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/AST.h"
19 #include "llvm/CallingConv.h"
20 #include "llvm/Constants.h"
21 #include "llvm/DerivedTypes.h"
22 #include "llvm/Function.h"
23 #include "llvm/Analysis/Verifier.h"
24 #include "llvm/Support/CFG.h"
25 using namespace clang;
26 using namespace CodeGen;
27 
28 CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
29   : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
30     CaseRangeBlock(NULL) {
31     LLVMIntTy = ConvertType(getContext().IntTy);
32     LLVMPointerWidth = Target.getPointerWidth(0);
33 }
34 
35 ASTContext &CodeGenFunction::getContext() const {
36   return CGM.getContext();
37 }
38 
39 
40 llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
41   llvm::BasicBlock *&BB = LabelMap[S];
42   if (BB) return BB;
43 
44   // Create, but don't insert, the new block.
45   return BB = llvm::BasicBlock::Create(S->getName());
46 }
47 
48 llvm::Constant *
49 CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
50   return cast<llvm::Constant>(LocalDeclMap[BVD]);
51 }
52 
53 const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
54   return CGM.getTypes().ConvertType(T);
55 }
56 
57 bool CodeGenFunction::isObjCPointerType(QualType T) {
58   // All Objective-C types are pointers.
59   return T->isObjCInterfaceType() ||
60     T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
61 }
62 
63 bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
64   return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
65     !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
66 }
67 
68 void CodeGenFunction::GenerateFunction(const Stmt *Body) {
69   // Emit the function body.
70   EmitStmt(Body);
71 
72   // Emit debug descriptor for function end.
73   CGDebugInfo *DI = CGM.getDebugInfo();
74   if (DI) {
75     const CompoundStmt* s = dyn_cast<CompoundStmt>(Body);
76     if (s && s->getRBracLoc().isValid()) {
77       DI->setLocation(s->getRBracLoc());
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     // FIXME: if this is C++ main, this should return 0.
89     if (CurFn->getReturnType() == llvm::Type::VoidTy)
90       Builder.CreateRetVoid();
91     else
92       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
93   }
94   assert(BreakContinueStack.empty() &&
95          "mismatched push/pop in break/continue stack!");
96 
97   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
98   AllocaInsertPt->eraseFromParent();
99   AllocaInsertPt = 0;
100 
101   // Verify that the function is well formed.
102   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
103 }
104 
105 void CodeGenFunction::GenerateCode(const FunctionDecl *FD) {
106   CurFuncDecl = FD;
107   FnRetTy = FD->getResultType();
108   CurFn = cast<llvm::Function>(CGM.GetAddrOfFunctionDecl(FD, true));
109   assert(CurFn->isDeclaration() && "Function already has body?");
110 
111   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
112 
113   // Create a marker to make it easy to insert allocas into the entryblock
114   // later.  Don't create this with the builder, because we don't want it
115   // folded.
116   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
117   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
118                                          EntryBB);
119 
120   Builder.SetInsertPoint(EntryBB);
121 
122   // Emit subprogram debug descriptor.
123   CGDebugInfo *DI = CGM.getDebugInfo();
124   if (DI) {
125     CompoundStmt* body = dyn_cast<CompoundStmt>(FD->getBody());
126     if (body && body->getLBracLoc().isValid()) {
127       DI->setLocation(body->getLBracLoc());
128     }
129     DI->EmitFunctionStart(FD, CurFn, Builder);
130   }
131 
132   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
133   llvm::Function::arg_iterator AI = CurFn->arg_begin();
134 
135   // Name the struct return argument.
136   if (hasAggregateLLVMType(FD->getResultType())) {
137     AI->setName("agg.result");
138     ++AI;
139   }
140 
141   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
142     assert(AI != CurFn->arg_end() && "Argument mismatch!");
143     EmitParmDecl(*FD->getParamDecl(i), AI);
144   }
145   GenerateFunction(FD->getBody());
146 }
147 
148 /// isDummyBlock - Return true if BB is an empty basic block
149 /// with no predecessors.
150 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
151   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
152     return true;
153   return false;
154 }
155 
156 /// StartBlock - Start new block named N. If insert block is a dummy block
157 /// then reuse it.
158 void CodeGenFunction::StartBlock(const char *N) {
159   llvm::BasicBlock *BB = Builder.GetInsertBlock();
160   if (!isDummyBlock(BB))
161     EmitBlock(llvm::BasicBlock::Create(N));
162   else
163     BB->setName(N);
164 }
165 
166 /// getCGRecordLayout - Return record layout info.
167 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
168                                                          QualType Ty) {
169   const RecordType *RTy = Ty->getAsRecordType();
170   assert (RTy && "Unexpected type. RecordType expected here.");
171 
172   return CGT.getCGRecordLayout(RTy->getDecl());
173 }
174 
175 /// WarnUnsupported - Print out a warning that codegen doesn't support the
176 /// specified stmt yet.
177 void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
178   CGM.WarnUnsupported(S, Type);
179 }
180 
181