CGDecl.cpp revision 194613 
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/Decl.h"
19#include "clang/AST/DeclObjC.h"
20#include "clang/Basic/SourceManager.h"
21#include "clang/Basic/TargetInfo.h"
22#include "llvm/GlobalVariable.h"
23#include "llvm/Intrinsics.h"
24#include "llvm/Target/TargetData.h"
25#include "llvm/Type.h"
26using namespace clang;
27using namespace CodeGen;
28
29
30void CodeGenFunction::EmitDecl(const Decl &D) {
31  switch (D.getKind()) {
32  default: assert(0 && "Unknown decl kind!");
33  case Decl::ParmVar:
34    assert(0 && "Parmdecls should not be in declstmts!");
35  case Decl::Function:  // void X();
36  case Decl::Record:    // struct/union/class X;
37  case Decl::Enum:      // enum X;
38  case Decl::EnumConstant: // enum ? { X = ? }
39  case Decl::CXXRecord: // struct/union/class X; [C++]
40    // None of these decls require codegen support.
41    return;
42
43  case Decl::Var: {
44    const VarDecl &VD = cast<VarDecl>(D);
45    assert(VD.isBlockVarDecl() &&
46           "Should not see file-scope variables inside a function!");
47    return EmitBlockVarDecl(VD);
48  }
49
50  case Decl::Typedef: {   // typedef int X;
51    const TypedefDecl &TD = cast<TypedefDecl>(D);
52    QualType Ty = TD.getUnderlyingType();
53
54    if (Ty->isVariablyModifiedType())
55      EmitVLASize(Ty);
56  }
57  }
58}
59
60/// EmitBlockVarDecl - This method handles emission of any variable declaration
61/// inside a function, including static vars etc.
62void CodeGenFunction::EmitBlockVarDecl(const VarDecl &D) {
63  if (D.hasAttr<AsmLabelAttr>(getContext()))
64    CGM.ErrorUnsupported(&D, "__asm__");
65
66  switch (D.getStorageClass()) {
67  case VarDecl::None:
68  case VarDecl::Auto:
69  case VarDecl::Register:
70    return EmitLocalBlockVarDecl(D);
71  case VarDecl::Static:
72    return EmitStaticBlockVarDecl(D);
73  case VarDecl::Extern:
74  case VarDecl::PrivateExtern:
75    // Don't emit it now, allow it to be emitted lazily on its first use.
76    return;
77  }
78
79  assert(0 && "Unknown storage class");
80}
81
82llvm::GlobalVariable *
83CodeGenFunction::CreateStaticBlockVarDecl(const VarDecl &D,
84                                          const char *Separator,
85                                          llvm::GlobalValue::LinkageTypes
86                                          Linkage) {
87  QualType Ty = D.getType();
88  assert(Ty->isConstantSizeType() && "VLAs can't be static");
89
90  std::string Name;
91  if (getContext().getLangOptions().CPlusPlus) {
92    Name = CGM.getMangledName(&D);
93  } else {
94    std::string ContextName;
95    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CurFuncDecl))
96      ContextName = CGM.getMangledName(FD);
97    else if (isa<ObjCMethodDecl>(CurFuncDecl))
98      ContextName = std::string(CurFn->getNameStart(),
99                                CurFn->getNameStart() + CurFn->getNameLen());
100    else
101      assert(0 && "Unknown context for block var decl");
102
103    Name = ContextName + Separator + D.getNameAsString();
104  }
105
106  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
107  return new llvm::GlobalVariable(LTy, Ty.isConstant(getContext()), Linkage,
108                                  llvm::Constant::getNullValue(LTy), Name,
109                                  &CGM.getModule(), D.isThreadSpecified(),
110                                  Ty.getAddressSpace());
111}
112
113void CodeGenFunction::EmitStaticBlockVarDecl(const VarDecl &D) {
114
115  llvm::Value *&DMEntry = LocalDeclMap[&D];
116  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
117
118  llvm::GlobalVariable *GV =
119    CreateStaticBlockVarDecl(D, ".", llvm::GlobalValue::InternalLinkage);
120
121  // Store into LocalDeclMap before generating initializer to handle
122  // circular references.
123  DMEntry = GV;
124
125  // Make sure to evaluate VLA bounds now so that we have them for later.
126  if (D.getType()->isVariablyModifiedType())
127    EmitVLASize(D.getType());
128
129  if (D.getType()->isReferenceType()) {
130    CGM.ErrorUnsupported(&D, "static declaration with reference type");
131    return;
132  }
133
134  if (D.getInit()) {
135    llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this);
136
137    // If constant emission failed, then this should be a C++ static
138    // initializer.
