CodeGenFunction.cpp revision d7c62b1929b024047a06697d2fedbd4c2e7d0cdf 
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/Support/CFG.h"
23#include "llvm/Target/TargetData.h"
24using namespace clang;
25using namespace CodeGen;
26
27CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
28  : BlockFunction(cgm, *this, Builder), CGM(cgm),
29    Target(CGM.getContext().Target),
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
70  // robust in 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 there are no explicit
85    // jumps to the return block.
86    if (ReturnBlock->use_empty())
87      delete ReturnBlock;
88    else
89      EmitBlock(ReturnBlock);
90    return;
91  }
92
93  // Otherwise, if the return block is the target of a single direct
94  // branch then we can just put the code in that block instead. This
95  // cleans up functions which started with a unified return block.
96  if (ReturnBlock->hasOneUse()) {
97    llvm::BranchInst *BI =
98      dyn_cast<llvm::BranchInst>(*ReturnBlock->use_begin());
99    if (BI && BI->isUnconditional() && BI->getSuccessor(0) == ReturnBlock) {
100      // Reset insertion point and delete the branch.
101      Builder.SetInsertPoint(BI->getParent());
102      BI->eraseFromParent();
103      delete ReturnBlock;
104      return;
105    }
106  }
107
108  // FIXME: We are at an unreachable point, there is no reason to emit
109  // the block unless it has uses. However, we still need a place to
110  // put the debug region.end for now.
111
112  EmitBlock(ReturnBlock);
113}
114
115void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
116  // Finish emission of indirect switches.
117  EmitIndirectSwitches();
118
119  assert(BreakContinueStack.empty() &&
120         "mismatched push/pop in break/continue stack!");
121  assert(BlockScopes.empty() &&
122         "did not remove all blocks from block scope map!");
123  assert(CleanupEntries.empty() &&
124         "mismatched push/pop in cleanup stack!");
125
126  // Emit function epilog (to return).
127  EmitReturnBlock();
128
129  // Emit debug descriptor for function end.
130  if (CGDebugInfo *DI = getDebugInfo()) {
131    DI->setLocation(EndLoc);
132    DI->EmitRegionEnd(CurFn, Builder);
133  }
134
135  EmitFunctionEpilog(*CurFnInfo, ReturnValue);
136
137  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
138  llvm::Instruction *Ptr = AllocaInsertPt;
139  AllocaInsertPt = 0;
140  Ptr->eraseFromParent();
141}
142
143void CodeGenFunction::StartFunction(const Decl *D, QualType RetTy,
144                                    llvm::Function *Fn,
145                                    const FunctionArgList &Args,
146                                    SourceLocation StartLoc) {
147  DidCallStackSave = false;
148  CurFuncDecl = D;
149  FnRetTy = RetTy;
150  CurFn = Fn;
151  assert(CurFn->isDeclaration() && "Function already has body?");
152
153  llvm::BasicBlock *EntryBB = createBasicBlock("entry", CurFn);
154
155  // Create a marker to make it easy to insert allocas into the entryblock
156  // later.  Don't create this with the builder, because we don't want it
157  // folded.
158  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::Int32Ty);
159  AllocaInsertPt = new llvm::BitCastInst(Undef, llvm::Type::Int32Ty, "",
160                                         EntryBB);
161  if (Builder.isNamePreserving())
162    AllocaInsertPt->setName("allocapt");
163
164  ReturnBlock = createBasicBlock("return");
165  ReturnValue = 0;
166  if (!RetTy->isVoidType())
167    ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
168
169  Builder.SetInsertPoint(EntryBB);
170
171  // Emit subprogram debug descriptor.
172  // FIXME: The cast here is a huge hack.
173  if (CGDebugInfo *DI = getDebugInfo()) {
174    DI->setLocation(StartLoc);
175    if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
176      DI->EmitFunctionStart(CGM.getMangledName(FD), RetTy, CurFn, Builder);
177    } else {
178      // Just use LLVM function name.
179      DI->EmitFunctionStart(Fn->getName().c_str(),
180                            RetTy, CurFn, Builder);
181    }
182  }
183
184  // FIXME: Leaked.
185  CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
186  EmitFunctionProlog(*CurFnInfo, CurFn, Args);
187
188  // If any of the arguments have a variably modified type, make sure to
189  // emit the type size.
