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/Support/CFG.h"
21 using namespace clang;
22 using namespace CodeGen;
23 
24 CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
25   : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
26     CaseRangeBlock(NULL) {
27     LLVMIntTy = ConvertType(getContext().IntTy);
28     LLVMPointerWidth = Target.getPointerWidth(0);
29 }
30 
31 ASTContext &CodeGenFunction::getContext() const {
32   return CGM.getContext();
33 }
34 
35 
36 llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
37   llvm::BasicBlock *&BB = LabelMap[S];
38   if (BB) return BB;
39 
40   // Create, but don't insert, the new block.
41   return BB = createBasicBlock(S->getName());
42 }
43 
44 llvm::Constant *
45 CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
46   return cast<llvm::Constant>(LocalDeclMap[BVD]);
47 }
48 
49 llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD)
50 {
51   return LocalDeclMap[VD];
52 }
53 
54 const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
55   return CGM.getTypes().ConvertType(T);
56 }
57 
58 bool CodeGenFunction::isObjCPointerType(QualType T) {
59   // All Objective-C types are pointers.
60   return T->isObjCInterfaceType() ||
61     T->isObjCQualifiedInterfaceType() || T->isObjCQualifiedIdType();
62 }
63 
64 bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
65   return !isObjCPointerType(T) &&!T->isRealType() && !T->isPointerLikeType() &&
66     !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
67 }
68 
69 void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
70   // Finish emission of indirect switches.
71   EmitIndirectSwitches();
72 
73   assert(BreakContinueStack.empty() &&
74          "mismatched push/pop in break/continue stack!");
75 
76   // Emit function epilog (to return). This has the nice side effect
77   // of also automatically handling code that falls off the end.
78   EmitBlock(ReturnBlock);
79 
80   // Emit debug descriptor for function end.
81   if (CGDebugInfo *DI = CGM.getDebugInfo()) {
82     DI->setLocation(EndLoc);
83     DI->EmitRegionEnd(CurFn, Builder);
84   }
85 
86   EmitFunctionEpilog(FnRetTy, ReturnValue);
87 
88   // Remove the AllocaInsertPt instruction, which is just a convenience for us.
89   AllocaInsertPt->eraseFromParent();
90   AllocaInsertPt = 0;
91 }
92 
93 void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
94                                     llvm::Function *Fn,
95                                     const FunctionArgList &Args,
96                                     SourceLocation StartLoc) {
97   CurFuncDecl = D;
98   FnRetTy = RetTy;
99   CurFn = Fn;
100   assert(CurFn->isDeclaration() && "Function already has body?");
101 
102   llvm::BasicBlock *EntryBB = createBasicBlock("entry", CurFn);
103 
104   // Create a marker to make it easy to insert allocas into the entryblock
105   // later.  Don't create this with the builder, because we don't want it
106   // folded.
107   llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
108   AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
109                                          EntryBB);
110 
111   ReturnBlock = createBasicBlock("return");
112   ReturnValue = 0;
113   if (!RetTy->isVoidType())
114     ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
115 
116   Builder.SetInsertPoint(EntryBB);
117 
118   // Emit subprogram debug descriptor.
119   // FIXME: The cast here is a huge hack.
120   if (CGDebugInfo *DI = CGM.getDebugInfo()) {
121     DI->setLocation(StartLoc);
122     if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
123       DI->EmitFunctionStart(FD->getName(), RetTy, CurFn, Builder);
124     } else {
125       // Just use LLVM function name.
126       DI->EmitFunctionStart(Fn->getName().c_str(),
127                             RetTy, CurFn, Builder);
128     }
129   }
130 
131   EmitFunctionProlog(CurFn, FnRetTy, Args);
132 }
133 
134 void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
135                                    llvm::Function *Fn) {
136   FunctionArgList Args;
137   if (FD->getNumParams()) {
138     const FunctionTypeProto* FProto = FD->getType()->getAsFunctionTypeProto();
139     assert(FProto && "Function def must have prototype!");
140 
141     for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
142       Args.push_back(std::make_pair(FD->getParamDecl(i),
143                                     FProto->getArgType(i)));
144   }
145 
146   StartFunction(FD, FD->getResultType(), Fn, Args,
147                 cast<CompoundStmt>(FD->getBody())->getLBracLoc());
148 
149   EmitStmt(FD->getBody());
150 
151   const CompoundStmt *S = dyn_cast<CompoundStmt>(FD->getBody());
152   if (S) {
153     FinishFunction(S->getRBracLoc());
154   } else {
155     FinishFunction();
156   }
157 }
158 
159 /// isDummyBlock - Return true if BB is an empty basic block
160 /// with no predecessors.
