CodeGenFunction.cpp revision 69243825cb5c91ec7207256aa57ae327cfaf8cb2 
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    Builder(cgm.getModule().getContext()),
31    DebugInfo(0), SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
32    CXXThisDecl(0) {
33  LLVMIntTy = ConvertType(getContext().IntTy);
34  LLVMPointerWidth = Target.getPointerWidth(0);
35}
36
37ASTContext &CodeGenFunction::getContext() const {
38  return CGM.getContext();
39}
40
41
42llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
43  llvm::BasicBlock *&BB = LabelMap[S];
44  if (BB) return BB;
45
46  // Create, but don't insert, the new block.
47  return BB = createBasicBlock(S->getName());
48}
49
50llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD) {
51  llvm::Value *Res = LocalDeclMap[VD];
52  assert(Res && "Invalid argument to GetAddrOfLocalVar(), no decl!");
53  return Res;
54}
55
56llvm::Constant *
57CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
58  return cast<llvm::Constant>(GetAddrOfLocalVar(BVD));
59}
60
61const llvm::Type *CodeGenFunction::ConvertTypeForMem(QualType T) {
62  return CGM.getTypes().ConvertTypeForMem(T);
63}
64
65const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
66  return CGM.getTypes().ConvertType(T);
67}
68
69bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
70  // FIXME: Use positive checks instead of negative ones to be more robust in
71  // the face of extension.
72  return !T->hasPointerRepresentation() &&!T->isRealType() &&
73    !T->isVoidType() && !T->isVectorType() && !T->isFunctionType() &&
74    !T->isBlockPointerType();
75}
76
77void CodeGenFunction::EmitReturnBlock() {
78  // For cleanliness, we try to avoid emitting the return block for
79  // simple cases.
80  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
81
82  if (CurBB) {
83    assert(!CurBB->getTerminator() && "Unexpected terminated block.");
84
85    // We have a valid insert point, reuse it if there are no explicit
86    // jumps to the return block.
87    if (ReturnBlock->use_empty())
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      DI->EmitFunctionStart(Fn->getName().c_str(),
181                            RetTy, CurFn, Builder);
182    }
183  }
184
185  // FIXME: Leaked.
186  CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
187  EmitFunctionProlog(*CurFnInfo, CurFn, Args);
188
189  // If any of the arguments have a variably modified type, make sure to
190  // emit the type size.
191  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
192       i != e; ++i) {
193    QualType Ty = i->second;
194
195    if (Ty->isVariablyModifiedType())
196      EmitVLASize(Ty);
197  }
198}
199
200void CodeGenFunction::GenerateCode(const FunctionDecl *FD,
201                                   llvm::Function *Fn) {
202  // Check if we should generate debug info for this function.
203  if (CGM.getDebugInfo() && !FD->hasAttr<NodebugAttr>())
204    DebugInfo = CGM.getDebugInfo();
205
206  FunctionArgList Args;
207
208  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
209    if (MD->isInstance()) {
210      // Create the implicit 'this' decl.
211      // FIXME: I'm not entirely sure I like using a fake decl just for code
212      // generation. Maybe we can come up with a better way?
213      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
214                                              &getContext().Idents.get("this"),
215                                              MD->getThisType(getContext()));
216      Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
217    }
218  }
219
220  if (FD->getNumParams()) {
221    const FunctionProtoType* FProto = FD->getType()->getAsFunctionProtoType();
222    assert(FProto && "Function def must have prototype!");
223
224    for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
225      Args.push_back(std::make_pair(FD->getParamDecl(i),
226                                    FProto->getArgType(i)));
227  }
228
229  // FIXME: Support CXXTryStmt here, too.
230  if (const CompoundStmt *S = FD->getCompoundBody()) {
231    StartFunction(FD, FD->getResultType(), Fn, Args, S->getLBracLoc());
232    EmitStmt(S);
233    FinishFunction(S->getRBracLoc());
234  }
235
236  // Destroy the 'this' declaration.
237  if (CXXThisDecl)
238    CXXThisDecl->Destroy(getContext());
239}
240
241/// ContainsLabel - Return true if the statement contains a label in it.  If
242/// this statement is not executed normally, it not containing a label means
243/// that we can just remove the code.
244bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
245  // Null statement, not a label!
246  if (S == 0) return false;
247
248  // If this is a label, we have to emit the code, consider something like:
249  // if (0) {  ...  foo:  bar(); }  goto foo;
250  if (isa<LabelStmt>(S))
251    return true;
252
253  // If this is a case/default statement, and we haven't seen a switch, we have
254  // to emit the code.
255  if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
256    return true;
257
258  // If this is a switch statement, we want to ignore cases below it.
259  if (isa<SwitchStmt>(S))
260    IgnoreCaseStmts = true;
261
262  // Scan subexpressions for verboten labels.
263  for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
264       I != E; ++I)
265    if (ContainsLabel(*I, IgnoreCaseStmts))
266      return true;
267
268  return false;
269}
270
271
272/// ConstantFoldsToSimpleInteger - If the sepcified expression does not fold to
273/// a constant, or if it does but contains a label, return 0.  If it constant
274/// folds to 'true' and does not contain a label, return 1, if it constant folds
275/// to 'false' and does not contain a label, return -1.
276int CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond) {
277  // FIXME: Rename and handle conversion of other evaluatable things
278  // to bool.
279  Expr::EvalResult Result;
280  if (!Cond->Evaluate(Result, getContext()) || !Result.Val.isInt() ||
281      Result.HasSideEffects)
282    return 0;  // Not foldable, not integer or not fully evaluatable.
283
284  if (CodeGenFunction::ContainsLabel(Cond))
285    return 0;  // Contains a label.
286
287  return Result.Val.getInt().getBoolValue() ? 1 : -1;
288}
289
290
291/// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
292/// statement) to the specified blocks.  Based on the condition, this might try
293/// to simplify the codegen of the conditional based on the branch.
294///
295void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
296                                           llvm::BasicBlock *TrueBlock,
297                                           llvm::BasicBlock *FalseBlock) {
298  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
299    return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
300
301  if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
302    // Handle X && Y in a condition.
303    if (CondBOp->getOpcode() == BinaryOperator::LAnd) {
304      // If we have "1 && X", simplify the code.  "0 && X" would have constant
305      // folded if the case was simple enough.
306      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == 1) {
307        // br(1 && X) -> br(X).
308        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
309      }
310
311      // If we have "X && 1", simplify the code to use an uncond branch.
312      // "X && 0" would have been constant folded to 0.
313      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == 1) {
314        // br(X && 1) -> br(X).
315        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
316      }
317
318      // Emit the LHS as a conditional.  If the LHS conditional is false, we
319      // want to jump to the FalseBlock.
320      llvm::BasicBlock *LHSTrue = createBasicBlock("land.lhs.true");
321      EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock);
322      EmitBlock(LHSTrue);
323
324      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
325      return;
326    } else if (CondBOp->getOpcode() == BinaryOperator::LOr) {
327      // If we have "0 || X", simplify the code.  "1 || X" would have constant
328      // folded if the case was simple enough.
329      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == -1) {
330        // br(0 || X) -> br(X).
331        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
332      }
333
334      // If we have "X || 0", simplify the code to use an uncond branch.
335      // "X || 1" would have been constant folded to 1.
336      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == -1) {
337        // br(X || 0) -> br(X).
338        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
339      }
340
341      // Emit the LHS as a conditional.  If the LHS conditional is true, we
342      // want to jump to the TrueBlock.
343      llvm::BasicBlock *LHSFalse = createBasicBlock("lor.lhs.false");
344      EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse);
345      EmitBlock(LHSFalse);
346
347      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
348      return;
349    }
350  }
351
352  if (const UnaryOperator *CondUOp = dyn_cast<UnaryOperator>(Cond)) {
353    // br(!x, t, f) -> br(x, f, t)
354    if (CondUOp->getOpcode() == UnaryOperator::LNot)
355      return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock);
356  }
357
358  if (const ConditionalOperator *CondOp = dyn_cast<ConditionalOperator>(Cond)) {
359    // Handle ?: operator.
360
361    // Just ignore GNU ?: extension.
