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 a return for code that falls off the end. If insert point
73   // is a dummy block with no predecessors then remove the block itself.
74   llvm::BasicBlock *BB = Builder.GetInsertBlock();
75   if (isDummyBlock(BB))
76     BB->eraseFromParent();
77   else {
78     // FIXME: if this is C++ main, this should return 0.
79     if (CurFn->getReturnType() == llvm::Type::VoidTy)
80       Builder.CreateRetVoid();
81     else
82       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
83   }
84   assert(BreakContinueStack.empty() &&
85          "mismatched push/pop in break/continue stack!");
86 
87   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
88   AllocaInsertPt->eraseFromParent();
89   AllocaInsertPt = 0;
90 
91   // Verify that the function is well formed.
92   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
93 }
94 
95 void CodeGenFunction::GenerateCode(const FunctionDecl *FD) {
96   CurFuncDecl = FD;
97   FnRetTy = FD->getResultType();
98   CurFn = cast<llvm::Function>(CGM.GetAddrOfFunctionDecl(FD, true));
99   assert(CurFn->isDeclaration() && "Function already has body?");
100 
101   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
102 
103   // Create a marker to make it easy to insert allocas into the entryblock
104   // later.  Don't create this with the builder, because we don't want it
105   // folded.
106   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
107   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
108                                          EntryBB);
109 
110   Builder.SetInsertPoint(EntryBB);
111 
112   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
113   llvm::Function::arg_iterator AI = CurFn->arg_begin();
114 
115   // Name the struct return argument.
116   if (hasAggregateLLVMType(FD->getResultType())) {
117     AI->setName("agg.result");
118     ++AI;
119   }
120 
121   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
122     assert(AI != CurFn->arg_end() && "Argument mismatch!");
123     EmitParmDecl(*FD->getParamDecl(i), AI);
124   }
125   GenerateFunction(FD->getBody());
126 }
127 
128 /// isDummyBlock - Return true if BB is an empty basic block
129 /// with no predecessors.
130 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
131   if (BB->empty() && pred_begin(BB) == pred_end(BB))
132     return true;
133   return false;
134 }
135 
136 /// StartBlock - Start new block named N. If insert block is a dummy block
137 /// then reuse it.
138 void CodeGenFunction::StartBlock(const char *N) {
139   llvm::BasicBlock *BB = Builder.GetInsertBlock();
140   if (!isDummyBlock(BB))
141     EmitBlock(llvm::BasicBlock::Create(N));
142   else
143     BB->setName(N);
144 }
145 
146 /// getCGRecordLayout - Return record layout info.
147 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
148                                                          QualType Ty) {
149   const RecordType *RTy = Ty->getAsRecordType();
150   assert (RTy && "Unexpected type. RecordType expected here.");
151 
152   return CGT.getCGRecordLayout(RTy->getDecl());
153 }
154 
155 /// WarnUnsupported - Print out a warning that codegen doesn't support the
156 /// specified stmt yet.
157 void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
158   CGM.WarnUnsupported(S, Type);
159 }
160 
161