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22efc18f12
llvm/lib/CodeGen/DwarfEHPrepare.cpp
Duncan Sands 22efc18f12 Stop using the dom frontier in DwarfEHPrepare by not promoting alloca's 
any more.  I plan to reimplement alloca promotion using SSAUpdater later.
It looks like Bill's URoR logic really always needs domtree, so the pass
now always asks for domtree info.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@112597 91177308-0d34-0410-b5e6-96231b3b80d8
2010-08-31 09:05:06 +00:00

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//===-- DwarfEHPrepare - Prepare exception handling for code generation ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This pass mulches exception handling code into a form adapted to code
// generation. Required if using dwarf exception handling.
//
//===----------------------------------------------------------------------===//
#define DEBUG_TYPE "dwarfehprepare"
#include "llvm/Function.h"
#include "llvm/Instructions.h"
#include "llvm/IntrinsicInst.h"
#include "llvm/Module.h"
#include "llvm/Pass.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/Analysis/Dominators.h"
#include "llvm/CodeGen/Passes.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/Support/CallSite.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Transforms/Utils/BasicBlockUtils.h"
using namespace llvm;
STATISTIC(NumLandingPadsSplit, "Number of landing pads split");
STATISTIC(NumUnwindsLowered, "Number of unwind instructions lowered");
STATISTIC(NumExceptionValuesMoved, "Number of eh.exception calls moved");
STATISTIC(NumStackTempsIntroduced, "Number of stack temporaries introduced");
namespace {
class DwarfEHPrepare : public FunctionPass {
const TargetMachine *TM;
const TargetLowering *TLI;
// The eh.exception intrinsic.
Function *ExceptionValueIntrinsic;
// The eh.selector intrinsic.
Function *SelectorIntrinsic;
// _Unwind_Resume_or_Rethrow call.
Constant *URoR;
// The EH language-specific catch-all type.
GlobalVariable *EHCatchAllValue;
// _Unwind_Resume or the target equivalent.
Constant *RewindFunction;
// We both use and preserve dominator info.
DominatorTree *DT;
// The function we are running on.
Function *F;
// The landing pads for this function.
typedef SmallPtrSet<BasicBlock*, 8> BBSet;
BBSet LandingPads;
// Stack temporary used to hold eh.exception values.
AllocaInst *ExceptionValueVar;
bool NormalizeLandingPads();
bool LowerUnwinds();
bool MoveExceptionValueCalls();
bool FinishStackTemporaries();
Instruction *CreateExceptionValueCall(BasicBlock *BB);
Instruction *CreateValueLoad(BasicBlock *BB);
/// CreateReadOfExceptionValue - Return the result of the eh.exception
/// intrinsic by calling the intrinsic if in a landing pad, or loading it
/// from the exception value variable otherwise.
Instruction *CreateReadOfExceptionValue(BasicBlock *BB) {
return LandingPads.count(BB) ?
CreateExceptionValueCall(BB) : CreateValueLoad(BB);
}
/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still
/// use the "llvm.eh.catch.all.value" call need to convert to using its
/// initializer instead.
bool CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels);
bool HasCatchAllInSelector(IntrinsicInst *);
/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
void FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels);
/// FindAllURoRInvokes - Find all URoR invokes in the function.
void FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes);
/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow"
/// calls. The "unwind" part of these invokes jump to a landing pad within
/// the current function. This is a candidate to merge the selector
/// associated with the URoR invoke with the one from the URoR's landing
/// pad.
bool HandleURoRInvokes();
/// FindSelectorAndURoR - Find the eh.selector call and URoR call associated
/// with the eh.exception call. This recursively looks past instructions
/// which don't change the EH pointer value, like casts or PHI nodes.
bool FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
SmallPtrSet<IntrinsicInst*, 8> &SelCalls);
public:
static char ID; // Pass identification, replacement for typeid.
DwarfEHPrepare(const TargetMachine *tm) :
FunctionPass(ID), TM(tm), TLI(TM->getTargetLowering()),
ExceptionValueIntrinsic(0), SelectorIntrinsic(0),
URoR(0), EHCatchAllValue(0), RewindFunction(0) {}
virtual bool runOnFunction(Function &Fn);
// getAnalysisUsage - We need dominance frontiers for memory promotion.
