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llvm-project/clang/lib/CodeGen/CodeGenFunction.cpp
Chris Lattner 2bb5cb490c reimplement codegen for indirect goto with the following advantages: 
1. CGF now has fewer bytes of state (one pointer instead of a vector).
2. The generated code is determinstic, instead of getting labels in
   'map order' based on pointer addresses.
3. Clang now emits one 'indirect goto switch' for each function, instead
   of one for each indirect goto.  This fixes an M*N = N^2 IR size issue
   when there are lots of address-taken labels and lots of indirect gotos.
4. This also makes the default cause do something useful, reducing the
   size of the jump table needed (by one).

llvm-svn: 83952
2009-10-13 06:55:33 +00:00

800 lines
28 KiB
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//===--- CodeGenFunction.cpp - Emit LLVM Code from ASTs for a Function ----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This coordinates the per-function state used while generating code.
//
//===----------------------------------------------------------------------===//
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "CGDebugInfo.h"
#include "clang/Basic/TargetInfo.h"
#include "clang/AST/APValue.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "llvm/Target/TargetData.h"
using namespace clang;
using namespace CodeGen;
CodeGenFunction::CodeGenFunction(CodeGenModule &cgm)
: BlockFunction(cgm, *this, Builder), CGM(cgm),
Target(CGM.getContext().Target),
Builder(cgm.getModule().getContext()),
DebugInfo(0), IndirectGotoSwitch(0),
SwitchInsn(0), CaseRangeBlock(0), InvokeDest(0),
CXXThisDecl(0) {
LLVMIntTy = ConvertType(getContext().IntTy);
LLVMPointerWidth = Target.getPointerWidth(0);
}
ASTContext &CodeGenFunction::getContext() const {
return CGM.getContext();
}
llvm::BasicBlock *CodeGenFunction::getBasicBlockForLabel(const LabelStmt *S) {
llvm::BasicBlock *&BB = LabelMap[S];
if (BB) return BB;
// Create, but don't insert, the new block.
return BB = createBasicBlock(S->getName());
}
llvm::Value *CodeGenFunction::GetAddrOfLocalVar(const VarDecl *VD) {
llvm::Value *Res = LocalDeclMap[VD];
assert(Res && "Invalid argument to GetAddrOfLocalVar(), no decl!");
return Res;
}
llvm::Constant *
CodeGenFunction::GetAddrOfStaticLocalVar(const VarDecl *BVD) {
return cast<llvm::Constant>(GetAddrOfLocalVar(BVD));
}
const llvm::Type *CodeGenFunction::ConvertTypeForMem(QualType T) {
return CGM.getTypes().ConvertTypeForMem(T);
}
const llvm::Type *CodeGenFunction::ConvertType(QualType T) {
return CGM.getTypes().ConvertType(T);
}
bool CodeGenFunction::hasAggregateLLVMType(QualType T) {
return T->isRecordType() || T->isArrayType() || T->isAnyComplexType() ||
T->isMemberFunctionPointerType();
}
void CodeGenFunction::EmitReturnBlock() {
// For cleanliness, we try to avoid emitting the return block for
// simple cases.
llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
if (CurBB) {
assert(!CurBB->getTerminator() && "Unexpected terminated block.");
// We have a valid insert point, reuse it if it is empty or there are no
// explicit jumps to the return block.
if (CurBB->empty() || ReturnBlock->use_empty()) {
ReturnBlock->replaceAllUsesWith(CurBB);
delete ReturnBlock;
} else
EmitBlock(ReturnBlock);
return;
}
// Otherwise, if the return block is the target of a single direct
// branch then we can just put the code in that block instead. This
// cleans up functions which started with a unified return block.
if (ReturnBlock->hasOneUse()) {
llvm::BranchInst *BI =
dyn_cast<llvm::BranchInst>(*ReturnBlock->use_begin());
if (BI && BI->isUnconditional() && BI->getSuccessor(0) == ReturnBlock) {
// Reset insertion point and delete the branch.
Builder.SetInsertPoint(BI->getParent());
BI->eraseFromParent();
delete ReturnBlock;
return;
}
}
// FIXME: We are at an unreachable point, there is no reason to emit the block
// unless it has uses. However, we still need a place to put the debug
// region.end for now.
