CGDecl.cpp revision 9ad5513b0f9d3999705659fb1aeb0e6c53455f43 
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.getInit()) {
130    llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this);
131
132    // If constant emission failed, then this should be a C++ static
133    // initializer.
134    if (!Init) {
135      if (!getContext().getLangOptions().CPlusPlus)
136        CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
137      else
138        EmitStaticCXXBlockVarDeclInit(D, GV);
139    } else {
140      // The initializer may differ in type from the global. Rewrite
141      // the global to match the initializer.  (We have to do this
142      // because some types, like unions, can't be completely represented
143      // in the LLVM type system.)
144      if (GV->getType() != Init->getType()) {
145        llvm::GlobalVariable *OldGV = GV;
146
147        GV = new llvm::GlobalVariable(CGM.getModule(), Init->getType(),
148                                      OldGV->isConstant(),
149                                      OldGV->getLinkage(), Init, "",
150                                      0, D.isThreadSpecified(),
151                                      D.getType().getAddressSpace());
152
153        // Steal the name of the old global
154        GV->takeName(OldGV);
155
156        // Replace all uses of the old global with the new global
157        llvm::Constant *NewPtrForOldDecl =
158          llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
159        OldGV->replaceAllUsesWith(NewPtrForOldDecl);
160
161        // Erase the old global, since it is no longer used.
162        OldGV->eraseFromParent();
163      }
164
165      GV->setInitializer(Init);
166    }
167  }
168
169  // FIXME: Merge attribute handling.
170  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) {
171    SourceManager &SM = CGM.getContext().getSourceManager();
172    llvm::Constant *Ann =
173      CGM.EmitAnnotateAttr(GV, AA,
174                           SM.getInstantiationLineNumber(D.getLocation()));
175    CGM.AddAnnotation(Ann);
176  }
177
178  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
179    GV->setSection(SA->getName());
180
181  if (D.hasAttr<UsedAttr>())
182    CGM.AddUsedGlobal(GV);
183
184  // We may have to cast the constant because of the initializer
185  // mismatch above.
186  //
187  // FIXME: It is really dangerous to store this in the map; if anyone
188  // RAUW's the GV uses of this constant will be invalid.
189  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
190  const llvm::Type *LPtrTy =
191    llvm::PointerType::get(LTy, D.getType().getAddressSpace());
192  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
193
194  // Emit global variable debug descriptor for static vars.
195  CGDebugInfo *DI = getDebugInfo();
196  if (DI) {
197    DI->setLocation(D.getLocation());
198    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
199  }
200}
201
202/// BuildByRefType - This routine changes a __block variable declared as T x
203///   into:
204///
205///      struct {
206///        void *__isa;
207///        void *__forwarding;
208///        int32_t __flags;
209///        int32_t __size;
210///        void *__copy_helper;
211///        void *__destroy_helper;
212///        T x;
213///      } x
214///
215/// Align is the alignment needed in bytes for x.
216const llvm::Type *CodeGenFunction::BuildByRefType(const ValueDecl *D) {
217  QualType Ty = D->getType();
218  uint64_t Align = getContext().getDeclAlignInBytes(D);
219
220  const llvm::Type *LTy = ConvertType(Ty);
221  bool needsCopyDispose = BlockRequiresCopying(Ty);
222  std::vector<const llvm::Type *> Types(needsCopyDispose*2+5);
223  const llvm::PointerType *PtrToInt8Ty
224    = llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
225  Types[0] = PtrToInt8Ty;
226  Types[1] = PtrToInt8Ty;
227  Types[2] = llvm::Type::getInt32Ty(VMContext);
228  Types[3] = llvm::Type::getInt32Ty(VMContext);
229  if (needsCopyDispose) {
230    Types[4] = PtrToInt8Ty;
231    Types[5] = PtrToInt8Ty;
232  }
233  // FIXME: Align this on at least an Align boundary, assert if we can't.
