CGDecl.cpp revision 830937bc1100fba7682f7c32c40512085870f50c 
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 "clang/AST/ASTContext.h"
18#include "clang/AST/CharUnits.h"
19#include "clang/AST/Decl.h"
20#include "clang/AST/DeclObjC.h"
21#include "clang/Basic/SourceManager.h"
22#include "clang/Basic/TargetInfo.h"
23#include "clang/Frontend/CodeGenOptions.h"
24#include "llvm/GlobalVariable.h"
25#include "llvm/Intrinsics.h"
26#include "llvm/Target/TargetData.h"
27#include "llvm/Type.h"
28using namespace clang;
29using namespace CodeGen;
30
31
32void CodeGenFunction::EmitDecl(const Decl &D) {
33  switch (D.getKind()) {
34  case Decl::TranslationUnit:
35  case Decl::Namespace:
36  case Decl::UnresolvedUsingTypename:
37  case Decl::ClassTemplateSpecialization:
38  case Decl::ClassTemplatePartialSpecialization:
39  case Decl::TemplateTypeParm:
40  case Decl::UnresolvedUsingValue:
41  case Decl::NonTypeTemplateParm:
42  case Decl::CXXMethod:
43  case Decl::CXXConstructor:
44  case Decl::CXXDestructor:
45  case Decl::CXXConversion:
46  case Decl::Field:
47  case Decl::IndirectField:
48  case Decl::ObjCIvar:
49  case Decl::ObjCAtDefsField:
50  case Decl::ParmVar:
51  case Decl::ImplicitParam:
52  case Decl::ClassTemplate:
53  case Decl::FunctionTemplate:
54  case Decl::TemplateTemplateParm:
55  case Decl::ObjCMethod:
56  case Decl::ObjCCategory:
57  case Decl::ObjCProtocol:
58  case Decl::ObjCInterface:
59  case Decl::ObjCCategoryImpl:
60  case Decl::ObjCImplementation:
61  case Decl::ObjCProperty:
62  case Decl::ObjCCompatibleAlias:
63  case Decl::AccessSpec:
64  case Decl::LinkageSpec:
65  case Decl::ObjCPropertyImpl:
66  case Decl::ObjCClass:
67  case Decl::ObjCForwardProtocol:
68  case Decl::FileScopeAsm:
69  case Decl::Friend:
70  case Decl::FriendTemplate:
71  case Decl::Block:
72
73    assert(0 && "Declaration not 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    // None of these decls require codegen support.
85    return;
86
87  case Decl::Var: {
88    const VarDecl &VD = cast<VarDecl>(D);
89    assert(VD.isLocalVarDecl() &&
90           "Should not see file-scope variables inside a function!");
91    return EmitVarDecl(VD);
92  }
93
94  case Decl::Typedef: {   // typedef int X;
95    const TypedefDecl &TD = cast<TypedefDecl>(D);
96    QualType Ty = TD.getUnderlyingType();
97
98    if (Ty->isVariablyModifiedType())
99      EmitVLASize(Ty);
100  }
101  }
102}
103
104/// EmitVarDecl - This method handles emission of any variable declaration
105/// inside a function, including static vars etc.
106void CodeGenFunction::EmitVarDecl(const VarDecl &D) {
107  if (D.hasAttr<AsmLabelAttr>())
108    CGM.ErrorUnsupported(&D, "__asm__");
109
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().getLangOptions().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  }
135
136  assert(0 && "Unknown storage class");
137}
138
139static std::string GetStaticDeclName(CodeGenFunction &CGF, const VarDecl &D,
140                                     const char *Separator) {
141  CodeGenModule &CGM = CGF.CGM;
142  if (CGF.getContext().getLangOptions().CPlusPlus) {
143    llvm::StringRef Name = CGM.getMangledName(&D);
144    return Name.str();
145  }
146
147  std::string ContextName;
148  if (!CGF.CurFuncDecl) {
149    // Better be in a block declared in global scope.