362    if (CondOp->getLHS()) {
363      // br(c ? x : y, t, f) -> br(c, br(x, t, f), br(y, t, f))
364      llvm::BasicBlock *LHSBlock = createBasicBlock("cond.true");
365      llvm::BasicBlock *RHSBlock = createBasicBlock("cond.false");
366      EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock);
367      EmitBlock(LHSBlock);
368      EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock);
369      EmitBlock(RHSBlock);
370      EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock);
371      return;
372    }
373  }
374
375  // Emit the code with the fully general case.
376  llvm::Value *CondV = EvaluateExprAsBool(Cond);
377  Builder.CreateCondBr(CondV, TrueBlock, FalseBlock);
378}
379
380/// getCGRecordLayout - Return record layout info.
381const CGRecordLayout *CodeGenFunction::getCGRecordLayout(CodeGenTypes &CGT,
382                                                         QualType Ty) {
383  const RecordType *RTy = Ty->getAsRecordType();
384  assert (RTy && "Unexpected type. RecordType expected here.");
385
386  return CGT.getCGRecordLayout(RTy->getDecl());
387}
388
389/// ErrorUnsupported - Print out an error that codegen doesn't support the
390/// specified stmt yet.
391void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
392                                       bool OmitOnError) {
393  CGM.ErrorUnsupported(S, Type, OmitOnError);
394}
395
396unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
397  // Use LabelIDs.size() as the new ID if one hasn't been assigned.
398  return LabelIDs.insert(std::make_pair(L, LabelIDs.size())).first->second;
399}
400
401void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
402  const llvm::Type *BP = llvm::PointerType::getUnqual(llvm::Type::Int8Ty);
403  if (DestPtr->getType() != BP)
404    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
405
406  // Get size and alignment info for this aggregate.
407  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
408
409  // Don't bother emitting a zero-byte memset.
410  if (TypeInfo.first == 0)
411    return;
412
413  // FIXME: Handle variable sized types.
414  const llvm::Type *IntPtr = llvm::IntegerType::get(LLVMPointerWidth);
415
416  Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
417                      getLLVMContext().getNullValue(llvm::Type::Int8Ty),
418                      // TypeInfo.first describes size in bits.
419                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
420                      llvm::ConstantInt::get(llvm::Type::Int32Ty,
421                                             TypeInfo.second/8));
422}
423
424void CodeGenFunction::EmitIndirectSwitches() {
425  llvm::BasicBlock *Default;
426
427  if (IndirectSwitches.empty())
428    return;
429
430  if (!LabelIDs.empty()) {
431    Default = getBasicBlockForLabel(LabelIDs.begin()->first);
432  } else {
433    // No possible targets for indirect goto, just emit an infinite
434    // loop.
435    Default = createBasicBlock("indirectgoto.loop", CurFn);
436    llvm::BranchInst::Create(Default, Default);
437  }
438
439  for (std::vector<llvm::SwitchInst*>::iterator i = IndirectSwitches.begin(),
440         e = IndirectSwitches.end(); i != e; ++i) {
441    llvm::SwitchInst *I = *i;
442
443    I->setSuccessor(0, Default);
444    for (std::map<const LabelStmt*,unsigned>::iterator LI = LabelIDs.begin(),
445           LE = LabelIDs.end(); LI != LE; ++LI) {
446      I->addCase(llvm::ConstantInt::get(llvm::Type::Int32Ty,
447                                        LI->second),
448                 getBasicBlockForLabel(LI->first));
449    }
450  }
451}
452
453llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT)
454{
455  llvm::Value *&SizeEntry = VLASizeMap[VAT];
456
457  assert(SizeEntry && "Did not emit size for type");
458  return SizeEntry;
459}
460
461llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty)
462{
463  assert(Ty->isVariablyModifiedType() &&
464         "Must pass variably modified type to EmitVLASizes!");
465
466  if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
467    llvm::Value *&SizeEntry = VLASizeMap[VAT];
468
469    if (!SizeEntry) {
470      // Get the element size;
471      llvm::Value *ElemSize;
472
473      QualType ElemTy = VAT->getElementType();