EmitBlock(ReturnBlock);
}
void CodeGenFunction::FinishFunction(SourceLocation EndLoc) {
assert(BreakContinueStack.empty() &&
"mismatched push/pop in break/continue stack!");
assert(BlockScopes.empty() &&
"did not remove all blocks from block scope map!");
assert(CleanupEntries.empty() &&
"mismatched push/pop in cleanup stack!");
// Emit function epilog (to return).
EmitReturnBlock();
// Emit debug descriptor for function end.
if (CGDebugInfo *DI = getDebugInfo()) {
DI->setLocation(EndLoc);
DI->EmitRegionEnd(CurFn, Builder);
}
EmitFunctionEpilog(*CurFnInfo, ReturnValue);
// Remove the AllocaInsertPt instruction, which is just a convenience for us.
llvm::Instruction *Ptr = AllocaInsertPt;
AllocaInsertPt = 0;
Ptr->eraseFromParent();
}
void CodeGenFunction::StartFunction(GlobalDecl GD, QualType RetTy,
llvm::Function *Fn,
const FunctionArgList &Args,
SourceLocation StartLoc) {
const Decl *D = GD.getDecl();
DidCallStackSave = false;
CurCodeDecl = CurFuncDecl = D;
FnRetTy = RetTy;
CurFn = Fn;
assert(CurFn->isDeclaration() && "Function already has body?");
llvm::BasicBlock *EntryBB = createBasicBlock("entry", CurFn);
// Create a marker to make it easy to insert allocas into the entryblock
// later. Don't create this with the builder, because we don't want it
// folded.
llvm::Value *Undef = llvm::UndefValue::get(llvm::Type::getInt32Ty(VMContext));
AllocaInsertPt = new llvm::BitCastInst(Undef,
llvm::Type::getInt32Ty(VMContext), "",
EntryBB);
if (Builder.isNamePreserving())
AllocaInsertPt->setName("allocapt");
ReturnBlock = createBasicBlock("return");
ReturnValue = 0;
if (!RetTy->isVoidType())
ReturnValue = CreateTempAlloca(ConvertType(RetTy), "retval");
Builder.SetInsertPoint(EntryBB);
// Emit subprogram debug descriptor.
// FIXME: The cast here is a huge hack.
if (CGDebugInfo *DI = getDebugInfo()) {
DI->setLocation(StartLoc);
if (isa<FunctionDecl>(D)) {
DI->EmitFunctionStart(CGM.getMangledName(GD), RetTy, CurFn, Builder);
} else {
// Just use LLVM function name.
// FIXME: Remove unnecessary conversion to std::string when API settles.
DI->EmitFunctionStart(std::string(Fn->getName()).c_str(),
RetTy, CurFn, Builder);
}
}
// FIXME: Leaked.
CurFnInfo = &CGM.getTypes().getFunctionInfo(FnRetTy, Args);
EmitFunctionProlog(*CurFnInfo, CurFn, Args);
// If any of the arguments have a variably modified type, make sure to
// emit the type size.
for (FunctionArgList::const_iterator i = Args.begin(), e = Args.end();
i != e; ++i) {
QualType Ty = i->second;
if (Ty->isVariablyModifiedType())
EmitVLASize(Ty);
}
}
void CodeGenFunction::GenerateCode(GlobalDecl GD,
llvm::Function *Fn) {
const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
// Check if we should generate debug info for this function.
if (CGM.getDebugInfo() && !FD->hasAttr<NoDebugAttr>())
DebugInfo = CGM.getDebugInfo();
FunctionArgList Args;
if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
if (MD->isInstance()) {
// Create the implicit 'this' decl.
// FIXME: I'm not entirely sure I like using a fake decl just for code
// generation. Maybe we can come up with a better way?