150    const NamedDecl *ND = cast<NamedDecl>(&D);
151    const DeclContext *DC = ND->getDeclContext();
152    if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) {
153      MangleBuffer Name;
154      CGM.getMangledName(GlobalDecl(), Name, BD);
155      ContextName = Name.getString();
156    }
157    else
158      assert(0 && "Unknown context for block static var decl");
159  } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CGF.CurFuncDecl)) {
160    llvm::StringRef Name = CGM.getMangledName(FD);
161    ContextName = Name.str();
162  } else if (isa<ObjCMethodDecl>(CGF.CurFuncDecl))
163    ContextName = CGF.CurFn->getName();
164  else
165    assert(0 && "Unknown context for static var decl");
166
167  return ContextName + Separator + D.getNameAsString();
168}
169
170llvm::GlobalVariable *
171CodeGenFunction::CreateStaticVarDecl(const VarDecl &D,
172                                     const char *Separator,
173                                     llvm::GlobalValue::LinkageTypes Linkage) {
174  QualType Ty = D.getType();
175  assert(Ty->isConstantSizeType() && "VLAs can't be static");
176
177  std::string Name = GetStaticDeclName(*this, D, Separator);
178
179  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
180  llvm::GlobalVariable *GV =
181    new llvm::GlobalVariable(CGM.getModule(), LTy,
182                             Ty.isConstant(getContext()), Linkage,
183                             CGM.EmitNullConstant(D.getType()), Name, 0,
184                             D.isThreadSpecified(), Ty.getAddressSpace());
185  GV->setAlignment(getContext().getDeclAlign(&D).getQuantity());
186  if (Linkage != llvm::GlobalValue::InternalLinkage)
187    GV->setVisibility(CurFn->getVisibility());
188  return GV;
189}
190
191/// AddInitializerToStaticVarDecl - Add the initializer for 'D' to the
192/// global variable that has already been created for it.  If the initializer
193/// has a different type than GV does, this may free GV and return a different
194/// one.  Otherwise it just returns GV.
195llvm::GlobalVariable *
196CodeGenFunction::AddInitializerToStaticVarDecl(const VarDecl &D,
197                                               llvm::GlobalVariable *GV) {
198  llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this);
199
200  // If constant emission failed, then this should be a C++ static
201  // initializer.
202  if (!Init) {
203    if (!getContext().getLangOptions().CPlusPlus)
204      CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
205    else if (Builder.GetInsertBlock()) {
206      // Since we have a static initializer, this global variable can't
207      // be constant.
208      GV->setConstant(false);
209
210      EmitCXXGuardedInit(D, GV);
211    }
212    return GV;
213  }
214
215  // The initializer may differ in type from the global. Rewrite
216  // the global to match the initializer.  (We have to do this
217  // because some types, like unions, can't be completely represented
218  // in the LLVM type system.)
219  if (GV->getType()->getElementType() != Init->getType()) {
220    llvm::GlobalVariable *OldGV = GV;
221
222    GV = new llvm::GlobalVariable(CGM.getModule(), Init->getType(),
223                                  OldGV->isConstant(),
224                                  OldGV->getLinkage(), Init, "",
225                                  /*InsertBefore*/ OldGV,
226                                  D.isThreadSpecified(),
227                                  D.getType().getAddressSpace());
228    GV->setVisibility(OldGV->getVisibility());
229
230    // Steal the name of the old global
231    GV->takeName(OldGV);
232
233    // Replace all uses of the old global with the new global
234    llvm::Constant *NewPtrForOldDecl =
235    llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
236    OldGV->replaceAllUsesWith(NewPtrForOldDecl);
237
238    // Erase the old global, since it is no longer used.
239    OldGV->eraseFromParent();
240  }
241
242  GV->setInitializer(Init);
243  return GV;
244}
245
246void CodeGenFunction::EmitStaticVarDecl(const VarDecl &D,
247                                      llvm::GlobalValue::LinkageTypes Linkage) {
248  llvm::Value *&DMEntry = LocalDeclMap[&D];
249  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
250
251  llvm::GlobalVariable *GV = CreateStaticVarDecl(D, ".", Linkage);
252
253  // Store into LocalDeclMap before generating initializer to handle
254  // circular references.
255  DMEntry = GV;
256
257  // We can't have a VLA here, but we can have a pointer to a VLA,
258  // even though that doesn't really make any sense.
259  // Make sure to evaluate VLA bounds now so that we have them for later.
260  if (D.getType()->isVariablyModifiedType())
261    EmitVLASize(D.getType());
262
263  // Local static block variables must be treated as globals as they may be
264  // referenced in their RHS initializer block-literal expresion.
265  CGM.setStaticLocalDeclAddress(&D, GV);
266
267  // If this value has an initializer, emit it.
268  if (D.getInit())
269    GV = AddInitializerToStaticVarDecl(D, GV);
270
271  GV->setAlignment(getContext().getDeclAlign(&D).getQuantity());
272
273  // FIXME: Merge attribute handling.
274  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) {
275    SourceManager &SM = CGM.getContext().getSourceManager();
276    llvm::Constant *Ann =
277      CGM.EmitAnnotateAttr(GV, AA,
278                           SM.getInstantiationLineNumber(D.getLocation()));
279    CGM.AddAnnotation(Ann);
280  }
281
282  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
283    GV->setSection(SA->getName());
284
285  if (D.hasAttr<UsedAttr>())
286    CGM.AddUsedGlobal(GV);
287
288  // We may have to cast the constant because of the initializer
289  // mismatch above.