234  assert((Align <= unsigned(Target.getPointerAlign(0))/8)
235         && "Can't align more than pointer yet");
236  Types[needsCopyDispose*2 + 4] = LTy;
237  return llvm::StructType::get(VMContext, Types, false);
238}
239
240/// EmitLocalBlockVarDecl - Emit code and set up an entry in LocalDeclMap for a
241/// variable declaration with auto, register, or no storage class specifier.
242/// These turn into simple stack objects, or GlobalValues depending on target.
243void CodeGenFunction::EmitLocalBlockVarDecl(const VarDecl &D) {
244  QualType Ty = D.getType();
245  bool isByRef = D.hasAttr<BlocksAttr>();
246  bool needsDispose = false;
247  unsigned Align = 0;
248
249  llvm::Value *DeclPtr;
250  if (Ty->isConstantSizeType()) {
251    if (!Target.useGlobalsForAutomaticVariables()) {
252      // A normal fixed sized variable becomes an alloca in the entry block.
253      const llvm::Type *LTy = ConvertTypeForMem(Ty);
254      Align = getContext().getDeclAlignInBytes(&D);
255      if (isByRef)
256        LTy = BuildByRefType(&D);
257      llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
258      Alloc->setName(D.getNameAsString().c_str());
259
260      if (isByRef)
261        Align = std::max(Align, unsigned(Target.getPointerAlign(0) / 8));
262      Alloc->setAlignment(Align);
263      DeclPtr = Alloc;
264    } else {
265      // Targets that don't support recursion emit locals as globals.
266      const char *Class =
267        D.getStorageClass() == VarDecl::Register ? ".reg." : ".auto.";
268      DeclPtr = CreateStaticBlockVarDecl(D, Class,
269                                         llvm::GlobalValue
270                                         ::InternalLinkage);
271    }
272
273    // FIXME: Can this happen?
274    if (Ty->isVariablyModifiedType())
275      EmitVLASize(Ty);
276  } else {
277    EnsureInsertPoint();
278
279    if (!DidCallStackSave) {
280      // Save the stack.
281      const llvm::Type *LTy =
282        llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
283      llvm::Value *Stack = CreateTempAlloca(LTy, "saved_stack");
284
285      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
286      llvm::Value *V = Builder.CreateCall(F);
287
288      Builder.CreateStore(V, Stack);
289
290      DidCallStackSave = true;
291
292      {
293        // Push a cleanup block and restore the stack there.
294        CleanupScope scope(*this);
295
296        V = Builder.CreateLoad(Stack, "tmp");
297        llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
298        Builder.CreateCall(F, V);
299      }
300    }
301
302    // Get the element type.
303    const llvm::Type *LElemTy = ConvertTypeForMem(Ty);
304    const llvm::Type *LElemPtrTy =
305      llvm::PointerType::get(LElemTy, D.getType().getAddressSpace());
306
307    llvm::Value *VLASize = EmitVLASize(Ty);
308
309    // Downcast the VLA size expression
310    VLASize = Builder.CreateIntCast(VLASize, llvm::Type::getInt32Ty(VMContext),
311                                    false, "tmp");
312
313    // Allocate memory for the array.
314    llvm::Value *VLA = Builder.CreateAlloca(llvm::Type::getInt8Ty(VMContext),
315                                            VLASize, "vla");
316    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
317  }
318
319  llvm::Value *&DMEntry = LocalDeclMap[&D];
320  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
321  DMEntry = DeclPtr;
322
323  // Emit debug info for local var declaration.
324  if (CGDebugInfo *DI = getDebugInfo()) {
325    assert(HaveInsertPoint() && "Unexpected unreachable point!");
326
327    DI->setLocation(D.getLocation());
328    if (Target.useGlobalsForAutomaticVariables()) {
329      DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
330    } else if (isByRef) {
331      // FIXME: This code is broken and will not emit debug info for the
332      // variable. The right way to do this would be to tell LLVM that this is a
333      // byref pointer, and what the offset is. Unfortunately, right now it's
334      // not possible unless we create a DIType that corresponds to the byref
335      // struct.