190  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
191       i != e; ++i) {
192    QualType Ty = i->second;
193
194    if (Ty->isVariablyModifiedType())
195      EmitVLASize(Ty);
196  }
197}
198
199void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
200                                   llvm::Function *Fn) {
201  // Check if we should generate debug info for this function.
202  if (CGM.getDebugInfo() && !FD->hasAttr<NodebugAttr>())
203    DebugInfo = CGM.getDebugInfo();
204
205  FunctionArgList Args;
206
207  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
208    if (MD->isInstance()) {
209      // Create the implicit 'this' decl.
210      // FIXME: I'm not entirely sure I like using a fake decl just for code
211      // generation. Maybe we can come up with a better way?
212      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
213                                              &getContext().Idents.get("this"),
214                                              MD->getThisType(getContext()));
215      Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
216    }
217  }
218
219  if (FD->getNumParams()) {
220    const FunctionProtoType* FProto = FD->getType()->getAsFunctionProtoType();
221    assert(FProto && "Function def must have prototype!");
222
223    for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
224      Args.push_back(std::make_pair(FD->getParamDecl(i),
225                                    FProto->getArgType(i)));
226  }
227
228  const CompoundStmt *S = FD->getBody();
229
230  StartFunction(FD, FD->getResultType(), Fn, Args, S->getLBracLoc());
231  EmitStmt(S);
232  FinishFunction(S->getRBracLoc());
233
234  // Destroy the 'this' declaration.
235  if (CXXThisDecl)
236    CXXThisDecl->Destroy(getContext());
237}
238
239/// ContainsLabel - Return true if the statement contains a label in it.  If
240/// this statement is not executed normally, it not containing a label means
241/// that we can just remove the code.
242bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
243  // Null statement, not a label!
244  if (S == 0) return false;
245
246  // If this is a label, we have to emit the code, consider something like:
247  // if (0) {  ...  foo:  bar(); }  goto foo;
248  if (isa<LabelStmt>(S))
249    return true;
250
251  // If this is a case/default statement, and we haven't seen a switch, we have
252  // to emit the code.
253  if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
254    return true;
255
256  // If this is a switch statement, we want to ignore cases below it.
257  if (isa<SwitchStmt>(S))
258    IgnoreCaseStmts = true;
259
260  // Scan subexpressions for verboten labels.
261  for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
262       I != E; ++I)
263    if (ContainsLabel(*I, IgnoreCaseStmts))
264      return true;
265
266  return false;
267}
268
269
270/// ConstantFoldsToSimpleInteger - If the sepcified expression does not fold to
271/// a constant, or if it does but contains a label, return 0.  If it constant
272/// folds to 'true' and does not contain a label, return 1, if it constant folds
273/// to 'false' and does not contain a label, return -1.
274int CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond) {
275  // FIXME: Rename and handle conversion of other evaluatable things
276  // to bool.
277  Expr::EvalResult Result;
278  if (!Cond->Evaluate(Result, getContext()) || !Result.Val.isInt() ||
279      Result.HasSideEffects)
280    return 0;  // Not foldable, not integer or not fully evaluatable.
281
282  if (CodeGenFunction::ContainsLabel(Cond))
283    return 0;  // Contains a label.
284
285  return Result.Val.getInt().getBoolValue() ? 1 : -1;
286}
287
288
289/// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
290/// statement) to the specified blocks.  Based on the condition, this might try
291/// to simplify the codegen of the conditional based on the branch.
292///
293void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
294                                           llvm::BasicBlock *TrueBlock,
295                                           llvm::BasicBlock *FalseBlock) {
296  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
297    return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
298
299  if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
300    // Handle X && Y in a condition.
301    if (CondBOp->getOpcode() == BinaryOperator::LAnd) {
302      // If we have "1 && X", simplify the code.  "0 && X" would have constant
303      // folded if the case was simple enough.
304      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == 1) {
305        // br(1 && X) -> br(X).
306        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
307      }
308
309      // If we have "X && 1", simplify the code to use an uncond branch.
310      // "X && 0" would have been constant folded to 0.
311      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == 1) {
312        // br(X && 1) -> br(X).
313        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
314      }
315
316      // Emit the LHS as a conditional.  If the LHS conditional is false, we
317      // want to jump to the FalseBlock.
