CodeGenFunction.cpp revision b17daf9ab790ae71aacad2cc4aa11cd8d86c25d1 
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), IndirectBranch(0),
31    SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
32    CXXThisDecl(0), CXXVTTDecl(0),
33    ConditionalBranchLevel(0) {
34  LLVMIntTy = ConvertType(getContext().IntTy);
35  LLVMPointerWidth = Target.getPointerWidth(0);
36}
37
38ASTContext &CodeGenFunction::getContext() const {
39  return CGM.getContext();
40}
41
42
43llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
44  llvm::BasicBlock *&BB = LabelMap[S];
45  if (BB) return BB;
46
47  // Create, but don't insert, the new block.
48  return BB = createBasicBlock(S->getName());
49}
50
51llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD) {
52  llvm::Value *Res = LocalDeclMap[VD];
53  assert(Res && "Invalid argument to GetAddrOfLocalVar(), no decl!");
54  return Res;
55}
56
57llvm::Constant *
58CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
59  return cast<llvm::Constant>(GetAddrOfLocalVar(BVD));
60}
61
62const llvm::Type *CodeGenFunction::ConvertTypeForMem(QualType T) {
63  return CGM.getTypes().ConvertTypeForMem(T);
64}
65
66const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
67  return CGM.getTypes().ConvertType(T);
68}
69
70bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
71  return T->isRecordType() || T->isArrayType() || T->isAnyComplexType() ||
72    T->isMemberFunctionPointerType();
73}
74
75void CodeGenFunction::EmitReturnBlock() {
76  // For cleanliness, we try to avoid emitting the return block for
77  // simple cases.
78  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
79
80  if (CurBB) {
81    assert(!CurBB->getTerminator() && "Unexpected terminated block.");
82
83    // We have a valid insert point, reuse it if it is empty or there are no
84    // explicit jumps to the return block.
85    if (CurBB->empty() || ReturnBlock->use_empty()) {
86      ReturnBlock->replaceAllUsesWith(CurBB);
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 the block
109  // unless it has uses. However, we still need a place to put the debug
110  // region.end for now.
111
112  EmitBlock(ReturnBlock);
113}
114
115void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
116  assert(BreakContinueStack.empty() &&
117         "mismatched push/pop in break/continue stack!");
118  assert(BlockScopes.empty() &&
119         "did not remove all blocks from block scope map!");
120  assert(CleanupEntries.empty() &&
121         "mismatched push/pop in cleanup stack!");
122
123  // Emit function epilog (to return).
124  EmitReturnBlock();
125
126  // Emit debug descriptor for function end.
127  if (CGDebugInfo *DI = getDebugInfo()) {
128    DI->setLocation(EndLoc);
129    DI->EmitRegionEnd(CurFn, Builder);
130  }
131
132  EmitFunctionEpilog(*CurFnInfo, ReturnValue);
133
134  // If someone did an indirect goto, emit the indirect goto block at the end of
135  // the function.
136  if (IndirectBranch) {
137    EmitBlock(IndirectBranch->getParent());
138    Builder.ClearInsertionPoint();
139  }
140
141  // Remove the AllocaInsertPt instruction, which is just a convenience for us.
142  llvm::Instruction *Ptr = AllocaInsertPt;
143  AllocaInsertPt = 0;
144  Ptr->eraseFromParent();
145
146  // If someone took the address of a label but never did an indirect goto, we
147  // made a zero entry PHI node, which is illegal, zap it now.
148  if (IndirectBranch) {
149    llvm::PHINode *PN = cast<llvm::PHINode>(IndirectBranch->getAddress());
150    if (PN->getNumIncomingValues() == 0) {
151      PN->replaceAllUsesWith(llvm::UndefValue::get(PN->getType()));
152      PN->eraseFromParent();
153    }
154  }
155}
156
157void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
158                                    llvm::Function *Fn,
159                                    const FunctionArgList &Args,
160                                    SourceLocation StartLoc) {
161  const Decl *D = GD.getDecl();
162
163  DidCallStackSave = false;
164  CurCodeDecl = CurFuncDecl = D;
165  FnRetTy = RetTy;
166  CurFn = Fn;
167  assert(CurFn->isDeclaration() && "Function already has body?");
168
169  llvm::BasicBlock *EntryBB = createBasicBlock("entry", CurFn);
170
171  // Create a marker to make it easy to insert allocas into the entryblock
172  // later.  Don't create this with the builder, because we don't want it
173  // folded.