CXXThisDecl = ImplicitParamDecl::Create(getContext(), 0, SourceLocation(),
&getContext().Idents.get("this"),
MD->getThisType(getContext()));
Args.push_back(std::make_pair(CXXThisDecl, CXXThisDecl->getType()));
}
}
if (FD->getNumParams()) {
const FunctionProtoType* FProto = FD->getType()->getAs<FunctionProtoType>();
assert(FProto && "Function def must have prototype!");
for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
Args.push_back(std::make_pair(FD->getParamDecl(i),
FProto->getArgType(i)));
}
// FIXME: Support CXXTryStmt here, too.
if (const CompoundStmt *S = FD->getCompoundBody()) {
StartFunction(GD, FD->getResultType(), Fn, Args, S->getLBracLoc());
const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(FD);
llvm::BasicBlock *DtorEpilogue = 0;
if (DD) {
DtorEpilogue = createBasicBlock("dtor.epilogue");
PushCleanupBlock(DtorEpilogue);
}
if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD))
EmitCtorPrologue(CD, GD.getCtorType());
EmitStmt(S);
if (DD) {
CleanupBlockInfo Info = PopCleanupBlock();
assert(Info.CleanupBlock == DtorEpilogue && "Block mismatch!");
EmitBlock(DtorEpilogue);
EmitDtorEpilogue(DD, GD.getDtorType());
if (Info.SwitchBlock)
EmitBlock(Info.SwitchBlock);
if (Info.EndBlock)
EmitBlock(Info.EndBlock);
}
FinishFunction(S->getRBracLoc());
} else if (FD->isImplicit()) {
const CXXRecordDecl *ClassDecl =
cast<CXXRecordDecl>(FD->getDeclContext());
(void) ClassDecl;
if (const CXXConstructorDecl *CD = dyn_cast<CXXConstructorDecl>(FD)) {
// FIXME: For C++0x, we want to look for implicit *definitions* of
// these special member functions, rather than implicit *declarations*.
if (CD->isCopyConstructor(getContext())) {
assert(!ClassDecl->hasUserDeclaredCopyConstructor() &&
"Cannot synthesize a non-implicit copy constructor");
SynthesizeCXXCopyConstructor(CD, GD.getCtorType(), Fn, Args);
} else if (CD->isDefaultConstructor()) {
assert(!ClassDecl->hasUserDeclaredConstructor() &&
"Cannot synthesize a non-implicit default constructor.");
SynthesizeDefaultConstructor(CD, GD.getCtorType(), Fn, Args);
} else {
assert(false && "Implicit constructor cannot be synthesized");
}
} else if (const CXXDestructorDecl *CD = dyn_cast<CXXDestructorDecl>(FD)) {
assert(!ClassDecl->hasUserDeclaredDestructor() &&
"Cannot synthesize a non-implicit destructor");
SynthesizeDefaultDestructor(CD, GD.getDtorType(), Fn, Args);
} else if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
assert(MD->isCopyAssignment() &&
!ClassDecl->hasUserDeclaredCopyAssignment() &&
"Cannot synthesize a method that is not an implicit-defined "
"copy constructor");
SynthesizeCXXCopyAssignment(MD, Fn, Args);
} else {
assert(false && "Cannot synthesize unknown implicit function");
}
}
// Destroy the 'this' declaration.
if (CXXThisDecl)
CXXThisDecl->Destroy(getContext());
}
/// ContainsLabel - Return true if the statement contains a label in it. If
/// this statement is not executed normally, it not containing a label means
/// that we can just remove the code.
bool CodeGenFunction::ContainsLabel(const Stmt *S, bool IgnoreCaseStmts) {
// Null statement, not a label!
if (S == 0) return false;
// If this is a label, we have to emit the code, consider something like:
// if (0) { ... foo: bar(); } goto foo;
if (isa<LabelStmt>(S))
return true;
// If this is a case/default statement, and we haven't seen a switch, we have
// to emit the code.
if (isa<SwitchCase>(S) && !IgnoreCaseStmts)
return true;
// If this is a switch statement, we want to ignore cases below it.
if (isa<SwitchStmt>(S))
IgnoreCaseStmts = true;
// Scan subexpressions for verboten labels.
for (Stmt::const_child_iterator I = S->child_begin(), E = S->child_end();
I != E; ++I)
if (ContainsLabel(*I, IgnoreCaseStmts))
return true;
return false;
}
/// ConstantFoldsToSimpleInteger - If the sepcified expression does not fold to
/// a constant, or if it does but contains a label, return 0. If it constant
/// folds to 'true' and does not contain a label, return 1, if it constant folds
/// to 'false' and does not contain a label, return -1.
int CodeGenFunction::ConstantFoldsToSimpleInteger(const Expr *Cond) {
// FIXME: Rename and handle conversion of other evaluatable things
// to bool.
