CGDecl.cpp revision 6ec3668a2608b63473207319f5ceff9bbd22ea51 
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/Type.h"
25using namespace clang;
26using namespace CodeGen;
27
28
29void CodeGenFunction::EmitDecl(const Decl &D) {
30  switch (D.getKind()) {
31  default: assert(0 && "Unknown decl kind!");
32  case Decl::ParmVar:
33    assert(0 && "Parmdecls should not be in declstmts!");
34  case Decl::Function:  // void X();
35  case Decl::Record:    // struct/union/class X;
36  case Decl::Enum:      // enum X;
37  case Decl::EnumConstant: // enum ? { X = ? }
38  case Decl::CXXRecord: // struct/union/class X; [C++]
39    // None of these decls require codegen support.
40    return;
41
42  case Decl::Var: {
43    const VarDecl &VD = cast<VarDecl>(D);
44    assert(VD.isBlockVarDecl() &&
45           "Should not see file-scope variables inside a function!");
46    return EmitBlockVarDecl(VD);
47  }
48
49  case Decl::Typedef: {   // typedef int X;
50    const TypedefDecl &TD = cast<TypedefDecl>(D);
51    QualType Ty = TD.getUnderlyingType();
52
53    if (Ty->isVariablyModifiedType())
54      EmitVLASize(Ty);
55  }
56  }
57}
58
59/// EmitBlockVarDecl - This method handles emission of any variable declaration
60/// inside a function, including static vars etc.
61void CodeGenFunction::EmitBlockVarDecl(const VarDecl &D) {
62  switch (D.getStorageClass()) {
63  case VarDecl::Static:
64    return EmitStaticBlockVarDecl(D);
65  case VarDecl::Extern:
66    // Don't emit it now, allow it to be emitted lazily on its first use.
67    return;
68  default:
69    assert((D.getStorageClass() == VarDecl::None ||
70            D.getStorageClass() == VarDecl::Auto ||
71            D.getStorageClass() == VarDecl::Register) &&
72           "Unknown storage class");
73    return EmitLocalBlockVarDecl(D);
74  }
75}
76
77llvm::GlobalValue *
78CodeGenFunction::GenerateStaticBlockVarDecl(const VarDecl &D,
79                                            bool NoInit,
80                                            const char *Separator,
81                                            llvm::GlobalValue
82					    	::LinkageTypes Linkage) {
83  QualType Ty = D.getType();
84  assert(Ty->isConstantSizeType() && "VLAs can't be static");
85
86  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(Ty);
87  llvm::Constant *Init = 0;
88  if ((D.getInit() == 0) || NoInit) {
89    Init = llvm::Constant::getNullValue(LTy);
90  } else {
91    Init = CGM.EmitConstantExpr(D.getInit(), this);
92
93    // If constant emission failed, then this should be a C++ static
94    // initializer.
95    if (!Init) {
96      if (!getContext().getLangOptions().CPlusPlus) {
97        CGM.ErrorUnsupported(D.getInit(), "constant l-value expression");
98        Init = llvm::Constant::getNullValue(LTy);
99      } else {
100        return GenerateStaticCXXBlockVarDecl(D);
101      }
102    }
103  }
104
105  assert(Init && "Unable to create initialiser for static decl");
106
107  std::string ContextName;
108  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(CurFuncDecl))
109    ContextName = CGM.getMangledName(FD);
110  else if (isa<ObjCMethodDecl>(CurFuncDecl))
111    ContextName = std::string(CurFn->getNameStart(),
112                              CurFn->getNameStart() + CurFn->getNameLen());
113  else
114    assert(0 && "Unknown context for block var decl");
115
116  llvm::GlobalValue *GV =
117    new llvm::GlobalVariable(Init->getType(), Ty.isConstant(getContext()),
118                             Linkage,
119                             Init, ContextName + Separator +D.getNameAsString(),
120                             &CGM.getModule(), 0, Ty.getAddressSpace());
121
122  return GV;
123}
124
125void CodeGenFunction::EmitStaticBlockVarDecl(const VarDecl &D) {
126
127  llvm::Value *&DMEntry = LocalDeclMap[&D];
128  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
129
130  llvm::GlobalValue *GV;
131  GV = GenerateStaticBlockVarDecl(D, false, ".",
132                                  llvm::GlobalValue::InternalLinkage);
133
134  // FIXME: Merge attribute handling.
