CodeGenFunction.cpp revision 7c086516f3cc9fba2733b1919973206c6ba4b171 
1//===--- CodeGenFunction.cpp - Emit LLVM Code from ASTs for a Function ----===//
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 coordinates the per-function state used while generating code.
11//
12//===----------------------------------------------------------------------===//
13
14#include "CodeGenFunction.h"
15#include "CodeGenModule.h"
16#include "CGDebugInfo.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/AST/ASTContext.h"
19#include "clang/AST/Decl.h"
20#include "llvm/Analysis/Verifier.h"
21#include "llvm/Support/CFG.h"
22using namespace clang;
23using namespace CodeGen;
24
25CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
26  : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
27    CaseRangeBlock(NULL) {
28    LLVMIntTy = ConvertType(getContext().IntTy);
29    LLVMPointerWidth = Target.getPointerWidth(0);
30}
31
32ASTContext &CodeGenFunction::getContext() const {
33  return CGM.getContext();
34}
35
36
37llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
38  llvm::BasicBlock *&BB = LabelMap[S];
39  if (BB) return BB;
40
41  // Create, but don't insert, the new block.
42  return BB = llvm::BasicBlock::Create(S->getName());
43}
44
45llvm::Constant *
46CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
47  return cast<llvm::Constant>(LocalDeclMap[BVD]);
48}
49
50const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
51  return CGM.getTypes().ConvertType(T);
52}
53
54bool CodeGenFunction::isObjCPointerType(QualType T) {
55  // All Objective-C types are pointers.
56  return T->isObjCInterfaceType() ||
57    T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
58}
59
60bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
61  return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
62    !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
63}
64
65void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
66  // Finish emission of indirect switches.
67  EmitIndirectSwitches();
68
69  // Emit debug descriptor for function end.
70  if (CGDebugInfo *DI = CGM.getDebugInfo()) {
71    if (EndLoc.isValid()) {
72      DI->setLocation(EndLoc);
73    }
74    DI->EmitRegionEnd(CurFn, Builder);
75  }
76
77  // Emit a return for code that falls off the end. If insert point
78  // is a dummy block with no predecessors then remove the block itself.
79  llvm::BasicBlock *BB = Builder.GetInsertBlock();
80  if (isDummyBlock(BB)) {
81    BB->eraseFromParent();
82  } else {
83    // Just transfer to return
84    Builder.CreateBr(ReturnBlock);
85  }
86  assert(BreakContinueStack.empty() &&
87         "mismatched push/pop in break/continue stack!");
88
89  // Emit code to actually return.
90  Builder.SetInsertPoint(ReturnBlock);
91  if (!ReturnValue) {
92    Builder.CreateRetVoid();
93  } else {
94    if (!hasAggregateLLVMType(FnRetTy)) {
95      Builder.CreateRet(Builder.CreateLoad(ReturnValue));
96    } else if (FnRetTy->isAnyComplexType()) {
97      EmitAggregateCopy(CurFn->arg_begin(), ReturnValue, FnRetTy);
98      Builder.CreateRetVoid();
99    } else {
100      EmitAggregateCopy(CurFn->arg_begin(), ReturnValue, FnRetTy);
101      Builder.CreateRetVoid();
102    }
103  }
104
105  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
106  AllocaInsertPt->eraseFromParent();
107  AllocaInsertPt = 0;
108
109  // Verify that the function is well formed.
110  assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
111}
112
113void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
114                                    llvm::Function *Fn,
115                                    const FunctionArgList &Args) {
116  CurFuncDecl = D;
117  FnRetTy = RetTy;
118  CurFn = Fn;
119  assert(CurFn->isDeclaration() && "Function already has body?");
120
121  llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
122
123  // Create a marker to make it easy to insert allocas into the entryblock
124  // later.  Don't create this with the builder, because we don't want it
125  // folded.
126  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
127  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
128                                         EntryBB);
129
130  ReturnBlock = llvm::BasicBlock::Create("return", CurFn);
131  ReturnValue = 0;
132  if (!RetTy->isVoidType())
133    ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
134
135  Builder.SetInsertPoint(EntryBB);
136
137  // Emit subprogram debug descriptor.
138  // FIXME: The cast here is a huge hack.
