CGDecl.cpp revision 3b2e16b3d25f6b311dba2871e2a566c96238c3d2 
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>())
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 = CurFn->getName();
99    else
100      assert(0 && "Unknown context for block var decl");
101
102    Name = ContextName + Separator + D.getNameAsString();
103  }
104
105  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
106  return new llvm::GlobalVariable(CGM.getModule(), LTy,
107                                  Ty.isConstant(getContext()), Linkage,
108                                  CGM.EmitNullConstant(D.getType()), Name, 0,
109                                  D.isThreadSpecified(), Ty.getAddressSpace());
110}
111
112void CodeGenFunction::EmitStaticBlockVarDecl(const VarDecl &D) {
113  llvm::Value *&DMEntry = LocalDeclMap[&D];
114  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
115
116  llvm::GlobalVariable *GV =
117    CreateStaticBlockVarDecl(D, ".", llvm::GlobalValue::InternalLinkage);
118
119  // Store into LocalDeclMap before generating initializer to handle
120  // circular references.
121  DMEntry = GV;
122
123  // Make sure to evaluate VLA bounds now so that we have them for later.
124  //
125  // FIXME: Can this happen?
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        EmitStaticCXXBlockVarDeclInit(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(CGM.getModule(), Init->getType(),
153                                      OldGV->isConstant(),
154                                      OldGV->getLinkage(), Init, "",
155                                      0, D.isThreadSpecified(),
156                                      D.getType().getAddressSpace());
157
158        // Steal the name of the old global
159        GV->takeName(OldGV);
160
161        // Replace all uses of the old global with the new global
162        llvm::Constant *NewPtrForOldDecl =
163          llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
164        OldGV->replaceAllUsesWith(NewPtrForOldDecl);
165
166        // Erase the old global, since it is no longer used.
167        OldGV->eraseFromParent();
168      }
169
170      GV->setInitializer(Init);
171    }
172  }
173
174  // FIXME: Merge attribute handling.
175  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) {
176    SourceManager &SM = CGM.getContext().getSourceManager();
177    llvm::Constant *Ann =
178      CGM.EmitAnnotateAttr(GV, AA,
179                           SM.getInstantiationLineNumber(D.getLocation()));
180    CGM.AddAnnotation(Ann);
181  }
182
183  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
184    GV->setSection(SA->getName());
185
186  if (D.hasAttr<UsedAttr>())
187    CGM.AddUsedGlobal(GV);
188
189  // We may have to cast the constant because of the initializer
190  // mismatch above.
191  //
192  // FIXME: It is really dangerous to store this in the map; if anyone
193  // RAUW's the GV uses of this constant will be invalid.
194  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
195  const llvm::Type *LPtrTy =
196    llvm::PointerType::get(LTy, D.getType().getAddressSpace());
197  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
198
199  // Emit global variable debug descriptor for static vars.
200  CGDebugInfo *DI = getDebugInfo();
201  if (DI) {
202    DI->setLocation(D.getLocation());
203    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
204  }
205}
206
207/// BuildByRefType - This routine changes a __block variable declared as T x
208///   into:
209///
210///      struct {
211///        void *__isa;
212///        void *__forwarding;
213///        int32_t __flags;
214///        int32_t __size;
215///        void *__copy_helper;
216///        void *__destroy_helper;
217///        T x;
218///      } x
219///
220/// Align is the alignment needed in bytes for x.
221const llvm::Type *CodeGenFunction::BuildByRefType(QualType Ty,
222                                                  uint64_t Align) {
223  const llvm::Type *LTy = ConvertType(Ty);
224  bool needsCopyDispose = BlockRequiresCopying(Ty);
225  std::vector<const llvm::Type *> Types(needsCopyDispose*2+5);
226  const llvm::PointerType *PtrToInt8Ty
227    = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
228  Types[0] = PtrToInt8Ty;
229  Types[1] = PtrToInt8Ty;
230  Types[2] = llvm::Type::Int32Ty;
231  Types[3] = llvm::Type::Int32Ty;
232  if (needsCopyDispose) {
233    Types[4] = PtrToInt8Ty;
234    Types[5] = PtrToInt8Ty;
235  }
236  // FIXME: Align this on at least an Align boundary, assert if we can't.