290  //
291  // FIXME: It is really dangerous to store this in the map; if anyone
292  // RAUW's the GV uses of this constant will be invalid.
293  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
294  const llvm::Type *LPtrTy = LTy->getPointerTo(D.getType().getAddressSpace());
295  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
296
297  // Emit global variable debug descriptor for static vars.
298  CGDebugInfo *DI = getDebugInfo();
299  if (DI) {
300    DI->setLocation(D.getLocation());
301    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
302  }
303}
304
305unsigned CodeGenFunction::getByRefValueLLVMField(const ValueDecl *VD) const {
306  assert(ByRefValueInfo.count(VD) && "Did not find value!");
307
308  return ByRefValueInfo.find(VD)->second.second;
309}
310
311/// BuildByRefType - This routine changes a __block variable declared as T x
312///   into:
313///
314///      struct {
315///        void *__isa;
316///        void *__forwarding;
317///        int32_t __flags;
318///        int32_t __size;
319///        void *__copy_helper;       // only if needed
320///        void *__destroy_helper;    // only if needed
321///        char padding[X];           // only if needed
322///        T x;
323///      } x
324///
325const llvm::Type *CodeGenFunction::BuildByRefType(const ValueDecl *D) {
326  std::pair<const llvm::Type *, unsigned> &Info = ByRefValueInfo[D];
327  if (Info.first)
328    return Info.first;
329
330  QualType Ty = D->getType();
331
332  std::vector<const llvm::Type *> Types;
333
334  const llvm::PointerType *Int8PtrTy = llvm::Type::getInt8PtrTy(VMContext);
335
336  llvm::PATypeHolder ByRefTypeHolder = llvm::OpaqueType::get(VMContext);
337
338  // void *__isa;
339  Types.push_back(Int8PtrTy);
340
341  // void *__forwarding;
342  Types.push_back(llvm::PointerType::getUnqual(ByRefTypeHolder));
343
344  // int32_t __flags;
345  Types.push_back(Int32Ty);
346
347  // int32_t __size;
348  Types.push_back(Int32Ty);
349
350  bool HasCopyAndDispose = BlockRequiresCopying(Ty);
351  if (HasCopyAndDispose) {
352    /// void *__copy_helper;
353    Types.push_back(Int8PtrTy);
354
355    /// void *__destroy_helper;
356    Types.push_back(Int8PtrTy);
357  }
358
359  bool Packed = false;
360  CharUnits Align = getContext().getDeclAlign(D);
361  if (Align > CharUnits::fromQuantity(Target.getPointerAlign(0) / 8)) {
362    // We have to insert padding.
363
364    // The struct above has 2 32-bit integers.
365    unsigned CurrentOffsetInBytes = 4 * 2;
366
367    // And either 2 or 4 pointers.
368    CurrentOffsetInBytes += (HasCopyAndDispose ? 4 : 2) *
369      CGM.getTargetData().getTypeAllocSize(Int8PtrTy);
370
371    // Align the offset.
372    unsigned AlignedOffsetInBytes =
373      llvm::RoundUpToAlignment(CurrentOffsetInBytes, Align.getQuantity());
374
375    unsigned NumPaddingBytes = AlignedOffsetInBytes - CurrentOffsetInBytes;
376    if (NumPaddingBytes > 0) {
377      const llvm::Type *Ty = llvm::Type::getInt8Ty(VMContext);
378      // FIXME: We need a sema error for alignment larger than the minimum of
379      // the maximal stack alignmint and the alignment of malloc on the system.
380      if (NumPaddingBytes > 1)
381        Ty = llvm::ArrayType::get(Ty, NumPaddingBytes);
382
383      Types.push_back(Ty);
384
385      // We want a packed struct.