318      llvm::BasicBlock *LHSTrue = createBasicBlock("land.lhs.true");
319      EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock);
320      EmitBlock(LHSTrue);
321
322      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
323      return;
324    } else if (CondBOp->getOpcode() == BinaryOperator::LOr) {
325      // If we have "0 || X", simplify the code.  "1 || X" would have constant
326      // folded if the case was simple enough.
327      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == -1) {
328        // br(0 || X) -> br(X).
329        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
330      }
331
332      // If we have "X || 0", simplify the code to use an uncond branch.
333      // "X || 1" would have been constant folded to 1.
334      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == -1) {
335        // br(X || 0) -> br(X).
336        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
337      }
338
339      // Emit the LHS as a conditional.  If the LHS conditional is true, we
340      // want to jump to the TrueBlock.
341      llvm::BasicBlock *LHSFalse = createBasicBlock("lor.lhs.false");
342      EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse);
343      EmitBlock(LHSFalse);
344
345      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
346      return;
347    }
348  }
349
350  if (const UnaryOperator *CondUOp = dyn_cast<UnaryOperator>(Cond)) {
351    // br(!x, t, f) -> br(x, f, t)
352    if (CondUOp->getOpcode() == UnaryOperator::LNot)
353      return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock);
354  }
355
356  if (const ConditionalOperator *CondOp = dyn_cast<ConditionalOperator>(Cond)) {
357    // Handle ?: operator.
358
359    // Just ignore GNU ?: extension.
360    if (CondOp->getLHS()) {
361      // br(c ? x : y, t, f) -> br(c, br(x, t, f), br(y, t, f))
362      llvm::BasicBlock *LHSBlock = createBasicBlock("cond.true");
363      llvm::BasicBlock *RHSBlock = createBasicBlock("cond.false");
364      EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock);
365      EmitBlock(LHSBlock);
366      EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock);
367      EmitBlock(RHSBlock);
368      EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock);
369      return;
370    }
371  }
372
373  // Emit the code with the fully general case.
374  llvm::Value *CondV = EvaluateExprAsBool(Cond);
375  Builder.CreateCondBr(CondV, TrueBlock, FalseBlock);
376}
377
378/// getCGRecordLayout - Return record layout info.
379const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
380                                                         QualType Ty) {
381  const RecordType *RTy = Ty->getAsRecordType();
382  assert (RTy && "Unexpected type. RecordType expected here.");
383
384  return CGT.getCGRecordLayout(RTy->getDecl());
385}
386
387/// ErrorUnsupported - Print out an error that codegen doesn't support the
388/// specified stmt yet.
389void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
390                                       bool OmitOnError) {
391  CGM.ErrorUnsupported(S, Type, OmitOnError);
392}
393
394unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
395  // Use LabelIDs.size() as the new ID if one hasn't been assigned.
396  return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
397}
398
399void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty)
400{
401  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
402  if (DestPtr->getType() != BP)
403    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
404
405  // Get size and alignment info for this aggregate.
406  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
407
408  // FIXME: Handle variable sized types.
409  const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
410
411  Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
412                      llvm::ConstantInt::getNullValue(llvm::Type::Int8Ty),
413                      // TypeInfo.first describes size in bits.
414                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
415                      llvm::ConstantInt::get(llvm::Type::Int32Ty,
416                                             TypeInfo.second/8));
417}
418
419void CodeGenFunction::EmitIndirectSwitches() {
420  llvm::BasicBlock *Default;
421
422  if (IndirectSwitches.empty())
423    return;
424
425  if (!LabelIDs.empty()) {
426    Default = getBasicBlockForLabel(LabelIDs.begin()->first);
427  } else {
428    // No possible targets for indirect goto, just emit an infinite
429    // loop.
