CodeGenFunction.cpp revision 8c241a2844428eb1589c7b77fc6c1888295a2045 
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/APValue.h"
19#include "clang/AST/ASTContext.h"
20#include "clang/AST/Decl.h"
21#include "clang/AST/DeclCXX.h"
22#include "llvm/Target/TargetData.h"
23using namespace clang;
24using namespace CodeGen;
25
26CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
27  : BlockFunction(cgm, *this, Builder), CGM(cgm),
28    Target(CGM.getContext().Target),
29    Builder(cgm.getModule().getContext()),
30    DebugInfo(0), SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
31    CXXThisDecl(0) {
32  LLVMIntTy = ConvertType(getContext().IntTy);
33  LLVMPointerWidth = Target.getPointerWidth(0);
34}
35
36ASTContext &CodeGenFunction::getContext() const {
37  return CGM.getContext();
38}
39
40
41llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
42  llvm::BasicBlock *&BB = LabelMap[S];
43  if (BB) return BB;
44
45  // Create, but don't insert, the new block.
46  return BB = createBasicBlock(S->getName());
47}
48
49llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD) {
50  llvm::Value *Res = LocalDeclMap[VD];
51  assert(Res && "Invalid argument to GetAddrOfLocalVar(), no decl!");
52  return Res;
53}
54
55llvm::Constant *
56CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
57  return cast<llvm::Constant>(GetAddrOfLocalVar(BVD));
58}
59
60const llvm::Type *CodeGenFunction::ConvertTypeForMem(QualType T) {
61  return CGM.getTypes().ConvertTypeForMem(T);
62}
63
64const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
65  return CGM.getTypes().ConvertType(T);
66}
67
68bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
69  // FIXME: Use positive checks instead of negative ones to be more robust in
70  // the face of extension.
71  return !T->hasPointerRepresentation() &&!T->isRealType() &&
72    !T->isVoidType() && !T->isVectorType() && !T->isFunctionType() &&
73    !T->isBlockPointerType();
74}
75
76void CodeGenFunction::EmitReturnBlock() {
77  // For cleanliness, we try to avoid emitting the return block for
78  // simple cases.
79  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
80
81  if (CurBB) {
82    assert(!CurBB->getTerminator() && "Unexpected terminated block.");
83
84    // We have a valid insert point, reuse it if it is empty or there are no
85    // explicit jumps to the return block.
86    if (CurBB->empty() || ReturnBlock->use_empty()) {
87      ReturnBlock->replaceAllUsesWith(CurBB);
88      delete ReturnBlock;
89    } else
90      EmitBlock(ReturnBlock);
91    return;
92  }
93
94  // Otherwise, if the return block is the target of a single direct
95  // branch then we can just put the code in that block instead. This
96  // cleans up functions which started with a unified return block.
97  if (ReturnBlock->hasOneUse()) {
98    llvm::BranchInst *BI =
99      dyn_cast<llvm::BranchInst>(*ReturnBlock->use_begin());
100    if (BI && BI->isUnconditional() && BI->getSuccessor(0) == ReturnBlock) {
101      // Reset insertion point and delete the branch.
102      Builder.SetInsertPoint(BI->getParent());
103      BI->eraseFromParent();
104      delete ReturnBlock;
105      return;
106    }
107  }
108
109  // FIXME: We are at an unreachable point, there is no reason to emit the block
110  // unless it has uses. However, we still need a place to put the debug
111  // region.end for now.
112
113  EmitBlock(ReturnBlock);
114}
115
116void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
117  // Finish emission of indirect switches.
118  EmitIndirectSwitches();
119
120  assert(BreakContinueStack.empty() &&
121         "mismatched push/pop in break/continue stack!");
122  assert(BlockScopes.empty() &&
123         "did not remove all blocks from block scope map!");
124  assert(CleanupEntries.empty() &&
125         "mismatched push/pop in cleanup stack!");
126
127  // Emit function epilog (to return).
128  EmitReturnBlock();
129
130  // Emit debug descriptor for function end.