174  llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::getInt32Ty(VMContext));
175  AllocaInsertPt = new llvm::BitCastInst(Undef,
176                                         llvm::Type::getInt32Ty(VMContext), "",
177                                         EntryBB);
178  if (Builder.isNamePreserving())
179    AllocaInsertPt->setName("allocapt");
180
181  ReturnBlock = createBasicBlock("return");
182
183  Builder.SetInsertPoint(EntryBB);
184
185  QualType FnType = getContext().getFunctionType(RetTy, 0, 0, false, 0);
186
187  // Emit subprogram debug descriptor.
188  // FIXME: The cast here is a huge hack.
189  if (CGDebugInfo *DI = getDebugInfo()) {
190    DI->setLocation(StartLoc);
191    if (isa<FunctionDecl>(D)) {
192      DI->EmitFunctionStart(CGM.getMangledName(GD), FnType, CurFn, Builder);
193    } else {
194      // Just use LLVM function name.
195
196      // FIXME: Remove unnecessary conversion to std::string when API settles.
197      DI->EmitFunctionStart(std::string(Fn->getName()).c_str(),
198                            FnType, CurFn, Builder);
199    }
200  }
201
202  // FIXME: Leaked.
203  CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
204
205  if (RetTy->isVoidType()) {
206    // Void type; nothing to return.
207    ReturnValue = 0;
208  } else if (CurFnInfo->getReturnInfo().getKind() == ABIArgInfo::Indirect &&
209             hasAggregateLLVMType(CurFnInfo->getReturnType())) {
210    // Indirect aggregate return; emit returned value directly into sret slot.
211    // This reduces code size, and is also affects correctness in C++.
212    ReturnValue = CurFn->arg_begin();
213  } else {
214    ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
215  }
216
217  EmitFunctionProlog(*CurFnInfo, CurFn, Args);
218
219  // If any of the arguments have a variably modified type, make sure to
220  // emit the type size.
221  for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
222       i != e; ++i) {
223    QualType Ty = i->second;
224
225    if (Ty->isVariablyModifiedType())
226      EmitVLASize(Ty);
227  }
228}
229
230static bool NeedsVTTParameter(GlobalDecl GD) {
231  const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
232
233  // We don't have any virtual bases, just return early.
234  if (!MD->getParent()->getNumVBases())
235    return false;
236
237  // Check if we have a base constructor.
238  if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
239    return true;
240
241  // Check if we have a base destructor.
242  if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
243    return true;
244
245  return false;
246}
247
248void CodeGenFunction::GenerateCode(GlobalDecl GD,
249                                   llvm::Function *Fn) {
250  const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
251
252  // Check if we should generate debug info for this function.
253  if (CGM.getDebugInfo() && !FD->hasAttr<NoDebugAttr>())
254    DebugInfo = CGM.getDebugInfo();
255
256  FunctionArgList Args;
257
258  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
259    if (MD->isInstance()) {
260      // Create the implicit 'this' decl.
261      // FIXME: I'm not entirely sure I like using a fake decl just for code
262      // generation. Maybe we can come up with a better way?
263      CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
264                                              &getContext().Idents.get("this"),
265                                              MD->getThisType(getContext()));
266      Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
267
268      // Check if we need a VTT parameter as well.
269      if (NeedsVTTParameter(GD)) {
270        // FIXME: The comment about using a fake decl above applies here too.
271        QualType T = getContext().getPointerType(getContext().VoidPtrTy);
272        CXXVTTDecl =
273          ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
274                                    &getContext().Idents.get("vtt"), T);
275        Args.push_back(std::make_pair(CXXVTTDecl, CXXVTTDecl->getType()));
276      }
277    }
278  }
279
280  if (FD->getNumParams()) {
281    const FunctionProtoType* FProto = FD->getType()->getAs<FunctionProtoType>();
282    assert(FProto && "Function def must have prototype!");
283
284    for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
285      Args.push_back(std::make_pair(FD->getParamDecl(i),
286                                    FProto->getArgType(i)));
287  }
288
289  // FIXME: Support CXXTryStmt here, too.
