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 llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD)
51 {
52   return LocalDeclMap[VD];
53 }
54 
55 const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
56   return CGM.getTypes().ConvertType(T);
57 }
58 
59 bool CodeGenFunction::isObjCPointerType(QualType T) {
60   // All Objective-C types are pointers.
61   return T->isObjCInterfaceType() ||
62     T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
63 }
64 
65 bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
66   return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
67     !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
68 }
69 
70 void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
71   // Finish emission of indirect switches.
72   EmitIndirectSwitches();
73 
74   // Emit debug descriptor for function end.
75   if (CGDebugInfo *DI = CGM.getDebugInfo()) {
76     if (EndLoc.isValid()) {
77       DI->setLocation(EndLoc);
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     // Just transfer to return
89     Builder.CreateBr(ReturnBlock);
90   }
91   assert(BreakContinueStack.empty() &&
92          "mismatched push/pop in break/continue stack!");
93 
94   // Emit function epilog (to return).
95   Builder.SetInsertPoint(ReturnBlock);
96   EmitFunctionEpilog(FnRetTy, ReturnValue);
97 
98   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
99   AllocaInsertPt->eraseFromParent();
100   AllocaInsertPt = 0;
101 
102   // Verify that the function is well formed.
103   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
104 }
105 
106 void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
107                                     llvm::Function *Fn,
108                                     const FunctionArgList &Args) {
109   CurFuncDecl = D;
110   FnRetTy = RetTy;
111   CurFn = Fn;
112   assert(CurFn->isDeclaration() && "Function already has body?");
113 
114   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
115 
116   // Create a marker to make it easy to insert allocas into the entryblock
117   // later.  Don't create this with the builder, because we don't want it
118   // folded.
119   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
120   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
121                                          EntryBB);
122 
123   ReturnBlock = llvm::BasicBlock::Create("return", CurFn);
124   ReturnValue = 0;
125   if (!RetTy->isVoidType())
126     ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
127 
128   Builder.SetInsertPoint(EntryBB);
129 
130   // Emit subprogram debug descriptor.
131   // FIXME: The cast here is a huge hack.
132   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
133     if (CGDebugInfo *DI = CGM.getDebugInfo()) {
134       CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
135       if (body && body->getLBracLoc().isValid()) {
136         DI->setLocation(body->getLBracLoc());
137       }
138       DI->EmitFunctionStart(FD, CurFn, Builder);
139     }
140   }
141 
142   EmitFunctionProlog(CurFn, FnRetTy, Args);
143 }
144 
145 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
146                                    llvm::Function *Fn) {
147   FunctionArgList Args;
148   if (FD->getNumParams()) {
149     const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
150     assert(FProto && "Function def must have prototype!");
151 
152     for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
153       Args.push_back(std::make_pair(FD->getParamDecl(i),
154                                     FProto->getArgType(i)));
155   }
156 
157   StartFunction(FD, FD->getResultType(), Fn, Args);
158 
159   EmitStmt(FD->getBody());
160 
161   const CompoundStmt *S = dyn_cast<CompoundStmt>(FD->getBody());
162   if (S) {
163     FinishFunction(S->getRBracLoc());
164   } else {
165     FinishFunction();
166   }
167 }
168 
169 /// isDummyBlock - Return true if BB is an empty basic block
170 /// with no predecessors.
171 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
172   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
173     return true;
174   return false;
175 }
176 
177 /// StartBlock - Start new block named N. If insert block is a dummy block
178 /// then reuse it.
179 void CodeGenFunction::StartBlock(const char *N) {
180   llvm::BasicBlock *BB = Builder.GetInsertBlock();
181   if (!isDummyBlock(BB))
182     EmitBlock(llvm::BasicBlock::Create(N));
183   else
184     BB->setName(N);
185 }
186 
187 /// getCGRecordLayout - Return record layout info.
188 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
189                                                          QualType Ty) {
190   const RecordType *RTy = Ty->getAsRecordType();
191   assert (RTy && "Unexpected type. RecordType expected here.");
192 
193   return CGT.getCGRecordLayout(RTy->getDecl());
194 }
195 
196 /// ErrorUnsupported - Print out an error that codegen doesn't support the
197 /// specified stmt yet.
198 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
199                                        bool OmitOnError) {
200   CGM.ErrorUnsupported(S, Type, OmitOnError);
201 }
202 
203 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
204   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
205   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
206 }
207 
208 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
209 {
210   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
211   if (DestPtr->getType() != BP)
212     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
213 
214   // Get size and alignment info for this aggregate.
215   std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
216 
217   // FIXME: Handle variable sized types.
218   const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
219 
220   Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
221                       llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
222                       // TypeInfo.first describes size in bits.
223                       llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
224                       llvm::ConstantInt::get(llvm::Type::Int32Ty,
225                                              TypeInfo.second/8));
226 }
227 
228 void CodeGenFunction::EmitIndirectSwitches() {
229   llvm::BasicBlock *Default;
230 
231   if (IndirectSwitches.empty())
232     return;
233 
234   if (!LabelIDs.empty()) {
235     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
236   } else {
237     // No possible targets for indirect goto, just emit an infinite
238     // loop.
239     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
240     llvm::BranchInst::Create(Default, Default);
241   }
242 
243   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
244          e = IndirectSwitches.end(); i != e; ++i) {
245     llvm::SwitchInst *I = *i;
246 
247     I->setSuccessor(0, Default);
248     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
249            LE = LabelIDs.end(); LI != LE; ++LI) {
250       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
251                                         LI->second),
252                  getBasicBlockForLabel(LI->first));
253     }
254   }
255 }
256