237  assert((Align <= unsigned(Target.getPointerAlign(0))/8)
238         && "Can't align more than pointer yet");
239  Types[needsCopyDispose*2 + 4] = LTy;
240  return llvm::StructType::get(VMContext, Types, false);
241}
242
243/// EmitLocalBlockVarDecl - Emit code and set up an entry in LocalDeclMap for a
244/// variable declaration with auto, register, or no storage class specifier.
245/// These turn into simple stack objects, or GlobalValues depending on target.
246void CodeGenFunction::EmitLocalBlockVarDecl(const VarDecl &D) {
247  QualType Ty = D.getType();
248  bool isByRef = D.hasAttr<BlocksAttr>();
249  bool needsDispose = false;
250  unsigned Align = 0;
251
252  llvm::Value *DeclPtr;
253  if (Ty->isConstantSizeType()) {
254    if (!Target.useGlobalsForAutomaticVariables()) {
255      // A normal fixed sized variable becomes an alloca in the entry block.
256      const llvm::Type *LTy = ConvertTypeForMem(Ty);
257      Align = getContext().getDeclAlignInBytes(&D);
258      if (isByRef)
259        LTy = BuildByRefType(Ty, Align);
260      llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
261      Alloc->setName(D.getNameAsString().c_str());
262
263      if (isByRef)
264        Align = std::max(Align, unsigned(Target.getPointerAlign(0) / 8));
265      Alloc->setAlignment(Align);
266      DeclPtr = Alloc;
267    } else {
268      // Targets that don't support recursion emit locals as globals.
269      const char *Class =
270        D.getStorageClass() == VarDecl::Register ? ".reg." : ".auto.";
271      DeclPtr = CreateStaticBlockVarDecl(D, Class,
272                                         llvm::GlobalValue
273                                         ::InternalLinkage);
274    }
275
276    // FIXME: Can this happen?
277    if (Ty->isVariablyModifiedType())
278      EmitVLASize(Ty);
279  } else {
280    EnsureInsertPoint();
281
282    if (!DidCallStackSave) {
283      // Save the stack.
284      const llvm::Type *LTy =
285        llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
286      llvm::Value *Stack = CreateTempAlloca(LTy, "saved_stack");
287
288      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
289      llvm::Value *V = Builder.CreateCall(F);
290
291      Builder.CreateStore(V, Stack);
292
293      DidCallStackSave = true;
294
295      {
296        // Push a cleanup block and restore the stack there.
297        CleanupScope scope(*this);
298
299        V = Builder.CreateLoad(Stack, "tmp");
300        llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
301        Builder.CreateCall(F, V);
302      }
303    }
304
305    // Get the element type.
306    const llvm::Type *LElemTy = ConvertTypeForMem(Ty);
307    const llvm::Type *LElemPtrTy =
308      llvm::PointerType::get(LElemTy, D.getType().getAddressSpace());
309
310    llvm::Value *VLASize = EmitVLASize(Ty);
311
312    // Downcast the VLA size expression
313    VLASize = Builder.CreateIntCast(VLASize, llvm::Type::Int32Ty, false, "tmp");
314
315    // Allocate memory for the array.
316    llvm::Value *VLA = Builder.CreateAlloca(llvm::Type::Int8Ty, VLASize, "vla");
317    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
318  }
319
320  llvm::Value *&DMEntry = LocalDeclMap[&D];
321  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
322  DMEntry = DeclPtr;
323
324  // Emit debug info for local var declaration.
