return false;
}
-/// Return true if the Value is a gc reference type which is potentially used
-/// after the instruction 'loc'. This is only used with the edge reachability
-/// liveness code. Note: It is assumed the V dominates loc.
-static bool isLiveGCReferenceAt(Value &V, Instruction *loc, DominatorTree &DT,
- LoopInfo *LI) {
- if (!isGCPointerType(V.getType()))
- return false;
-
- if (V.use_empty())
- return false;
-
- // Given assumption that V dominates loc, this may be live
- return true;
+// Return true if this type is one which a) is a gc pointer or contains a GC
+// pointer and b) is of a type this code expects to encounter as a live value.
+// (The insertion code will assert that a type which matches (a) and not (b)
+// is not encountered.)
+static bool isHandledGCPointerType(Type *T) {
+ // We fully support gc pointers
+ if (isGCPointerType(T))
+ return true;
+ // We partially support vectors of gc pointers. The code will assert if it
+ // can't handle something.
+ if (auto VT = dyn_cast<VectorType>(T))
+ if (isGCPointerType(VT->getElementType()))
+ return true;
+ return false;
}
#ifndef NDEBUG
-static bool isAggWhichContainsGCPtrType(Type *Ty) {
+/// Returns true if this type contains a gc pointer whether we know how to
+/// handle that type or not.
+static bool containsGCPtrType(Type *Ty) {
+ if(isGCPointerType(Ty))
+ return true;
if (VectorType *VT = dyn_cast<VectorType>(Ty))
return isGCPointerType(VT->getScalarType());
if (ArrayType *AT = dyn_cast<ArrayType>(Ty))
- return isGCPointerType(AT->getElementType()) ||
- isAggWhichContainsGCPtrType(AT->getElementType());
+ return containsGCPtrType(AT->getElementType());
if (StructType *ST = dyn_cast<StructType>(Ty))
return std::any_of(ST->subtypes().begin(), ST->subtypes().end(),
[](Type *SubType) {
- return isGCPointerType(SubType) ||
- isAggWhichContainsGCPtrType(SubType);
+ return containsGCPtrType(SubType);
});
return false;
}
+
+// Returns true if this is a type which a) is a gc pointer or contains a GC
+// pointer and b) is of a type which the code doesn't expect (i.e. first class
+// aggregates). Used to trip assertions.
+static bool isUnhandledGCPointerType(Type *Ty) {
+ return containsGCPtrType(Ty) && !isHandledGCPointerType(Ty);
+}
#endif
+/// Return true if the Value is a gc reference type which is potentially used
+/// after the instruction 'loc'. This is only used with the edge reachability
+/// liveness code. Note: It is assumed the V dominates loc.
+static bool isLiveGCReferenceAt(Value &V, Instruction *Loc, DominatorTree &DT,
+ LoopInfo *LI) {
+ if (!isHandledGCPointerType(V.getType()))
+ return false;
+
+ if (V.use_empty())
+ return false;
+
+ // Given assumption that V dominates loc, this may be live
+ return true;
+}
+
// Conservatively identifies any definitions which might be live at the
// given instruction. The analysis is performed immediately before the
// given instruction. Values defined by that instruction are not considered
// Are there any gc pointer arguments live over this point? This needs to be
// special cased since arguments aren't defined in basic blocks.
for (Argument &arg : F->args()) {
- assert(!isAggWhichContainsGCPtrType(arg.getType()) &&
+ assert(!isUnhandledGCPointerType(arg.getType()) &&
"support for FCA unimplemented");
if (is_live_gc_reference(arg)) {
break;
}
- assert(!isAggWhichContainsGCPtrType(inst.getType()) &&
+ assert(!isUnhandledGCPointerType(inst.getType()) &&
"support for FCA unimplemented");
if (is_live_gc_reference(inst)) {
result.liveset = liveset;
}
+/// If we can trivially determine that this vector contains only base pointers,
+/// return the base instruction.