290  if (const CompoundStmt *S = FD->getCompoundBody()) {
291    StartFunction(GD, FD->getResultType(), Fn, Args, S->getLBracLoc());
292
293    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
294      EmitCtorPrologue(CD, GD.getCtorType());
295      EmitStmt(S);
296
297      // If any of the member initializers are temporaries bound to references
298      // make sure to emit their destructors.
299      EmitCleanupBlocks(0);
300
301    } else if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(FD)) {
302      llvm::BasicBlock *DtorEpilogue  = createBasicBlock("dtor.epilogue");
303      PushCleanupBlock(DtorEpilogue);
304
305      EmitStmt(S);
306
307      CleanupBlockInfo Info = PopCleanupBlock();
308
309      assert(Info.CleanupBlock == DtorEpilogue && "Block mismatch!");
310      EmitBlock(DtorEpilogue);
311      EmitDtorEpilogue(DD, GD.getDtorType());
312
313      if (Info.SwitchBlock)
314        EmitBlock(Info.SwitchBlock);
315      if (Info.EndBlock)
316        EmitBlock(Info.EndBlock);
317    } else {
318      // Just a regular function, emit its body.
319      EmitStmt(S);
320    }
321
322    FinishFunction(S->getRBracLoc());
323  } else if (FD->isImplicit()) {
324    const CXXRecordDecl *ClassDecl =
325      cast<CXXRecordDecl>(FD->getDeclContext());
326    (void) ClassDecl;
327    if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
328      // FIXME: For C++0x, we want to look for implicit *definitions* of
329      // these special member functions, rather than implicit *declarations*.
330      if (CD->isCopyConstructor(getContext())) {
331        assert(!ClassDecl->hasUserDeclaredCopyConstructor() &&
332               "Cannot synthesize a non-implicit copy constructor");
333        SynthesizeCXXCopyConstructor(CD, GD.getCtorType(), Fn, Args);
334      } else if (CD->isDefaultConstructor()) {
335        assert(!ClassDecl->hasUserDeclaredConstructor() &&
336               "Cannot synthesize a non-implicit default constructor.");
337        SynthesizeDefaultConstructor(CD, GD.getCtorType(), Fn, Args);
338      } else {
339        assert(false && "Implicit constructor cannot be synthesized");
340      }
341    } else if (const CXXDestructorDecl *CD = dyn_cast<CXXDestructorDecl>(FD)) {
342      assert(!ClassDecl->hasUserDeclaredDestructor() &&
343             "Cannot synthesize a non-implicit destructor");
344      SynthesizeDefaultDestructor(CD, GD.getDtorType(), Fn, Args);
345    } else if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
346      assert(MD->isCopyAssignment() &&
347             !ClassDecl->hasUserDeclaredCopyAssignment() &&
348             "Cannot synthesize a method that is not an implicit-defined "
349             "copy constructor");
350      SynthesizeCXXCopyAssignment(MD, Fn, Args);
351    } else {
352      assert(false && "Cannot synthesize unknown implicit function");
353    }
354  }
355
356  // Destroy the 'this' declaration.
357  if (CXXThisDecl)
358    CXXThisDecl->Destroy(getContext());
359
360  // Destroy the VTT declaration.
361  if (CXXVTTDecl)
362    CXXVTTDecl->Destroy(getContext());
363}
364
365/// ContainsLabel - Return true if the statement contains a label in it.  If
366/// this statement is not executed normally, it not containing a label means
367/// that we can just remove the code.
368bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
369  // Null statement, not a label!
370  if (S == 0) return false;
371
372  // If this is a label, we have to emit the code, consider something like:
373  // if (0) {  ...  foo:  bar(); }  goto foo;
374  if (isa<LabelStmt>(S))
375    return true;
376
377  // If this is a case/default statement, and we haven't seen a switch, we have
378  // to emit the code.
