CGDecl.cpp revision c14f0d230257a8db58aee6329116a7e245e6bbd6 
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 = 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(CGM.getModule().getContext(),
108                                  LTy, Ty.isConstant(getContext()), Linkage,
109                                  llvm::Constant::getNullValue(LTy), Name,
110                                  &CGM.getModule(), D.isThreadSpecified(),
111                                  Ty.getAddressSpace());
112}
113
114void CodeGenFunction::EmitStaticBlockVarDecl(const VarDecl &D) {
115
116  llvm::Value *&DMEntry = LocalDeclMap[&D];
117  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
118
119  llvm::GlobalVariable *GV =
120    CreateStaticBlockVarDecl(D, ".", llvm::GlobalValue::InternalLinkage);
121
122  // Store into LocalDeclMap before generating initializer to handle
123  // circular references.
124  DMEntry = GV;
125
126  // Make sure to evaluate VLA bounds now so that we have them for later.
127  if (D.getType()->isVariablyModifiedType())
128    EmitVLASize(D.getType());
129
130  if (D.getType()->isReferenceType()) {
131    CGM.ErrorUnsupported(&D, "static declaration with reference type");
132    return;
133  }
134
135  if (D.getInit()) {
136    llvm::Constant *Init = CGM.EmitConstantExpr(D.getInit(), D.getType(), this);
137
138    // If constant emission failed, then this should be a C++ static
139    // initializer.
140    if (!Init) {
141      if (!getContext().getLangOptions().CPlusPlus)
142        CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
143      else
144        GenerateStaticCXXBlockVarDeclInit(D, GV);
145    } else {
146      // The initializer may differ in type from the global. Rewrite
147      // the global to match the initializer.  (We have to do this
148      // because some types, like unions, can't be completely represented
149      // in the LLVM type system.)
150      if (GV->getType() != Init->getType()) {
151        llvm::GlobalVariable *OldGV = GV;
152
153        GV = new llvm::GlobalVariable(CGM.getModule().getContext(),
154                                      Init->getType(), OldGV->isConstant(),
155                                      OldGV->getLinkage(), Init, "",
156                                      &CGM.getModule(), D.isThreadSpecified(),
157                                      D.getType().getAddressSpace());
158
159        // Steal the name of the old global
160        GV->takeName(OldGV);
161
162        // Replace all uses of the old global with the new global
163        llvm::Constant *NewPtrForOldDecl =
164          llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
165        OldGV->replaceAllUsesWith(NewPtrForOldDecl);
166
167        // Erase the old global, since it is no longer used.
168        OldGV->eraseFromParent();
169      }
170
171      GV->setInitializer(Init);
172    }
173  }
174
175  // FIXME: Merge attribute handling.
176  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) {
177    SourceManager &SM = CGM.getContext().getSourceManager();
178    llvm::Constant *Ann =
179      CGM.EmitAnnotateAttr(GV, AA,
180                           SM.getInstantiationLineNumber(D.getLocation()));
181    CGM.AddAnnotation(Ann);
182  }
183
184  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
185    GV->setSection(SA->getName());
186
187  if (D.hasAttr<UsedAttr>())
188    CGM.AddUsedGlobal(GV);
189
190  // We may have to cast the constant because of the initializer
191  // mismatch above.
192  //
193  // FIXME: It is really dangerous to store this in the map; if anyone
194  // RAUW's the GV uses of this constant will be invalid.
195  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
196  const llvm::Type *LPtrTy =
197    llvm::PointerType::get(LTy, D.getType().getAddressSpace());
198  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
199
200  // Emit global variable debug descriptor for static vars.
201  CGDebugInfo *DI = getDebugInfo();
202  if (DI) {
203    DI->setLocation(D.getLocation());
204    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
205  }
206}
207
208/// BuildByRefType - This routine changes a __block variable declared as T x
209///   into:
210///
211///      struct {
212///        void *__isa;
213///        void *__forwarding;
214///        int32_t __flags;
215///        int32_t __size;
216///        void *__copy_helper;
217///        void *__destroy_helper;
218///        T x;
219///      } x
220///
221/// Align is the alignment needed in bytes for x.
222const llvm::Type *CodeGenFunction::BuildByRefType(QualType Ty,
223                                                  uint64_t Align) {
224  const llvm::Type *LTy = ConvertType(Ty);
225  bool needsCopyDispose = BlockRequiresCopying(Ty);
226  std::vector<const llvm::Type *> Types(needsCopyDispose*2+5);
227  const llvm::PointerType *PtrToInt8Ty
228    = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
229  Types[0] = PtrToInt8Ty;
230  Types[1] = PtrToInt8Ty;
231  Types[2] = llvm::Type::Int32Ty;
232  Types[3] = llvm::Type::Int32Ty;
233  if (needsCopyDispose) {
234    Types[4] = PtrToInt8Ty;
235    Types[5] = PtrToInt8Ty;
236  }
237  // FIXME: Align this on at least an Align boundary, assert if we can't.