+static Value *findBaseOfVector(Value *I) {
+ assert(I->getType()->isVectorTy() &&
+ cast<VectorType>(I->getType())->getElementType()->isPointerTy() &&
+ "Illegal to ask for the base pointer of a non-pointer type");
+
+ // Each case parallels findBaseDefiningValue below, see that code for
+ // detailed motivation.
+
+ if (isa<Argument>(I))
+ // An incoming argument to the function is a base pointer
+ return I;
+
+ // We shouldn't see the address of a global as a vector value?
+ assert(!isa<GlobalVariable>(I) &&
+ "unexpected global variable found in base of vector");
+
+ // inlining could possibly introduce phi node that contains
+ // undef if callee has multiple returns
+ if (isa<UndefValue>(I))
+ // utterly meaningless, but useful for dealing with partially optimized
+ // code.
+ return I;
+
+ // Due to inheritance, this must be _after_ the global variable and undef
+ // checks
+ if (Constant *Con = dyn_cast<Constant>(I)) {
+ assert(!isa<GlobalVariable>(I) && !isa<UndefValue>(I) &&
+ "order of checks wrong!");
+ assert(Con->isNullValue() && "null is the only case which makes sense");
+ return Con;
+ }
+
+ if (isa<LoadInst>(I))
+ return I;
+
+ // Note: This code is currently rather incomplete. We are essentially only
+ // handling cases where the vector element is trivially a base pointer. We
+ // need to update the entire base pointer construction algorithm to know how
+ // to track vector elements and potentially scalarize, but the case which
+ // would motivate the work hasn't shown up in real workloads yet.
+ llvm_unreachable("no base found for vector element");
+}
+
/// Helper function for findBasePointer - Will return a value which either a)
/// defines the base pointer for the input or b) blocks the simple search
/// (i.e. a PHI or Select of two derived pointers)
assert(I->getType()->isPointerTy() &&
"Illegal to ask for the base pointer of a non-pointer type");
- // There are instructions which can never return gc pointer values. Sanity
- // check that this is actually true.
- assert(!isa<InsertElementInst>(I) && !isa<ExtractElementInst>(I) &&
- !isa<ShuffleVectorInst>(I) && "Vector types are not gc pointers");
+ // This case is a bit of a hack - it only handles extracts from vectors which
+ // trivially contain only base pointers. See note inside the function for
+ // how to improve this.
+ if (auto *EEI = dyn_cast<ExtractElementInst>(I)) {
+ Value *VectorOperand = EEI->getVectorOperand();
+ Value *VectorBase = findBaseOfVector(VectorOperand);
+ assert(VectorBase && "extract element not known to be a trivial base");
+ return EEI;
+ }
if (isa<Argument>(I))
// An incoming argument to the function is a base pointer
assert(liveset.size() == PointerToBase.size());
}
+/// Remove any vector of pointers from the liveset by scalarizing them over the
+/// statepoint instruction. Adds the scalarized pieces to the liveset. It
+/// would be preferrable to include the vector in the statepoint itself, but
+/// the lowering code currently does not handle that. Extending it would be
+/// slightly non-trivial since it requires a format change. Given how rare
+/// such cases are (for the moment?) scalarizing is an acceptable comprimise.