379  if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
380    return true;
381
382  // If this is a switch statement, we want to ignore cases below it.
383  if (isa<SwitchStmt>(S))
384    IgnoreCaseStmts = true;
385
386  // Scan subexpressions for verboten labels.
387  for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
388       I != E; ++I)
389    if (ContainsLabel(*I, IgnoreCaseStmts))
390      return true;
391
392  return false;
393}
394
395
396/// ConstantFoldsToSimpleInteger - If the sepcified expression does not fold to
397/// a constant, or if it does but contains a label, return 0.  If it constant
398/// folds to 'true' and does not contain a label, return 1, if it constant folds
399/// to 'false' and does not contain a label, return -1.
400int CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond) {
401  // FIXME: Rename and handle conversion of other evaluatable things
402  // to bool.
403  Expr::EvalResult Result;
404  if (!Cond->Evaluate(Result, getContext()) || !Result.Val.isInt() ||
405      Result.HasSideEffects)
406    return 0;  // Not foldable, not integer or not fully evaluatable.
407
408  if (CodeGenFunction::ContainsLabel(Cond))
409    return 0;  // Contains a label.
410
411  return Result.Val.getInt().getBoolValue() ? 1 : -1;
412}
413
414
415/// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
416/// statement) to the specified blocks.  Based on the condition, this might try
417/// to simplify the codegen of the conditional based on the branch.
418///
419void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
420                                           llvm::BasicBlock *TrueBlock,
421                                           llvm::BasicBlock *FalseBlock) {
422  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
423    return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
424
425  if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
426    // Handle X && Y in a condition.
427    if (CondBOp->getOpcode() == BinaryOperator::LAnd) {
428      // If we have "1 && X", simplify the code.  "0 && X" would have constant
429      // folded if the case was simple enough.
430      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == 1) {
431        // br(1 && X) -> br(X).
432        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
433      }
434
435      // If we have "X && 1", simplify the code to use an uncond branch.
436      // "X && 0" would have been constant folded to 0.
437      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == 1) {
438        // br(X && 1) -> br(X).
439        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
440      }
441
442      // Emit the LHS as a conditional.  If the LHS conditional is false, we
443      // want to jump to the FalseBlock.
444      llvm::BasicBlock *LHSTrue = createBasicBlock("land.lhs.true");
445      EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock);
446      EmitBlock(LHSTrue);
447
448      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
449      return;
450    } else if (CondBOp->getOpcode() == BinaryOperator::LOr) {
451      // If we have "0 || X", simplify the code.  "1 || X" would have constant
452      // folded if the case was simple enough.
453      if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == -1) {
454        // br(0 || X) -> br(X).
455        return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
456      }
457
458      // If we have "X || 0", simplify the code to use an uncond branch.
459      // "X || 1" would have been constant folded to 1.
460      if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == -1) {
461        // br(X || 0) -> br(X).
462        return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
463      }
464
465      // Emit the LHS as a conditional.  If the LHS conditional is true, we
466      // want to jump to the TrueBlock.
467      llvm::BasicBlock *LHSFalse = createBasicBlock("lor.lhs.false");
468      EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse);
469      EmitBlock(LHSFalse);
470
471      EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
472      return;
473    }
474  }
475
476  if (const UnaryOperator *CondUOp = dyn_cast<UnaryOperator>(Cond)) {
477    // br(!x, t, f) -> br(x, f, t)
478    if (CondUOp->getOpcode() == UnaryOperator::LNot)
479      return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock);
480  }
481
482  if (const ConditionalOperator *CondOp = dyn_cast<ConditionalOperator>(Cond)) {
483    // Handle ?: operator.
484
485    // Just ignore GNU ?: extension.
486    if (CondOp->getLHS()) {
487      // br(c ? x : y, t, f) -> br(c, br(x, t, f), br(y, t, f))
488      llvm::BasicBlock *LHSBlock = createBasicBlock("cond.true");
489      llvm::BasicBlock *RHSBlock = createBasicBlock("cond.false");
490      EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock);
491      EmitBlock(LHSBlock);
492      EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock);
493      EmitBlock(RHSBlock);
494      EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock);
495      return;
496    }
497  }
498
499  // Emit the code with the fully general case.