386      Packed = true;
387    }
388  }
389
390  // T x;
391  Types.push_back(ConvertTypeForMem(Ty));
392
393  const llvm::Type *T = llvm::StructType::get(VMContext, Types, Packed);
394
395  cast<llvm::OpaqueType>(ByRefTypeHolder.get())->refineAbstractTypeTo(T);
396  CGM.getModule().addTypeName("struct.__block_byref_" + D->getNameAsString(),
397                              ByRefTypeHolder.get());
398
399  Info.first = ByRefTypeHolder.get();
400
401  Info.second = Types.size() - 1;
402
403  return Info.first;
404}
405
406namespace {
407  struct CallArrayDtor : EHScopeStack::Cleanup {
408    CallArrayDtor(const CXXDestructorDecl *Dtor,
409                  const ConstantArrayType *Type,
410                  llvm::Value *Loc)
411      : Dtor(Dtor), Type(Type), Loc(Loc) {}
412
413    const CXXDestructorDecl *Dtor;
414    const ConstantArrayType *Type;
415    llvm::Value *Loc;
416
417    void Emit(CodeGenFunction &CGF, bool IsForEH) {
418      QualType BaseElementTy = CGF.getContext().getBaseElementType(Type);
419      const llvm::Type *BasePtr = CGF.ConvertType(BaseElementTy);
420      BasePtr = llvm::PointerType::getUnqual(BasePtr);
421      llvm::Value *BaseAddrPtr = CGF.Builder.CreateBitCast(Loc, BasePtr);
422      CGF.EmitCXXAggrDestructorCall(Dtor, Type, BaseAddrPtr);
423    }
424  };
425
426  struct CallVarDtor : EHScopeStack::Cleanup {
427    CallVarDtor(const CXXDestructorDecl *Dtor,
428                llvm::Value *NRVOFlag,
429                llvm::Value *Loc)
430      : Dtor(Dtor), NRVOFlag(NRVOFlag), Loc(Loc) {}
431
432    const CXXDestructorDecl *Dtor;
433    llvm::Value *NRVOFlag;
434    llvm::Value *Loc;
435
436    void Emit(CodeGenFunction &CGF, bool IsForEH) {
437      // Along the exceptions path we always execute the dtor.
438      bool NRVO = !IsForEH && NRVOFlag;
439
440      llvm::BasicBlock *SkipDtorBB = 0;
441      if (NRVO) {
442        // If we exited via NRVO, we skip the destructor call.
443        llvm::BasicBlock *RunDtorBB = CGF.createBasicBlock("nrvo.unused");
444        SkipDtorBB = CGF.createBasicBlock("nrvo.skipdtor");
445        llvm::Value *DidNRVO = CGF.Builder.CreateLoad(NRVOFlag, "nrvo.val");
446        CGF.Builder.CreateCondBr(DidNRVO, SkipDtorBB, RunDtorBB);
447        CGF.EmitBlock(RunDtorBB);
448      }
449
450      CGF.EmitCXXDestructorCall(Dtor, Dtor_Complete,
451                                /*ForVirtualBase=*/false, Loc);
452
453      if (NRVO) CGF.EmitBlock(SkipDtorBB);
454    }
455  };
456}
457
458namespace {
459  struct CallStackRestore : EHScopeStack::Cleanup {
460    llvm::Value *Stack;
461    CallStackRestore(llvm::Value *Stack) : Stack(Stack) {}
462    void Emit(CodeGenFunction &CGF, bool IsForEH) {
463      llvm::Value *V = CGF.Builder.CreateLoad(Stack, "tmp");
464      llvm::Value *F = CGF.CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
465      CGF.Builder.CreateCall(F, V);
466    }
467  };
468
469  struct CallCleanupFunction : EHScopeStack::Cleanup {
470    llvm::Constant *CleanupFn;
471    const CGFunctionInfo &FnInfo;
472    llvm::Value *Addr;
473    const VarDecl &Var;
474
475    CallCleanupFunction(llvm::Constant *CleanupFn, const CGFunctionInfo *Info,
476                        llvm::Value *Addr, const VarDecl *Var)
477      : CleanupFn(CleanupFn), FnInfo(*Info), Addr(Addr), Var(*Var) {}
478
479    void Emit(CodeGenFunction &CGF, bool IsForEH) {
480      // In some cases, the type of the function argument will be different from
481      // the type of the pointer. An example of this is
482      // void f(void* arg);
483      // __attribute__((cleanup(f))) void *g;
484      //
485      // To fix this we insert a bitcast here.
486      QualType ArgTy = FnInfo.arg_begin()->type;
487      llvm::Value *Arg =
488        CGF.Builder.CreateBitCast(Addr, CGF.ConvertType(ArgTy));
489
490      CallArgList Args;
491      Args.push_back(std::make_pair(RValue::get(Arg),
492                            CGF.getContext().getPointerType(Var.getType())));
493      CGF.EmitCall(FnInfo, CleanupFn, ReturnValueSlot(), Args);
494    }
495  };
496
497  struct CallBlockRelease : EHScopeStack::Cleanup {
498    llvm::Value *Addr;
499    CallBlockRelease(llvm::Value *Addr) : Addr(Addr) {}
500
501    void Emit(CodeGenFunction &CGF, bool IsForEH) {
502      llvm::Value *V = CGF.Builder.CreateStructGEP(Addr, 1, "forwarding");
503      V = CGF.Builder.CreateLoad(V);
504      CGF.BuildBlockRelease(V);
505    }
506  };
507}
508
509
510/// canEmitInitWithFewStoresAfterMemset - Decide whether we can emit the
511/// non-zero parts of the specified initializer with equal or fewer than
512/// NumStores scalar stores.