Expr::EvalResult Result;
if (!Cond->Evaluate(Result, getContext()) || !Result.Val.isInt() ||
Result.HasSideEffects)
return 0; // Not foldable, not integer or not fully evaluatable.
if (CodeGenFunction::ContainsLabel(Cond))
return 0; // Contains a label.
return Result.Val.getInt().getBoolValue() ? 1 : -1;
}
/// EmitBranchOnBoolExpr - Emit a branch on a boolean condition (e.g. for an if
/// statement) to the specified blocks. Based on the condition, this might try
/// to simplify the codegen of the conditional based on the branch.
///
void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
llvm::BasicBlock *TrueBlock,
llvm::BasicBlock *FalseBlock) {
if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
// Handle X && Y in a condition.
if (CondBOp->getOpcode() == BinaryOperator::LAnd) {
// If we have "1 && X", simplify the code. "0 && X" would have constant
// folded if the case was simple enough.
if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == 1) {
// br(1 && X) -> br(X).
return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
}
// If we have "X && 1", simplify the code to use an uncond branch.
// "X && 0" would have been constant folded to 0.
if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == 1) {
// br(X && 1) -> br(X).
return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
}
// Emit the LHS as a conditional. If the LHS conditional is false, we
// want to jump to the FalseBlock.
llvm::BasicBlock *LHSTrue = createBasicBlock("land.lhs.true");
EmitBranchOnBoolExpr(CondBOp->getLHS(), LHSTrue, FalseBlock);
EmitBlock(LHSTrue);
EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
return;
} else if (CondBOp->getOpcode() == BinaryOperator::LOr) {
// If we have "0 || X", simplify the code. "1 || X" would have constant
// folded if the case was simple enough.
if (ConstantFoldsToSimpleInteger(CondBOp->getLHS()) == -1) {
// br(0 || X) -> br(X).
return EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
}
// If we have "X || 0", simplify the code to use an uncond branch.
// "X || 1" would have been constant folded to 1.
if (ConstantFoldsToSimpleInteger(CondBOp->getRHS()) == -1) {
// br(X || 0) -> br(X).
return EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, FalseBlock);
}
// Emit the LHS as a conditional. If the LHS conditional is true, we
// want to jump to the TrueBlock.
llvm::BasicBlock *LHSFalse = createBasicBlock("lor.lhs.false");
EmitBranchOnBoolExpr(CondBOp->getLHS(), TrueBlock, LHSFalse);
EmitBlock(LHSFalse);
EmitBranchOnBoolExpr(CondBOp->getRHS(), TrueBlock, FalseBlock);
return;
}
}
if (const UnaryOperator *CondUOp = dyn_cast<UnaryOperator>(Cond)) {
// br(!x, t, f) -> br(x, f, t)
if (CondUOp->getOpcode() == UnaryOperator::LNot)
return EmitBranchOnBoolExpr(CondUOp->getSubExpr(), FalseBlock, TrueBlock);
}
if (const ConditionalOperator *CondOp = dyn_cast<ConditionalOperator>(Cond)) {
// Handle ?: operator.
// Just ignore GNU ?: extension.
if (CondOp->getLHS()) {
// br(c ? x : y, t, f) -> br(c, br(x, t, f), br(y, t, f))
llvm::BasicBlock *LHSBlock = createBasicBlock("cond.true");
llvm::BasicBlock *RHSBlock = createBasicBlock("cond.false");
EmitBranchOnBoolExpr(CondOp->getCond(), LHSBlock, RHSBlock);
EmitBlock(LHSBlock);
EmitBranchOnBoolExpr(CondOp->getLHS(), TrueBlock, FalseBlock);
EmitBlock(RHSBlock);
EmitBranchOnBoolExpr(CondOp->getRHS(), TrueBlock, FalseBlock);
return;
}
}
// Emit the code with the fully general case.
llvm::Value *CondV = EvaluateExprAsBool(Cond);
Builder.CreateCondBr(CondV, TrueBlock, FalseBlock);
}
/// ErrorUnsupported - Print out an error that codegen doesn't support the
/// specified stmt yet.
void CodeGenFunction::ErrorUnsupported(const Stmt *S, const char *Type,
bool OmitOnError) {
CGM.ErrorUnsupported(S, Type, OmitOnError);
}
void CodeGenFunction::EmitMemSetToZero(llvm::Value *DestPtr, QualType Ty) {
const llvm::Type *BP = llvm::Type::getInt8PtrTy(VMContext);
if (DestPtr->getType() != BP)
DestPtr = Builder.CreateBitCast(DestPtr, BP, "tmp");
// Get size and alignment info for this aggregate.