500  llvm::Value *CondV = EvaluateExprAsBool(Cond);
501  Builder.CreateCondBr(CondV, TrueBlock, FalseBlock);
502}
503
504/// ErrorUnsupported - Print out an error that codegen doesn't support the
505/// specified stmt yet.
506void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
507                                       bool OmitOnError) {
508  CGM.ErrorUnsupported(S, Type, OmitOnError);
509}
510
511void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
512  const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
513  if (DestPtr->getType() != BP)
514    DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
515
516  // Get size and alignment info for this aggregate.
517  std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
518
519  // Don't bother emitting a zero-byte memset.
520  if (TypeInfo.first == 0)
521    return;
522
523  // FIXME: Handle variable sized types.
524  const llvm::Type *IntPtr = llvm::IntegerType::get(VMContext,
525                                                    LLVMPointerWidth);
526
527  Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
528                 llvm::Constant::getNullValue(llvm::Type::getInt8Ty(VMContext)),
529                      // TypeInfo.first describes size in bits.
530                      llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
531                      llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
532                                             TypeInfo.second/8));
533}
534
535llvm::BlockAddress *CodeGenFunction::GetAddrOfLabel(const LabelStmt *L) {
536  // Make sure that there is a block for the indirect goto.
537  if (IndirectBranch == 0)
538    GetIndirectGotoBlock();
539
540  llvm::BasicBlock *BB = getBasicBlockForLabel(L);
541
542  // Make sure the indirect branch includes all of the address-taken blocks.
543  IndirectBranch->addDestination(BB);
544  return llvm::BlockAddress::get(CurFn, BB);
545}
546
547llvm::BasicBlock *CodeGenFunction::GetIndirectGotoBlock() {
548  // If we already made the indirect branch for indirect goto, return its block.
549  if (IndirectBranch) return IndirectBranch->getParent();
550
551  CGBuilderTy TmpBuilder(createBasicBlock("indirectgoto"));
552
553  const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(VMContext);
554
555  // Create the PHI node that indirect gotos will add entries to.
556  llvm::Value *DestVal = TmpBuilder.CreatePHI(Int8PtrTy, "indirect.goto.dest");
557
558  // Create the indirect branch instruction.
559  IndirectBranch = TmpBuilder.CreateIndirectBr(DestVal);
560  return IndirectBranch->getParent();
561}
562
563llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT) {
564  llvm::Value *&SizeEntry = VLASizeMap[VAT->getSizeExpr()];
565
566  assert(SizeEntry && "Did not emit size for type");
567  return SizeEntry;
568}
569
570llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty) {
571  assert(Ty->isVariablyModifiedType() &&
572         "Must pass variably modified type to EmitVLASizes!");
573
574  EnsureInsertPoint();
575
576  if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
577    llvm::Value *&SizeEntry = VLASizeMap[VAT->getSizeExpr()];
578
579    if (!SizeEntry) {
580      const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
581
582      // Get the element size;
583      QualType ElemTy = VAT->getElementType();
584      llvm::Value *ElemSize;
585      if (ElemTy->isVariableArrayType())
586        ElemSize = EmitVLASize(ElemTy);
587      else
588        ElemSize = llvm::ConstantInt::get(SizeTy,
589                                          getContext().getTypeSize(ElemTy) / 8);
590
591      llvm::Value *NumElements = EmitScalarExpr(VAT->getSizeExpr());
592      NumElements = Builder.CreateIntCast(NumElements, SizeTy, false, "tmp");
593
594      SizeEntry = Builder.CreateMul(ElemSize, NumElements);
595    }
596
597    return SizeEntry;
598  }
599
600  if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
601    EmitVLASize(AT->getElementType());
602    return 0;
603  }
604
605  const PointerType *PT = Ty->getAs<PointerType>();