513static bool canEmitInitWithFewStoresAfterMemset(llvm::Constant *Init,
514                                                unsigned &NumStores) {
515  // Zero and Undef never requires any extra stores.
516  if (isa<llvm::ConstantAggregateZero>(Init) ||
517      isa<llvm::ConstantPointerNull>(Init) ||
518      isa<llvm::UndefValue>(Init))
519    return true;
520  if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) ||
521      isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) ||
522      isa<llvm::ConstantExpr>(Init))
523    return Init->isNullValue() || NumStores--;
524
525  // See if we can emit each element.
526  if (isa<llvm::ConstantArray>(Init) || isa<llvm::ConstantStruct>(Init)) {
527    for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) {
528      llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i));
529      if (!canEmitInitWithFewStoresAfterMemset(Elt, NumStores))
530        return false;
531    }
532    return true;
533  }
534
535  // Anything else is hard and scary.
536  return false;
537}
538
539/// emitStoresForInitAfterMemset - For inits that
540/// canEmitInitWithFewStoresAfterMemset returned true for, emit the scalar
541/// stores that would be required.
542static void emitStoresForInitAfterMemset(llvm::Constant *Init, llvm::Value *Loc,
543                                         CGBuilderTy &Builder) {
544  // Zero doesn't require any stores.
545  if (isa<llvm::ConstantAggregateZero>(Init) ||
546      isa<llvm::ConstantPointerNull>(Init) ||
547      isa<llvm::UndefValue>(Init))
548    return;
549
550  if (isa<llvm::ConstantInt>(Init) || isa<llvm::ConstantFP>(Init) ||
551      isa<llvm::ConstantVector>(Init) || isa<llvm::BlockAddress>(Init) ||
552      isa<llvm::ConstantExpr>(Init)) {
553    if (!Init->isNullValue())
554      Builder.CreateStore(Init, Loc);
555    return;
556  }
557
558  assert((isa<llvm::ConstantStruct>(Init) || isa<llvm::ConstantArray>(Init)) &&
559         "Unknown value type!");
560
561  for (unsigned i = 0, e = Init->getNumOperands(); i != e; ++i) {
562    llvm::Constant *Elt = cast<llvm::Constant>(Init->getOperand(i));
563    if (Elt->isNullValue()) continue;
564
565    // Otherwise, get a pointer to the element and emit it.
566    emitStoresForInitAfterMemset(Elt, Builder.CreateConstGEP2_32(Loc, 0, i),
567                                 Builder);
568  }
569}
570
571
572/// shouldUseMemSetPlusStoresToInitialize - Decide whether we should use memset
573/// plus some stores to initialize a local variable instead of using a memcpy
574/// from a constant global.  It is beneficial to use memset if the global is all
575/// zeros, or mostly zeros and large.
576static bool shouldUseMemSetPlusStoresToInitialize(llvm::Constant *Init,
577                                                  uint64_t GlobalSize) {
578  // If a global is all zeros, always use a memset.
579  if (isa<llvm::ConstantAggregateZero>(Init)) return true;
580
581
582  // If a non-zero global is <= 32 bytes, always use a memcpy.  If it is large,
583  // do it if it will require 6 or fewer scalar stores.
584  // TODO: Should budget depends on the size?  Avoiding a large global warrants
585  // plopping in more stores.
586  unsigned StoreBudget = 6;
587  uint64_t SizeLimit = 32;
588
589  return GlobalSize > SizeLimit &&
590         canEmitInitWithFewStoresAfterMemset(Init, StoreBudget);
591}
592
593
594/// EmitLocalVarDecl - Emit code and set up an entry in LocalDeclMap for a
595/// variable declaration with auto, register, or no storage class specifier.
596/// These turn into simple stack objects, or GlobalValues depending on target.
597void CodeGenFunction::EmitAutoVarDecl(const VarDecl &D,
598                                      SpecialInitFn *SpecialInit) {
599  QualType Ty = D.getType();
600  unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
601  bool isByRef = D.hasAttr<BlocksAttr>();
602  bool needsDispose = false;
603  CharUnits Align = CharUnits::Zero();
604  bool IsSimpleConstantInitializer = false;
605
606  bool NRVO = false;
607  llvm::Value *NRVOFlag = 0;
608  llvm::Value *DeclPtr;
609  if (Ty->isConstantSizeType()) {
610    if (!Target.useGlobalsForAutomaticVariables()) {
611      NRVO = getContext().getLangOptions().ElideConstructors &&
612             D.isNRVOVariable();
613      // If this value is an array or struct, is POD, and if the initializer is
614      // a staticly determinable constant, try to optimize it (unless the NRVO
615      // is already optimizing this).