131  if (CGDebugInfo *DI = getDebugInfo()) {
132    DI->setLocation(EndLoc);
133    DI->EmitRegionEnd(CurFn, Builder);
134  }
135
136  EmitFunctionEpilog(*CurFnInfo, ReturnValue);
137
138  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
139  llvm::Instruction *Ptr = AllocaInsertPt;
140  AllocaInsertPt = 0;
141  Ptr->eraseFromParent();
142}
143
144void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
145                                    llvm::Function *Fn,
146                                    const FunctionArgList &Args,
147                                    SourceLocation StartLoc) {
148  DidCallStackSave = false;
149  CurCodeDecl = CurFuncDecl = D;
150  FnRetTy = RetTy;
151  CurFn = Fn;
152  assert(CurFn->isDeclaration() && "Function already has body?");
153
154  llvm::BasicBlock *EntryBB = createBasicBlock("entry", CurFn);
155
156  // Create a marker to make it easy to insert allocas into the entryblock
157  // later.  Don't create this with the builder, because we don't want it
158  // folded.
159  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
160  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "",
161                                         EntryBB);
162  if (Builder.isNamePreserving())
163    AllocaInsertPt->setName("allocapt");
164
165  ReturnBlock = createBasicBlock("return");
166  ReturnValue = 0;
167  if (!RetTy->isVoidType())
168    ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
169
170  Builder.SetInsertPoint(EntryBB);
171
172  // Emit subprogram debug descriptor.
173  // FIXME: The cast here is a huge hack.
174  if (CGDebugInfo *DI = getDebugInfo()) {
175    DI->setLocation(StartLoc);
176    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
177      DI->EmitFunctionStart(CGM.getMangledName(FD), RetTy, CurFn, Builder);
178    } else {
179      // Just use LLVM function name.
180
181      // FIXME: Remove unnecessary conversion to std::string when API settles.
182      DI->EmitFunctionStart(std::string(Fn->getName()).c_str(),
183                            RetTy, CurFn, Builder);
184    }
185  }
186
187  // FIXME: Leaked.
188  CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
189  EmitFunctionProlog(*CurFnInfo, CurFn, Args);
190
191  // If any of the arguments have a variably modified type, make sure to
192  // emit the type size.
193  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
194       i != e; ++i) {
195    QualType Ty = i->second;
196
197    if (Ty->isVariablyModifiedType())
198      EmitVLASize(Ty);
199  }
200}
201
202void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
203                                   llvm::Function *Fn) {
204  // Check if we should generate debug info for this function.
205  if (CGM.getDebugInfo() && !FD->hasAttr<NodebugAttr>())
206    DebugInfo = CGM.getDebugInfo();
207
208  FunctionArgList Args;
209
210  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
211    if (MD->isInstance()) {
212      // Create the implicit 'this' decl.
213      // FIXME: I'm not entirely sure I like using a fake decl just for code
214      // generation. Maybe we can come up with a better way?
215      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
216                                              &getContext().Idents.get("this"),
217                                              MD->getThisType(getContext()));
218      Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
219    }
220  }
221
222  if (FD->getNumParams()) {
223    const FunctionProtoType* FProto = FD->getType()->getAsFunctionProtoType();
224    assert(FProto && "Function def must have prototype!");
225
226    for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
227      Args.push_back(std::make_pair(FD->getParamDecl(i),
228                                    FProto->getArgType(i)));
229  }
230
231  // FIXME: Support CXXTryStmt here, too.
232  if (const CompoundStmt *S = FD->getCompoundBody()) {
233    StartFunction(FD, FD->getResultType(), Fn, Args, S->getLBracLoc());
234    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD))
235      EmitCtorPrologue(CD);
236    EmitStmt(S);
237    if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(FD))
238      EmitDtorEpilogue(DD);
239    FinishFunction(S->getRBracLoc());
240  }
241  else
242    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
243      const CXXRecordDecl *ClassDecl =
244        cast<CXXRecordDecl>(CD->getDeclContext());
245      (void) ClassDecl;
246      if (CD->isCopyConstructor(getContext())) {
247        assert(!ClassDecl->hasUserDeclaredCopyConstructor() &&
248               "bogus constructor is being synthesize");
249        SynthesizeCXXCopyConstructor(CD, FD, Fn, Args);
250      }
251      else {
252        assert(!ClassDecl->hasUserDeclaredConstructor() &&
253               "bogus constructor is being synthesize");
254        StartFunction(FD, FD->getResultType(), Fn, Args, SourceLocation());
255        EmitCtorPrologue(CD);
256        FinishFunction();
257      }
258    }
259
260  // Destroy the 'this' declaration.