606  assert(PT && "unknown VM type!");
607  EmitVLASize(PT->getPointeeType());
608  return 0;
609}
610
611llvm::Value* CodeGenFunction::EmitVAListRef(const Expr* E) {
612  if (CGM.getContext().getBuiltinVaListType()->isArrayType()) {
613    return EmitScalarExpr(E);
614  }
615  return EmitLValue(E).getAddress();
616}
617
618void CodeGenFunction::PushCleanupBlock(llvm::BasicBlock *CleanupEntryBlock,
619                                       llvm::BasicBlock *CleanupExitBlock,
620                                       bool EHOnly) {
621  CleanupEntries.push_back(CleanupEntry(CleanupEntryBlock, CleanupExitBlock,
622                                        EHOnly));
623}
624
625void CodeGenFunction::EmitCleanupBlocks(size_t OldCleanupStackSize) {
626  assert(CleanupEntries.size() >= OldCleanupStackSize &&
627         "Cleanup stack mismatch!");
628
629  while (CleanupEntries.size() > OldCleanupStackSize)
630    EmitCleanupBlock();
631}
632
633CodeGenFunction::CleanupBlockInfo CodeGenFunction::PopCleanupBlock() {
634  CleanupEntry &CE = CleanupEntries.back();
635
636  llvm::BasicBlock *CleanupEntryBlock = CE.CleanupEntryBlock;
637
638  std::vector<llvm::BasicBlock *> Blocks;
639  std::swap(Blocks, CE.Blocks);
640
641  std::vector<llvm::BranchInst *> BranchFixups;
642  std::swap(BranchFixups, CE.BranchFixups);
643
644  bool EHOnly = CE.EHOnly;
645
646  CleanupEntries.pop_back();
647
648  // Check if any branch fixups pointed to the scope we just popped. If so,
649  // we can remove them.
650  for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
651    llvm::BasicBlock *Dest = BranchFixups[i]->getSuccessor(0);
652    BlockScopeMap::iterator I = BlockScopes.find(Dest);
653
654    if (I == BlockScopes.end())
655      continue;
656
657    assert(I->second <= CleanupEntries.size() && "Invalid branch fixup!");
658
659    if (I->second == CleanupEntries.size()) {
660      // We don't need to do this branch fixup.
661      BranchFixups[i] = BranchFixups.back();
662      BranchFixups.pop_back();
663      i--;
664      e--;
665      continue;
666    }
667  }
668
669  llvm::BasicBlock *SwitchBlock = CE.CleanupExitBlock;
670  llvm::BasicBlock *EndBlock = 0;
671  if (!BranchFixups.empty()) {
672    if (!SwitchBlock)
673      SwitchBlock = createBasicBlock("cleanup.switch");
674    EndBlock = createBasicBlock("cleanup.end");
675
676    llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
677
678    Builder.SetInsertPoint(SwitchBlock);
679
680    llvm::Value *DestCodePtr
681      = CreateTempAlloca(llvm::Type::getInt32Ty(VMContext),
682                         "cleanup.dst");
683    llvm::Value *DestCode = Builder.CreateLoad(DestCodePtr, "tmp");
684
685    // Create a switch instruction to determine where to jump next.
686    llvm::SwitchInst *SI = Builder.CreateSwitch(DestCode, EndBlock,
687                                                BranchFixups.size());
688
689    // Restore the current basic block (if any)
690    if (CurBB) {
691      Builder.SetInsertPoint(CurBB);
692
693      // If we had a current basic block, we also need to emit an instruction
694      // to initialize the cleanup destination.
695      Builder.CreateStore(llvm::Constant::getNullValue(llvm::Type::getInt32Ty(VMContext)),
696                          DestCodePtr);
697    } else
698      Builder.ClearInsertionPoint();
699
700    for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
701      llvm::BranchInst *BI = BranchFixups[i];
702      llvm::BasicBlock *Dest = BI->getSuccessor(0);
703
704      // Fixup the branch instruction to point to the cleanup block.
705      BI->setSuccessor(0, CleanupEntryBlock);
706
707      if (CleanupEntries.empty()) {
708        llvm::ConstantInt *ID;
709
710        // Check if we already have a destination for this block.
711        if (Dest == SI->getDefaultDest())
712          ID = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), 0);
713        else {
714          ID = SI->findCaseDest(Dest);
715          if (!ID) {
716            // No code found, get a new unique one by using the number of
717            // switch successors.