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired<DominatorTree>();
AU.addPreserved<DominatorTree>();
}
const char *getPassName() const {
return "Exception handling preparation";
}
};
} // end anonymous namespace
char DwarfEHPrepare::ID = 0;
FunctionPass *llvm::createDwarfEHPass(const TargetMachine *tm) {
return new DwarfEHPrepare(tm);
}
/// HasCatchAllInSelector - Return true if the intrinsic instruction has a
/// catch-all.
bool DwarfEHPrepare::HasCatchAllInSelector(IntrinsicInst *II) {
if (!EHCatchAllValue) return false;
unsigned ArgIdx = II->getNumArgOperands() - 1;
GlobalVariable *GV = dyn_cast<GlobalVariable>(II->getArgOperand(ArgIdx));
return GV == EHCatchAllValue;
}
/// FindAllCleanupSelectors - Find all eh.selector calls that are clean-ups.
void DwarfEHPrepare::
FindAllCleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels,
SmallPtrSet<IntrinsicInst*, 32> &CatchAllSels) {
for (Value::use_iterator
I = SelectorIntrinsic->use_begin(),
E = SelectorIntrinsic->use_end(); I != E; ++I) {
IntrinsicInst *II = cast<IntrinsicInst>(*I);
if (II->getParent()->getParent() != F)
continue;
if (!HasCatchAllInSelector(II))
Sels.insert(II);
else
CatchAllSels.insert(II);
}
}
/// FindAllURoRInvokes - Find all URoR invokes in the function.
void DwarfEHPrepare::
FindAllURoRInvokes(SmallPtrSet<InvokeInst*, 32> &URoRInvokes) {
for (Value::use_iterator
I = URoR->use_begin(),
E = URoR->use_end(); I != E; ++I) {
if (InvokeInst *II = dyn_cast<InvokeInst>(*I))
URoRInvokes.insert(II);
}
}
/// CleanupSelectors - Any remaining eh.selector intrinsic calls which still use
/// the "llvm.eh.catch.all.value" call need to convert to using its
/// initializer instead.
bool DwarfEHPrepare::CleanupSelectors(SmallPtrSet<IntrinsicInst*, 32> &Sels) {
if (!EHCatchAllValue) return false;
if (!SelectorIntrinsic) {
SelectorIntrinsic =
Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
if (!SelectorIntrinsic) return false;
}
bool Changed = false;
for (SmallPtrSet<IntrinsicInst*, 32>::iterator
I = Sels.begin(), E = Sels.end(); I != E; ++I) {
IntrinsicInst *Sel = *I;
// Index of the "llvm.eh.catch.all.value" variable.
unsigned OpIdx = Sel->getNumArgOperands() - 1;
GlobalVariable *GV = dyn_cast<GlobalVariable>(Sel->getArgOperand(OpIdx));
if (GV != EHCatchAllValue) continue;
Sel->setArgOperand(OpIdx, EHCatchAllValue->getInitializer());
Changed = true;
}
return Changed;
}
/// FindSelectorAndURoR - Find the eh.selector call associated with the
/// eh.exception call. And indicate if there is a URoR "invoke" associated with
/// the eh.exception call. This recursively looks past instructions which don't
/// change the EH pointer value, like casts or PHI nodes.
bool
DwarfEHPrepare::FindSelectorAndURoR(Instruction *Inst, bool &URoRInvoke,
SmallPtrSet<IntrinsicInst*, 8> &SelCalls) {
SmallPtrSet<PHINode*, 32> SeenPHIs;
bool Changed = false;
for (Value::use_iterator
I = Inst->use_begin(), E = Inst->use_end(); I != E; ++I) {
Instruction *II = dyn_cast<Instruction>(*I);
if (!II || II->getParent()->getParent() != F) continue;
if (IntrinsicInst *Sel = dyn_cast<IntrinsicInst>(II)) {
if (Sel->getIntrinsicID() == Intrinsic::eh_selector)
SelCalls.insert(Sel);
} else if (InvokeInst *Invoke = dyn_cast<InvokeInst>(II)) {
if (Invoke->getCalledFunction() == URoR)
URoRInvoke = true;
} else if (CastInst *CI = dyn_cast<CastInst>(II)) {
Changed |= FindSelectorAndURoR(CI, URoRInvoke, SelCalls);
} else if (PHINode *PN = dyn_cast<PHINode>(II)) {
if (SeenPHIs.insert(PN))
// Don't process a PHI node more than once.