261  if (CXXThisDecl)
262    CXXThisDecl->Destroy(getContext());
263}
264
265/// ContainsLabel - Return true if the statement contains a label in it.  If
266/// this statement is not executed normally, it not containing a label means
267/// that we can just remove the code.
268bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
269  // Null statement, not a label!
270  if (S == 0) return false;
271
272  // If this is a label, we have to emit the code, consider something like:
273  // if (0) {  ...  foo:  bar(); }  goto foo;
274  if (isa<LabelStmt>(S))
275    return true;
276
277  // If this is a case/default statement, and we haven't seen a switch, we have
278  // to emit the code.
279  if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
280    return true;
281
282  // If this is a switch statement, we want to ignore cases below it.
283  if (isa<SwitchStmt>(S))
284    IgnoreCaseStmts = true;
285
286  // Scan subexpressions for verboten labels.
287  for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
288       I != E; ++I)
289    if (ContainsLabel(*I, IgnoreCaseStmts))
290      return true;
291
292  return false;
293}
294
295
296/// ConstantFoldsToSimpleInteger - If the sepcified expression does not fold to
297/// a constant, or if it does but contains a label, return 0.  If it constant
298/// folds to 'true' and does not contain a label, return 1, if it constant folds
299/// to 'false' and does not contain a label, return -1.
300int CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond) {
301  // FIXME: Rename and handle conversion of other evaluatable things
302  // to bool.
303  Expr::EvalResult Result;
304  if (!Cond->Evaluate(Result, getContext()) || !Result.Val.isInt() ||
305      Result.HasSideEffects)
306    return 0;  // Not foldable, not integer or not fully evaluatable.
307
308  if (CodeGenFunction::ContainsLabel(Cond))
309    return 0;  // Contains a label.
310
311  return Result.Val.getInt().getBoolValue() ? 1 : -1;
312}
313
314
315/// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
316/// statement) to the specified blocks.  Based on the condition, this might try
317/// to simplify the codegen of the conditional based on the branch.
318///
319void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
320                                           llvm::BasicBlock *TrueBlock,
321                                           llvm::BasicBlock *FalseBlock) {
322  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
323    return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
324
325  if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
326    // Handle X && Y in a condition.
327    if (CondBOp->getOpcode() == BinaryOperator::LAnd) {
328      // If we have "1 && X", simplify the code.  "0 && X" would have constant
329      // folded if the case was simple enough.
330      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == 1) {
331        // br(1 && X) -> br(X).
332        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
333      }
334
335      // If we have "X && 1", simplify the code to use an uncond branch.
336      // "X && 0" would have been constant folded to 0.
337      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == 1) {
338        // br(X && 1) -> br(X).
339        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
340      }
341
342      // Emit the LHS as a conditional.  If the LHS conditional is false, we
343      // want to jump to the FalseBlock.
344      llvm::BasicBlock *LHSTrue = createBasicBlock("land.lhs.true");
345      EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock);
346      EmitBlock(LHSTrue);
347
348      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
349      return;
350    } else if (CondBOp->getOpcode() == BinaryOperator::LOr) {
351      // If we have "0 || X", simplify the code.  "1 || X" would have constant
352      // folded if the case was simple enough.
353      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == -1) {
354        // br(0 || X) -> br(X).
355        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
356      }
357
358      // If we have "X || 0", simplify the code to use an uncond branch.
359      // "X || 1" would have been constant folded to 1.
360      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == -1) {
361        // br(X || 0) -> br(X).
362        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
363      }
364
365      // Emit the LHS as a conditional.  If the LHS conditional is true, we
366      // want to jump to the TrueBlock.