336      /*
337      llvm::Value *Loc;
338      bool needsCopyDispose = BlockRequiresCopying(Ty);
339      Loc = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
340      Loc = Builder.CreateLoad(Loc, false);
341      Loc = Builder.CreateBitCast(Loc, DeclPtr->getType());
342      Loc = Builder.CreateStructGEP(Loc, needsCopyDispose*2+4, "x");
343      DI->EmitDeclareOfAutoVariable(&D, Loc, Builder);
344      */
345    } else
346      DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
347  }
348
349  // If this local has an initializer, emit it now.
350  const Expr *Init = D.getInit();
351
352  // If we are at an unreachable point, we don't need to emit the initializer
353  // unless it contains a label.
354  if (!HaveInsertPoint()) {
355    if (!ContainsLabel(Init))
356      Init = 0;
357    else
358      EnsureInsertPoint();
359  }
360
361  if (Init) {
362    llvm::Value *Loc = DeclPtr;
363    if (isByRef) {
364      bool needsCopyDispose = BlockRequiresCopying(Ty);
365      Loc = Builder.CreateStructGEP(DeclPtr, needsCopyDispose*2+4, "x");
366    }
367    if (Ty->isReferenceType()) {
368      RValue RV = EmitReferenceBindingToExpr(Init, Ty, /*IsInitializer=*/true);
369      EmitStoreOfScalar(RV.getScalarVal(), Loc, false, Ty);
370    } else if (!hasAggregateLLVMType(Init->getType())) {
371      llvm::Value *V = EmitScalarExpr(Init);
372      EmitStoreOfScalar(V, Loc, D.getType().isVolatileQualified(),
373                        D.getType());
374    } else if (Init->getType()->isAnyComplexType()) {
375      EmitComplexExprIntoAddr(Init, Loc, D.getType().isVolatileQualified());
376    } else {
377      EmitAggExpr(Init, Loc, D.getType().isVolatileQualified());
378    }
379  }
380
381  if (isByRef) {
382    const llvm::PointerType *PtrToInt8Ty
383      = llvm::PointerType::getUnqual(llvm::Type::getInt8Ty(VMContext));
384
385    EnsureInsertPoint();
386    llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
387    llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
388    llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
389    llvm::Value *size_field = Builder.CreateStructGEP(DeclPtr, 3);
390    llvm::Value *V;
391    int flag = 0;
392    int flags = 0;
393
394    needsDispose = true;
395
396    if (Ty->isBlockPointerType()) {
397      flag |= BLOCK_FIELD_IS_BLOCK;
398      flags |= BLOCK_HAS_COPY_DISPOSE;
399    } else if (BlockRequiresCopying(Ty)) {
400      flag |= BLOCK_FIELD_IS_OBJECT;
401      flags |= BLOCK_HAS_COPY_DISPOSE;
402    }
403
404    // FIXME: Someone double check this.
405    if (Ty.isObjCGCWeak())
406      flag |= BLOCK_FIELD_IS_WEAK;
407
408    int isa = 0;
409    if (flag&BLOCK_FIELD_IS_WEAK)
410      isa = 1;
411    V = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), isa);
412    V = Builder.CreateIntToPtr(V, PtrToInt8Ty, "isa");
413    Builder.CreateStore(V, isa_field);
414
415    V = Builder.CreateBitCast(DeclPtr, PtrToInt8Ty, "forwarding");
416    Builder.CreateStore(V, forwarding_field);
417
418    V = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), flags);
419    Builder.CreateStore(V, flags_field);
420
421    const llvm::Type *V1;
422    V1 = cast<llvm::PointerType>(DeclPtr->getType())->getElementType();
423    V = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
424                               (CGM.getTargetData().getTypeStoreSizeInBits(V1)
425                                / 8));
426    Builder.CreateStore(V, size_field);
427
428    if (flags & BLOCK_HAS_COPY_DISPOSE) {
429      BlockHasCopyDispose = true;
430      llvm::Value *copy_helper = Builder.CreateStructGEP(DeclPtr, 4);
431      Builder.CreateStore(BuildbyrefCopyHelper(DeclPtr->getType(), flag, Align),
432                          copy_helper);
433
434      llvm::Value *destroy_helper = Builder.CreateStructGEP(DeclPtr, 5);
435      Builder.CreateStore(BuildbyrefDestroyHelper(DeclPtr->getType(), flag,
436                                                  Align),
437                          destroy_helper);
438    }
439  }
440
441  // Handle CXX destruction of variables.
