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::GenerateFunction(const Stmt *Body) {
66   // Emit the function body.
67   EmitStmt(Body);
68 
69   // Finish emission of indirect switches.
70   EmitIndirectSwitches();
71 
72   // Emit debug descriptor for function end.
73   CGDebugInfo *DI = CGM.getDebugInfo();
74   if (DI) {
75     const CompoundStmt* s = dyn_cast<CompoundStmt>(Body);
76     if (s && s->getRBracLoc().isValid()) {
77       DI->setLocation(s->getRBracLoc());
78     }
79     DI->EmitRegionEnd(CurFn, Builder);
80   }
81 
82   // Emit a return for code that falls off the end. If insert point
83   // is a dummy block with no predecessors then remove the block itself.
84   llvm::BasicBlock *BB = Builder.GetInsertBlock();
85   if (isDummyBlock(BB))
86     BB->eraseFromParent();
87   else {
88     // FIXME: if this is C++ main, this should return 0.
89     if (CurFn->getReturnType() == llvm::Type::VoidTy)
90       Builder.CreateRetVoid();
91     else
92       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
93   }
94   assert(BreakContinueStack.empty() &&
95          "mismatched push/pop in break/continue stack!");
96 
97   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
98   AllocaInsertPt->eraseFromParent();
99   AllocaInsertPt = 0;
100 
101   // Verify that the function is well formed.
102   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
103 }
104 
105 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
106                                    llvm::Function *Fn) {
107   CurFuncDecl = FD;
108   FnRetTy = FD->getResultType();
109   CurFn = Fn;
110   assert(CurFn->isDeclaration() && "Function already has body?");
111 
112   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
113 
114   // Create a marker to make it easy to insert allocas into the entryblock
115   // later.  Don't create this with the builder, because we don't want it
116   // folded.
117   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
118   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
119                                          EntryBB);
120 
121   Builder.SetInsertPoint(EntryBB);
122 
123   // Emit subprogram debug descriptor.
124   CGDebugInfo *DI = CGM.getDebugInfo();
125   if (DI) {
126     CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
127     if (body && body->getLBracLoc().isValid()) {
128       DI->setLocation(body->getLBracLoc());
129     }
130     DI->EmitFunctionStart(FD, CurFn, Builder);
131   }
132 
133   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
134   llvm::Function::arg_iterator AI = CurFn->arg_begin();
135 
136   // Name the struct return argument.
137   if (hasAggregateLLVMType(FD->getResultType())) {
138     AI->setName("agg.result");
139     ++AI;
140   }
141 
142   if (FD->getNumParams()) {
143     const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
144     assert(FProto && "Function def must have prototype!");
145     for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
146       assert(AI != CurFn->arg_end() && "Argument mismatch!");
147       const ParmVarDecl* CurParam = FD->getParamDecl(i);
148       llvm::Value* V = AI;
149       if (!getContext().typesAreCompatible(FProto->getArgType(i),
150                                            CurParam->getType())) {
151         // This must be a promotion, for something like
152         // "void a(x) short x; {..."
153         V = EmitScalarConversion(V, FProto->getArgType(i),
154                                  CurParam->getType());
155       }
156       EmitParmDecl(*CurParam, V);
157     }
158   }
159   GenerateFunction(FD->getBody());
160 }
161 
162 /// isDummyBlock - Return true if BB is an empty basic block
163 /// with no predecessors.
164 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
165   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
166     return true;
167   return false;
168 }
169 
170 /// StartBlock - Start new block named N. If insert block is a dummy block
171 /// then reuse it.
172 void CodeGenFunction::StartBlock(const char *N) {
173   llvm::BasicBlock *BB = Builder.GetInsertBlock();
174   if (!isDummyBlock(BB))
175     EmitBlock(llvm::BasicBlock::Create(N));
176   else
177     BB->setName(N);
178 }
179 
180 /// getCGRecordLayout - Return record layout info.
181 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
182                                                          QualType Ty) {
183   const RecordType *RTy = Ty->getAsRecordType();
184   assert (RTy && "Unexpected type. RecordType expected here.");
185 
186   return CGT.getCGRecordLayout(RTy->getDecl());
187 }
188 
189 /// ErrorUnsupported - Print out an error that codegen doesn't support the
190 /// specified stmt yet.
191 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type) {
192   CGM.ErrorUnsupported(S, Type);
193 }
194 
195 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
196   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
197   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
198 }
199 
200 void CodeGenFunction::EmitIndirectSwitches() {
201   llvm::BasicBlock *Default;
202 
203   if (IndirectSwitches.empty())
204     return;
205 
206   if (!LabelIDs.empty()) {
207     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
208   } else {
209     // No possible targets for indirect goto, just emit an infinite
210     // loop.
211     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
212     llvm::BranchInst::Create(Default, Default);
213   }
214 
215   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
216          e = IndirectSwitches.end(); i != e; ++i) {
217     llvm::SwitchInst *I = *i;
218 
219     I->setSuccessor(0, Default);
220     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
221            LE = LabelIDs.end(); LI != LE; ++LI) {
222       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
223                                         LI->second),
224                  getBasicBlockForLabel(LI->first));
225     }
226   }
227 }
228