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 code to actually return.
90   Builder.SetInsertPoint(ReturnBlock);
91   if (!ReturnValue) {
92     Builder.CreateRetVoid();
93   } else {
94     if (!hasAggregateLLVMType(FnRetTy)) {
95       Builder.CreateRet(Builder.CreateLoad(ReturnValue));
96     } else if (FnRetTy->isAnyComplexType()) {
97       EmitAggregateCopy(CurFn->arg_begin(), ReturnValue, FnRetTy);
98       Builder.CreateRetVoid();
99     } else {
100       EmitAggregateCopy(CurFn->arg_begin(), ReturnValue, FnRetTy);
101       Builder.CreateRetVoid();
102     }
103   }
104 
105   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
106   AllocaInsertPt->eraseFromParent();
107   AllocaInsertPt = 0;
108 
109   // Verify that the function is well formed.
110   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
111 }
112 
113 void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
114                                     llvm::Function *Fn,
115                                     const FunctionArgList &Args) {
116   CurFuncDecl = D;
117   FnRetTy = RetTy;
118   CurFn = Fn;
119   assert(CurFn->isDeclaration() && "Function already has body?");
120 
121   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
122 
123   // Create a marker to make it easy to insert allocas into the entryblock
124   // later.  Don't create this with the builder, because we don't want it
125   // folded.
126   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
127   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
128                                          EntryBB);
129 
130   ReturnBlock = llvm::BasicBlock::Create("return", CurFn);
131   ReturnValue = 0;
132   if (!RetTy->isVoidType())
133     ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
134 
135   Builder.SetInsertPoint(EntryBB);
136 
137   // Emit subprogram debug descriptor.
138   // FIXME: The cast here is a huge hack.
139   if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
140     if (CGDebugInfo *DI = CGM.getDebugInfo()) {
141       CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
142       if (body && body->getLBracLoc().isValid()) {
143         DI->setLocation(body->getLBracLoc());
144       }
145       DI->EmitFunctionStart(FD, CurFn, Builder);
146     }
147   }
148 
149   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
150   llvm::Function::arg_iterator AI = CurFn->arg_begin();
151 
152   // Name the struct return argument.
153   if (hasAggregateLLVMType(FnRetTy)) {
154     AI->setName("agg.result");
155     ++AI;
156   }
157 
158   for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
159        i != e; ++i, ++AI) {
160     const VarDecl *Arg = i->first;
161     QualType T = i->second;
162     assert(AI != CurFn->arg_end() && "Argument mismatch!");
163     llvm::Value* V = AI;
164     if (!getContext().typesAreCompatible(T, Arg->getType())) {
165       // This must be a promotion, for something like
166       // "void a(x) short x; {..."
167       V = EmitScalarConversion(V, T, Arg->getType());
168       }
169     EmitParmDecl(*Arg, V);
170   }
171   assert(AI == CurFn->arg_end() && "Argument mismatch!");
172 }
173 
174 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
175                                    llvm::Function *Fn) {
176   FunctionArgList Args;
177   if (FD->getNumParams()) {
178     const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
179     assert(FProto && "Function def must have prototype!");
180 
181     for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
182       Args.push_back(std::make_pair(FD->getParamDecl(i),
183                                     FProto->getArgType(i)));
184   }
185 
186   StartFunction(FD, FD->getResultType(), Fn, Args);
187 
188   EmitStmt(FD->getBody());
189 
190   const CompoundStmt *S = dyn_cast<CompoundStmt>(FD->getBody());
191   if (S) {
192     FinishFunction(S->getRBracLoc());
193   } else {
194     FinishFunction();
195   }
196 }
197 
198 /// isDummyBlock - Return true if BB is an empty basic block
199 /// with no predecessors.
200 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
201   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
202     return true;
203   return false;
204 }
205 
206 /// StartBlock - Start new block named N. If insert block is a dummy block
207 /// then reuse it.
208 void CodeGenFunction::StartBlock(const char *N) {
209   llvm::BasicBlock *BB = Builder.GetInsertBlock();
210   if (!isDummyBlock(BB))
211     EmitBlock(llvm::BasicBlock::Create(N));
212   else
213     BB->setName(N);
214 }
215 
216 /// getCGRecordLayout - Return record layout info.
217 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
218                                                          QualType Ty) {
219   const RecordType *RTy = Ty->getAsRecordType();
220   assert (RTy && "Unexpected type. RecordType expected here.");
221 
222   return CGT.getCGRecordLayout(RTy->getDecl());
223 }
224 
225 /// ErrorUnsupported - Print out an error that codegen doesn't support the
226 /// specified stmt yet.
227 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
228                                        bool OmitOnError) {
229   CGM.ErrorUnsupported(S, Type, OmitOnError);
230 }
231 
232 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
233   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
234   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
235 }
236 
237 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
238 {
239   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
240   if (DestPtr->getType() != BP)
241     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
242 
243   // Get size and alignment info for this aggregate.
244   std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
245 
246   // FIXME: Handle variable sized types.
247   const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
248 
249   Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
250                       llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
251                       // TypeInfo.first describes size in bits.
252                       llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
253                       llvm::ConstantInt::get(llvm::Type::Int32Ty,
254                                              TypeInfo.second/8));
255 }
256 
257 void CodeGenFunction::EmitIndirectSwitches() {
258   llvm::BasicBlock *Default;
259 
260   if (IndirectSwitches.empty())
261     return;
262 
263   if (!LabelIDs.empty()) {
264     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
265   } else {
266     // No possible targets for indirect goto, just emit an infinite
267     // loop.
268     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
269     llvm::BranchInst::Create(Default, Default);
270   }
271 
272   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
273          e = IndirectSwitches.end(); i != e; ++i) {
274     llvm::SwitchInst *I = *i;
275 
276     I->setSuccessor(0, Default);
277     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
278            LE = LabelIDs.end(); LI != LE; ++LI) {
279       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
280                                         LI->second),
281                  getBasicBlockForLabel(LI->first));
282     }
283   }
284 }
285