std::pair<uint64_t, unsigned> TypeInfo = getContext().getTypeInfo(Ty);
// Don't bother emitting a zero-byte memset.
if (TypeInfo.first == 0)
return;
// FIXME: Handle variable sized types.
const llvm::Type *IntPtr = llvm::IntegerType::get(VMContext,
LLVMPointerWidth);
Builder.CreateCall4(CGM.getMemSetFn(), DestPtr,
llvm::Constant::getNullValue(llvm::Type::getInt8Ty(VMContext)),
// TypeInfo.first describes size in bits.
llvm::ConstantInt::get(IntPtr, TypeInfo.first/8),
llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
TypeInfo.second/8));
}
unsigned CodeGenFunction::GetIDForAddrOfLabel(const LabelStmt *L) {
// Use LabelIDs.size()+1 as the new ID if one hasn't been assigned.
unsigned &Entry = LabelIDs[L];
if (Entry) return Entry;
Entry = LabelIDs.size();
// If this is the first "address taken" of a label and the indirect goto has
// already been seen, add this to it.
if (IndirectGotoSwitch) {
// If this is the first address-taken label, set it as the default dest.
if (Entry == 1)
IndirectGotoSwitch->setSuccessor(0, getBasicBlockForLabel(L));
else {
// Otherwise add it to the switch as a new dest.
const llvm::IntegerType *Int32Ty = llvm::Type::getInt32Ty(VMContext);
IndirectGotoSwitch->addCase(llvm::ConstantInt::get(Int32Ty, Entry),
getBasicBlockForLabel(L));
}
}
return Entry;
}
llvm::BasicBlock *CodeGenFunction::GetIndirectGotoBlock() {
// If we already made the switch stmt for indirect goto, return its block.
if (IndirectGotoSwitch) return IndirectGotoSwitch->getParent();
EmitBlock(createBasicBlock("indirectgoto"));
// Create the PHI node that indirect gotos will add entries to.
llvm::Value *DestVal =
Builder.CreatePHI(llvm::Type::getInt32Ty(VMContext), "indirect.goto.dest");
// Create the switch instruction. For now, set the insert block to this block
// which will be fixed as labels are added.
IndirectGotoSwitch = Builder.CreateSwitch(DestVal, Builder.GetInsertBlock());
// Clear the insertion point to indicate we are in unreachable code.
Builder.ClearInsertionPoint();
// If we already have labels created, add them.
if (!LabelIDs.empty()) {
// Invert LabelID's so that the order is determinstic.
std::vector<const LabelStmt*> AddrTakenLabelsByID;
AddrTakenLabelsByID.resize(LabelIDs.size());
for (std::map<const LabelStmt*,unsigned>::iterator
LI = LabelIDs.begin(), LE = LabelIDs.end(); LI != LE; ++LI) {
assert(LI->second-1 < AddrTakenLabelsByID.size() &&
"Numbering inconsistent");
AddrTakenLabelsByID[LI->second-1] = LI->first;
}
// Set the default entry as the first block.
IndirectGotoSwitch->setSuccessor(0,
getBasicBlockForLabel(AddrTakenLabelsByID[0]));
const llvm::IntegerType *Int32Ty = llvm::Type::getInt32Ty(VMContext);
// FIXME: The iteration order of this is nondeterminstic!
for (unsigned i = 1, e = AddrTakenLabelsByID.size(); i != e; ++i)
IndirectGotoSwitch->addCase(llvm::ConstantInt::get(Int32Ty, i+1),
getBasicBlockForLabel(AddrTakenLabelsByID[i]));
} else {
// Otherwise, create a dead block and set it as the default dest. This will
// be removed by the optimizers after the indirect goto is set up.