139    if (!Init) {
140      if (!getContext().getLangOptions().CPlusPlus)
141        CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
142      else
143        GenerateStaticCXXBlockVarDeclInit(D, GV);
144    } else {
145      // The initializer may differ in type from the global. Rewrite
146      // the global to match the initializer.  (We have to do this
147      // because some types, like unions, can't be completely represented
148      // in the LLVM type system.)
149      if (GV->getType() != Init->getType()) {
150        llvm::GlobalVariable *OldGV = GV;
151
152        GV = new llvm::GlobalVariable(Init->getType(), OldGV->isConstant(),
153                                      OldGV->getLinkage(), Init, "",
154                                      &CGM.getModule(), D.isThreadSpecified(),
155                                      D.getType().getAddressSpace());
156
157        // Steal the name of the old global
158        GV->takeName(OldGV);
159
160        // Replace all uses of the old global with the new global
161        llvm::Constant *NewPtrForOldDecl =
162          llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
163        OldGV->replaceAllUsesWith(NewPtrForOldDecl);
164
165        // Erase the old global, since it is no longer used.
166        OldGV->eraseFromParent();
167      }
168
169      GV->setInitializer(Init);
170    }
171  }
172
173  // FIXME: Merge attribute handling.
174  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>(getContext())) {
175    SourceManager &SM = CGM.getContext().getSourceManager();
176    llvm::Constant *Ann =
177      CGM.EmitAnnotateAttr(GV, AA,
178                           SM.getInstantiationLineNumber(D.getLocation()));
179    CGM.AddAnnotation(Ann);
180  }
181
182  if (const SectionAttr *SA = D.getAttr<SectionAttr>(getContext()))
183    GV->setSection(SA->getName());
184
185  if (D.hasAttr<UsedAttr>(getContext()))
186    CGM.AddUsedGlobal(GV);
187
188  // We may have to cast the constant because of the initializer
189  // mismatch above.
190  //
191  // FIXME: It is really dangerous to store this in the map; if anyone
192  // RAUW's the GV uses of this constant will be invalid.
193  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
194  const llvm::Type *LPtrTy =
195    llvm::PointerType::get(LTy, D.getType().getAddressSpace());
196  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
197
198  // Emit global variable debug descriptor for static vars.
199  CGDebugInfo *DI = getDebugInfo();
200  if (DI) {
201    DI->setLocation(D.getLocation());
202    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
203  }
204}
205
206/// BuildByRefType - This routine changes a __block variable declared as T x
207///   into:
208///
209///      struct {
210///        void *__isa;
211///        void *__forwarding;
212///        int32_t __flags;
213///        int32_t __size;
214///        void *__copy_helper;
215///        void *__destroy_helper;
216///        T x;
217///      } x
218///
219/// Align is the alignment needed in bytes for x.
220const llvm::Type *CodeGenFunction::BuildByRefType(QualType Ty,
221                                                  uint64_t Align) {
222  const llvm::Type *LTy = ConvertType(Ty);
223  bool needsCopyDispose = BlockRequiresCopying(Ty);
224  std::vector<const llvm::Type *> Types(needsCopyDispose*2+5);
225  const llvm::PointerType *PtrToInt8Ty
226    = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
227  Types[0] = PtrToInt8Ty;
228  Types[1] = PtrToInt8Ty;
229  Types[2] = llvm::Type::Int32Ty;
230  Types[3] = llvm::Type::Int32Ty;
231  if (needsCopyDispose) {
232    Types[4] = PtrToInt8Ty;
233    Types[5] = PtrToInt8Ty;
234  }
235  // FIXME: Align this on at least an Align boundary, assert if we can't.
236  assert((Align <= unsigned(Target.getPointerAlign(0))/8)
237         && "Can't align more thqn pointer yet");
238  Types[needsCopyDispose*2 + 4] = LTy;
239  return llvm::StructType::get(Types, false);
240}
241
242/// EmitLocalBlockVarDecl - Emit code and set up an entry in LocalDeclMap for a
243/// variable declaration with auto, register, or no storage class specifier.
244/// These turn into simple stack objects, or GlobalValues depending on target.
245void CodeGenFunction::EmitLocalBlockVarDecl(const VarDecl &D) {
246  QualType Ty = D.getType();
247  bool isByRef = D.hasAttr<BlocksAttr>(getContext());
248  bool needsDispose = false;
249  unsigned Align = 0;
250
251  llvm::Value *DeclPtr;
252  if (Ty->isConstantSizeType()) {
253    if (!Target.useGlobalsForAutomaticVariables()) {
254      // A normal fixed sized variable becomes an alloca in the entry block.