238  assert((Align <= unsigned(Target.getPointerAlign(0))/8)
239         && "Can't align more than pointer yet");
240  Types[needsCopyDispose*2 + 4] = LTy;
241  return llvm::StructType::get(Types, false);
242}
243
244/// EmitLocalBlockVarDecl - Emit code and set up an entry in LocalDeclMap for a
245/// variable declaration with auto, register, or no storage class specifier.
246/// These turn into simple stack objects, or GlobalValues depending on target.
247void CodeGenFunction::EmitLocalBlockVarDecl(const VarDecl &D) {
248  QualType Ty = D.getType();
249  bool isByRef = D.hasAttr<BlocksAttr>();
250  bool needsDispose = false;
251  unsigned Align = 0;
252
253  llvm::Value *DeclPtr;
254  if (Ty->isConstantSizeType()) {
255    if (!Target.useGlobalsForAutomaticVariables()) {
256      // A normal fixed sized variable becomes an alloca in the entry block.
257      const llvm::Type *LTy = ConvertTypeForMem(Ty);
258      Align = getContext().getDeclAlignInBytes(&D);
259      if (isByRef)
260        LTy = BuildByRefType(Ty, Align);
261      llvm::AllocaInst *Alloc = CreateTempAlloca(LTy);
262      Alloc->setName(D.getNameAsString().c_str());
263
264      if (isByRef)
265        Align = std::max(Align, unsigned(Target.getPointerAlign(0) / 8));
266      Alloc->setAlignment(Align);
267      DeclPtr = Alloc;
268    } else {
269      // Targets that don't support recursion emit locals as globals.
270      const char *Class =
271        D.getStorageClass() == VarDecl::Register ? ".reg." : ".auto.";
272      DeclPtr = CreateStaticBlockVarDecl(D, Class,
273                                         llvm::GlobalValue
274                                         ::InternalLinkage);
275    }
276
277    if (Ty->isVariablyModifiedType())
278      EmitVLASize(Ty);
279  } else {
280    if (!DidCallStackSave) {
281      // Save the stack.
282      const llvm::Type *LTy = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
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::Int32Ty, false, "tmp");
311
312    // Allocate memory for the array.
313    llvm::Value *VLA = Builder.CreateAlloca(llvm::Type::Int8Ty, VLASize, "vla");
314    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
315  }
316
317  llvm::Value *&DMEntry = LocalDeclMap[&D];
318  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
319  DMEntry = DeclPtr;
320
321  // Emit debug info for local var declaration.
322  if (CGDebugInfo *DI = getDebugInfo()) {
323    DI->setLocation(D.getLocation());
324    if (Target.useGlobalsForAutomaticVariables()) {
325      DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(DeclPtr), &D);
326    }
327    else if (isByRef) {
328      llvm::Value *Loc;
329      bool needsCopyDispose = BlockRequiresCopying(Ty);
330      Loc = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
331      Loc = Builder.CreateLoad(Loc, false);
332      Loc = Builder.CreateBitCast(Loc, DeclPtr->getType());
333      Loc = Builder.CreateStructGEP(Loc, needsCopyDispose*2+4, "x");
334      DI->EmitDeclareOfAutoVariable(&D, Loc, Builder);
335    } else
336      DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
337  }
338
339  // If this local has an initializer, emit it now.
340  if (const Expr *Init = D.getInit()) {
341    llvm::Value *Loc = DeclPtr;
342    if (isByRef) {
343      bool needsCopyDispose = BlockRequiresCopying(Ty);
344      Loc = Builder.CreateStructGEP(DeclPtr, needsCopyDispose*2+4, "x");
345    }
346    if (Ty->isReferenceType()) {
347      llvm::Value *V = EmitReferenceBindingToExpr(Init, Ty).getScalarVal();
348      EmitStoreOfScalar(V, Loc, false, Ty);
349    } else if (!hasAggregateLLVMType(Init->getType())) {
350      llvm::Value *V = EmitScalarExpr(Init);
351      EmitStoreOfScalar(V, Loc, D.getType().isVolatileQualified(),
352                        D.getType());
353    } else if (Init->getType()->isAnyComplexType()) {
354      EmitComplexExprIntoAddr(Init, Loc, D.getType().isVolatileQualified());
355    } else {
356      EmitAggExpr(Init, Loc, D.getType().isVolatileQualified());
357    }
358  }
359  if (isByRef) {
360    const llvm::PointerType *PtrToInt8Ty
361      = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
362
363    llvm::Value *isa_field = Builder.CreateStructGEP(DeclPtr, 0);
364    llvm::Value *forwarding_field = Builder.CreateStructGEP(DeclPtr, 1);
365    llvm::Value *flags_field = Builder.CreateStructGEP(DeclPtr, 2);
366    llvm::Value *size_field = Builder.CreateStructGEP(DeclPtr, 3);
367    llvm::Value *V;
368    int flag = 0;
369    int flags = 0;
370
371    needsDispose = true;
372
373    if (Ty->isBlockPointerType()) {
374      flag |= BLOCK_FIELD_IS_BLOCK;
375      flags |= BLOCK_HAS_COPY_DISPOSE;
376    } else if (BlockRequiresCopying(Ty)) {
377      flag |= BLOCK_FIELD_IS_OBJECT;
378      flags |= BLOCK_HAS_COPY_DISPOSE;
379    }
380
381    // FIXME: Someone double check this.
