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 
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::hasAggregateLLVMType(QualType T) {
55   return !T->isRealType() && !T->isPointerLikeType() &&
56          !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
57 }
58 
59 /// Generate an Objective-C method.  An Objective-C method is a C function with
60 /// its pointer, name, and types registered in the class struture.
61 // FIXME: This method contains a lot of code copied and pasted from
62 // GenerateCode.  This should be factored out.
63 void CodeGenFunction::GenerateObjCMethod(const ObjCMethodDecl *OMD) {
64   llvm::SmallVector<const llvm::Type *, 16> ParamTypes;
65   for (unsigned i=0 ; i<OMD->param_size() ; i++) {
66     ParamTypes.push_back(ConvertType(OMD->getParamDecl(i)->getType()));
67   }
68   CurFn =CGM.getObjCRuntime()->MethodPreamble(ConvertType(OMD->getResultType()),
69                       llvm::PointerType::getUnqual(llvm::Type::Int32Ty),
70                                               ParamTypes.begin(),
71                                               OMD->param_size(),
72                                               OMD->isVariadic());
73   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
74 
75   // Create a marker to make it easy to insert allocas into the entryblock
76   // later.  Don't create this with the builder, because we don't want it
77   // folded.
78   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
79   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
80                                          EntryBB);
81 
82   FnRetTy = OMD->getResultType();
83 
84   Builder.SetInsertPoint(EntryBB);
85 
86   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
87   llvm::Function::arg_iterator AI = CurFn->arg_begin();
88 
89   // Name the struct return argument.
90   // FIXME: Probably should be in the runtime, or it will trample the other
91   // hidden arguments.
92   if (hasAggregateLLVMType(OMD->getResultType())) {
93     AI->setName("agg.result");
94     ++AI;
95   }
96 
97   // Add implicit parameters to the decl map.
98   // TODO: Add something to AST to let the runtime specify the names and types
99   // of these.
100   llvm::Value *&DMEntry = LocalDeclMap[&(*OMD->getSelfDecl())];
101   const llvm::Type *SelfTy = AI->getType();
102   llvm::Value *DeclPtr = new llvm::AllocaInst(SelfTy, 0, "self.addr",
103                                    AllocaInsertPt);
104 
105   // Store the initial value into the alloca.
106   Builder.CreateStore(AI, DeclPtr);
107   DMEntry = DeclPtr;
108   ++AI; ++AI;
109 
110 
111   for (unsigned i = 0, e = OMD->getNumParams(); i != e; ++i, ++AI) {
112     assert(AI != CurFn->arg_end() && "Argument mismatch!");
113     EmitParmDecl(*OMD->getParamDecl(i), AI);
114   }
115 
116   // Emit the function body.
117   EmitStmt(OMD->getBody());
118 
119   // Emit a return for code that falls off the end. If insert point
120   // is a dummy block with no predecessors then remove the block itself.
121   llvm::BasicBlock *BB = Builder.GetInsertBlock();
122   if (isDummyBlock(BB))
123     BB->eraseFromParent();
124   else {
125     if (CurFn->getReturnType() == llvm::Type::VoidTy)
126       Builder.CreateRetVoid();
127     else
128       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
129   }
130   assert(BreakContinueStack.empty() &&
131          "mismatched push/pop in break/continue stack!");
132 
133   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
134   AllocaInsertPt->eraseFromParent();
135   AllocaInsertPt = 0;
136   // Verify that the function is well formed.
137   assert(!verifyFunction(*CurFn) && "Generated method is not well formed.");
138 }
139 
140 llvm::Value *CodeGenFunction::LoadObjCSelf(void)
141 {
142   if(const ObjCMethodDecl *OMD = dyn_cast<ObjCMethodDecl>(CurFuncDecl)) {
143     llvm::Value *SelfPtr = LocalDeclMap[&(*OMD->getSelfDecl())];
144     return Builder.CreateLoad(SelfPtr, "self");
145   }
146   return NULL;
147 }
148 
149 void CodeGenFunction::GenerateCode(const FunctionDecl *FD) {
150   LLVMIntTy = ConvertType(getContext().IntTy);
151   LLVMPointerWidth = static_cast<unsigned>(
152     getContext().getTypeSize(getContext().getPointerType(getContext().VoidTy)));
153 
154   CurFuncDecl = FD;
155   FnRetTy = FD->getType()->getAsFunctionType()->getResultType();
156 
157   CurFn = cast<llvm::Function>(CGM.GetAddrOfFunctionDecl(FD, true));
158   assert(CurFn->isDeclaration() && "Function already has body?");
159 
160   // TODO: Set up linkage and many other things.  Note, this is a simple
161   // approximation of what we really want.