255      const llvm::Type *LTy = ConvertTypeForMem(Ty);
256      Align = getContext().getDeclAlignInBytes(&D);
257      if (isByRef)
258        LTy = BuildByRefType(Ty, Align);
259      llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
260      Alloc->setName(D.getNameAsString().c_str());
261
262      if (isByRef)
263        Align = std::max(Align, unsigned(Target.getPointerAlign(0) / 8));
264      Alloc->setAlignment(Align);
265      DeclPtr = Alloc;
266    } else {
267      // Targets that don't support recursion emit locals as globals.
268      const char *Class =
269        D.getStorageClass() == VarDecl::Register ? ".reg." : ".auto.";
270      DeclPtr = CreateStaticBlockVarDecl(D, Class,
271                                         llvm::GlobalValue
272                                         ::InternalLinkage);
273    }
274
275    if (Ty->isVariablyModifiedType())
276      EmitVLASize(Ty);
277  } else {
278    if (!DidCallStackSave) {
279      // Save the stack.
280      const llvm::Type *LTy = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
281      llvm::Value *Stack = CreateTempAlloca(LTy, "saved_stack");
282
283      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
284      llvm::Value *V = Builder.CreateCall(F);
285
286      Builder.CreateStore(V, Stack);
287
288      DidCallStackSave = true;
289
290      {
291        // Push a cleanup block and restore the stack there.
292        CleanupScope scope(*this);
293
294        V = Builder.CreateLoad(Stack, "tmp");
295        llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
296        Builder.CreateCall(F, V);
297      }
298    }
299
300    // Get the element type.
301    const llvm::Type *LElemTy = ConvertTypeForMem(Ty);
302    const llvm::Type *LElemPtrTy =
303      llvm::PointerType::get(LElemTy, D.getType().getAddressSpace());
304
305    llvm::Value *VLASize = EmitVLASize(Ty);
306
307    // Downcast the VLA size expression
308    VLASize = Builder.CreateIntCast(VLASize, llvm::Type::Int32Ty, false, "tmp");
309
310    // Allocate memory for the array.
311    llvm::Value *VLA = Builder.CreateAlloca(llvm::Type::Int8Ty, VLASize, "vla");
312    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
313  }
314
315  llvm::Value *&DMEntry = LocalDeclMap[&D];
316  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
317  DMEntry = DeclPtr;
318
319  // Emit debug info for local var declaration.
320  if (CGDebugInfo *DI = getDebugInfo()) {
321    DI->setLocation(D.getLocation());
322    if (Target.useGlobalsForAutomaticVariables()) {
323      DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
324    }
325    else if (isByRef) {
326      llvm::Value *Loc;
327      bool needsCopyDispose = BlockRequiresCopying(Ty);
328      Loc = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
329      Loc = Builder.CreateLoad(Loc, false);
330      Loc = Builder.CreateBitCast(Loc, DeclPtr->getType());
331      Loc = Builder.CreateStructGEP(Loc, needsCopyDispose*2+4, "x");
332      DI->EmitDeclareOfAutoVariable(&D, Loc, Builder);
333    } else
334      DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
335  }
336
337  // If this local has an initializer, emit it now.
338  if (const Expr *Init = D.getInit()) {
339    llvm::Value *Loc = DeclPtr;
340    if (isByRef) {
341      bool needsCopyDispose = BlockRequiresCopying(Ty);
342      Loc = Builder.CreateStructGEP(DeclPtr, needsCopyDispose*2+4, "x");
343    }
344    if (Ty->isReferenceType()) {
345      llvm::Value *V = EmitReferenceBindingToExpr(Init, Ty).getScalarVal();
346      EmitStoreOfScalar(V, Loc, false, Ty);
347    } else if (!hasAggregateLLVMType(Init->getType())) {
348      llvm::Value *V = EmitScalarExpr(Init);
349      EmitStoreOfScalar(V, Loc, D.getType().isVolatileQualified(),
350                        D.getType());
351    } else if (Init->getType()->isAnyComplexType()) {
352      EmitComplexExprIntoAddr(Init, Loc, D.getType().isVolatileQualified());
353    } else {
354      EmitAggExpr(Init, Loc, D.getType().isVolatileQualified());
355    }
356  }
357  if (isByRef) {
358    const llvm::PointerType *PtrToInt8Ty
359      = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
360
361    llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
362    llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
363    llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
364    llvm::Value *size_field = Builder.CreateStructGEP(DeclPtr, 3);
365    llvm::Value *V;
366    int flag = 0;
367    int flags = 0;
368
369    needsDispose = true;
370
371    if (Ty->isBlockPointerType()) {
372      flag |= BLOCK_FIELD_IS_BLOCK;
373      flags |= BLOCK_HAS_COPY_DISPOSE;
374    } else if (BlockRequiresCopying(Ty)) {
375      flag |= BLOCK_FIELD_IS_OBJECT;
376      flags |= BLOCK_HAS_COPY_DISPOSE;
377    }
378
379    // FIXME: Someone double check this.