Changed |= FindSelectorAndURoR(PN, URoRInvoke, SelCalls);
}
}
return Changed;
}
/// HandleURoRInvokes - Handle invokes of "_Unwind_Resume_or_Rethrow" calls. The
/// "unwind" part of these invokes jump to a landing pad within the current
/// function. This is a candidate to merge the selector associated with the URoR
/// invoke with the one from the URoR's landing pad.
bool DwarfEHPrepare::HandleURoRInvokes() {
if (!EHCatchAllValue) {
EHCatchAllValue =
F->getParent()->getNamedGlobal("llvm.eh.catch.all.value");
if (!EHCatchAllValue) return false;
}
if (!SelectorIntrinsic) {
SelectorIntrinsic =
Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_selector);
if (!SelectorIntrinsic) return false;
}
SmallPtrSet<IntrinsicInst*, 32> Sels;
SmallPtrSet<IntrinsicInst*, 32> CatchAllSels;
FindAllCleanupSelectors(Sels, CatchAllSels);
if (!URoR) {
URoR = F->getParent()->getFunction("_Unwind_Resume_or_Rethrow");
if (!URoR) return CleanupSelectors(CatchAllSels);
}
SmallPtrSet<InvokeInst*, 32> URoRInvokes;
FindAllURoRInvokes(URoRInvokes);
SmallPtrSet<IntrinsicInst*, 32> SelsToConvert;
for (SmallPtrSet<IntrinsicInst*, 32>::iterator
SI = Sels.begin(), SE = Sels.end(); SI != SE; ++SI) {
const BasicBlock *SelBB = (*SI)->getParent();
for (SmallPtrSet<InvokeInst*, 32>::iterator
UI = URoRInvokes.begin(), UE = URoRInvokes.end(); UI != UE; ++UI) {
const BasicBlock *URoRBB = (*UI)->getParent();
if (DT->dominates(SelBB, URoRBB)) {
SelsToConvert.insert(*SI);
break;
}
}
}
bool Changed = false;
if (Sels.size() != SelsToConvert.size()) {
// If we haven't been able to convert all of the clean-up selectors, then
// loop through the slow way to see if they still need to be converted.
if (!ExceptionValueIntrinsic) {
ExceptionValueIntrinsic =
Intrinsic::getDeclaration(F->getParent(), Intrinsic::eh_exception);
if (!ExceptionValueIntrinsic)
return CleanupSelectors(CatchAllSels);
}
for (Value::use_iterator
I = ExceptionValueIntrinsic->use_begin(),
E = ExceptionValueIntrinsic->use_end(); I != E; ++I) {
IntrinsicInst *EHPtr = dyn_cast<IntrinsicInst>(*I);
if (!EHPtr || EHPtr->getParent()->getParent() != F) continue;
bool URoRInvoke = false;
SmallPtrSet<IntrinsicInst*, 8> SelCalls;
Changed |= FindSelectorAndURoR(EHPtr, URoRInvoke, SelCalls);
if (URoRInvoke) {
// This EH pointer is being used by an invoke of an URoR instruction and
// an eh.selector intrinsic call. If the eh.selector is a 'clean-up', we
// need to convert it to a 'catch-all'.
for (SmallPtrSet<IntrinsicInst*, 8>::iterator
SI = SelCalls.begin(), SE = SelCalls.end(); SI != SE; ++SI)
if (!HasCatchAllInSelector(*SI))
SelsToConvert.insert(*SI);
}
}
}
if (!SelsToConvert.empty()) {
// Convert all clean-up eh.selectors, which are associated with "invokes" of
// URoR calls, into catch-all eh.selectors.
Changed = true;
for (SmallPtrSet<IntrinsicInst*, 8>::iterator
SI = SelsToConvert.begin(), SE = SelsToConvert.end();
SI != SE; ++SI) {
IntrinsicInst *II = *SI;
// Use the exception object pointer and the personality function
// from the original selector.
