF.emitArrayDestroy(begin, end, type, destroyer,
1372                       /*checkZeroLength*/ true, /*useEHCleanup*/ false);
1373}
1374
1375namespace {
1376  /// RegularPartialArrayDestroy - a cleanup which performs a partial
1377  /// array destroy where the end pointer is regularly determined and
1378  /// does not need to be loaded from a local.
1379  class RegularPartialArrayDestroy : public EHScopeStack::Cleanup {
1380    llvm::Value *ArrayBegin;
1381    llvm::Value *ArrayEnd;
1382    QualType ElementType;
1383    CodeGenFunction::Destroyer *Destroyer;
1384  public:
1385    RegularPartialArrayDestroy(llvm::Value *arrayBegin, llvm::Value *arrayEnd,
1386                               QualType elementType,
1387                               CodeGenFunction::Destroyer *destroyer)
1388      : ArrayBegin(arrayBegin), ArrayEnd(arrayEnd),
1389        ElementType(elementType), Destroyer(destroyer) {}
1390
1391    void Emit(CodeGenFunction &CGF, Flags flags) {
1392      emitPartialArrayDestroy(CGF, ArrayBegin, ArrayEnd,
1393                              ElementType, Destroyer);
1394    }
1395  };
1396
1397  /// IrregularPartialArrayDestroy - a cleanup which performs a
1398  /// partial array destroy where the end pointer is irregularly
1399  /// determined and must be loaded from a local.
1400  class IrregularPartialArrayDestroy : public EHScopeStack::Cleanup {
1401    llvm::Value *ArrayBegin;
1402    llvm::Value *ArrayEndPointer;
1403    QualType ElementType;
1404    CodeGenFunction::Destroyer *Destroyer;
1405  public:
1406    IrregularPartialArrayDestroy(llvm::Value *arrayBegin,
1407                                 llvm::Value *arrayEndPointer,
1408                                 QualType elementType,
1409                                 CodeGenFunction::Destroyer *destroyer)
1410      : ArrayBegin(arrayBegin), ArrayEndPointer(arrayEndPointer),
1411        ElementType(elementType), Destroyer(destroyer) {}
1412
1413    void Emit(CodeGenFunction &CGF, Flags flags) {
1414      llvm::Value *arrayEnd = CGF.Builder.CreateLoad(ArrayEndPointer);
1415      emitPartialArrayDestroy(CGF, ArrayBegin, arrayEnd,
1416                              ElementType, Destroyer);
1417    }
1418  };
1419}
1420
1421/// pushIrregularPartialArrayCleanup - Push an EH cleanup to destroy
1422/// already-constructed elements of the given array.  The cleanup
1423/// may be popped with DeactivateCleanupBlock or PopCleanupBlock.
1424///
1425/// \param elementType - the immediate element type of the array;
1426///   possibly still an array type
1427/// \param array - a value of type elementType*
1428/// \param destructionKind - the kind of destruction required
1429/// \param initializedElementCount - a value of type size_t* holding
1430///   the number of successfully-constructed elements
1431void CodeGenFunction::pushIrregularPartialArrayCleanup(llvm::Value *arrayBegin,
1432                                                 llvm::Value *arrayEndPointer,
1433                                                       QualType elementType,
1434                                                       Destroyer *destroyer) {
1435  pushFullExprCleanup<IrregularPartialArrayDestroy>(EHCleanup,
1436                                                    arrayBegin, arrayEndPointer,
1437                                                    elementType, destroyer);
1438}
1439
1440/// pushRegularPartialArrayCleanup - Push an EH cleanup to destroy
1441/// already-constructed elements of the given array.  The cleanup
1442/// may be popped with DeactivateCleanupBlock or PopCleanupBlock.
1443///
1444/// \param elementType - the immediate element type of the array;
1445///   possibly still an array type
1446/// \param array - a value of type elementType*
1447/// \param destructionKind - the kind of destruction required
1448/// \param initializedElementCount - a value of type size_t* holding
1449///   the number of successfully-constructed elements
1450void CodeGenFunction::pushRegularPartialArrayCleanup(llvm::Value *arrayBegin,
1451                                                     llvm::Value *arrayEnd,
1452                                                     QualType elementType,
1453                                                     Destroyer *destroyer) {
1454  pushFullExprCleanup<RegularPartialArrayDestroy>(EHCleanup,
1455                                                  arrayBegin, arrayEnd,
1456                                                  elementType, destroyer);
1457}
1458
1459namespace {
1460  /// A cleanup to perform a release of an object at the end of a
1461  /// function.  This is used to balance out the incoming +1 of a
1462  /// ns_consumed argument when we can't reasonably do that just by
1463  /// not doing the initial retain for a __block argument.
