CodeGenFunction.cpp revision ce5605ecf76d8cde6372138f830bb144d174ced9 
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 "clang/Basic/TargetInfo.h"
17#include "clang/AST/AST.h"
18#include "llvm/CallingConv.h"
19#include "llvm/Constants.h"
20#include "llvm/DerivedTypes.h"
21#include "llvm/Function.h"
22#include "llvm/Analysis/Verifier.h"
23#include "llvm/Support/CFG.h"
24using namespace clang;
25using namespace CodeGen;
26
27CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
28  : CGM(cgm), Target(CGM.getContext().Target), SwitchInsn(NULL),
29    CaseRangeBlock(NULL) {}
30
31ASTContext &CodeGenFunction::getContext() const {
32  return CGM.getContext();
33}
34
35
36llvm::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 = new llvm::BasicBlock(S->getName());
42}
43
44llvm::Constant *
45CodeGenFunction::GetAddrOfStaticLocalVar(const BlockVarDecl *BVD) {
46  return cast<llvm::Constant>(LocalDeclMap[BVD]);
47}
48
49const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
50  return CGM.getTypes().ConvertType(T);
51}
52
53bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
54  return !T->isRealType() && !T->isPointerType() && !T->isReferenceType() &&
55         !T->isVoidType() && !T->isVectorType() && !T->isFunctionType();
56}
57
58/// Generate an Objective-C method.  An Objective-C method is a C function with
59/// its pointer, name, and types registered in the class struture.
60// FIXME: This method contains a lot of code copied and pasted from
61// GenerateCode.  This should be factored out.
62void CodeGenFunction::GenerateObjCMethod(const ObjCMethodDecl *OMD) {
63  llvm::SmallVector<const llvm::Type *, 16> ParamTypes;
64  for (unsigned i=0 ; i<OMD->param_size() ; i++) {
65    ParamTypes.push_back(ConvertType(OMD->getParamDecl(i)->getType()));
66  }
67  CurFn =CGM.getObjCRuntime()->MethodPreamble(ConvertType(OMD->getResultType()),
68                      llvm::PointerType::getUnqual(llvm::Type::Int32Ty),
69                                              ParamTypes.begin(),
70                                              OMD->param_size(),
71                                              OMD->isVariadic());
72  llvm::BasicBlock *EntryBB = new llvm::BasicBlock("entry", CurFn);
73
74  // Create a marker to make it easy to insert allocas into the entryblock
75  // later.  Don't create this with the builder, because we don't want it
76  // folded.
77  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
78  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
79                                         EntryBB);
80
81  FnRetTy = OMD->getResultType();
82
83  Builder.SetInsertPoint(EntryBB);
84
85  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
86  llvm::Function::arg_iterator AI = CurFn->arg_begin();
87
88  // Name the struct return argument.
89  // FIXME: Probably should be in the runtime, or it will trample the other
90  // hidden arguments.
91  if (hasAggregateLLVMType(OMD->getResultType())) {
92    AI->setName("agg.result");
93    ++AI;
94  }
95
96  // Add implicit parameters to the decl map.
97  // TODO: Add something to AST to let the runtime specify the names and types
98  // of these.
99  llvm::Value *&DMEntry = LocalDeclMap[&(*OMD->getSelfDecl())];
100  DMEntry = AI;
101  ++AI; ++AI;
102
103
104  for (unsigned i = 0, e = OMD->getNumParams(); i != e; ++i, ++AI) {
105    assert(AI != CurFn->arg_end() && "Argument mismatch!");
106    EmitParmDecl(*OMD->getParamDecl(i), AI);
107  }
108
109  // Emit the function body.
110  EmitStmt(OMD->getBody());
111
112  // Emit a return for code that falls off the end. If insert point
113  // is a dummy block with no predecessors then remove the block itself.
114  llvm::BasicBlock *BB = Builder.GetInsertBlock();
115  if (isDummyBlock(BB))
116    BB->eraseFromParent();
117  else {
118    if (CurFn->getReturnType() == llvm::Type::VoidTy)
119      Builder.CreateRetVoid();
120    else
121      Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
122  }
123  assert(BreakContinueStack.empty() &&
124         "mismatched push/pop in break/continue stack!");
125
126  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
127  AllocaInsertPt->eraseFromParent();
128  AllocaInsertPt = 0;
129  // Verify that the function is well formed.
130  assert(!verifyFunction(*CurFn) && "Generated method is not well formed.");
131}
132
133void CodeGenFunction::GenerateCode(const FunctionDecl *FD) {
134  LLVMIntTy = ConvertType(getContext().IntTy);
135  LLVMPointerWidth = static_cast<unsigned>(
136    getContext().getTypeSize(getContext().getPointerType(getContext().VoidTy)));
137
138  CurFuncDecl = FD;
139  FnRetTy = CurFuncDecl->getType()->getAsFunctionType()->getResultType();
140
141
142  CurFn = cast<llvm::Function>(CGM.GetAddrOfFunctionDecl(FD, true));
143  assert(CurFn->isDeclaration() && "Function already has body?");
144
145  // TODO: Set up linkage and many other things.  Note, this is a simple
146  // approximation of what we really want.
