/// substituteLPadValues - Substitute the values returned by the landingpad
/// instruction with those returned by the personality function.
void SjLjEHPrepare::substituteLPadValues(LandingPadInst *LPI, Value *ExnVal,
Value *SelVal) {
SmallVector<Value *, 8> UseWorkList(LPI->user_begin(), LPI->user_end());
while (!UseWorkList.empty()) {
Value *Val = UseWorkList.pop_back_val();
ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(Val);
if (!EVI)
continue;
if (EVI->getNumIndices() != 1)
continue;
if (*EVI->idx_begin() == 0)
EVI->replaceAllUsesWith(ExnVal);
else if (*EVI->idx_begin() == 1)
EVI->replaceAllUsesWith(SelVal);
if (EVI->getNumUses() == 0)
EVI->eraseFromParent();
}
if (LPI->getNumUses() == 0)
return;
// There are still some uses of LPI. Construct an aggregate with the exception
// values and replace the LPI with that aggregate.
Type *LPadType = LPI->getType();
Value *LPadVal = UndefValue::get(LPadType);
auto *SelI = cast<Instruction>(SelVal);
IRBuilder<> Builder(SelI->getParent(), std::next(SelI->getIterator()));
LPadVal = Builder.CreateInsertValue(LPadVal, ExnVal, 0, "lpad.val");
LPadVal = Builder.CreateInsertValue(LPadVal, SelVal, 1, "lpad.val");
LPI->replaceAllUsesWith(LPadVal);
}
bool AtomicExpand::expandAtomicCmpXchg(AtomicCmpXchgInst *CI) {
AtomicOrdering SuccessOrder = CI->getSuccessOrdering();
AtomicOrdering FailureOrder = CI->getFailureOrdering();
Value *Addr = CI->getPointerOperand();
BasicBlock *BB = CI->getParent();
Function *F = BB->getParent();
LLVMContext &Ctx = F->getContext();
// If getInsertFencesForAtomic() returns true, then the target does not want
// to deal with memory orders, and emitLeading/TrailingFence should take care
// of everything. Otherwise, emitLeading/TrailingFence are no-op and we
// should preserve the ordering.
AtomicOrdering MemOpOrder =
TLI->getInsertFencesForAtomic() ? Monotonic : SuccessOrder;
// Given: cmpxchg some_op iN* %addr, iN %desired, iN %new success_ord fail_ord
//
// The full expansion we produce is:
// [...]
// fence?
// cmpxchg.start:
// %loaded = @load.linked(%addr)
// %should_store = icmp eq %loaded, %desired
// br i1 %should_store, label %cmpxchg.trystore,
// label %cmpxchg.nostore
// cmpxchg.trystore:
// %stored = @store_conditional(%new, %addr)
// %success = icmp eq i32 %stored, 0
// br i1 %success, label %cmpxchg.success, label %loop/%cmpxchg.failure
// cmpxchg.success:
// fence?
// br label %cmpxchg.end
// cmpxchg.nostore:
// @load_linked_fail_balance()?
// br label %cmpxchg.failure
// cmpxchg.failure:
// fence?
// br label %cmpxchg.end
// cmpxchg.end:
// %success = phi i1 [true, %cmpxchg.success], [false, %cmpxchg.failure]
// %restmp = insertvalue { iN, i1 } undef, iN %loaded, 0
// %res = insertvalue { iN, i1 } %restmp, i1 %success, 1
// [...]
BasicBlock *ExitBB = BB->splitBasicBlock(CI->getIterator(), "cmpxchg.end");
auto FailureBB = BasicBlock::Create(Ctx, "cmpxchg.failure", F, ExitBB);
auto NoStoreBB = BasicBlock::Create(Ctx, "cmpxchg.nostore", F, FailureBB);
auto SuccessBB = BasicBlock::Create(Ctx, "cmpxchg.success", F, NoStoreBB);
auto TryStoreBB = BasicBlock::Create(Ctx, "cmpxchg.trystore", F, SuccessBB);
auto LoopBB = BasicBlock::Create(Ctx, "cmpxchg.start", F, TryStoreBB);
// This grabs the DebugLoc from CI
IRBuilder<> Builder(CI);
// The split call above "helpfully" added a branch at the end of BB (to the
// wrong place), but we might want a fence too. It's easiest to just remove
// the branch entirely.
std::prev(BB->end())->eraseFromParent();
Builder.SetInsertPoint(BB);
TLI->emitLeadingFence(Builder, SuccessOrder, /*IsStore=*/true,
/*IsLoad=*/true);
Builder.CreateBr(LoopBB);
// Start the main loop block now that we've taken care of the preliminaries.