474
475      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
476
477      if (ElemTy->isVariableArrayType())
478        ElemSize = EmitVLASize(ElemTy);
479      else {
480        ElemSize = llvm::ConstantInt::get(SizeTy,
481                                          getContext().getTypeSize(ElemTy) / 8);
482      }
483
484      llvm::Value *NumElements = EmitScalarExpr(VAT->getSizeExpr());
485      NumElements = Builder.CreateIntCast(NumElements, SizeTy, false, "tmp");
486
487      SizeEntry = Builder.CreateMul(ElemSize, NumElements);
488    }
489
490    return SizeEntry;
491  } else if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
492    EmitVLASize(AT->getElementType());
493  } else if (const PointerType *PT = Ty->getAsPointerType())
494    EmitVLASize(PT->getPointeeType());
495  else {
496    assert(0 && "unknown VM type!");
497  }
498
499  return 0;
500}
501
502llvm::Value* CodeGenFunction::EmitVAListRef(const Expr* E) {
503  if (CGM.getContext().getBuiltinVaListType()->isArrayType()) {
504    return EmitScalarExpr(E);
505  }
506  return EmitLValue(E).getAddress();
507}
508
509void CodeGenFunction::PushCleanupBlock(llvm::BasicBlock *CleanupBlock)
510{
511  CleanupEntries.push_back(CleanupEntry(CleanupBlock));
512}
513
514void CodeGenFunction::EmitCleanupBlocks(size_t OldCleanupStackSize)
515{
516  assert(CleanupEntries.size() >= OldCleanupStackSize &&
517         "Cleanup stack mismatch!");
518
519  while (CleanupEntries.size() > OldCleanupStackSize)
520    EmitCleanupBlock();
521}
522
523CodeGenFunction::CleanupBlockInfo CodeGenFunction::PopCleanupBlock()
524{
525  CleanupEntry &CE = CleanupEntries.back();
526
527  llvm::BasicBlock *CleanupBlock = CE.CleanupBlock;
528
529  std::vector<llvm::BasicBlock *> Blocks;
530  std::swap(Blocks, CE.Blocks);
531
532  std::vector<llvm::BranchInst *> BranchFixups;
533  std::swap(BranchFixups, CE.BranchFixups);
534
535  CleanupEntries.pop_back();
536
537  // Check if any branch fixups pointed to the scope we just popped. If so,
538  // we can remove them.
539  for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
540    llvm::BasicBlock *Dest = BranchFixups[i]->getSuccessor(0);
541    BlockScopeMap::iterator I = BlockScopes.find(Dest);
542
543    if (I == BlockScopes.end())
544      continue;
545
546    assert(I->second <= CleanupEntries.size() && "Invalid branch fixup!");
547
548    if (I->second == CleanupEntries.size()) {
549      // We don't need to do this branch fixup.
550      BranchFixups[i] = BranchFixups.back();
551      BranchFixups.pop_back();
552      i--;
553      e--;
554      continue;
555    }
556  }
557
558  llvm::BasicBlock *SwitchBlock = 0;
559  llvm::BasicBlock *EndBlock = 0;
560  if (!BranchFixups.empty()) {
561    SwitchBlock = createBasicBlock("cleanup.switch");
562    EndBlock = createBasicBlock("cleanup.end");
563
564    llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
565
566    Builder.SetInsertPoint(SwitchBlock);
567
568    llvm::Value *DestCodePtr = CreateTempAlloca(llvm::Type::Int32Ty,
569                                                "cleanup.dst");
570    llvm::Value *DestCode = Builder.CreateLoad(DestCodePtr, "tmp");
571
572    // Create a switch instruction to determine where to jump next.
573    llvm::SwitchInst *SI = Builder.CreateSwitch(DestCode, EndBlock,
574                                                BranchFixups.size());
575
576    // Restore the current basic block (if any)
577    if (CurBB) {
578      Builder.SetInsertPoint(CurBB);
579
580      // If we had a current basic block, we also need to emit an instruction
581      // to initialize the cleanup destination.
582      Builder.CreateStore(getLLVMContext().getNullValue(llvm::Type::Int32Ty),
583                          DestCodePtr);
584    } else
585      Builder.ClearInsertionPoint();
586
587    for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
588      llvm::BranchInst *BI = BranchFixups[i];
589      llvm::BasicBlock *Dest = BI->getSuccessor(0);
590
591      // Fixup the branch instruction to point to the cleanup block.
592      BI->setSuccessor(0, CleanupBlock);
593
594      if (CleanupEntries.empty()) {
595        llvm::ConstantInt *ID;
596
597        // Check if we already have a destination for this block.