161 bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
162   if (BB->empty() && pred_begin(BB) == pred_end(BB) && !BB->hasName())
163     return true;
164   return false;
165 }
166 
167 /// ContainsLabel - Return true if the statement contains a label in it.  If
168 /// this statement is not executed normally, it not containing a label means
169 /// that we can just remove the code.
170 bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
171   // Null statement, not a label!
172   if (S == 0) return false;
173 
174   // If this is a label, we have to emit the code, consider something like:
175   // if (0) {  ...  foo:  bar(); }  goto foo;
176   if (isa<LabelStmt>(S))
177     return true;
178 
179   // If this is a case/default statement, and we haven't seen a switch, we have
180   // to emit the code.
181   if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
182     return true;
183 
184   // If this is a switch statement, we want to ignore cases below it.
185   if (isa<SwitchStmt>(S))
186     IgnoreCaseStmts = true;
187 
188   // Scan subexpressions for verboten labels.
189   for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
190        I != E; ++I)
191     if (ContainsLabel(*I, IgnoreCaseStmts))
192       return true;
193 
194   return false;
195 }
196 
197 /// getCGRecordLayout - Return record layout info.
198 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
199                                                          QualType Ty) {
200   const RecordType *RTy = Ty->getAsRecordType();
201   assert (RTy && "Unexpected type. RecordType expected here.");
202 
203   return CGT.getCGRecordLayout(RTy->getDecl());
204 }
205 
206 /// ErrorUnsupported - Print out an error that codegen doesn't support the
207 /// specified stmt yet.
208 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
209                                        bool OmitOnError) {
210   CGM.ErrorUnsupported(S, Type, OmitOnError);
211 }
212 
213 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
214   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
215   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
216 }
217 
218 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
219 {
220   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
221   if (DestPtr->getType() != BP)
222     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
223 
224   // Get size and alignment info for this aggregate.
225   std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
226 
227   // FIXME: Handle variable sized types.
228   const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
229 
230   Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
231                       llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
232                       // TypeInfo.first describes size in bits.
233                       llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
234                       llvm::ConstantInt::get(llvm::Type::Int32Ty,
235                                              TypeInfo.second/8));
236 }
237 
238 void CodeGenFunction::EmitIndirectSwitches() {
239   llvm::BasicBlock *Default;
240 
241   if (IndirectSwitches.empty())
242     return;
243 
244   if (!LabelIDs.empty()) {
245     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
246   } else {
247     // No possible targets for indirect goto, just emit an infinite
248     // loop.
249     Default = createBasicBlock("indirectgoto.loop", CurFn);
250     llvm::BranchInst::Create(Default, Default);
251   }
252 
253   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
254          e = IndirectSwitches.end(); i != e; ++i) {
255     llvm::SwitchInst *I = *i;
256 
257     I->setSuccessor(0, Default);
258     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
259            LE = LabelIDs.end(); LI != LE; ++LI) {
260       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
261                                         LI->second),
262                  getBasicBlockForLabel(LI->first));
263     }
264   }
265 }
266 
267 llvm::Value *CodeGenFunction::EmitVAArg(llvm::Value *VAListAddr, QualType Ty)
268 {
269   // FIXME: This entire method is hardcoded for 32-bit X86.
270 
271   const char *TargetPrefix = getContext().Target.getTargetPrefix();
272 
273   if (strcmp(TargetPrefix, "x86") != 0 ||
274       getContext().Target.getPointerWidth(0) != 32)
275     return 0;
276 
277   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
278   const llvm::Type *BPP = llvm::PointerType::getUnqual(BP);
279 
280   llvm::Value *VAListAddrAsBPP = Builder.CreateBitCast(VAListAddr, BPP,
281                                                        "ap");
282   llvm::Value *Addr = Builder.CreateLoad(VAListAddrAsBPP, "ap.cur");
283   llvm::Value *AddrTyped =
284     Builder.CreateBitCast(Addr,
285                           llvm::PointerType::getUnqual(ConvertType(Ty)));
286 
287   uint64_t SizeInBytes = getContext().getTypeSize(Ty) / 8;
288   const unsigned ArgumentSizeInBytes = 4;
289   if (SizeInBytes < ArgumentSizeInBytes)
290     SizeInBytes = ArgumentSizeInBytes;
291 
292   llvm::Value *NextAddr =
293     Builder.CreateGEP(Addr,
294                       llvm::ConstantInt::get(llvm::Type::Int32Ty, SizeInBytes),
295                       "ap.next");
296   Builder.CreateStore(NextAddr, VAListAddrAsBPP);
297 
298   return AddrTyped;
299 }
300 
301