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