430    Default = createBasicBlock("indirectgoto.loop", CurFn);
431    llvm::BranchInst::Create(Default, Default);
432  }
433
434  for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
435         e = IndirectSwitches.end(); i != e; ++i) {
436    llvm::SwitchInst *I = *i;
437
438    I->setSuccessor(0, Default);
439    for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
440           LE = LabelIDs.end(); LI != LE; ++LI) {
441      I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
442                                        LI->second),
443                 getBasicBlockForLabel(LI->first));
444    }
445  }
446}
447
448llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT)
449{
450  llvm::Value *&SizeEntry = VLASizeMap[VAT];
451
452  assert(SizeEntry && "Did not emit size for type");
453  return SizeEntry;
454}
455
456llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty)
457{
458  assert(Ty->isVariablyModifiedType() &&
459         "Must pass variably modified type to EmitVLASizes!");
460
461  if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
462    llvm::Value *&SizeEntry = VLASizeMap[VAT];
463
464    if (!SizeEntry) {
465      // Get the element size;
466      llvm::Value *ElemSize;
467
468      QualType ElemTy = VAT->getElementType();
469
470      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
471
472      if (ElemTy->isVariableArrayType())
473        ElemSize = EmitVLASize(ElemTy);
474      else {
475        ElemSize = llvm::ConstantInt::get(SizeTy,
476                                          getContext().getTypeSize(ElemTy) / 8);
477      }
478
479      llvm::Value *NumElements = EmitScalarExpr(VAT->getSizeExpr());
480      NumElements = Builder.CreateIntCast(NumElements, SizeTy, false, "tmp");
481
482      SizeEntry = Builder.CreateMul(ElemSize, NumElements);
483    }
484
485    return SizeEntry;
486  } else if (const PointerType *PT = Ty->getAsPointerType())
487    EmitVLASize(PT->getPointeeType());
488  else {
489    assert(0 && "unknown VM type!");
490  }
491
492  return 0;
493}
494
495llvm::Value* CodeGenFunction::EmitVAListRef(const Expr* E) {
496  if (CGM.getContext().getBuiltinVaListType()->isArrayType()) {
497    return EmitScalarExpr(E);
498  }
499  return EmitLValue(E).getAddress();
500}
501
502void CodeGenFunction::PushCleanupBlock(llvm::BasicBlock *CleanupBlock)
503{
504  CleanupEntries.push_back(CleanupEntry(CleanupBlock));
505}
506
507void CodeGenFunction::EmitCleanupBlocks(size_t OldCleanupStackSize)
508{
509  assert(CleanupEntries.size() >= OldCleanupStackSize &&
510         "Cleanup stack mismatch!");
511
512  while (CleanupEntries.size() > OldCleanupStackSize)
513    EmitCleanupBlock();
514}
515
516CodeGenFunction::CleanupBlockInfo CodeGenFunction::PopCleanupBlock()
517{
518  CleanupEntry &CE = CleanupEntries.back();
519
520  llvm::BasicBlock *CleanupBlock = CE.CleanupBlock;
521
522  std::vector<llvm::BasicBlock *> Blocks;
523  std::swap(Blocks, CE.Blocks);
524
525  std::vector<llvm::BranchInst *> BranchFixups;
526  std::swap(BranchFixups, CE.BranchFixups);
527
528  CleanupEntries.pop_back();
529
530  // Check if any branch fixups pointed to the scope we just popped. If so,
531  // we can remove them.
532  for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
533    llvm::BasicBlock *Dest = BranchFixups[i]->getSuccessor(0);
534    BlockScopeMap::iterator I = BlockScopes.find(Dest);
535
536    if (I == BlockScopes.end())
537      continue;
538
539    assert(I->second <= CleanupEntries.size() && "Invalid branch fixup!");
540
541    if (I->second == CleanupEntries.size()) {
542      // We don't need to do this branch fixup.
543      BranchFixups[i] = BranchFixups.back();
544      BranchFixups.pop_back();
545      i--;
546      e--;
547      continue;
548    }
549  }
550
551  llvm::BasicBlock *SwitchBlock = 0;
552  llvm::BasicBlock *EndBlock = 0;
553  if (!BranchFixups.empty()) {
554    SwitchBlock = createBasicBlock("cleanup.switch");
555    EndBlock = createBasicBlock("cleanup.end");
556
557    llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
558
559    Builder.SetInsertPoint(SwitchBlock);
560
561    llvm::Value *DestCodePtr = CreateTempAlloca(llvm::Type::Int32Ty,
562                                                "cleanup.dst");
563    llvm::Value *DestCode = Builder.CreateLoad(DestCodePtr, "tmp");
564
565    // Create a switch instruction to determine where to jump next.
566    llvm::SwitchInst *SI = Builder.CreateSwitch(DestCode, EndBlock,
567                                                BranchFixups.size());
568
569    // Restore the current basic block (if any)
570    if (CurBB) {
571      Builder.SetInsertPoint(CurBB);
572
573      // If we had a current basic block, we also need to emit an instruction
574      // to initialize the cleanup destination.