Builder.SetInsertPoint(LoopBB);
Value *Loaded = TLI->emitLoadLinked(Builder, Addr, MemOpOrder);
Value *ShouldStore =
Builder.CreateICmpEQ(Loaded, CI->getCompareOperand(), "should_store");
// If the cmpxchg doesn't actually need any ordering when it fails, we can
// jump straight past that fence instruction (if it exists).
Builder.CreateCondBr(ShouldStore, TryStoreBB, NoStoreBB);
Builder.SetInsertPoint(TryStoreBB);
Value *StoreSuccess = TLI->emitStoreConditional(
Builder, CI->getNewValOperand(), Addr, MemOpOrder);
StoreSuccess = Builder.CreateICmpEQ(
StoreSuccess, ConstantInt::get(Type::getInt32Ty(Ctx), 0), "success");
Builder.CreateCondBr(StoreSuccess, SuccessBB,
CI->isWeak() ? FailureBB : LoopBB);
// Make sure later instructions don't get reordered with a fence if necessary.
Builder.SetInsertPoint(SuccessBB);
TLI->emitTrailingFence(Builder, SuccessOrder, /*IsStore=*/true,
/*IsLoad=*/true);
Builder.CreateBr(ExitBB);
Builder.SetInsertPoint(NoStoreBB);
// In the failing case, where we don't execute the store-conditional, the
// target might want to balance out the load-linked with a dedicated
// instruction (e.g., on ARM, clearing the exclusive monitor).
TLI->emitAtomicCmpXchgNoStoreLLBalance(Builder);
Builder.CreateBr(FailureBB);
Builder.SetInsertPoint(FailureBB);
TLI->emitTrailingFence(Builder, FailureOrder, /*IsStore=*/true,
/*IsLoad=*/true);
Builder.CreateBr(ExitBB);
// Finally, we have control-flow based knowledge of whether the cmpxchg
// succeeded or not. We expose this to later passes by converting any
// subsequent "icmp eq/ne %loaded, %oldval" into a use of an appropriate PHI.
// Setup the builder so we can create any PHIs we need.
Builder.SetInsertPoint(ExitBB, ExitBB->begin());
PHINode *Success = Builder.CreatePHI(Type::getInt1Ty(Ctx), 2);
Success->addIncoming(ConstantInt::getTrue(Ctx), SuccessBB);
Success->addIncoming(ConstantInt::getFalse(Ctx), FailureBB);
// Look for any users of the cmpxchg that are just comparing the loaded value
// against the desired one, and replace them with the CFG-derived version.
SmallVector<ExtractValueInst *, 2> PrunedInsts;
for (auto User : CI->users()) {
ExtractValueInst *EV = dyn_cast<ExtractValueInst>(User);
if (!EV)
continue;
assert(EV->getNumIndices() == 1 && EV->getIndices()[0] <= 1 &&
"weird extraction from { iN, i1 }");
if (EV->getIndices()[0] == 0)
EV->replaceAllUsesWith(Loaded);
else
EV->replaceAllUsesWith(Success);
PrunedInsts.push_back(EV);
}
// We can remove the instructions now we're no longer iterating through them.
for (auto EV : PrunedInsts)
EV->eraseFromParent();
if (!CI->use_empty()) {
// Some use of the full struct return that we don't understand has happened,
// so we've got to reconstruct it properly.
Value *Res;
Res = Builder.CreateInsertValue(UndefValue::get(CI->getType()), Loaded, 0);
Res = Builder.CreateInsertValue(Res, Success, 1);
CI->replaceAllUsesWith(Res);
}
CI->eraseFromParent();
return true;
}
//
// Method: runOnModule()
//
// Description:
// Entry point for this LLVM pass. Search for insert/extractvalue instructions
// that can be simplified.
//
// Inputs:
// M - A reference to the LLVM module to transform.
//
// Outputs:
// M - The transformed LLVM module.
//
// Return value:
// true - The module was modified.
// false - The module was not modified.