598        if (Dest == SI->getDefaultDest())
599          ID = llvm::ConstantInt::get(llvm::Type::Int32Ty, 0);
600        else {
601          ID = SI->findCaseDest(Dest);
602          if (!ID) {
603            // No code found, get a new unique one by using the number of
604            // switch successors.
605            ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
606                                        SI->getNumSuccessors());
607            SI->addCase(ID, Dest);
608          }
609        }
610
611        // Store the jump destination before the branch instruction.
612        new llvm::StoreInst(ID, DestCodePtr, BI);
613      } else {
614        // We need to jump through another cleanup block. Create a pad block
615        // with a branch instruction that jumps to the final destination and
616        // add it as a branch fixup to the current cleanup scope.
617
618        // Create the pad block.
619        llvm::BasicBlock *CleanupPad = createBasicBlock("cleanup.pad", CurFn);
620
621        // Create a unique case ID.
622        llvm::ConstantInt *ID = llvm::ConstantInt::get(llvm::Type::Int32Ty,
623                                                       SI->getNumSuccessors());
624
625        // Store the jump destination before the branch instruction.
626        new llvm::StoreInst(ID, DestCodePtr, BI);
627
628        // Add it as the destination.
629        SI->addCase(ID, CleanupPad);
630
631        // Create the branch to the final destination.
632        llvm::BranchInst *BI = llvm::BranchInst::Create(Dest);
633        CleanupPad->getInstList().push_back(BI);
634
635        // And add it as a branch fixup.
636        CleanupEntries.back().BranchFixups.push_back(BI);
637      }
638    }
639  }
640
641  // Remove all blocks from the block scope map.
642  for (size_t i = 0, e = Blocks.size(); i != e; ++i) {
643    assert(BlockScopes.count(Blocks[i]) &&
644           "Did not find block in scope map!");
645
646    BlockScopes.erase(Blocks[i]);
647  }
648
649  return CleanupBlockInfo(CleanupBlock, SwitchBlock, EndBlock);
650}
651
652void CodeGenFunction::EmitCleanupBlock()
653{
654  CleanupBlockInfo Info = PopCleanupBlock();
655
656  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
657  if (CurBB && !CurBB->getTerminator() &&
658      Info.CleanupBlock->getNumUses() == 0) {
659    CurBB->getInstList().splice(CurBB->end(), Info.CleanupBlock->getInstList());
660    delete Info.CleanupBlock;
661  } else
662    EmitBlock(Info.CleanupBlock);
663
664  if (Info.SwitchBlock)
665    EmitBlock(Info.SwitchBlock);
666  if (Info.EndBlock)
667    EmitBlock(Info.EndBlock);
668}
669
670void CodeGenFunction::AddBranchFixup(llvm::BranchInst *BI)
671{
672  assert(!CleanupEntries.empty() &&
673         "Trying to add branch fixup without cleanup block!");
674
675  // FIXME: We could be more clever here and check if there's already a branch
676  // fixup for this destination and recycle it.
677  CleanupEntries.back().BranchFixups.push_back(BI);
678}
679
680void CodeGenFunction::EmitBranchThroughCleanup(llvm::BasicBlock *Dest)
681{
682  if (!HaveInsertPoint())
683    return;
684
685  llvm::BranchInst* BI = Builder.CreateBr(Dest);
686
687  Builder.ClearInsertionPoint();
688
689  // The stack is empty, no need to do any cleanup.
690  if (CleanupEntries.empty())
691    return;
692
693  if (!Dest->getParent()) {
694    // We are trying to branch to a block that hasn't been inserted yet.
695    AddBranchFixup(BI);
696    return;
697  }
698
699  BlockScopeMap::iterator I = BlockScopes.find(Dest);
700  if (I == BlockScopes.end()) {
701    // We are trying to jump to a block that is outside of any cleanup scope.
702    AddBranchFixup(BI);
703    return;
704  }
705
706  assert(I->second < CleanupEntries.size() &&
707         "Trying to branch into cleanup region");
708
709  if (I->second == CleanupEntries.size() - 1) {
710    // We have a branch to a block in the same scope.
711    return;
712  }
713
714  AddBranchFixup(BI);
715}
716