llvm::BasicBlock *Dummy = createBasicBlock("indgoto.dummy");
EmitBlock(Dummy);
IndirectGotoSwitch->setSuccessor(0, Dummy);
Builder.CreateUnreachable();
Builder.ClearInsertionPoint();
}
return IndirectGotoSwitch->getParent();
}
llvm::Value *CodeGenFunction::GetVLASize(const VariableArrayType *VAT) {
llvm::Value *&SizeEntry = VLASizeMap[VAT->getSizeExpr()];
assert(SizeEntry && "Did not emit size for type");
return SizeEntry;
}
llvm::Value *CodeGenFunction::EmitVLASize(QualType Ty) {
assert(Ty->isVariablyModifiedType() &&
"Must pass variably modified type to EmitVLASizes!");
EnsureInsertPoint();
if (const VariableArrayType *VAT = getContext().getAsVariableArrayType(Ty)) {
llvm::Value *&SizeEntry = VLASizeMap[VAT->getSizeExpr()];
if (!SizeEntry) {
const llvm::Type *SizeTy = ConvertType(getContext().getSizeType());
// Get the element size;
QualType ElemTy = VAT->getElementType();
llvm::Value *ElemSize;
if (ElemTy->isVariableArrayType())
ElemSize = EmitVLASize(ElemTy);
else
ElemSize = llvm::ConstantInt::get(SizeTy,
getContext().getTypeSize(ElemTy) / 8);
llvm::Value *NumElements = EmitScalarExpr(VAT->getSizeExpr());
NumElements = Builder.CreateIntCast(NumElements, SizeTy, false, "tmp");
SizeEntry = Builder.CreateMul(ElemSize, NumElements);
}
return SizeEntry;
}
if (const ArrayType *AT = dyn_cast<ArrayType>(Ty)) {
EmitVLASize(AT->getElementType());
return 0;
}
const PointerType *PT = Ty->getAs<PointerType>();
assert(PT && "unknown VM type!");
EmitVLASize(PT->getPointeeType());
return 0;
}
llvm::Value* CodeGenFunction::EmitVAListRef(const Expr* E) {
if (CGM.getContext().getBuiltinVaListType()->isArrayType()) {
return EmitScalarExpr(E);
}
return EmitLValue(E).getAddress();
}
void CodeGenFunction::PushCleanupBlock(llvm::BasicBlock *CleanupBlock) {
CleanupEntries.push_back(CleanupEntry(CleanupBlock));
}
void CodeGenFunction::EmitCleanupBlocks(size_t OldCleanupStackSize) {
assert(CleanupEntries.size() >= OldCleanupStackSize &&
"Cleanup stack mismatch!");
while (CleanupEntries.size() > OldCleanupStackSize)
EmitCleanupBlock();
}
CodeGenFunction::CleanupBlockInfo CodeGenFunction::PopCleanupBlock() {
CleanupEntry &CE = CleanupEntries.back();
llvm::BasicBlock *CleanupBlock = CE.CleanupBlock;
std::vector<llvm::BasicBlock *> Blocks;
std::swap(Blocks, CE.Blocks);
std::vector<llvm::BranchInst *> BranchFixups;
std::swap(BranchFixups, CE.BranchFixups);
CleanupEntries.pop_back();
// Check if any branch fixups pointed to the scope we just popped. If so,
// we can remove them.
for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
llvm::BasicBlock *Dest = BranchFixups[i]->getSuccessor(0);
BlockScopeMap::iterator I = BlockScopes.find(Dest);
if (I == BlockScopes.end())
continue;
assert(I->second <= CleanupEntries.size() && "Invalid branch fixup!");
if (I->second == CleanupEntries.size()) {
// We don't need to do this branch fixup.
BranchFixups[i] = BranchFixups.back();
BranchFixups.pop_back();
i--;
e--;
continue;
}
}
llvm::BasicBlock *SwitchBlock = 0;
llvm::BasicBlock *EndBlock = 0;
if (!BranchFixups.empty()) {
SwitchBlock = createBasicBlock("cleanup.switch");
EndBlock = createBasicBlock("cleanup.end");
llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
Builder.SetInsertPoint(SwitchBlock);
llvm::Value *DestCodePtr = CreateTempAlloca(llvm::Type::getInt32Ty(VMContext),
"cleanup.dst");
llvm::Value *DestCode = Builder.CreateLoad(DestCodePtr, "tmp");
// Create a switch instruction to determine where to jump next.
llvm::SwitchInst *SI = Builder.CreateSwitch(DestCode, EndBlock,
BranchFixups.size());
// Restore the current basic block (if any)
if (CurBB) {
Builder.SetInsertPoint(CurBB);
// If we had a current basic block, we also need to emit an instruction
// to initialize the cleanup destination.