575      Builder.CreateStore(llvm::Constant::getNullValue(llvm::Type::Int32Ty),
576                          DestCodePtr);
577    } else
578      Builder.ClearInsertionPoint();
579
580    for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
581      llvm::BranchInst *BI = BranchFixups[i];
582      llvm::BasicBlock *Dest = BI->getSuccessor(0);
583
584      // Fixup the branch instruction to point to the cleanup block.
585      BI->setSuccessor(0, CleanupBlock);
586
587      if (CleanupEntries.empty()) {
588        llvm::ConstantInt *ID;
589
590        // Check if we already have a destination for this block.
591        if (Dest == SI->getDefaultDest())
592          ID = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
593        else {
594          ID = SI->findCaseDest(Dest);
595          if (!ID) {
596            // No code found, get a new unique one by using the number of
597            // switch successors.
598            ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
599                                        SI->getNumSuccessors());
600            SI->addCase(ID, Dest);
601          }
602        }
603
604        // Store the jump destination before the branch instruction.
605        new llvm::StoreInst(ID, DestCodePtr, BI);
606      } else {
607        // We need to jump through another cleanup block. Create a pad block
608        // with a branch instruction that jumps to the final destination and
609        // add it as a branch fixup to the current cleanup scope.
610
611        // Create the pad block.
612        llvm::BasicBlock *CleanupPad = createBasicBlock("cleanup.pad", CurFn);
613
614        // Create a unique case ID.
615        llvm::ConstantInt *ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
616                                                       SI->getNumSuccessors());
617
618        // Store the jump destination before the branch instruction.
619        new llvm::StoreInst(ID, DestCodePtr, BI);
620
621        // Add it as the destination.
622        SI->addCase(ID, CleanupPad);
623
624        // Create the branch to the final destination.
625        llvm::BranchInst *BI = llvm::BranchInst::Create(Dest);
626        CleanupPad->getInstList().push_back(BI);
627
628        // And add it as a branch fixup.
629        CleanupEntries.back().BranchFixups.push_back(BI);
630      }
631    }
632  }
633
634  // Remove all blocks from the block scope map.
635  for (size_t i = 0, e = Blocks.size(); i != e; ++i) {
636    assert(BlockScopes.count(Blocks[i]) &&
637           "Did not find block in scope map!");
638
639    BlockScopes.erase(Blocks[i]);
640  }
641
642  return CleanupBlockInfo(CleanupBlock, SwitchBlock, EndBlock);
643}
644
645void CodeGenFunction::EmitCleanupBlock()
646{
647  CleanupBlockInfo Info = PopCleanupBlock();
648
649  EmitBlock(Info.CleanupBlock);
650
651  if (Info.SwitchBlock)
652    EmitBlock(Info.SwitchBlock);
653  if (Info.EndBlock)
654    EmitBlock(Info.EndBlock);
655}
656
657void CodeGenFunction::AddBranchFixup(llvm::BranchInst *BI)
658{
659  assert(!CleanupEntries.empty() &&
660         "Trying to add branch fixup without cleanup block!");
661
662  // FIXME: We could be more clever here and check if there's already a
663  // branch fixup for this destination and recycle it.
664  CleanupEntries.back().BranchFixups.push_back(BI);
665}
666
667void CodeGenFunction::EmitBranchThroughCleanup(llvm::BasicBlock *Dest)
668{
669  if (!HaveInsertPoint())
670    return;
671
672  llvm::BranchInst* BI = Builder.CreateBr(Dest);
673
674  Builder.ClearInsertionPoint();
675
676  // The stack is empty, no need to do any cleanup.
677  if (CleanupEntries.empty())
678    return;
679
680  if (!Dest->getParent()) {
681    // We are trying to branch to a block that hasn't been inserted yet.
682    AddBranchFixup(BI);
683    return;
684  }
685
686  BlockScopeMap::iterator I = BlockScopes.find(Dest);
687  if (I == BlockScopes.end()) {
688    // We are trying to jump to a block that is outside of any cleanup scope.
689    AddBranchFixup(BI);
690    return;
691  }
692
693  assert(I->second < CleanupEntries.size() &&
694         "Trying to branch into cleanup region");
695
696  if (I->second == CleanupEntries.size() - 1) {
697    // We have a branch to a block in the same scope.
698    return;
699  }
700
701  AddBranchFixup(BI);
702}
703