382    if (Ty.isObjCGCWeak())
383      flag |= BLOCK_FIELD_IS_WEAK;
384
385    int isa = 0;
386    if (flag&BLOCK_FIELD_IS_WEAK)
387      isa = 1;
388    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, isa);
389    V = Builder.CreateIntToPtr(V, PtrToInt8Ty, "isa");
390    Builder.CreateStore(V, isa_field);
391
392    V = Builder.CreateBitCast(DeclPtr, PtrToInt8Ty, "forwarding");
393    Builder.CreateStore(V, forwarding_field);
394
395    V = llvm::ConstantInt::get(llvm::Type::Int32Ty, flags);
396    Builder.CreateStore(V, flags_field);
397
398    const llvm::Type *V1;
399    V1 = cast<llvm::PointerType>(DeclPtr->getType())->getElementType();
400    V = llvm::ConstantInt::get(llvm::Type::Int32Ty,
401                               (CGM.getTargetData().getTypeStoreSizeInBits(V1)
402                                / 8));
403    Builder.CreateStore(V, size_field);
404
405    if (flags & BLOCK_HAS_COPY_DISPOSE) {
406      BlockHasCopyDispose = true;
407      llvm::Value *copy_helper = Builder.CreateStructGEP(DeclPtr, 4);
408      Builder.CreateStore(BuildbyrefCopyHelper(DeclPtr->getType(), flag, Align),
409                          copy_helper);
410
411      llvm::Value *destroy_helper = Builder.CreateStructGEP(DeclPtr, 5);
412      Builder.CreateStore(BuildbyrefDestroyHelper(DeclPtr->getType(), flag,
413                                                  Align),
414                          destroy_helper);
415    }
416  }
417
418  // Handle the cleanup attribute
419  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
420    const FunctionDecl *FD = CA->getFunctionDecl();
421
422    llvm::Constant* F = CGM.GetAddrOfFunction(GlobalDecl(FD));
423    assert(F && "Could not find function!");
424
425    CleanupScope scope(*this);
426
427    const CGFunctionInfo &Info = CGM.getTypes().getFunctionInfo(FD);
428
429    // In some cases, the type of the function argument will be different from
430    // the type of the pointer. An example of this is
431    // void f(void* arg);
432    // __attribute__((cleanup(f))) void *g;
433    //
434    // To fix this we insert a bitcast here.
435    QualType ArgTy = Info.arg_begin()->type;
436    DeclPtr = Builder.CreateBitCast(DeclPtr, ConvertType(ArgTy));
437
438    CallArgList Args;
439    Args.push_back(std::make_pair(RValue::get(DeclPtr),
440                                  getContext().getPointerType(D.getType())));
441
442    EmitCall(Info, F, Args);
443  }
444
445  if (needsDispose && CGM.getLangOptions().getGCMode() != LangOptions::GCOnly) {
446    CleanupScope scope(*this);
447    llvm::Value *V = Builder.CreateStructGEP(DeclPtr, 1, "forwarding");
448    V = Builder.CreateLoad(V, false);
449    BuildBlockRelease(V);
450  }
451}
452
453/// Emit an alloca (or GlobalValue depending on target)
454/// for the specified parameter and set up LocalDeclMap.
455void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
456  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
457  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
458         "Invalid argument to EmitParmDecl");
459  QualType Ty = D.getType();
460
461  llvm::Value *DeclPtr;
462  if (!Ty->isConstantSizeType()) {
463    // Variable sized values always are passed by-reference.
464    DeclPtr = Arg;
465  } else {
466    // A fixed sized single-value variable becomes an alloca in the entry block.
467    const llvm::Type *LTy = ConvertTypeForMem(Ty);
468    if (LTy->isSingleValueType()) {
469      // TODO: Alignment
470      std::string Name = D.getNameAsString();
471      Name += ".addr";
472      DeclPtr = CreateTempAlloca(LTy);
473      DeclPtr->setName(Name.c_str());
474
475      // Store the initial value into the alloca.
476      EmitStoreOfScalar(Arg, DeclPtr, Ty.isVolatileQualified(), Ty);
477    } else {
478      // Otherwise, if this is an aggregate, just use the input pointer.
479      DeclPtr = Arg;
480    }
481    Arg->setName(D.getNameAsString());
482  }
483
484  llvm::Value *&DMEntry = LocalDeclMap[&D];
485  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
486  DMEntry = DeclPtr;
487
488  // Emit debug info for param declaration.
489  if (CGDebugInfo *DI = getDebugInfo()) {
490    DI->setLocation(D.getLocation());
491    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
492  }
493}
494
495