CallSite CS(II);
IntrinsicInst::op_iterator I = CS.arg_begin();
IntrinsicInst::op_iterator E = CS.arg_end();
IntrinsicInst::op_iterator B = prior(E);
// Exclude last argument if it is an integer.
if (isa<ConstantInt>(B)) E = B;
// Add exception object pointer (front).
// Add personality function (next).
// Add in any filter IDs (rest).
SmallVector<Value*, 8> Args(I, E);
Args.push_back(EHCatchAllValue->getInitializer()); // Catch-all indicator.
CallInst *NewSelector =
CallInst::Create(SelectorIntrinsic, Args.begin(), Args.end(),
"eh.sel.catch.all", II);
NewSelector->setTailCall(II->isTailCall());
NewSelector->setAttributes(II->getAttributes());
NewSelector->setCallingConv(II->getCallingConv());
II->replaceAllUsesWith(NewSelector);
II->eraseFromParent();
}
}
Changed |= CleanupSelectors(CatchAllSels);
return Changed;
}
/// NormalizeLandingPads - Normalize and discover landing pads, noting them
/// in the LandingPads set. A landing pad is normal if the only CFG edges
/// that end at it are unwind edges from invoke instructions. If we inlined
/// through an invoke we could have a normal branch from the previous
/// unwind block through to the landing pad for the original invoke.
/// Abnormal landing pads are fixed up by redirecting all unwind edges to
/// a new basic block which falls through to the original.
bool DwarfEHPrepare::NormalizeLandingPads() {
bool Changed = false;
const MCAsmInfo *MAI = TM->getMCAsmInfo();
bool usingSjLjEH = MAI->getExceptionHandlingType() == ExceptionHandling::SjLj;
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
TerminatorInst *TI = I->getTerminator();
if (!isa<InvokeInst>(TI))
continue;
BasicBlock *LPad = TI->getSuccessor(1);
// Skip landing pads that have already been normalized.
if (LandingPads.count(LPad))
continue;
// Check that only invoke unwind edges end at the landing pad.
bool OnlyUnwoundTo = true;
bool SwitchOK = usingSjLjEH;
for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad);
PI != PE; ++PI) {
TerminatorInst *PT = (*PI)->getTerminator();
// The SjLj dispatch block uses a switch instruction. This is effectively
// an unwind edge, so we can disregard it here. There will only ever
// be one dispatch, however, so if there are multiple switches, one
// of them truly is a normal edge, not an unwind edge.
if (SwitchOK && isa<SwitchInst>(PT)) {
SwitchOK = false;
continue;
}
if (!isa<InvokeInst>(PT) || LPad == PT->getSuccessor(0)) {
OnlyUnwoundTo = false;
break;
}
}
if (OnlyUnwoundTo) {
// Only unwind edges lead to the landing pad. Remember the landing pad.
LandingPads.insert(LPad);
continue;
}
// At least one normal edge ends at the landing pad. Redirect the unwind
// edges to a new basic block which falls through into this one.
// Create the new basic block.
BasicBlock *NewBB = BasicBlock::Create(F->getContext(),
LPad->getName() + "_unwind_edge");
// Insert it into the function right before the original landing pad.
LPad->getParent()->getBasicBlockList().insert(LPad, NewBB);
// Redirect unwind edges from the original landing pad to NewBB.
for (pred_iterator PI = pred_begin(LPad), PE = pred_end(LPad); PI != PE; ) {
TerminatorInst *PT = (*PI++)->getTerminator();
if (isa<InvokeInst>(PT) && PT->getSuccessor(1) == LPad)
// Unwind to the new block.
PT->setSuccessor(1, NewBB);
}
// If there are any PHI nodes in LPad, we need to update them so that they
// merge incoming values from NewBB instead.
for (BasicBlock::iterator II = LPad->begin(); isa<PHINode>(II); ++II) {
PHINode *PN = cast<PHINode>(II);
pred_iterator PB = pred_begin(NewBB), PE = pred_end(NewBB);
// Check to see if all of the values coming in via unwind edges are the
// same. If so, we don't need to create a new PHI node.
