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 "llvm/CallingConv.h"
20 #include "llvm/Constants.h"
21 #include "llvm/DerivedTypes.h"
22 #include "llvm/Function.h"
23 #include "llvm/Analysis/Verifier.h"
24 #include "llvm/Support/CFG.h"
25 using namespace clang;
26 using namespace CodeGen;
27 
28 CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
29   : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
30     CaseRangeBlock(NULL) {
31     LLVMIntTy = ConvertType(getContext().IntTy);
32     LLVMPointerWidth = Target.getPointerWidth(0);
33 }
34 
35 ASTContext &CodeGenFunction::getContext() const {
36   return CGM.getContext();
37 }
38 
39 
40 llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
41   llvm::BasicBlock *&BB = LabelMap[S];
42   if (BB) return BB;
43 
44   // Create, but don't insert, the new block.
45   return BB = llvm::BasicBlock::Create(S->getName());
46 }
47 
48 llvm::Constant *
49 CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
50   return cast<llvm::Constant>(LocalDeclMap[BVD]);
51 }
52 
53 const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
54   return CGM.getTypes().ConvertType(T);
55 }
56 
57 bool CodeGenFunction::isObjCPointerType(QualType T) {
58   // All Objective-C types are pointers.
59   return T->isObjCInterfaceType() ||
60     T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
61 }
62 
63 bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
64   return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
65     !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
66 }
67 
68 void CodeGenFunction::GenerateFunction(const Stmt *Body) {
69   // Emit the function body.
70   EmitStmt(Body);
71 
72   // Finish emission of indirect switches.
73   EmitIndirectSwitches();
74 
75   // Emit debug descriptor for function end.
76   CGDebugInfo *DI = CGM.getDebugInfo();
77   if (DI) {
78     const CompoundStmt* s = dyn_cast<CompoundStmt>(Body);
79     if (s && s->getRBracLoc().isValid()) {
80       DI->setLocation(s->getRBracLoc());
81     }
82     DI->EmitRegionEnd(CurFn, Builder);
83   }
84 
85   // Emit a return for code that falls off the end. If insert point
86   // is a dummy block with no predecessors then remove the block itself.
87   llvm::BasicBlock *BB = Builder.GetInsertBlock();
88   if (isDummyBlock(BB))
89     BB->eraseFromParent();
90   else {
91     // FIXME: if this is C++ main, this should return 0.
92     if (CurFn->getReturnType() == llvm::Type::VoidTy)
93       Builder.CreateRetVoid();
94     else
95       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
96   }
97   assert(BreakContinueStack.empty() &&
98          "mismatched push/pop in break/continue stack!");
99 
100   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
101   AllocaInsertPt->eraseFromParent();
102   AllocaInsertPt = 0;
103 
104   // Verify that the function is well formed.
105   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
106 }
107 
108 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
109                                    llvm::Function *Fn) {
110   CurFuncDecl = FD;
111   FnRetTy = FD->getResultType();
112   CurFn = Fn;
113   assert(CurFn->isDeclaration() && "Function already has body?");
114 
115   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
116 
117   // Create a marker to make it easy to insert allocas into the entryblock
118   // later.  Don't create this with the builder, because we don't want it
119   // folded.
120   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
121   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
122                                          EntryBB);
123 
124   Builder.SetInsertPoint(EntryBB);
125 
126   // Emit subprogram debug descriptor.
127   CGDebugInfo *DI = CGM.getDebugInfo();
128   if (DI) {
129     CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
130     if (body && body->getLBracLoc().isValid()) {
131       DI->setLocation(body->getLBracLoc());
132     }
133     DI->EmitFunctionStart(FD, CurFn, Builder);
134   }
135 
136   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
137   llvm::Function::arg_iterator AI = CurFn->arg_begin();
138 
139   // Name the struct return argument.
140   if (hasAggregateLLVMType(FD->getResultType())) {
141     AI->setName("agg.result");
142     ++AI;
143   }
144 
145   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
146     assert(AI != CurFn->arg_end() && "Argument mismatch!");
147     EmitParmDecl(*FD->getParamDecl(i), AI);
148   }
149   GenerateFunction(FD->getBody());
150 }
151 
152 /// isDummyBlock - Return true if BB is an empty basic block
153 /// with no predecessors.
154 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
155   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
156     return true;
157   return false;
158 }
159 
160 /// StartBlock - Start new block named N. If insert block is a dummy block
161 /// then reuse it.
162 void CodeGenFunction::StartBlock(const char *N) {
163   llvm::BasicBlock *BB = Builder.GetInsertBlock();
164   if (!isDummyBlock(BB))
165     EmitBlock(llvm::BasicBlock::Create(N));
166   else
167     BB->setName(N);
168 }
169 
170 /// getCGRecordLayout - Return record layout info.
171 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
172                                                          QualType Ty) {
173   const RecordType *RTy = Ty->getAsRecordType();
174   assert (RTy && "Unexpected type. RecordType expected here.");
175 
176   return CGT.getCGRecordLayout(RTy->getDecl());
177 }
178 
179 /// WarnUnsupported - Print out a warning that codegen doesn't support the
180 /// specified stmt yet.
181 void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
182   CGM.WarnUnsupported(S, Type);
183 }
184 
185 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
186   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
187   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
188 }
189 
190 void CodeGenFunction::EmitIndirectSwitches() {
191   llvm::BasicBlock *Default;
192 
193   if (IndirectSwitches.empty())
194     return;
195 
196   if (!LabelIDs.empty()) {
197     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
198   } else {
199     // No possible targets for indirect goto, just emit an infinite
200     // loop.
201     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
202     llvm::BranchInst::Create(Default, Default);
203   }
204 
205   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
206          e = IndirectSwitches.end(); i != e; ++i) {
207     llvm::SwitchInst *I = *i;
208 
209     I->setSuccessor(0, Default);
210     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
211            LE = LabelIDs.end(); LI != LE; ++LI) {
212       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
213                                         LI->second),
214                  getBasicBlockForLabel(LI->first));
215     }
216   }
217 }
218