367      llvm::BasicBlock *LHSFalse = createBasicBlock("lor.lhs.false");
368      EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse);
369      EmitBlock(LHSFalse);
370
371      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
372      return;
373    }
374  }
375
376  if (const UnaryOperator *CondUOp = dyn_cast<UnaryOperator>(Cond)) {
377    // br(!x, t, f) -> br(x, f, t)
378    if (CondUOp->getOpcode() == UnaryOperator::LNot)
379      return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock);
380  }
381
382  if (const ConditionalOperator *CondOp = dyn_cast<ConditionalOperator>(Cond)) {
383    // Handle ?: operator.
384
385    // Just ignore GNU ?: extension.
386    if (CondOp->getLHS()) {
387      // br(c ? x : y, t, f) -> br(c, br(x, t, f), br(y, t, f))
388      llvm::BasicBlock *LHSBlock = createBasicBlock("cond.true");
389      llvm::BasicBlock *RHSBlock = createBasicBlock("cond.false");
390      EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock);
391      EmitBlock(LHSBlock);
392      EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock);
393      EmitBlock(RHSBlock);
394      EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock);
395      return;
396    }
397  }
398
399  // Emit the code with the fully general case.
400  llvm::Value *CondV = EvaluateExprAsBool(Cond);
401  Builder.CreateCondBr(CondV, TrueBlock, FalseBlock);
402}
403
404/// getCGRecordLayout - Return record layout info.
405const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
406                                                         QualType Ty) {
407  const RecordType *RTy = Ty->getAs<RecordType>();
408  assert (RTy && "Unexpected type. RecordType expected here.");
409
410  return CGT.getCGRecordLayout(RTy->getDecl());
411}
412
413/// ErrorUnsupported - Print out an error that codegen doesn't support the
414/// specified stmt yet.
415void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
416                                       bool OmitOnError) {
417  CGM.ErrorUnsupported(S, Type, OmitOnError);
418}
419
420unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
421  // Use LabelIDs.size() as the new ID if one hasn't been assigned.
422  return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
423}
424
425void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
426  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
427  if (DestPtr->getType() != BP)
428    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
429
430  // Get size and alignment info for this aggregate.
431  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
432
433  // Don't bother emitting a zero-byte memset.
434  if (TypeInfo.first == 0)
435    return;
436
437  // FIXME: Handle variable sized types.
438  const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
439
440  Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
441                      llvm::Constant::getNullValue(llvm::Type::Int8Ty),
442                      // TypeInfo.first describes size in bits.
443                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
444                      llvm::ConstantInt::get(llvm::Type::Int32Ty,
445                                             TypeInfo.second/8));
446}
447
448void CodeGenFunction::EmitIndirectSwitches() {
449  llvm::BasicBlock *Default;
450
451  if (IndirectSwitches.empty())
452    return;
453
454  if (!LabelIDs.empty()) {
455    Default = getBasicBlockForLabel(LabelIDs.begin()->first);
456  } else {
457    // No possible targets for indirect goto, just emit an infinite
458    // loop.
459    Default = createBasicBlock("indirectgoto.loop", CurFn);
460    llvm::BranchInst::Create(Default, Default);
461  }
462
463  for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
464         e = IndirectSwitches.end(); i != e; ++i) {
465    llvm::SwitchInst *I = *i;
466
467    I->setSuccessor(0, Default);
468    for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
469           LE = LabelIDs.end(); LI != LE; ++LI) {
470      I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
471                                        LI->second),
472                 getBasicBlockForLabel(LI->first));
473    }
474  }
475}
476
477llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT) {
478  llvm::Value *&SizeEntry = VLASizeMap[VAT];
479
480  assert(SizeEntry && "Did not emit size for type");
481  return SizeEntry;
482}
483
484llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty) {