616      if (!NRVO && D.getInit() && !isByRef &&
617          (Ty->isArrayType() || Ty->isRecordType()) &&
618          Ty->isPODType() &&
619          D.getInit()->isConstantInitializer(getContext(), false)) {
620        // If this variable is marked 'const', emit the value as a global.
621        if (CGM.getCodeGenOpts().MergeAllConstants &&
622            Ty.isConstant(getContext())) {
623          EmitStaticVarDecl(D, llvm::GlobalValue::InternalLinkage);
624          return;
625        }
626
627        IsSimpleConstantInitializer = true;
628      }
629
630      // A normal fixed sized variable becomes an alloca in the entry block,
631      // unless it's an NRVO variable.
632      const llvm::Type *LTy = ConvertTypeForMem(Ty);
633
634      if (NRVO) {
635        // The named return value optimization: allocate this variable in the
636        // return slot, so that we can elide the copy when returning this
637        // variable (C++0x [class.copy]p34).
638        DeclPtr = ReturnValue;
639
640        if (const RecordType *RecordTy = Ty->getAs<RecordType>()) {
641          if (!cast<CXXRecordDecl>(RecordTy->getDecl())->hasTrivialDestructor()) {
642            // Create a flag that is used to indicate when the NRVO was applied
643            // to this variable. Set it to zero to indicate that NRVO was not
644            // applied.
645            llvm::Value *Zero = Builder.getFalse();
646            NRVOFlag = CreateTempAlloca(Zero->getType(), "nrvo");
647            Builder.CreateStore(Zero, NRVOFlag);
648
649            // Record the NRVO flag for this variable.
650            NRVOFlags[&D] = NRVOFlag;
651          }
652        }
653      } else {
654        if (isByRef)
655          LTy = BuildByRefType(&D);
656
657        llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
658        Alloc->setName(D.getNameAsString());
659
660        Align = getContext().getDeclAlign(&D);
661        if (isByRef)
662          Align = std::max(Align,
663              CharUnits::fromQuantity(Target.getPointerAlign(0) / 8));
664        Alloc->setAlignment(Align.getQuantity());
665        DeclPtr = Alloc;
666      }
667    } else {
668      // Targets that don't support recursion emit locals as globals.
669      const char *Class =
670        D.getStorageClass() == SC_Register ? ".reg." : ".auto.";
671      DeclPtr = CreateStaticVarDecl(D, Class,
672                                    llvm::GlobalValue::InternalLinkage);
673    }
674
675    // FIXME: Can this happen?
676    if (Ty->isVariablyModifiedType())
677      EmitVLASize(Ty);
678  } else {
679    EnsureInsertPoint();
680
681    if (!DidCallStackSave) {
682      // Save the stack.
683      const llvm::Type *LTy = llvm::Type::getInt8PtrTy(VMContext);
684      llvm::Value *Stack = CreateTempAlloca(LTy, "saved_stack");
685
686      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
687      llvm::Value *V = Builder.CreateCall(F);
688
689      Builder.CreateStore(V, Stack);
690
691      DidCallStackSave = true;
692
693      // Push a cleanup block and restore the stack there.
694      EHStack.pushCleanup<CallStackRestore>(NormalCleanup, Stack);
695    }
696
697    // Get the element type.
698    const llvm::Type *LElemTy = ConvertTypeForMem(Ty);
699    const llvm::Type *LElemPtrTy = LElemTy->getPointerTo(Ty.getAddressSpace());
700
701    llvm::Value *VLASize = EmitVLASize(Ty);
702
703    // Allocate memory for the array.
704    llvm::AllocaInst *VLA =
705      Builder.CreateAlloca(llvm::Type::getInt8Ty(VMContext), VLASize, "vla");
706    VLA->setAlignment(getContext().getDeclAlign(&D).getQuantity());
707
708    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
709  }
710
711  llvm::Value *&DMEntry = LocalDeclMap[&D];
712  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
713  DMEntry = DeclPtr;
714
715  // Emit debug info for local var declaration.
716  if (CGDebugInfo *DI = getDebugInfo()) {
717    assert(HaveInsertPoint() && "Unexpected unreachable point!");
718
719    DI->setLocation(D.getLocation());
720    if (Target.useGlobalsForAutomaticVariables()) {
721      DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
722    } else
723      DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
724  }
725
726  // If this local has an initializer, emit it now.
727  const Expr *Init = D.getInit();
728
729  // If we are at an unreachable point, we don't need to emit the initializer
730  // unless it contains a label.