Builder.CreateStore(llvm::Constant::getNullValue(llvm::Type::getInt32Ty(VMContext)),
DestCodePtr);
} else
Builder.ClearInsertionPoint();
for (size_t i = 0, e = BranchFixups.size(); i != e; ++i) {
llvm::BranchInst *BI = BranchFixups[i];
llvm::BasicBlock *Dest = BI->getSuccessor(0);
// Fixup the branch instruction to point to the cleanup block.
BI->setSuccessor(0, CleanupBlock);
if (CleanupEntries.empty()) {
llvm::ConstantInt *ID;
// Check if we already have a destination for this block.
if (Dest == SI->getDefaultDest())
ID = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext), 0);
else {
ID = SI->findCaseDest(Dest);
if (!ID) {
// No code found, get a new unique one by using the number of
// switch successors.
ID = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
SI->getNumSuccessors());
SI->addCase(ID, Dest);
}
}
// Store the jump destination before the branch instruction.
new llvm::StoreInst(ID, DestCodePtr, BI);
} else {
// We need to jump through another cleanup block. Create a pad block
// with a branch instruction that jumps to the final destination and
// add it as a branch fixup to the current cleanup scope.
// Create the pad block.
llvm::BasicBlock *CleanupPad = createBasicBlock("cleanup.pad", CurFn);
// Create a unique case ID.
llvm::ConstantInt *ID = llvm::ConstantInt::get(llvm::Type::getInt32Ty(VMContext),
SI->getNumSuccessors());
// Store the jump destination before the branch instruction.
new llvm::StoreInst(ID, DestCodePtr, BI);
// Add it as the destination.
SI->addCase(ID, CleanupPad);
// Create the branch to the final destination.
llvm::BranchInst *BI = llvm::BranchInst::Create(Dest);
CleanupPad->getInstList().push_back(BI);
// And add it as a branch fixup.
CleanupEntries.back().BranchFixups.push_back(BI);
}
}
}
// Remove all blocks from the block scope map.
for (size_t i = 0, e = Blocks.size(); i != e; ++i) {
assert(BlockScopes.count(Blocks[i]) &&
"Did not find block in scope map!");
BlockScopes.erase(Blocks[i]);
}
return CleanupBlockInfo(CleanupBlock, SwitchBlock, EndBlock);
}
void CodeGenFunction::EmitCleanupBlock() {
CleanupBlockInfo Info = PopCleanupBlock();
llvm::BasicBlock *CurBB = Builder.GetInsertBlock();
if (CurBB && !CurBB->getTerminator() &&
Info.CleanupBlock->getNumUses() == 0) {
CurBB->getInstList().splice(CurBB->end(), Info.CleanupBlock->getInstList());
delete Info.CleanupBlock;
} else
EmitBlock(Info.CleanupBlock);
if (Info.SwitchBlock)
EmitBlock(Info.SwitchBlock);
if (Info.EndBlock)
EmitBlock(Info.EndBlock);
}
void CodeGenFunction::AddBranchFixup(llvm::BranchInst *BI) {
assert(!CleanupEntries.empty() &&
"Trying to add branch fixup without cleanup block!");
// FIXME: We could be more clever here and check if there's already a branch
// fixup for this destination and recycle it.
CleanupEntries.back().BranchFixups.push_back(BI);
}
void CodeGenFunction::EmitBranchThroughCleanup(llvm::BasicBlock *Dest) {
if (!HaveInsertPoint())
return;
llvm::BranchInst* BI = Builder.CreateBr(Dest);
Builder.ClearInsertionPoint();
// The stack is empty, no need to do any cleanup.
if (CleanupEntries.empty())
return;
if (!Dest->getParent()) {
// We are trying to branch to a block that hasn't been inserted yet.
AddBranchFixup(BI);
return;
}
BlockScopeMap::iterator I = BlockScopes.find(Dest);
if (I == BlockScopes.end()) {
// We are trying to jump to a block that is outside of any cleanup scope.
AddBranchFixup(BI);
return;
}
assert(I->second < CleanupEntries.size() &&
"Trying to branch into cleanup region");
if (I->second == CleanupEntries.size() - 1) {
// We have a branch to a block in the same scope.
return;
}
AddBranchFixup(BI);
}
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