135  if (const AnnotateAttr *AA = D.getAttr<AnnotateAttr>()) {
136    SourceManager &SM = CGM.getContext().getSourceManager();
137    llvm::Constant *Ann =
138      CGM.EmitAnnotateAttr(GV, AA,
139                           SM.getInstantiationLineNumber(D.getLocation()));
140    CGM.AddAnnotation(Ann);
141  }
142
143  if (const SectionAttr *SA = D.getAttr<SectionAttr>())
144    GV->setSection(SA->getName());
145
146  if (D.getAttr<UsedAttr>())
147    CGM.AddUsedGlobal(GV);
148
149  const llvm::Type *LTy = CGM.getTypes().ConvertTypeForMem(D.getType());
150  const llvm::Type *LPtrTy =
151    llvm::PointerType::get(LTy, D.getType().getAddressSpace());
152  DMEntry = llvm::ConstantExpr::getBitCast(GV, LPtrTy);
153
154  // Emit global variable debug descriptor for static vars.
155  CGDebugInfo *DI = getDebugInfo();
156  if(DI) {
157    DI->setLocation(D.getLocation());
158    DI->EmitGlobalVariable(static_cast<llvm::GlobalVariable *>(GV), &D);
159  }
160}
161
162/// EmitLocalBlockVarDecl - Emit code and set up an entry in LocalDeclMap for a
163/// variable declaration with auto, register, or no storage class specifier.
164/// These turn into simple stack objects, or GlobalValues depending on target.
165void CodeGenFunction::EmitLocalBlockVarDecl(const VarDecl &D) {
166  QualType Ty = D.getType();
167
168  llvm::Value *DeclPtr;
169  if (Ty->isConstantSizeType()) {
170    if (!Target.useGlobalsForAutomaticVariables()) {
171      // A normal fixed sized variable becomes an alloca in the entry block.
172      const llvm::Type *LTy = ConvertType(Ty);
173      llvm::AllocaInst *Alloc =
174        CreateTempAlloca(LTy, CGM.getMangledName(&D));
175      unsigned align = getContext().getTypeAlign(Ty);
176      if (const AlignedAttr* AA = D.getAttr<AlignedAttr>())
177        align = std::max(align, AA->getAlignment());
178      Alloc->setAlignment(align >> 3);
179      DeclPtr = Alloc;
180    } else {
181      // Targets that don't support recursion emit locals as globals.
182      const char *Class =
183        D.getStorageClass() == VarDecl::Register ? ".reg." : ".auto.";
184      DeclPtr = GenerateStaticBlockVarDecl(D, true, Class,
185                                           llvm::GlobalValue
186                                           ::InternalLinkage);
187    }
188
189    if (Ty->isVariablyModifiedType())
190      EmitVLASize(Ty);
191  } else {
192    if (!DidCallStackSave) {
193      // Save the stack.
194      const llvm::Type *LTy = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
195      llvm::Value *Stack = CreateTempAlloca(LTy, "saved_stack");
196
197      llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stacksave);
198      llvm::Value *V = Builder.CreateCall(F);
199
200      Builder.CreateStore(V, Stack);
201
202      DidCallStackSave = true;
203
204      {
205        // Push a cleanup block and restore the stack there.
206        CleanupScope scope(*this);
207
208        V = Builder.CreateLoad(Stack, "tmp");
209        llvm::Value *F = CGM.getIntrinsic(llvm::Intrinsic::stackrestore);
210        Builder.CreateCall(F, V);
211      }
212    }
213
214    // Get the element type.
215    const llvm::Type *LElemTy = ConvertType(Ty);
216    const llvm::Type *LElemPtrTy =
217      llvm::PointerType::get(LElemTy, D.getType().getAddressSpace());
218
219    llvm::Value *VLASize = EmitVLASize(Ty);
220
221    // Downcast the VLA size expression
222    VLASize = Builder.CreateIntCast(VLASize, llvm::Type::Int32Ty, false, "tmp");
223
224    // Allocate memory for the array.