731  if (!HaveInsertPoint()) {
732    if (!ContainsLabel(Init))
733      Init = 0;
734    else
735      EnsureInsertPoint();
736  }
737
738  if (isByRef) {
739    const llvm::PointerType *PtrToInt8Ty = llvm::Type::getInt8PtrTy(VMContext);
740
741    EnsureInsertPoint();
742    llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
743    llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
744    llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
745    llvm::Value *size_field = Builder.CreateStructGEP(DeclPtr, 3);
746    llvm::Value *V;
747    int flag = 0;
748    int flags = 0;
749
750    needsDispose = true;
751
752    if (Ty->isBlockPointerType()) {
753      flag |= BLOCK_FIELD_IS_BLOCK;
754      flags |= BLOCK_HAS_COPY_DISPOSE;
755    } else if (getContext().isObjCNSObjectType(Ty) ||
756               Ty->isObjCObjectPointerType()) {
757      flag |= BLOCK_FIELD_IS_OBJECT;
758      flags |= BLOCK_HAS_COPY_DISPOSE;
759    } else if (getContext().getBlockVarCopyInits(&D)) {
760        flag |= BLOCK_HAS_CXX_OBJ;
761        flags |= BLOCK_HAS_COPY_DISPOSE;
762    }
763
764    // FIXME: Someone double check this.
765    if (Ty.isObjCGCWeak())
766      flag |= BLOCK_FIELD_IS_WEAK;
767
768    int isa = 0;
769    if (flag & BLOCK_FIELD_IS_WEAK)
770      isa = 1;
771    V = Builder.CreateIntToPtr(Builder.getInt32(isa), PtrToInt8Ty, "isa");
772    Builder.CreateStore(V, isa_field);
773
774    Builder.CreateStore(DeclPtr, forwarding_field);
775
776    Builder.CreateStore(Builder.getInt32(flags), flags_field);
777
778    const llvm::Type *V1;
779    V1 = cast<llvm::PointerType>(DeclPtr->getType())->getElementType();
780    V = Builder.getInt32(CGM.GetTargetTypeStoreSize(V1).getQuantity());
781    Builder.CreateStore(V, size_field);
782
783    if (flags & BLOCK_HAS_COPY_DISPOSE) {
784      SynthesizeCopyDisposeHelpers = true;
785      llvm::Value *copy_helper = Builder.CreateStructGEP(DeclPtr, 4);
786      Builder.CreateStore(BuildbyrefCopyHelper(DeclPtr->getType(), flag,
787                                               Align.getQuantity(), &D),
788                          copy_helper);
789
790      llvm::Value *destroy_helper = Builder.CreateStructGEP(DeclPtr, 5);
791      Builder.CreateStore(BuildbyrefDestroyHelper(DeclPtr->getType(), flag,
792                                                  Align.getQuantity(), &D),
793                          destroy_helper);
794    }
795  }
796
797  if (SpecialInit) {
798    SpecialInit(*this, D, DeclPtr);
799  } else if (Init) {
800    llvm::Value *Loc = DeclPtr;
801    if (isByRef)
802      Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D),
803                                    D.getNameAsString());
804
805    bool isVolatile = getContext().getCanonicalType(Ty).isVolatileQualified();
806
807    // If the initializer was a simple constant initializer, we can optimize it
808    // in various ways.
809    if (IsSimpleConstantInitializer) {
810      llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), Ty,this);
811      assert(Init != 0 && "Wasn't a simple constant init?");
812
813      llvm::Value *AlignVal = Builder.getInt32(Align.getQuantity());
814      llvm::Value *SizeVal =
815      llvm::ConstantInt::get(CGF.IntPtrTy,
816                             getContext().getTypeSizeInChars(Ty).getQuantity());
817
818      const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
819      if (Loc->getType() != BP)
820        Loc = Builder.CreateBitCast(Loc, BP, "tmp");
821
822      llvm::Value *NotVolatile = Builder.getFalse();
823
824      // If the initializer is all or mostly zeros, codegen with memset then do
825      // a few stores afterward.
826      if (shouldUseMemSetPlusStoresToInitialize(Init,
827                      CGM.getTargetData().getTypeAllocSize(Init->getType()))) {
828        const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
829
830        Builder.CreateCall5(CGM.getMemSetFn(BP, SizeVal->getType()),
831                            Loc, Builder.getInt8(0), SizeVal, AlignVal,
832                            NotVolatile);
833        if (!Init->isNullValue()) {
834          Loc = Builder.CreateBitCast(Loc, Init->getType()->getPointerTo());
835          emitStoresForInitAfterMemset(Init, Loc, Builder);
836        }
837
838      } else {
839        // Otherwise, create a temporary global with the initializer then
840        // memcpy from the global to the alloca.