718            ID = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
719                                        SI->getNumSuccessors());
720            SI->addCase(ID, Dest);
721          }
722        }
723
724        // Store the jump destination before the branch instruction.
725        new llvm::StoreInst(ID, DestCodePtr, BI);
726      } else {
727        // We need to jump through another cleanup block. Create a pad block
728        // with a branch instruction that jumps to the final destination and add
729        // it as a branch fixup to the current cleanup scope.
730
731        // Create the pad block.
732        llvm::BasicBlock *CleanupPad = createBasicBlock("cleanup.pad", CurFn);
733
734        // Create a unique case ID.
735        llvm::ConstantInt *ID
736          = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
737                                   SI->getNumSuccessors());
738
739        // Store the jump destination before the branch instruction.
740        new llvm::StoreInst(ID, DestCodePtr, BI);
741
742        // Add it as the destination.
743        SI->addCase(ID, CleanupPad);
744
745        // Create the branch to the final destination.
746        llvm::BranchInst *BI = llvm::BranchInst::Create(Dest);
747        CleanupPad->getInstList().push_back(BI);
748
749        // And add it as a branch fixup.
750        CleanupEntries.back().BranchFixups.push_back(BI);
751      }
752    }
753  }
754
755  // Remove all blocks from the block scope map.
756  for (size_t i = 0, e = Blocks.size(); i != e; ++i) {
757    assert(BlockScopes.count(Blocks[i]) &&
758           "Did not find block in scope map!");
759
760    BlockScopes.erase(Blocks[i]);
761  }
762
763  return CleanupBlockInfo(CleanupEntryBlock, SwitchBlock, EndBlock, EHOnly);
764}
765
766void CodeGenFunction::EmitCleanupBlock() {
767  CleanupBlockInfo Info = PopCleanupBlock();
768
769  if (Info.EHOnly) {
770    // FIXME: Add this to the exceptional edge
771    if (Info.CleanupBlock->getNumUses() == 0)
772      delete Info.CleanupBlock;
773    return;
774  }
775
776  llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
777  if (CurBB && !CurBB->getTerminator() &&
778      Info.CleanupBlock->getNumUses() == 0) {
779    CurBB->getInstList().splice(CurBB->end(), Info.CleanupBlock->getInstList());
780    delete Info.CleanupBlock;
781  } else
782    EmitBlock(Info.CleanupBlock);
783
784  if (Info.SwitchBlock)
785    EmitBlock(Info.SwitchBlock);
786  if (Info.EndBlock)
787    EmitBlock(Info.EndBlock);
788}
789
790void CodeGenFunction::AddBranchFixup(llvm::BranchInst *BI) {
791  assert(!CleanupEntries.empty() &&
792         "Trying to add branch fixup without cleanup block!");
793
794  // FIXME: We could be more clever here and check if there's already a branch
795  // fixup for this destination and recycle it.
796  CleanupEntries.back().BranchFixups.push_back(BI);
797}
798
799void CodeGenFunction::EmitBranchThroughCleanup(llvm::BasicBlock *Dest) {
800  if (!HaveInsertPoint())
801    return;
802
803  llvm::BranchInst* BI = Builder.CreateBr(Dest);
804
805  Builder.ClearInsertionPoint();
806
807  // The stack is empty, no need to do any cleanup.
808  if (CleanupEntries.empty())
809    return;
810
811  if (!Dest->getParent()) {
812    // We are trying to branch to a block that hasn't been inserted yet.
813    AddBranchFixup(BI);
814    return;
815  }
816
817  BlockScopeMap::iterator I = BlockScopes.find(Dest);
818  if (I == BlockScopes.end()) {
819    // We are trying to jump to a block that is outside of any cleanup scope.
820    AddBranchFixup(BI);
821    return;
822  }
823
824  assert(I->second < CleanupEntries.size() &&
825         "Trying to branch into cleanup region");
826
827  if (I->second == CleanupEntries.size() - 1) {
828    // We have a branch to a block in the same scope.
829    return;
830  }
831
832  AddBranchFixup(BI);
833}
834