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 /// ContainsLabel - Return true if the statement contains a label in it.  If
160 /// this statement is not executed normally, it not containing a label means
161 /// that we can just remove the code.
162 bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
163   // Null statement, not a label!
164   if (S == 0) return false;
165 
166   // If this is a label, we have to emit the code, consider something like:
167   // if (0) {  ...  foo:  bar(); }  goto foo;
168   if (isa<LabelStmt>(S))
169     return true;
170 
171   // If this is a case/default statement, and we haven't seen a switch, we have
172   // to emit the code.
173   if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
174     return true;
175 
176   // If this is a switch statement, we want to ignore cases below it.
177   if (isa<SwitchStmt>(S))
178     IgnoreCaseStmts = true;
179 
180   // Scan subexpressions for verboten labels.
181   for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
182        I != E; ++I)
183     if (ContainsLabel(*I, IgnoreCaseStmts))
184       return true;
185 
186   return false;
187 }
188 
189 /// getCGRecordLayout - Return record layout info.
190 const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
191                                                          QualType Ty) {
192   const RecordType *RTy = Ty->getAsRecordType();
193   assert (RTy && "Unexpected type. RecordType expected here.");
194 
195   return CGT.getCGRecordLayout(RTy->getDecl());
196 }
197 
198 /// ErrorUnsupported - Print out an error that codegen doesn't support the
199 /// specified stmt yet.
200 void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
201                                        bool OmitOnError) {
202   CGM.ErrorUnsupported(S, Type, OmitOnError);
203 }
204 
205 unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
206   // Use LabelIDs.size() as the new ID if one hasn't been assigned.
207   return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
208 }
209 
210 void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
211 {
212   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
213   if (DestPtr->getType() != BP)
214     DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
215 
216   // Get size and alignment info for this aggregate.
217   std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
218 
219   // FIXME: Handle variable sized types.
220   const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
221 
222   Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
223                       llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
224                       // TypeInfo.first describes size in bits.
225                       llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
226                       llvm::ConstantInt::get(llvm::Type::Int32Ty,
227                                              TypeInfo.second/8));
228 }
229 
230 void CodeGenFunction::EmitIndirectSwitches() {
231   llvm::BasicBlock *Default;
232 
233   if (IndirectSwitches.empty())
234     return;
235 
236   if (!LabelIDs.empty()) {
237     Default = getBasicBlockForLabel(LabelIDs.begin()->first);
238   } else {
239     // No possible targets for indirect goto, just emit an infinite
240     // loop.
241     Default = createBasicBlock("indirectgoto.loop", CurFn);
242     llvm::BranchInst::Create(Default, Default);
243   }
244 
245   for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
246          e = IndirectSwitches.end(); i != e; ++i) {
247     llvm::SwitchInst *I = *i;
248 
249     I->setSuccessor(0, Default);
250     for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
251            LE = LabelIDs.end(); LI != LE; ++LI) {
252       I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
253                                         LI->second),
254                  getBasicBlockForLabel(LI->first));
255     }
256   }
257 }
258 
259 llvm::Value *CodeGenFunction::EmitVAArg(llvm::Value *VAListAddr, QualType Ty)
260 {
261   // FIXME: This entire method is hardcoded for 32-bit X86.
262 
263   const char *TargetPrefix = getContext().Target.getTargetPrefix();
264 
265   if (strcmp(TargetPrefix, "x86") != 0 ||
266       getContext().Target.getPointerWidth(0) != 32)
267     return 0;
268 
269   const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
270   const llvm::Type *BPP = llvm::PointerType::getUnqual(BP);
271 
272   llvm::Value *VAListAddrAsBPP = Builder.CreateBitCast(VAListAddr, BPP,
273                                                        "ap");
274   llvm::Value *Addr = Builder.CreateLoad(VAListAddrAsBPP, "ap.cur");
275   llvm::Value *AddrTyped =
276     Builder.CreateBitCast(Addr,
277                           llvm::PointerType::getUnqual(ConvertType(Ty)));
278 
279   uint64_t SizeInBytes = getContext().getTypeSize(Ty) / 8;
280   const unsigned ArgumentSizeInBytes = 4;
281   if (SizeInBytes < ArgumentSizeInBytes)
282     SizeInBytes = ArgumentSizeInBytes;
283 
284   llvm::Value *NextAddr =
285     Builder.CreateGEP(Addr,
286                       llvm::ConstantInt::get(llvm::Type::Int32Ty, SizeInBytes),
287                       "ap.next");
288   Builder.CreateStore(NextAddr, VAListAddrAsBPP);
289 
290   return AddrTyped;
291 }
292 
293