485  assert(Ty->isVariablyModifiedType() &&
486         "Must pass variably modified type to EmitVLASizes!");
487
488  EnsureInsertPoint();
489
490  if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
491    llvm::Value *&SizeEntry = VLASizeMap[VAT];
492
493    if (!SizeEntry) {
494      // Get the element size;
495      llvm::Value *ElemSize;
496
497      QualType ElemTy = VAT->getElementType();
498
499      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
500
501      if (ElemTy->isVariableArrayType())
502        ElemSize = EmitVLASize(ElemTy);
503      else {
504        ElemSize = llvm::ConstantInt::get(SizeTy,
505                                          getContext().getTypeSize(ElemTy) / 8);
506      }
507
508      llvm::Value *NumElements = EmitScalarExpr(VAT->getSizeExpr());
509      NumElements = Builder.CreateIntCast(NumElements, SizeTy, false, "tmp");
510
511      SizeEntry = Builder.CreateMul(ElemSize, NumElements);
512    }
513
514    return SizeEntry;
515  } else if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
516    EmitVLASize(AT->getElementType());
517  } else if (const PointerType *PT = Ty->getAs<PointerType>())
518    EmitVLASize(PT->getPointeeType());
519  else {
520    assert(0 && "unknown VM type!");
521  }
522
523  return 0;
524}
525
526llvm::Value* CodeGenFunction::EmitVAListRef(const Expr* E) {
527  if (CGM.getContext().getBuiltinVaListType()->isArrayType()) {
528    return EmitScalarExpr(E);
529  }
530  return EmitLValue(E).getAddress();
531}
532
533void CodeGenFunction::PushCleanupBlock(llvm::BasicBlock *CleanupBlock)
534{
535  CleanupEntries.push_back(CleanupEntry(CleanupBlock));
536}
537
538void CodeGenFunction::EmitCleanupBlocks(size_t OldCleanupStackSize)
539{
540  assert(CleanupEntries.size() >= OldCleanupStackSize &&
541         "Cleanup stack mismatch!");
542
543  while (CleanupEntries.size() > OldCleanupStackSize)
544    EmitCleanupBlock();
545}
546
547CodeGenFunction::CleanupBlockInfo CodeGenFunction::PopCleanupBlock()
548{
549  CleanupEntry &CE = CleanupEntries.back();
550
551  llvm::BasicBlock *CleanupBlock = CE.CleanupBlock;
552
553  std::vector<llvm::BasicBlock *> Blocks;
554  std::swap(Blocks, CE.Blocks);
555
556  std::vector<llvm::BranchInst *> BranchFixups;
557  std::swap(BranchFixups, CE.BranchFixups);
558
559  CleanupEntries.pop_back();
560
561  // Check if any branch fixups pointed to the scope we just popped. If so,
562  // we can remove them.
563  for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
564    llvm::BasicBlock *Dest = BranchFixups[i]->getSuccessor(0);
565    BlockScopeMap::iterator I = BlockScopes.find(Dest);
566
567    if (I == BlockScopes.end())
568      continue;
569
570    assert(I->second <= CleanupEntries.size() && "Invalid branch fixup!");
571
572    if (I->second == CleanupEntries.size()) {
573      // We don't need to do this branch fixup.
574      BranchFixups[i] = BranchFixups.back();
575      BranchFixups.pop_back();
576      i--;
577      e--;
578      continue;
579    }
580  }
581
582  llvm::BasicBlock *SwitchBlock = 0;
583  llvm::BasicBlock *EndBlock = 0;
584  if (!BranchFixups.empty()) {
585    SwitchBlock = createBasicBlock("cleanup.switch");
586    EndBlock = createBasicBlock("cleanup.end");
587
588    llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
589
590    Builder.SetInsertPoint(SwitchBlock);
591
592    llvm::Value *DestCodePtr = CreateTempAlloca(llvm::Type::Int32Ty,
593                                                "cleanup.dst");
594    llvm::Value *DestCode = Builder.CreateLoad(DestCodePtr, "tmp");
595
596    // Create a switch instruction to determine where to jump next.
597    llvm::SwitchInst *SI = Builder.CreateSwitch(DestCode, EndBlock,
598                                                BranchFixups.size());
599
600    // Restore the current basic block (if any)
601    if (CurBB) {
602      Builder.SetInsertPoint(CurBB);
603
604      // If we had a current basic block, we also need to emit an instruction
605      // to initialize the cleanup destination.
606      Builder.CreateStore(llvm::Constant::getNullValue(llvm::Type::Int32Ty),
607                          DestCodePtr);
608    } else
609      Builder.ClearInsertionPoint();
610
611    for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
612      llvm::BranchInst *BI = BranchFixups[i];
613      llvm::BasicBlock *Dest = BI->getSuccessor(0);
614
615      // Fixup the branch instruction to point to the cleanup block.