1464  struct ConsumeARCParameter : EHScopeStack::Cleanup {
1465    ConsumeARCParameter(llvm::Value *param) : Param(param) {}
1466
1467    llvm::Value *Param;
1468
1469    void Emit(CodeGenFunction &CGF, Flags flags) {
1470      CGF.EmitARCRelease(Param, /*precise*/ false);
1471    }
1472  };
1473}
1474
1475/// Emit an alloca (or GlobalValue depending on target)
1476/// for the specified parameter and set up LocalDeclMap.
1477void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg,
1478                                   unsigned ArgNo) {
1479  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
1480  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
1481         "Invalid argument to EmitParmDecl");
1482
1483  Arg->setName(D.getName());
1484
1485  // Use better IR generation for certain implicit parameters.
1486  if (isa<ImplicitParamDecl>(D)) {
1487    // The only implicit argument a block has is its literal.
1488    if (BlockInfo) {
1489      LocalDeclMap[&D] = Arg;
1490
1491      if (CGDebugInfo *DI = getDebugInfo()) {
1492        if (CGM.getCodeGenOpts().DebugInfo >=
1493            CodeGenOptions::LimitedDebugInfo) {
1494          DI->setLocation(D.getLocation());
1495          DI->EmitDeclareOfBlockLiteralArgVariable(*BlockInfo, Arg, Builder);
1496        }
1497      }
1498
1499      return;
1500    }
1501  }
1502
1503  QualType Ty = D.getType();
1504
1505  llvm::Value *DeclPtr;
1506  // If this is an aggregate or variable sized value, reuse the input pointer.
1507  if (!Ty->isConstantSizeType() ||
1508      CodeGenFunction::hasAggregateLLVMType(Ty)) {
1509    DeclPtr = Arg;
1510  } else {
1511    // Otherwise, create a temporary to hold the value.
1512    llvm::AllocaInst *Alloc = CreateTempAlloca(ConvertTypeForMem(Ty),
1513                                               D.getName() + ".addr");
1514    Alloc->setAlignment(getContext().getDeclAlign(&D).getQuantity());
1515    DeclPtr = Alloc;
1516
1517    bool doStore = true;
1518
1519    Qualifiers qs = Ty.getQualifiers();
1520
1521    if (Qualifiers::ObjCLifetime lt = qs.getObjCLifetime()) {
1522      // We honor __attribute__((ns_consumed)) for types with lifetime.
1523      // For __strong, it's handled by just skipping the initial retain;
1524      // otherwise we have to balance out the initial +1 with an extra
1525      // cleanup to do the release at the end of the function.
1526      bool isConsumed = D.hasAttr<NSConsumedAttr>();
1527
1528      // 'self' is always formally __strong, but if this is not an
1529      // init method then we don't want to retain it.
1530      if (D.isARCPseudoStrong()) {
1531        const ObjCMethodDecl *method = cast<ObjCMethodDecl>(CurCodeDecl);
1532        assert(&D == method->getSelfDecl());
1533        assert(lt == Qualifiers::OCL_Strong);
1534        assert(qs.hasConst());
1535        assert(method->getMethodFamily() != OMF_init);
1536        (void) method;
1537        lt = Qualifiers::OCL_ExplicitNone;
1538      }
1539
1540      if (lt == Qualifiers::OCL_Strong) {
1541        if (!isConsumed)
1542          // Don't use objc_retainBlock for block pointers, because we
1543          // don't want to Block_copy something just because we got it
1544          // as a parameter.
1545          Arg = EmitARCRetainNonBlock(Arg);
1546      } else {
1547        // Push the cleanup for a consumed parameter.
1548        if (isConsumed)
1549          EHStack.pushCleanup<ConsumeARCParameter>(getARCCleanupKind(), Arg);
1550
1551        if (lt == Qualifiers::OCL_Weak) {
1552          EmitARCInitWeak(DeclPtr, Arg);
1553          doStore = false; // The weak init is a store, no need to do two.
1554        }
1555      }
1556
1557      // Enter the cleanup scope.
1558      EmitAutoVarWithLifetime(*this, D, DeclPtr, lt);
1559    }
1560
1561    // Store the initial value into the alloca.
1562    if (doStore) {
1563      LValue lv = MakeAddrLValue(DeclPtr, Ty,
1564                                 getContext().getDeclAlign(&D));
1565      EmitStoreOfScalar(Arg, lv, /* isInitialization */ true);
1566    }
1567  }
1568
1569  llvm::Value *&DMEntry = LocalDeclMap[&D];
1570  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
1571  DMEntry = DeclPtr;
1572
1573  // Emit debug info for param declaration.
1574  if (CGDebugInfo *DI = getDebugInfo()) {
1575    if (CGM.getCodeGenOpts().DebugInfo >= CodeGenOptions::LimitedDebugInfo) {
1576      DI->EmitDeclareOfArgVariable(&D, DeclPtr, ArgNo, Builder);
1577    }
1578  }
1579
1580  if (D.hasAttr<AnnotateAttr>())
1581      EmitVarAnnotations(&D, DeclPtr);
1582}
1583