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 "clang/AST/DeclObjC.h"
21 #include "llvm/CallingConv.h"
22 #include "llvm/Constants.h"
23 #include "llvm/DerivedTypes.h"
24 #include "llvm/Function.h"
25 #include "llvm/Analysis/Verifier.h"
26 #include "llvm/Support/CFG.h"
27 using namespace clang;
28 using namespace CodeGen;
29 
30 CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
31   : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
32     CaseRangeBlock(NULL) {
33     LLVMIntTy = ConvertType(getContext().IntTy);
34     LLVMPointerWidth = Target.getPointerWidth(0);
35 }
36 
37 ASTContext &CodeGenFunction::getContext() const {
38   return CGM.getContext();
39 }
40 
41 
42 llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
43   llvm::BasicBlock *&BB = LabelMap[S];
44   if (BB) return BB;
45 
46   // Create, but don't insert, the new block.
47   return BB = llvm::BasicBlock::Create(S->getName());
48 }
49 
50 llvm::Constant *
51 CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
52   return cast<llvm::Constant>(LocalDeclMap[BVD]);
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::GenerateFunction(const Stmt *Body) {
71   // Emit the function body.
72   EmitStmt(Body);
73 
74   // Finish emission of indirect switches.
75   EmitIndirectSwitches();
76 
77   // Emit debug descriptor for function end.
78   CGDebugInfo *DI = CGM.getDebugInfo();
79   if (DI) {
80     const CompoundStmt* s = dyn_cast<CompoundStmt>(Body);
81     if (s && s->getRBracLoc().isValid()) {
82       DI->setLocation(s->getRBracLoc());
83     }
84     DI->EmitRegionEnd(CurFn, Builder);
85   }
86 
87   // Emit a return for code that falls off the end. If insert point
88   // is a dummy block with no predecessors then remove the block itself.
89   llvm::BasicBlock *BB = Builder.GetInsertBlock();
90   if (isDummyBlock(BB))
91     BB->eraseFromParent();
92   else {
93     // FIXME: if this is C++ main, this should return 0.
94     if (CurFn->getReturnType() == llvm::Type::VoidTy)
95       Builder.CreateRetVoid();
96     else
97       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
98   }
99   assert(BreakContinueStack.empty() &&
100          "mismatched push/pop in break/continue stack!");
101 
102   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
103   AllocaInsertPt->eraseFromParent();
104   AllocaInsertPt = 0;
105 
106   // Verify that the function is well formed.
107   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
108 }
109 
110 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
111                                    llvm::Function *Fn) {
112   CurFuncDecl = FD;
113   FnRetTy = FD->getResultType();
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   Builder.SetInsertPoint(EntryBB);
127 
128   // Emit subprogram debug descriptor.
129   CGDebugInfo *DI = CGM.getDebugInfo();
130   if (DI) {
131     CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
132     if (body && body->getLBracLoc().isValid()) {
133       DI->setLocation(body->getLBracLoc());
134     }
135     DI->EmitFunctionStart(FD, CurFn, Builder);
136   }
137 
138   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
139   llvm::Function::arg_iterator AI = CurFn->arg_begin();
140 
141   // Name the struct return argument.
142   if (hasAggregateLLVMType(FD->getResultType())) {
143     AI->setName("agg.result");
144     ++AI;
145   }
146 
147   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
148     assert(AI != CurFn->arg_end() && "Argument mismatch!");
149     EmitParmDecl(*FD->getParamDecl(i), AI);
150   }
151   GenerateFunction(FD->getBody());
152 }
153 
154 /// isDummyBlock - Return true if BB is an empty basic block
155 /// with no predecessors.
156 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
157   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
158     return true;
159   return false;
160 }
161 
162 /// StartBlock - Start new block named N. If insert block is a dummy block
163 /// then reuse it.
164 void CodeGenFunction::StartBlock(const char *N) {
165   llvm::BasicBlock *BB = Builder.GetInsertBlock();
166   if (!isDummyBlock(BB))
167     EmitBlock(llvm::BasicBlock::Create(N));
168   else
169     BB->setName(N);
170 }
171 
172 /// getCGRecordLayout - Return record layout info.
173 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
174                                                          QualType Ty) {
175   const RecordType *RTy = Ty->getAsRecordType();
176   assert (RTy && "Unexpected type. RecordType expected here.");
177 
178   return CGT.getCGRecordLayout(RTy->getDecl());
179 }
180 
181 /// WarnUnsupported - Print out a warning that codegen doesn't support the
182 /// specified stmt yet.
183 void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
184   CGM.WarnUnsupported(S, Type);
185 }
186 
187 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
188   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
189   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
190 }
191 
192 void CodeGenFunction::EmitIndirectSwitches() {
193   llvm::BasicBlock *Default;
194 
195   if (IndirectSwitches.empty())
196     return;
197 
198   if (!LabelIDs.empty()) {
199     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
200   } else {
201     // No possible targets for indirect goto, just emit an infinite
202     // loop.
203     Default = llvm::BasicBlock::Create("indirectgoto.loop", CurFn);
204     llvm::BranchInst::Create(Default, Default);
205   }
206 
207   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
208          e = IndirectSwitches.end(); i != e; ++i) {
209     llvm::SwitchInst *I = *i;
210 
211     I->setSuccessor(0, Default);
212     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
213            LE = LabelIDs.end(); LI != LE; ++LI) {
214       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
215                                         LI->second),
216                  getBasicBlockForLabel(LI->first));
217     }
218   }
219 }
220