162   if (FD->getStorageClass() == FunctionDecl::Static)
163     CurFn->setLinkage(llvm::Function::InternalLinkage);
164   else if (FD->getAttr<DLLImportAttr>())
165     CurFn->setLinkage(llvm::Function::DLLImportLinkage);
166   else if (FD->getAttr<DLLExportAttr>())
167     CurFn->setLinkage(llvm::Function::DLLExportLinkage);
168   else if (FD->getAttr<WeakAttr>() || FD->isInline())
169     CurFn->setLinkage(llvm::Function::WeakLinkage);
170 
171   if (FD->getAttr<FastCallAttr>())
172     CurFn->setCallingConv(llvm::CallingConv::Fast);
173 
174   if (const VisibilityAttr *attr = FD->getAttr<VisibilityAttr>())
175     CodeGenModule::setVisibility(CurFn, attr->getVisibility());
176   // FIXME: else handle -fvisibility
177 
178 
179   unsigned FuncAttrs = 0;
180   if (FD->getAttr<NoThrowAttr>())
181     FuncAttrs |= llvm::ParamAttr::NoUnwind;
182   if (FD->getAttr<NoReturnAttr>())
183     FuncAttrs |= llvm::ParamAttr::NoReturn;
184 
185   if (FuncAttrs) {
186     llvm::ParamAttrsWithIndex PAWI =
187       llvm::ParamAttrsWithIndex::get(0, FuncAttrs);
188     CurFn->setParamAttrs(llvm::PAListPtr::get(&PAWI, 1));
189   }
190 
191   llvm::BasicBlock *EntryBB = llvm::BasicBlock::Create("entry", CurFn);
192 
193   // Create a marker to make it easy to insert allocas into the entryblock
194   // later.  Don't create this with the builder, because we don't want it
195   // folded.
196   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
197   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
198                                          EntryBB);
199 
200   Builder.SetInsertPoint(EntryBB);
201 
202   CGDebugInfo *DI = CGM.getDebugInfo();
203   if (DI) {
204     CompoundStmt* body = cast<CompoundStmt>(CurFuncDecl->getBody());
205     if (body->getLBracLoc().isValid()) {
206       DI->setLocation(body->getLBracLoc());
207     }
208     DI->EmitFunctionStart(FD, CurFn, Builder);
209   }
210 
211   // Emit allocs for param decls.  Give the LLVM Argument nodes names.
212   llvm::Function::arg_iterator AI = CurFn->arg_begin();
213 
214   // Name the struct return argument.
215   if (hasAggregateLLVMType(FD->getResultType())) {
216     AI->setName("agg.result");
217     ++AI;
218   }
219 
220   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
221     assert(AI != CurFn->arg_end() && "Argument mismatch!");
222     EmitParmDecl(*FD->getParamDecl(i), AI);
223   }
224 
225   // Emit the function body.
226   EmitStmt(FD->getBody());
227 
228   if (DI) {
229     CompoundStmt* body = cast<CompoundStmt>(CurFuncDecl->getBody());
230     if (body->getRBracLoc().isValid()) {
231       DI->setLocation(body->getRBracLoc());
232     }
233     DI->EmitRegionEnd(CurFn, Builder);
234   }
235 
236   // Emit a return for code that falls off the end. If insert point
237   // is a dummy block with no predecessors then remove the block itself.
238   llvm::BasicBlock *BB = Builder.GetInsertBlock();
239   if (isDummyBlock(BB))
240     BB->eraseFromParent();
241   else {
242     // FIXME: if this is C++ main, this should return 0.
243     if (CurFn->getReturnType() == llvm::Type::VoidTy)
244       Builder.CreateRetVoid();
245     else
246       Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
247   }
248   assert(BreakContinueStack.empty() &&
249          "mismatched push/pop in break/continue stack!");
250 
251   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
252   AllocaInsertPt->eraseFromParent();
253   AllocaInsertPt = 0;
254 
255   // Verify that the function is well formed.
256   assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
257 }
258 
259 /// isDummyBlock - Return true if BB is an empty basic block
260 /// with no predecessors.
261 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
262   if (BB->empty() && pred_begin(BB) == pred_end(BB))
263     return true;
264   return false;
265 }
266 
267 /// StartBlock - Start new block named N. If insert block is a dummy block
268 /// then reuse it.
269 void CodeGenFunction::StartBlock(const char *N) {
270   llvm::BasicBlock *BB = Builder.GetInsertBlock();
271   if (!isDummyBlock(BB))
272     EmitBlock(llvm::BasicBlock::Create(N));
273   else
274     BB->setName(N);
275 }
276 
277 /// getCGRecordLayout - Return record layout info.
278 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
279                                                          QualType Ty) {
280   const RecordType *RTy = Ty->getAsRecordType();
281   assert (RTy && "Unexpected type. RecordType expected here.");
282 
283   return CGT.getCGRecordLayout(RTy->getDecl());
284 }
285 
286 /// WarnUnsupported - Print out a warning that codegen doesn't support the
287 /// specified stmt yet.
288 void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
289   CGM.WarnUnsupported(S, Type);
290 }
291 
292