225    llvm::Value *VLA = Builder.CreateAlloca(llvm::Type::Int8Ty, VLASize, "vla");
226    DeclPtr = Builder.CreateBitCast(VLA, LElemPtrTy, "tmp");
227  }
228
229  llvm::Value *&DMEntry = LocalDeclMap[&D];
230  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
231  DMEntry = DeclPtr;
232
233  // Emit debug info for local var declaration.
234  if (CGDebugInfo *DI = getDebugInfo()) {
235    DI->setLocation(D.getLocation());
236    DI->EmitDeclareOfAutoVariable(&D, DeclPtr, Builder);
237  }
238
239  // If this local has an initializer, emit it now.
240  if (const Expr *Init = D.getInit()) {
241    if (!hasAggregateLLVMType(Init->getType())) {
242      llvm::Value *V = EmitScalarExpr(Init);
243      Builder.CreateStore(V, DeclPtr, D.getType().isVolatileQualified());
244    } else if (Init->getType()->isAnyComplexType()) {
245      EmitComplexExprIntoAddr(Init, DeclPtr, D.getType().isVolatileQualified());
246    } else {
247      EmitAggExpr(Init, DeclPtr, D.getType().isVolatileQualified());
248    }
249  }
250
251  // Handle the cleanup attribute
252  if (const CleanupAttr *CA = D.getAttr<CleanupAttr>()) {
253    const FunctionDecl *FD = CA->getFunctionDecl();
254
255    llvm::Constant* F = CGM.GetAddrOfFunction(FD);
256    assert(F && "Could not find function!");
257
258    CleanupScope scope(*this);
259
260    CallArgList Args;
261    Args.push_back(std::make_pair(RValue::get(DeclPtr),
262                                  getContext().getPointerType(D.getType())));
263
264    EmitCall(CGM.getTypes().getFunctionInfo(FD), F, Args);
265  }
266}
267
268/// Emit an alloca (or GlobalValue depending on target)
269/// for the specified parameter and set up LocalDeclMap.
270void CodeGenFunction::EmitParmDecl(const VarDecl &D, llvm::Value *Arg) {
271  // FIXME: Why isn't ImplicitParamDecl a ParmVarDecl?
272  assert((isa<ParmVarDecl>(D) || isa<ImplicitParamDecl>(D)) &&
273         "Invalid argument to EmitParmDecl");
274  QualType Ty = D.getType();
275
276  llvm::Value *DeclPtr;
277  if (!Ty->isConstantSizeType()) {
278    // Variable sized values always are passed by-reference.
279    DeclPtr = Arg;
280  } else if (Target.useGlobalsForAutomaticVariables()) {
281    // Targets that don't have stack use global address space for parameters.
282    // Specify external linkage for such globals so that llvm optimizer do
283    // not assume there values initialized as zero.
284    DeclPtr = GenerateStaticBlockVarDecl(D, true, ".auto.",
285                                         llvm::GlobalValue::ExternalLinkage);
286  } else {
287    // A fixed sized single-value variable becomes an alloca in the entry block.
288    const llvm::Type *LTy = ConvertType(Ty);
289    if (LTy->isSingleValueType()) {
290      // TODO: Alignment
291      std::string Name = D.getNameAsString();
292      Name += ".addr";
293      DeclPtr = CreateTempAlloca(LTy, Name.c_str());
294
295      // Store the initial value into the alloca.
296      Builder.CreateStore(Arg, DeclPtr,Ty.isVolatileQualified());
297    } else {
298      // Otherwise, if this is an aggregate, just use the input pointer.
299      DeclPtr = Arg;
300    }
301    Arg->setName(D.getNameAsString());
302  }
303
304  llvm::Value *&DMEntry = LocalDeclMap[&D];
305  assert(DMEntry == 0 && "Decl already exists in localdeclmap!");
306  DMEntry = DeclPtr;
307
308  // Emit debug info for param declaration.
309  if (CGDebugInfo *DI = getDebugInfo()) {
310    DI->setLocation(D.getLocation());
311    DI->EmitDeclareOfArgVariable(&D, DeclPtr, Builder);
312  }
313}
314
315