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