139  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
140    if (CGDebugInfo *DI = CGM.getDebugInfo()) {
141      CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
142      if (body && body->getLBracLoc().isValid()) {
143        DI->setLocation(body->getLBracLoc());
144      }
145      DI->EmitFunctionStart(FD, CurFn, Builder);
146    }
147  }
148
149  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
150  llvm::Function::arg_iterator AI = CurFn->arg_begin();
151
152  // Name the struct return argument.
153  if (hasAggregateLLVMType(FnRetTy)) {
154    AI->setName("agg.result");
155    ++AI;
156  }
157
158  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
159       i != e; ++i, ++AI) {
160    const VarDecl *Arg = i->first;
161    QualType T = i->second;
162    assert(AI != CurFn->arg_end() && "Argument mismatch!");
163    llvm::Value* V = AI;
164    if (!getContext().typesAreCompatible(T, Arg->getType())) {
165      // This must be a promotion, for something like
166      // "void a(x) short x; {..."
167      V = EmitScalarConversion(V, T, Arg->getType());
168      }
169    EmitParmDecl(*Arg, V);
170  }
171  assert(AI == CurFn->arg_end() && "Argument mismatch!");
172}
173
174void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
175                                   llvm::Function *Fn) {
176  FunctionArgList Args;
177  if (FD->getNumParams()) {
178    const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
179    assert(FProto && "Function def must have prototype!");
180
181    for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
182      Args.push_back(std::make_pair(FD->getParamDecl(i),
183                                    FProto->getArgType(i)));
184  }
185
186  StartFunction(FD, FD->getResultType(), Fn, Args);
187
188  EmitStmt(FD->getBody());
189
190  const CompoundStmt *S = dyn_cast<CompoundStmt>(FD->getBody());
191  if (S) {
192    FinishFunction(S->getRBracLoc());
193  } else {
194    FinishFunction();
195  }
196}
197
198/// isDummyBlock - Return true if BB is an empty basic block
199/// with no predecessors.
200bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
201  if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
202    return true;
203  return false;
204}
205
206/// StartBlock - Start new block named N. If insert block is a dummy block
207/// then reuse it.
208void CodeGenFunction::StartBlock(const char *N) {
209  llvm::BasicBlock *BB = Builder.GetInsertBlock();
210  if (!isDummyBlock(BB))
211    EmitBlock(llvm::BasicBlock::Create(N));
212  else
213    BB->setName(N);
214}
215
216/// getCGRecordLayout - Return record layout info.
217const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
218                                                         QualType Ty) {
219  const RecordType *RTy = Ty->getAsRecordType();
220  assert (RTy && "Unexpected type. RecordType expected here.");
221
222  return CGT.getCGRecordLayout(RTy->getDecl());
223}
224
225/// ErrorUnsupported - Print out an error that codegen doesn't support the
226/// specified stmt yet.
227void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
228                                       bool OmitOnError) {
229  CGM.ErrorUnsupported(S, Type, OmitOnError);
230}
231
232unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
233  // Use LabelIDs.size() as the new ID if one hasn't been assigned.
234  return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
235}
236
237void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
238{
239  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
240  if (DestPtr->getType() != BP)
241    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
242
243  // Get size and alignment info for this aggregate.
244  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
245
246  // FIXME: Handle variable sized types.
247  const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
248
249  Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
250                      llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
251                      // TypeInfo.first describes size in bits.
252                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
253                      llvm::ConstantInt::get(llvm::Type::Int32Ty,
254                                             TypeInfo.second/8));
255}
256
257void CodeGenFunction::EmitIndirectSwitches() {
258  llvm::BasicBlock *Default;
259
260  if (IndirectSwitches.empty())
261    return;
262
263  if (!LabelIDs.empty()) {
264    Default = getBasicBlockForLabel(LabelIDs.begin()->first);
265  } else {
266    // No possible targets for indirect goto, just emit an infinite
267    // loop.
268    Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
269    llvm::BranchInst::Create(Default, Default);
270  }
271
272  for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
273         e = IndirectSwitches.end(); i != e; ++i) {
274    llvm::SwitchInst *I = *i;
275
276    I->setSuccessor(0, Default);
277    for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
278           LE = LabelIDs.end(); LI != LE; ++LI) {
279      I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
280                                        LI->second),
281                 getBasicBlockForLabel(LI->first));
282    }
283  }
284}
285