841        std::string Name = GetStaticDeclName(*this, D, ".");
842        llvm::GlobalVariable *GV =
843        new llvm::GlobalVariable(CGM.getModule(), Init->getType(), true,
844                                 llvm::GlobalValue::InternalLinkage,
845                                 Init, Name, 0, false, 0);
846        GV->setAlignment(Align.getQuantity());
847
848        llvm::Value *SrcPtr = GV;
849        if (SrcPtr->getType() != BP)
850          SrcPtr = Builder.CreateBitCast(SrcPtr, BP, "tmp");
851
852        Builder.CreateCall5(CGM.getMemCpyFn(Loc->getType(), SrcPtr->getType(),
853                                            SizeVal->getType()),
854                            Loc, SrcPtr, SizeVal, AlignVal, NotVolatile);
855      }
856    } else if (Ty->isReferenceType()) {
857      RValue RV = EmitReferenceBindingToExpr(Init, &D);
858      EmitStoreOfScalar(RV.getScalarVal(), Loc, false, Alignment, Ty);
859    } else if (!hasAggregateLLVMType(Init->getType())) {
860      llvm::Value *V = EmitScalarExpr(Init);
861      EmitStoreOfScalar(V, Loc, isVolatile, Alignment, Ty);
862    } else if (Init->getType()->isAnyComplexType()) {
863      EmitComplexExprIntoAddr(Init, Loc, isVolatile);
864    } else {
865      EmitAggExpr(Init, AggValueSlot::forAddr(Loc, isVolatile, true, false));
866    }
867  }
868
869  // Handle CXX destruction of variables.
870  QualType DtorTy(Ty);
871  while (const ArrayType *Array = getContext().getAsArrayType(DtorTy))
872    DtorTy = getContext().getBaseElementType(Array);
873  if (const RecordType *RT = DtorTy->getAs<RecordType>())
874    if (CXXRecordDecl *ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
875      if (!ClassDecl->hasTrivialDestructor()) {
876        // Note: We suppress the destructor call when the corresponding NRVO
877        // flag has been set.
878        llvm::Value *Loc = DeclPtr;
879        if (isByRef)
880          Loc = Builder.CreateStructGEP(DeclPtr, getByRefValueLLVMField(&D),
881                                        D.getNameAsString());
882
883        const CXXDestructorDecl *D = ClassDecl->getDestructor();
884        assert(D && "EmitLocalBlockVarDecl - destructor is nul");
885
886        if (const ConstantArrayType *Array =
887              getContext().getAsConstantArrayType(Ty)) {
888          EHStack.pushCleanup<CallArrayDtor>(NormalAndEHCleanup,
889                                             D, Array, Loc);
890        } else {
891          EHStack.pushCleanup<CallVarDtor>(NormalAndEHCleanup,
892                                           D, NRVOFlag, Loc);
893        }
894      }
895  }
896
897  // Handle the cleanup attribute
898  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
899    const FunctionDecl *FD = CA->getFunctionDecl();
900
901    llvm::Constant* F = CGM.GetAddrOfFunction(FD);
902    assert(F && "Could not find function!");
903
904    const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD);
905    EHStack.pushCleanup<CallCleanupFunction>(NormalAndEHCleanup,
906                                             F, &Info, DeclPtr, &D);
907  }
908
909  // If this is a block variable, clean it up.
910  if (needsDispose && CGM.getLangOptions().getGCMode() != LangOptions::GCOnly)
911    EHStack.pushCleanup<CallBlockRelease>(NormalAndEHCleanup, DeclPtr);
912}
913
914/// Emit an alloca (or GlobalValue depending on target)
915/// for the specified parameter and set up LocalDeclMap.
916void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
917  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
918  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
919         "Invalid argument to EmitParmDecl");
920  QualType Ty = D.getType();
921  CanQualType CTy = getContext().getCanonicalType(Ty);
922
923  llvm::Value *DeclPtr;
924  // If this is an aggregate or variable sized value, reuse the input pointer.
925  if (!Ty->isConstantSizeType() ||
926      CodeGenFunction::hasAggregateLLVMType(Ty)) {
927    DeclPtr = Arg;
928  } else {
929    // Otherwise, create a temporary to hold the value.
930    DeclPtr = CreateMemTemp(Ty, D.getName() + ".addr");
931
932    // Store the initial value into the alloca.
933    unsigned Alignment = getContext().getDeclAlign(&D).getQuantity();
934    EmitStoreOfScalar(Arg, DeclPtr, CTy.isVolatileQualified(), Alignment, Ty);
935  }
936  Arg->setName(D.getName());
937
938  llvm::Value *&DMEntry = LocalDeclMap[&D];
939  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
940  DMEntry = DeclPtr;
941
942  // Emit debug info for param declaration.
943  if (CGDebugInfo *DI = getDebugInfo()) {
944    DI->setLocation(D.getLocation());
945    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
946  }
947}
948