442  QualType DtorTy(Ty);
443  if (const ArrayType *Array = DtorTy->getAs<ArrayType>())
444    DtorTy = Array->getElementType();
445  if (const RecordType *RT = DtorTy->getAs<RecordType>())
446    if (CXXRecordDecl *ClassDecl = dyn_cast<CXXRecordDecl>(RT->getDecl())) {
447      if (!ClassDecl->hasTrivialDestructor()) {
448        const CXXDestructorDecl *D = ClassDecl->getDestructor(getContext());
449        assert(D && "EmitLocalBlockVarDecl - destructor is nul");
450        assert(!Ty->getAs<ArrayType>() && "FIXME - destruction of arrays NYI");
451
452        CleanupScope scope(*this);
453        EmitCXXDestructorCall(D, Dtor_Complete, DeclPtr);
454      }
455  }
456
457  // Handle the cleanup attribute
458  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
459    const FunctionDecl *FD = CA->getFunctionDecl();
460
461    llvm::Constant* F = CGM.GetAddrOfFunction(GlobalDecl(FD));
462    assert(F && "Could not find function!");
463
464    CleanupScope scope(*this);
465
466    const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD);
467
468    // In some cases, the type of the function argument will be different from
469    // the type of the pointer. An example of this is
470    // void f(void* arg);
471    // __attribute__((cleanup(f))) void *g;
472    //
473    // To fix this we insert a bitcast here.
474    QualType ArgTy = Info.arg_begin()->type;
475    DeclPtr = Builder.CreateBitCast(DeclPtr, ConvertType(ArgTy));
476
477    CallArgList Args;
478    Args.push_back(std::make_pair(RValue::get(DeclPtr),
479                                  getContext().getPointerType(D.getType())));
480
481    EmitCall(Info, F, Args);
482  }
483
484  if (needsDispose && CGM.getLangOptions().getGCMode() != LangOptions::GCOnly) {
485    CleanupScope scope(*this);
486    llvm::Value *V = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
487    V = Builder.CreateLoad(V, false);
488    BuildBlockRelease(V);
489  }
490}
491
492/// Emit an alloca (or GlobalValue depending on target)
493/// for the specified parameter and set up LocalDeclMap.
494void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
495  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
496  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
497         "Invalid argument to EmitParmDecl");
498  QualType Ty = D.getType();
499
500  llvm::Value *DeclPtr;
501  if (!Ty->isConstantSizeType()) {
502    // Variable sized values always are passed by-reference.
503    DeclPtr = Arg;
504  } else {
505    // A fixed sized single-value variable becomes an alloca in the entry block.
506    const llvm::Type *LTy = ConvertTypeForMem(Ty);
507    if (LTy->isSingleValueType()) {
508      // TODO: Alignment
509      std::string Name = D.getNameAsString();
510      Name += ".addr";
511      DeclPtr = CreateTempAlloca(LTy);
512      DeclPtr->setName(Name.c_str());
513
514      // Store the initial value into the alloca.
515      EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), Ty);
516    } else {
517      // Otherwise, if this is an aggregate, just use the input pointer.
518      DeclPtr = Arg;
519    }
520    Arg->setName(D.getNameAsString());
521  }
522
523  llvm::Value *&DMEntry = LocalDeclMap[&D];
524  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
525  DMEntry = DeclPtr;
526
527  // Emit debug info for param declaration.
528  if (CGDebugInfo *DI = getDebugInfo()) {
529    DI->setLocation(D.getLocation());
530    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
531  }
532}
533
534