325  if (CGDebugInfo *DI = getDebugInfo()) {
326    assert(HaveInsertPoint() && "Unexpected unreachable point!");
327
328    DI->setLocation(D.getLocation());
329    if (Target.useGlobalsForAutomaticVariables()) {
330      DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
331    } else if (isByRef) {
332      llvm::Value *Loc;
333      bool needsCopyDispose = BlockRequiresCopying(Ty);
334      Loc = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
335      Loc = Builder.CreateLoad(Loc, false);
336      Loc = Builder.CreateBitCast(Loc, DeclPtr->getType());
337      Loc = Builder.CreateStructGEP(Loc, needsCopyDispose*2+4, "x");
338      DI->EmitDeclareOfAutoVariable(&D, Loc, Builder);
339    } else
340      DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
341  }
342
343  // If this local has an initializer, emit it now.
344  const Expr *Init = D.getInit();
345
346  // If we are at an unreachable point, we don't need to emit the initializer
347  // unless it contains a label.
348  if (!HaveInsertPoint()) {
349    if (!ContainsLabel(Init))
350      Init = 0;
351    else
352      EnsureInsertPoint();
353  }
354
355  if (Init) {
356    llvm::Value *Loc = DeclPtr;
357    if (isByRef) {
358      bool needsCopyDispose = BlockRequiresCopying(Ty);
359      Loc = Builder.CreateStructGEP(DeclPtr, needsCopyDispose*2+4, "x");
360    }
361    if (Ty->isReferenceType()) {
362      llvm::Value *V = EmitReferenceBindingToExpr(Init, Ty).getScalarVal();
363      EmitStoreOfScalar(V, Loc, false, Ty);
364    } else if (!hasAggregateLLVMType(Init->getType())) {
365      llvm::Value *V = EmitScalarExpr(Init);
366      EmitStoreOfScalar(V, Loc, D.getType().isVolatileQualified(),
367                        D.getType());
368    } else if (Init->getType()->isAnyComplexType()) {
369      EmitComplexExprIntoAddr(Init, Loc, D.getType().isVolatileQualified());
370    } else {
371      EmitAggExpr(Init, Loc, D.getType().isVolatileQualified());
372    }
373  }
374
375  if (isByRef) {
376    const llvm::PointerType *PtrToInt8Ty
377      = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
378
379    EnsureInsertPoint();
380    llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
381    llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
382    llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
383    llvm::Value *size_field = Builder.CreateStructGEP(DeclPtr, 3);
384    llvm::Value *V;
385    int flag = 0;
386    int flags = 0;
387
388    needsDispose = true;
389
390    if (Ty->isBlockPointerType()) {
391      flag |= BLOCK_FIELD_IS_BLOCK;
392      flags |= BLOCK_HAS_COPY_DISPOSE;
393    } else if (BlockRequiresCopying(Ty)) {
394      flag |= BLOCK_FIELD_IS_OBJECT;
395      flags |= BLOCK_HAS_COPY_DISPOSE;
396    }
397
398    // FIXME: Someone double check this.
399    if (Ty.isObjCGCWeak())
400      flag |= BLOCK_FIELD_IS_WEAK;
401
402    int isa = 0;
403    if (flag&BLOCK_FIELD_IS_WEAK)
404      isa = 1;
405    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, isa);
406    V = Builder.CreateIntToPtr(V, PtrToInt8Ty, "isa");
407    Builder.CreateStore(V, isa_field);
408
409    V = Builder.CreateBitCast(DeclPtr, PtrToInt8Ty, "forwarding");
410    Builder.CreateStore(V, forwarding_field);
411
412    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, flags);
413    Builder.CreateStore(V, flags_field);
414
415    const llvm::Type *V1;
416    V1 = cast<llvm::PointerType>(DeclPtr->getType())->getElementType();
417    V = llvm::ConstantInt::get(llvm::Type::Int32Ty,
418                               (CGM.getTargetData().getTypeStoreSizeInBits(V1)
419                                / 8));
420    Builder.CreateStore(V, size_field);
421
422    if (flags & BLOCK_HAS_COPY_DISPOSE) {
423      BlockHasCopyDispose = true;
424      llvm::Value *copy_helper = Builder.CreateStructGEP(DeclPtr, 4);
425      Builder.CreateStore(BuildbyrefCopyHelper(DeclPtr->getType(), flag, Align),
426                          copy_helper);
427
428      llvm::Value *destroy_helper = Builder.CreateStructGEP(DeclPtr, 5);
429      Builder.CreateStore(BuildbyrefDestroyHelper(DeclPtr->getType(), flag,
430                                                  Align),
431                          destroy_helper);
432    }
433  }
434
435  // Handle CXX destruction of variables.
