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