//
bool SimplifyEV::runOnModule(Module& M) {
// Repeat till no change
bool changed;
do {
changed = false;
for (Module::iterator F = M.begin(); F != M.end(); ++F) {
for (Function::iterator B = F->begin(), FE = F->end(); B != FE; ++B) {
for (BasicBlock::iterator I = B->begin(), BE = B->end(); I != BE;) {
ExtractValueInst *EV = dyn_cast<ExtractValueInst>(I++);
if(!EV)
continue;
Value *Agg = EV->getAggregateOperand();
if (!EV->hasIndices()) {
EV->replaceAllUsesWith(Agg);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
if (Constant *C = dyn_cast<Constant>(Agg)) {
if (isa<UndefValue>(C)) {
EV->replaceAllUsesWith(UndefValue::get(EV->getType()));
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
if (isa<ConstantAggregateZero>(C)) {
EV->replaceAllUsesWith(Constant::getNullValue(EV->getType()));
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
if (isa<ConstantArray>(C) || isa<ConstantStruct>(C)) {
// Extract the element indexed by the first index out of the constant
Value *V = C->getOperand(*EV->idx_begin());
if (EV->getNumIndices() > 1) {
// Extract the remaining indices out of the constant indexed by the
// first index
ExtractValueInst *EV_new = ExtractValueInst::Create(V,
EV->getIndices().slice(1),
"", EV);
EV->replaceAllUsesWith(EV_new);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
} else {
EV->replaceAllUsesWith(V);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
}
continue;
}
if (LoadInst * LI = dyn_cast<LoadInst>(Agg)) {
// if the Agg value came from a load instruction
// replace the extract value intruction with
// a gep and a load.
SmallVector<Value*, 8> Indices;
Type *Int32Ty = Type::getInt32Ty(M.getContext());
Indices.push_back(Constant::getNullValue(Int32Ty));
for (ExtractValueInst::idx_iterator I = EV->idx_begin(), E = EV->idx_end();
I != E; ++I) {
Indices.push_back(ConstantInt::get(Int32Ty, *I));
}
GetElementPtrInst *GEP = GetElementPtrInst::CreateInBounds(LI->getOperand(0), Indices,
LI->getName(), LI) ;
LoadInst *LINew = new LoadInst(GEP, "", LI);
EV->replaceAllUsesWith(LINew);
EV->eraseFromParent();
changed = true;
numErased++;
continue;
}
if (InsertValueInst *IV = dyn_cast<InsertValueInst>(Agg)) {
bool done = false;
// We're extracting from an insertvalue instruction, compare the indices
const unsigned *exti, *exte, *insi, *inse;
for (exti = EV->idx_begin(), insi = IV->idx_begin(),
exte = EV->idx_end(), inse = IV->idx_end();
exti != exte && insi != inse;
++exti, ++insi) {
if (*insi != *exti) {
// The insert and extract both reference distinctly different elements.
// This means the extract is not influenced by the insert, and we can
// replace the aggregate operand of the extract with the aggregate
// operand of the insert. i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 0
// with
// %E = extractvalue { i32, { i32 } } %A, 0
ExtractValueInst *EV_new = ExtractValueInst::Create(IV->getAggregateOperand(),
EV->getIndices(), "", EV);
EV->replaceAllUsesWith(EV_new);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
done = true;
changed = true;
break;
}
}
if(done)
continue;
if (exti == exte && insi == inse) {
// Both iterators are at the end: Index lists are identical. Replace
// %B = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %C = extractvalue { i32, { i32 } } %B, 1, 0
// with "i32 42"
EV->replaceAllUsesWith(IV->getInsertedValueOperand());
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
if (exti == exte) {
// The extract list is a prefix of the insert list. i.e. replace
// %I = insertvalue { i32, { i32 } } %A, i32 42, 1, 0
// %E = extractvalue { i32, { i32 } } %I, 1
// with
// %X = extractvalue { i32, { i32 } } %A, 1
// %E = insertvalue { i32 } %X, i32 42, 0
// by switching the order of the insert and extract (though the
// insertvalue should be left in, since it may have other uses).
Value *NewEV = ExtractValueInst::Create(IV->getAggregateOperand(),
EV->getIndices(), "", EV);
Value *NewIV = InsertValueInst::Create(NewEV, IV->getInsertedValueOperand(),
makeArrayRef(insi, inse), "", EV);
EV->replaceAllUsesWith(NewIV);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
if (insi == inse) {
// The insert list is a prefix of the extract list
// We can simply remove the common indices from the extract and make it
// operate on the inserted value instead of the insertvalue result.
// i.e., replace
// %I = insertvalue { i32, { i32 } } %A, { i32 } { i32 42 }, 1
// %E = extractvalue { i32, { i32 } } %I, 1, 0
// with
// %E extractvalue { i32 } { i32 42 }, 0
ExtractValueInst *EV_new = ExtractValueInst::Create(IV->getInsertedValueOperand(),
makeArrayRef(exti, exte), "", EV);
EV->replaceAllUsesWith(EV_new);
DEBUG(errs() << "EV:");
DEBUG(errs() << "ERASE:");
DEBUG(EV->dump());
EV->eraseFromParent();
numErased++;
changed = true;
continue;
}
}
}
}
}
} while(changed);
return (numErased > 0);
}