Value *InVal = PN->getIncomingValueForBlock(*PB);
for (pred_iterator PI = PB; PI != PE; ++PI) {
if (PI != PB && InVal != PN->getIncomingValueForBlock(*PI)) {
InVal = 0;
break;
}
}
if (InVal == 0) {
// Different unwind edges have different values. Create a new PHI node
// in NewBB.
PHINode *NewPN = PHINode::Create(PN->getType(), PN->getName()+".unwind",
NewBB);
// Add an entry for each unwind edge, using the value from the old PHI.
for (pred_iterator PI = PB; PI != PE; ++PI)
NewPN->addIncoming(PN->getIncomingValueForBlock(*PI), *PI);
// Now use this new PHI as the common incoming value for NewBB in PN.
InVal = NewPN;
}
// Revector exactly one entry in the PHI node to come from NewBB
// and delete all other entries that come from unwind edges. If
// there are both normal and unwind edges from the same predecessor,
// this leaves an entry for the normal edge.
for (pred_iterator PI = PB; PI != PE; ++PI)
PN->removeIncomingValue(*PI);
PN->addIncoming(InVal, NewBB);
}
// Add a fallthrough from NewBB to the original landing pad.
BranchInst::Create(LPad, NewBB);
// Now update DominatorTree analysis information.
DT->splitBlock(NewBB);
// Remember the newly constructed landing pad. The original landing pad
// LPad is no longer a landing pad now that all unwind edges have been
// revectored to NewBB.
LandingPads.insert(NewBB);
++NumLandingPadsSplit;
Changed = true;
}
return Changed;
}
/// LowerUnwinds - Turn unwind instructions into calls to _Unwind_Resume,
/// rethrowing any previously caught exception. This will crash horribly
/// at runtime if there is no such exception: using unwind to throw a new
/// exception is currently not supported.
bool DwarfEHPrepare::LowerUnwinds() {
SmallVector<TerminatorInst*, 16> UnwindInsts;
for (Function::iterator I = F->begin(), E = F->end(); I != E; ++I) {
TerminatorInst *TI = I->getTerminator();
if (isa<UnwindInst>(TI))
UnwindInsts.push_back(TI);
}
if (UnwindInsts.empty()) return false;
// Find the rewind function if we didn't already.
if (!RewindFunction) {
LLVMContext &Ctx = UnwindInsts[0]->getContext();
std::vector<const Type*>
Params(1, Type::getInt8PtrTy(Ctx));
FunctionType *FTy = FunctionType::get(Type::getVoidTy(Ctx),
Params, false);
const char *RewindName = TLI->getLibcallName(RTLIB::UNWIND_RESUME);
RewindFunction = F->getParent()->getOrInsertFunction(RewindName, FTy);
}
bool Changed = false;
for (SmallVectorImpl<TerminatorInst*>::iterator
I = UnwindInsts.begin(), E = UnwindInsts.end(); I != E; ++I) {
TerminatorInst *TI = *I;
// Replace the unwind instruction with a call to _Unwind_Resume (or the
// appropriate target equivalent) followed by an UnreachableInst.
// Create the call...
CallInst *CI = CallInst::Create(RewindFunction,
CreateReadOfExceptionValue(TI->getParent()),
"", TI);
CI->setCallingConv(TLI->getLibcallCallingConv(RTLIB::UNWIND_RESUME));
// ...followed by an UnreachableInst.
new UnreachableInst(TI->getContext(), TI);
// Nuke the unwind instruction.
TI->eraseFromParent();
++NumUnwindsLowered;
Changed = true;
}
return Changed;
}
/// MoveExceptionValueCalls - Ensure that eh.exception is only ever called from
/// landing pads by replacing calls outside of landing pads with loads from a
/// stack temporary. Move eh.exception calls inside landing pads to the start
/// of the landing pad (optional, but may make things simpler for later passes).
bool DwarfEHPrepare::MoveExceptionValueCalls() {
// If the eh.exception intrinsic is not declared in the module then there is
// nothing to do. Speed up compilation by checking for this common case.