436  QualType DtorTy(Ty);
437  if (const ArrayType *Array = DtorTy->getAs<ArrayType>())
438    DtorTy = Array->getElementType();
439  if (const RecordType *RT = DtorTy->getAs<RecordType>())
440    if (CXXRecordDecl *ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
441      if (!ClassDecl->hasTrivialDestructor()) {
442        const CXXDestructorDecl *D = ClassDecl->getDestructor(getContext());
443        assert(D && "EmitLocalBlockVarDecl - destructor is nul");
444        assert(!Ty->getAs<ArrayType>() && "FIXME - destruction of arrays NYI");
445
446        CleanupScope scope(*this);
447        EmitCXXDestructorCall(D, Dtor_Complete, DeclPtr);
448      }
449  }
450
451  // Handle the cleanup attribute
452  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
453    const FunctionDecl *FD = CA->getFunctionDecl();
454
455    llvm::Constant* F = CGM.GetAddrOfFunction(GlobalDecl(FD));
456    assert(F && "Could not find function!");
457
458    CleanupScope scope(*this);
459
460    const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD);
461
462    // In some cases, the type of the function argument will be different from
463    // the type of the pointer. An example of this is
464    // void f(void* arg);
465    // __attribute__((cleanup(f))) void *g;
466    //
467    // To fix this we insert a bitcast here.
468    QualType ArgTy = Info.arg_begin()->type;
469    DeclPtr = Builder.CreateBitCast(DeclPtr, ConvertType(ArgTy));
470
471    CallArgList Args;
472    Args.push_back(std::make_pair(RValue::get(DeclPtr),
473                                  getContext().getPointerType(D.getType())));
474
475    EmitCall(Info, F, Args);
476  }
477
478  if (needsDispose && CGM.getLangOptions().getGCMode() != LangOptions::GCOnly) {
479    CleanupScope scope(*this);
480    llvm::Value *V = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
481    V = Builder.CreateLoad(V, false);
482    BuildBlockRelease(V);
483  }
484}
485
486/// Emit an alloca (or GlobalValue depending on target)
487/// for the specified parameter and set up LocalDeclMap.
488void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
489  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
490  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
491         "Invalid argument to EmitParmDecl");
492  QualType Ty = D.getType();
493
494  llvm::Value *DeclPtr;
495  if (!Ty->isConstantSizeType()) {
496    // Variable sized values always are passed by-reference.
497    DeclPtr = Arg;
498  } else {
499    // A fixed sized single-value variable becomes an alloca in the entry block.
500    const llvm::Type *LTy = ConvertTypeForMem(Ty);
501    if (LTy->isSingleValueType()) {
502      // TODO: Alignment
503      std::string Name = D.getNameAsString();
504      Name += ".addr";
505      DeclPtr = CreateTempAlloca(LTy);
506      DeclPtr->setName(Name.c_str());
507
508      // Store the initial value into the alloca.
509      EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), Ty);
510    } else {
511      // Otherwise, if this is an aggregate, just use the input pointer.
512      DeclPtr = Arg;
513    }
514    Arg->setName(D.getNameAsString());
515  }
516
517  llvm::Value *&DMEntry = LocalDeclMap[&D];
518  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
519  DMEntry = DeclPtr;
520
521  // Emit debug info for param declaration.
522  if (CGDebugInfo *DI = getDebugInfo()) {
523    DI->setLocation(D.getLocation());
524    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
525  }
526}
527
528