147  if (FD->getAttr<DLLImportAttr>())
148    CurFn->setLinkage(llvm::Function::DLLImportLinkage);
149  else if (FD->getAttr<DLLExportAttr>())
150    CurFn->setLinkage(llvm::Function::DLLExportLinkage);
151  else if (FD->getAttr<WeakAttr>() || FD->isInline())
152    CurFn->setLinkage(llvm::Function::WeakLinkage);
153  else if (FD->getStorageClass() == FunctionDecl::Static)
154    CurFn->setLinkage(llvm::Function::InternalLinkage);
155
156  if (FD->getAttr<FastCallAttr>())
157    CurFn->setCallingConv(llvm::CallingConv::Fast);
158
159  if (const VisibilityAttr *attr = FD->getAttr<VisibilityAttr>())
160    CurFn->setVisibility(attr->getVisibility());
161  // FIXME: else handle -fvisibility
162
163
164  unsigned FuncAttrs = 0;
165  if (FD->getAttr<NoThrowAttr>())
166    FuncAttrs |= llvm::ParamAttr::NoUnwind;
167  if (FD->getAttr<NoReturnAttr>())
168    FuncAttrs |= llvm::ParamAttr::NoReturn;
169
170  if (FuncAttrs) {
171    llvm::ParamAttrsWithIndex PAWI =
172      llvm::ParamAttrsWithIndex::get(0, FuncAttrs);
173    CurFn->setParamAttrs(llvm::PAListPtr::get(&PAWI, 1));
174  }
175
176  llvm::BasicBlock *EntryBB = new llvm::BasicBlock("entry", CurFn);
177
178  // Create a marker to make it easy to insert allocas into the entryblock
179  // later.  Don't create this with the builder, because we don't want it
180  // folded.
181  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
182  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "allocapt",
183                                         EntryBB);
184
185  Builder.SetInsertPoint(EntryBB);
186
187  // Emit allocs for param decls.  Give the LLVM Argument nodes names.
188  llvm::Function::arg_iterator AI = CurFn->arg_begin();
189
190  // Name the struct return argument.
191  if (hasAggregateLLVMType(FD->getResultType())) {
192    AI->setName("agg.result");
193    ++AI;
194  }
195
196  for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i, ++AI) {
197    assert(AI != CurFn->arg_end() && "Argument mismatch!");
198    EmitParmDecl(*FD->getParamDecl(i), AI);
199  }
200
201  // Emit the function body.
202  EmitStmt(FD->getBody());
203
204  // Emit a return for code that falls off the end. If insert point
205  // is a dummy block with no predecessors then remove the block itself.
206  llvm::BasicBlock *BB = Builder.GetInsertBlock();
207  if (isDummyBlock(BB))
208    BB->eraseFromParent();
209  else {
210    // FIXME: if this is C++ main, this should return 0.
211    if (CurFn->getReturnType() == llvm::Type::VoidTy)
212      Builder.CreateRetVoid();
213    else
214      Builder.CreateRet(llvm::UndefValue::get(CurFn->getReturnType()));
215  }
216  assert(BreakContinueStack.empty() &&
217         "mismatched push/pop in break/continue stack!");
218
219  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
220  AllocaInsertPt->eraseFromParent();
221  AllocaInsertPt = 0;
222
223  // Verify that the function is well formed.
224  assert(!verifyFunction(*CurFn) && "Generated function is not well formed.");
225}
226
227/// isDummyBlock - Return true if BB is an empty basic block
228/// with no predecessors.
229bool CodeGenFunction::isDummyBlock(const llvm::BasicBlock *BB) {
230  if (BB->empty() && pred_begin(BB) == pred_end(BB))
231    return true;
232  return false;
233}
234
235/// StartBlock - Start new block named N. If insert block is a dummy block
236/// then reuse it.
237void CodeGenFunction::StartBlock(const char *N) {
238  llvm::BasicBlock *BB = Builder.GetInsertBlock();
239  if (!isDummyBlock(BB))
240    EmitBlock(new llvm::BasicBlock(N));
241  else
242    BB->setName(N);
243}
244
245/// getCGRecordLayout - Return record layout info.
246const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
247                                                         QualType Ty) {
248  const RecordType *RTy = Ty->getAsRecordType();
249  assert (RTy && "Unexpected type. RecordType expected here.");
250
251  return CGT.getCGRecordLayout(RTy->getDecl());
252}
253
254/// WarnUnsupported - Print out a warning that codegen doesn't support the
255/// specified stmt yet.
256void CodeGenFunction::WarnUnsupported(const Stmt *S, const char *Type) {
257  CGM.WarnUnsupported(S, Type);
258}
259
260