616      BI->setSuccessor(0, CleanupBlock);
617
618      if (CleanupEntries.empty()) {
619        llvm::ConstantInt *ID;
620
621        // Check if we already have a destination for this block.
622        if (Dest == SI->getDefaultDest())
623          ID = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
624        else {
625          ID = SI->findCaseDest(Dest);
626          if (!ID) {
627            // No code found, get a new unique one by using the number of
628            // switch successors.
629            ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
630                                        SI->getNumSuccessors());
631            SI->addCase(ID, Dest);
632          }
633        }
634
635        // Store the jump destination before the branch instruction.
636        new llvm::StoreInst(ID, DestCodePtr, BI);
637      } else {
638        // We need to jump through another cleanup block. Create a pad block
639        // with a branch instruction that jumps to the final destination and
640        // add it as a branch fixup to the current cleanup scope.
641
642        // Create the pad block.
643        llvm::BasicBlock *CleanupPad = createBasicBlock("cleanup.pad", CurFn);
644
645        // Create a unique case ID.
646        llvm::ConstantInt *ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
647                                                       SI->getNumSuccessors());
648
649        // Store the jump destination before the branch instruction.
650        new llvm::StoreInst(ID, DestCodePtr, BI);
651
652        // Add it as the destination.
653        SI->addCase(ID, CleanupPad);
654
655        // Create the branch to the final destination.
656        llvm::BranchInst *BI = llvm::BranchInst::Create(Dest);
657        CleanupPad->getInstList().push_back(BI);
658
659        // And add it as a branch fixup.
660        CleanupEntries.back().BranchFixups.push_back(BI);
661      }
662    }
663  }
664
665  // Remove all blocks from the block scope map.
666  for (size_t i = 0, e = Blocks.size(); i != e; ++i) {
667    assert(BlockScopes.count(Blocks[i]) &&
668           "Did not find block in scope map!");
669
670    BlockScopes.erase(Blocks[i]);
671  }
672
673  return CleanupBlockInfo(CleanupBlock, SwitchBlock, EndBlock);
674}
675
676void CodeGenFunction::EmitCleanupBlock()
677{
678  CleanupBlockInfo Info = PopCleanupBlock();
679
680  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
681  if (CurBB && !CurBB->getTerminator() &&
682      Info.CleanupBlock->getNumUses() == 0) {
683    CurBB->getInstList().splice(CurBB->end(), Info.CleanupBlock->getInstList());
684    delete Info.CleanupBlock;
685  } else
686    EmitBlock(Info.CleanupBlock);
687
688  if (Info.SwitchBlock)
689    EmitBlock(Info.SwitchBlock);
690  if (Info.EndBlock)
691    EmitBlock(Info.EndBlock);
692}
693
694void CodeGenFunction::AddBranchFixup(llvm::BranchInst *BI)
695{
696  assert(!CleanupEntries.empty() &&
697         "Trying to add branch fixup without cleanup block!");
698
699  // FIXME: We could be more clever here and check if there's already a branch
700  // fixup for this destination and recycle it.
701  CleanupEntries.back().BranchFixups.push_back(BI);
702}
703
704void CodeGenFunction::EmitBranchThroughCleanup(llvm::BasicBlock *Dest)
705{
706  if (!HaveInsertPoint())
707    return;
708
709  llvm::BranchInst* BI = Builder.CreateBr(Dest);
710
711  Builder.ClearInsertionPoint();
712
713  // The stack is empty, no need to do any cleanup.
714  if (CleanupEntries.empty())
715    return;
716
717  if (!Dest->getParent()) {
718    // We are trying to branch to a block that hasn't been inserted yet.
719    AddBranchFixup(BI);
720    return;
721  }
722
723  BlockScopeMap::iterator I = BlockScopes.find(Dest);
724  if (I == BlockScopes.end()) {
725    // We are trying to jump to a block that is outside of any cleanup scope.
726    AddBranchFixup(BI);
727    return;
728  }
729
730  assert(I->second < CleanupEntries.size() &&
731         "Trying to branch into cleanup region");
732
733  if (I->second == CleanupEntries.size() - 1) {
734    // We have a branch to a block in the same scope.
735    return;
736  }
737
738  AddBranchFixup(BI);
739}
740