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"
22 using namespace clang;
23 using namespace CodeGen;
24 
25 CodeGenFunction::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 
32 ASTContext &CodeGenFunction::getContext() const {
33   return CGM.getContext();
34 }
35 
36 
37 llvm::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 
45 llvm::Constant *
46 CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
47   return cast<llvm::Constant>(LocalDeclMap[BVD]);
48 }
49 
50 const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
51   return CGM.getTypes().ConvertType(T);
52 }
53 
54 bool CodeGenFunction::isObjCPointerType(QualType T) {
55   // All Objective-C types are pointers.
56   return T->isObjCInterfaceType() ||
57     T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
58 }
59 
60 bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
61   return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
62     !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
63 }
64 
65 void 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 
113 // FIXME: There is parallel code in StartObjCMethod.
114 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
115                                    llvm::Function *Fn) {
116   CurFuncDecl = FD;
117   FnRetTy = FD->getResultType();
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 (!FnRetTy->isVoidType())
133     ReturnValue = CreateTempAlloca(ConvertType(FnRetTy), "retval");
134 
135   Builder.SetInsertPoint(EntryBB);
136 
137   // Emit subprogram debug descriptor.
138   CGDebugInfo *DI = CGM.getDebugInfo();
139   if (DI) {
140     CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
141     if (body && body->getLBracLoc().isValid()) {
142       DI->setLocation(body->getLBracLoc());
143     }
144     DI->EmitFunctionStart(FD, CurFn, Builder);
145   }
146 
147   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
148   llvm::Function::arg_iterator AI = CurFn->arg_begin();
149 
150   // Name the struct return argument.
151   if (hasAggregateLLVMType(FD->getResultType())) {
152     AI->setName("agg.result");
153     ++AI;
154   }
155 
156   if (FD->getNumParams()) {
157     const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
158     assert(FProto && "Function def must have prototype!");
159     for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
160       assert(AI != CurFn->arg_end() && "Argument mismatch!");
161       const ParmVarDecl* CurParam = FD->getParamDecl(i);
162       llvm::Value* V = AI;
163       if (!getContext().typesAreCompatible(FProto->getArgType(i),
164                                            CurParam->getType())) {
165         // This must be a promotion, for something like
166         // "void a(x) short x; {..."
167         V = EmitScalarConversion(V, FProto->getArgType(i),
168                                  CurParam->getType());
169       }
170       EmitParmDecl(*CurParam, V);
171     }
172   }
173 
174   EmitStmt(FD->getBody());
175 
176   const CompoundStmt *S = dyn_cast<CompoundStmt>(FD->getBody());
177   if (S) {
178     FinishFunction(S->getRBracLoc());
179   } else {
180     FinishFunction();
181   }
182 }
183 
184 /// isDummyBlock - Return true if BB is an empty basic block
185 /// with no predecessors.
186 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
187   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
188     return true;
189   return false;
190 }
191 
192 /// StartBlock - Start new block named N. If insert block is a dummy block
193 /// then reuse it.
194 void CodeGenFunction::StartBlock(const char *N) {
195   llvm::BasicBlock *BB = Builder.GetInsertBlock();
196   if (!isDummyBlock(BB))
197     EmitBlock(llvm::BasicBlock::Create(N));
198   else
199     BB->setName(N);
200 }
201 
202 /// getCGRecordLayout - Return record layout info.
203 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
204                                                          QualType Ty) {
205   const RecordType *RTy = Ty->getAsRecordType();
206   assert (RTy && "Unexpected type. RecordType expected here.");
207 
208   return CGT.getCGRecordLayout(RTy->getDecl());
209 }
210 
211 /// ErrorUnsupported - Print out an error that codegen doesn't support the
212 /// specified stmt yet.
213 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
214                                        bool OmitOnError) {
215   CGM.ErrorUnsupported(S, Type, OmitOnError);
216 }
217 
218 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
219   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
220   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
221 }
222 
223 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
224 {
225   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
226   if (DestPtr->getType() != BP)
227     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
228 
229   // Get size and alignment info for this aggregate.
230   std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
231 
232   // FIXME: Handle variable sized types.
233   const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
234 
235   Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
236                       llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
237                       // TypeInfo.first describes size in bits.
238                       llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
239                       llvm::ConstantInt::get(llvm::Type::Int32Ty,
240                                              TypeInfo.second/8));
241 }
242 
243 void CodeGenFunction::EmitIndirectSwitches() {
244   llvm::BasicBlock *Default;
245 
246   if (IndirectSwitches.empty())
247     return;
248 
249   if (!LabelIDs.empty()) {
250     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
251   } else {
252     // No possible targets for indirect goto, just emit an infinite
253     // loop.
254     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
255     llvm::BranchInst::Create(Default, Default);
256   }
257 
258   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
259          e = IndirectSwitches.end(); i != e; ++i) {
260     llvm::SwitchInst *I = *i;
261 
262     I->setSuccessor(0, Default);
263     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
264            LE = LabelIDs.end(); LI != LE; ++LI) {
265       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
266                                         LI->second),
267                  getBasicBlockForLabel(LI->first));
268     }
269   }
270 }
271