if (!ExceptionValueIntrinsic &&
!F->getParent()->getFunction(Intrinsic::getName(Intrinsic::eh_exception)))
return false;
bool Changed = false;
for (Function::iterator BB = F->begin(), E = F->end(); BB != E; ++BB) {
for (BasicBlock::iterator II = BB->begin(), E = BB->end(); II != E;)
if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(II++))
if (CI->getIntrinsicID() == Intrinsic::eh_exception) {
if (!CI->use_empty()) {
Value *ExceptionValue = CreateReadOfExceptionValue(BB);
if (CI == ExceptionValue) {
// The call was at the start of a landing pad - leave it alone.
assert(LandingPads.count(BB) &&
"Created eh.exception call outside landing pad!");
continue;
}
CI->replaceAllUsesWith(ExceptionValue);
}
CI->eraseFromParent();
++NumExceptionValuesMoved;
Changed = true;
}
}
return Changed;
}
/// FinishStackTemporaries - If we introduced a stack variable to hold the
/// exception value then initialize it in each landing pad.
bool DwarfEHPrepare::FinishStackTemporaries() {
if (!ExceptionValueVar)
// Nothing to do.
return false;
bool Changed = false;
// Make sure that there is a store of the exception value at the start of
// each landing pad.
for (BBSet::iterator LI = LandingPads.begin(), LE = LandingPads.end();
LI != LE; ++LI) {
Instruction *ExceptionValue = CreateReadOfExceptionValue(*LI);
Instruction *Store = new StoreInst(ExceptionValue, ExceptionValueVar);
Store->insertAfter(ExceptionValue);
Changed = true;
}
return Changed;
}
/// CreateExceptionValueCall - Insert a call to the eh.exception intrinsic at
/// the start of the basic block (unless there already is one, in which case
/// the existing call is returned).
Instruction *DwarfEHPrepare::CreateExceptionValueCall(BasicBlock *BB) {
Instruction *Start = BB->getFirstNonPHIOrDbg();
// Is this a call to eh.exception?
if (IntrinsicInst *CI = dyn_cast<IntrinsicInst>(Start))
if (CI->getIntrinsicID() == Intrinsic::eh_exception)
// Reuse the existing call.
return Start;
// Find the eh.exception intrinsic if we didn't already.
if (!ExceptionValueIntrinsic)
ExceptionValueIntrinsic = Intrinsic::getDeclaration(F->getParent(),
Intrinsic::eh_exception);
// Create the call.
return CallInst::Create(ExceptionValueIntrinsic, "eh.value.call", Start);
}
/// CreateValueLoad - Insert a load of the exception value stack variable
/// (creating it if necessary) at the start of the basic block (unless
/// there already is a load, in which case the existing load is returned).
Instruction *DwarfEHPrepare::CreateValueLoad(BasicBlock *BB) {
Instruction *Start = BB->getFirstNonPHIOrDbg();
// Is this a load of the exception temporary?
if (ExceptionValueVar)
if (LoadInst* LI = dyn_cast<LoadInst>(Start))
if (LI->getPointerOperand() == ExceptionValueVar)
// Reuse the existing load.
return Start;
// Create the temporary if we didn't already.
if (!ExceptionValueVar) {
ExceptionValueVar = new AllocaInst(PointerType::getUnqual(
Type::getInt8Ty(BB->getContext())), "eh.value", F->begin()->begin());
++NumStackTempsIntroduced;
}
// Load the value.
return new LoadInst(ExceptionValueVar, "eh.value.load", Start);
}
bool DwarfEHPrepare::runOnFunction(Function &Fn) {
bool Changed = false;
// Initialize internal state.
DT = &getAnalysis<DominatorTree>();
ExceptionValueVar = 0;
F = &Fn;
// Ensure that only unwind edges end at landing pads (a landing pad is a
// basic block where an invoke unwind edge ends).
Changed |= NormalizeLandingPads();
// Turn unwind instructions into libcalls.
Changed |= LowerUnwinds();
// TODO: Move eh.selector calls to landing pads and combine them.
// Move eh.exception calls to landing pads.
Changed |= MoveExceptionValueCalls();
// Initialize any stack temporaries we introduced.
Changed |= FinishStackTemporaries();
// TODO: Turn any stack temporaries into registers if possible.
Changed |= HandleURoRInvokes();
LandingPads.clear();
return Changed;
}
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