380    if (Ty.isObjCGCWeak())
381      flag |= BLOCK_FIELD_IS_WEAK;
382
383    int isa = 0;
384    if (flag&BLOCK_FIELD_IS_WEAK)
385      isa = 1;
386    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, isa);
387    V = Builder.CreateIntToPtr(V, PtrToInt8Ty, "isa");
388    Builder.CreateStore(V, isa_field);
389
390    V = Builder.CreateBitCast(DeclPtr, PtrToInt8Ty, "forwarding");
391    Builder.CreateStore(V, forwarding_field);
392
393    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, flags);
394    Builder.CreateStore(V, flags_field);
395
396    const llvm::Type *V1;
397    V1 = cast<llvm::PointerType>(DeclPtr->getType())->getElementType();
398    V = llvm::ConstantInt::get(llvm::Type::Int32Ty,
399                               (CGM.getTargetData().getTypeStoreSizeInBits(V1)
400                                / 8));
401    Builder.CreateStore(V, size_field);
402
403    if (flags & BLOCK_HAS_COPY_DISPOSE) {
404      BlockHasCopyDispose = true;
405      llvm::Value *copy_helper = Builder.CreateStructGEP(DeclPtr, 4);
406      Builder.CreateStore(BuildbyrefCopyHelper(DeclPtr->getType(), flag, Align),
407                          copy_helper);
408
409      llvm::Value *destroy_helper = Builder.CreateStructGEP(DeclPtr, 5);
410      Builder.CreateStore(BuildbyrefDestroyHelper(DeclPtr->getType(), flag,
411                                                  Align),
412                          destroy_helper);
413    }
414  }
415
416  // Handle the cleanup attribute
417  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>(getContext())) {
418    const FunctionDecl *FD = CA->getFunctionDecl();
419
420    llvm::Constant* F = CGM.GetAddrOfFunction(GlobalDecl(FD));
421    assert(F && "Could not find function!");
422
423    CleanupScope scope(*this);
424
425    const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD);
426
427    // In some cases, the type of the function argument will be different from
428    // the type of the pointer. An example of this is
429    // void f(void* arg);
430    // __attribute__((cleanup(f))) void *g;
431    //
432    // To fix this we insert a bitcast here.
433    QualType ArgTy = Info.arg_begin()->type;
434    DeclPtr = Builder.CreateBitCast(DeclPtr, ConvertType(ArgTy));
435
436    CallArgList Args;
437    Args.push_back(std::make_pair(RValue::get(DeclPtr),
438                                  getContext().getPointerType(D.getType())));
439
440    EmitCall(Info, F, Args);
441  }
442
443  if (needsDispose && CGM.getLangOptions().getGCMode() != LangOptions::GCOnly) {
444    CleanupScope scope(*this);
445    llvm::Value *V = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
446    V = Builder.CreateLoad(V, false);
447    BuildBlockRelease(V);
448  }
449}
450
451/// Emit an alloca (or GlobalValue depending on target)
452/// for the specified parameter and set up LocalDeclMap.
453void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
454  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
455  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
456         "Invalid argument to EmitParmDecl");
457  QualType Ty = D.getType();
458
459  llvm::Value *DeclPtr;
460  if (!Ty->isConstantSizeType()) {
461    // Variable sized values always are passed by-reference.
462    DeclPtr = Arg;
463  } else {
464    // A fixed sized single-value variable becomes an alloca in the entry block.
465    const llvm::Type *LTy = ConvertTypeForMem(Ty);
466    if (LTy->isSingleValueType()) {
467      // TODO: Alignment
468      std::string Name = D.getNameAsString();
469      Name += ".addr";
470      DeclPtr = CreateTempAlloca(LTy);
471      DeclPtr->setName(Name.c_str());
472
473      // Store the initial value into the alloca.
474      EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), Ty);
475    } else {
476      // Otherwise, if this is an aggregate, just use the input pointer.
477      DeclPtr = Arg;
478    }
479    Arg->setName(D.getNameAsString());
480  }
481
482  llvm::Value *&DMEntry = LocalDeclMap[&D];
483  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
484  DMEntry = DeclPtr;
485
486  // Emit debug info for param declaration.
487  if (CGDebugInfo *DI = getDebugInfo()) {
488    DI->setLocation(D.getLocation());
489    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
490  }
491}
492
493