+static void splitVectorValues(Instruction *StatepointInst,
+ StatepointLiveSetTy& LiveSet, DominatorTree &DT) {
+ SmallVector<Value *, 16> ToSplit;
+ for (Value *V : LiveSet)
+ if (isa<VectorType>(V->getType()))
+ ToSplit.push_back(V);
+
+ if (ToSplit.empty())
+ return;
+
+ Function &F = *(StatepointInst->getParent()->getParent());
+
+ DenseMap<Value*, AllocaInst*> AllocaMap;
+ // First is normal return, second is exceptional return (invoke only)
+ DenseMap<Value*, std::pair<Value*,Value*>> Replacements;
+ for (Value *V : ToSplit) {
+ LiveSet.erase(V);
+
+ AllocaInst *Alloca = new AllocaInst(V->getType(), "",
+ F.getEntryBlock().getFirstNonPHI());
+ AllocaMap[V] = Alloca;
+
+ VectorType *VT = cast<VectorType>(V->getType());
+ IRBuilder<> Builder(StatepointInst);
+ SmallVector<Value*, 16> Elements;
+ for (unsigned i = 0; i < VT->getNumElements(); i++)
+ Elements.push_back(Builder.CreateExtractElement(V, Builder.getInt32(i)));
+ LiveSet.insert(Elements.begin(), Elements.end());
+
+ auto InsertVectorReform = [&](Instruction *IP) {
+ Builder.SetInsertPoint(IP);
+ Builder.SetCurrentDebugLocation(IP->getDebugLoc());
+ Value *ResultVec = UndefValue::get(VT);
+ for (unsigned i = 0; i < VT->getNumElements(); i++)
+ ResultVec = Builder.CreateInsertElement(ResultVec, Elements[i],
+ Builder.getInt32(i));
+ return ResultVec;
+ };
+
+ if (isa<CallInst>(StatepointInst)) {
+ BasicBlock::iterator Next(StatepointInst);
+ Next++;
+ Instruction *IP = &*(Next);
+ Replacements[V].first = InsertVectorReform(IP);
+ Replacements[V].second = nullptr;
+ } else {
+ InvokeInst *Invoke = cast<InvokeInst>(StatepointInst);
+ // We've already normalized - check that we don't have shared destination
+ // blocks
+ BasicBlock *NormalDest = Invoke->getNormalDest();
+ assert(!isa<PHINode>(NormalDest->begin()));
+ BasicBlock *UnwindDest = Invoke->getUnwindDest();
+ assert(!isa<PHINode>(UnwindDest->begin()));
+ // Insert insert element sequences in both successors
+ Instruction *IP = &*(NormalDest->getFirstInsertionPt());
+ Replacements[V].first = InsertVectorReform(IP);
+ IP = &*(UnwindDest->getFirstInsertionPt());
+ Replacements[V].second = InsertVectorReform(IP);
+ }
+ }
+ for (Value *V : ToSplit) {
+ AllocaInst *Alloca = AllocaMap[V];
+
+ // Capture all users before we start mutating use lists
+ SmallVector<Instruction*, 16> Users;
+ for (User *U : V->users())
+ Users.push_back(cast<Instruction>(U));
+
+ for (Instruction *I : Users) {
+ if (auto Phi = dyn_cast<PHINode>(I)) {
+ for (unsigned i = 0; i < Phi->getNumIncomingValues(); i++)
+ if (V == Phi->getIncomingValue(i)) {
+ LoadInst *Load = new LoadInst(Alloca, "",
+ Phi->getIncomingBlock(i)->getTerminator());
+ Phi->setIncomingValue(i, Load);
+ }
+ } else {
+ LoadInst *Load = new LoadInst(Alloca, "", I);
+ I->replaceUsesOfWith(V, Load);
+ }
+ }
+
+ // Store the original value and the replacement value into the alloca
+ StoreInst *Store = new StoreInst(V, Alloca);
+ if (auto I = dyn_cast<Instruction>(V))
+ Store->insertAfter(I);
+ else
+ Store->insertAfter(Alloca);
+
+ // Normal return for invoke, or call return
+ Instruction *Replacement = cast<Instruction>(Replacements[V].first);
+ (new StoreInst(Replacement, Alloca))->insertAfter(Replacement);
+ // Unwind return for invoke only
+ Replacement = cast_or_null<Instruction>(Replacements[V].second);
+ if (Replacement)
+ (new StoreInst(Replacement, Alloca))->insertAfter(Replacement);
+ }
+
+ // apply mem2reg to promote alloca to SSA
+ SmallVector<AllocaInst*, 16> Allocas;
+ for (Value *V : ToSplit)
+ Allocas.push_back(AllocaMap[V]);
+ PromoteMemToReg(Allocas, DT);
+}
+
static bool insertParsePoints(Function &F, DominatorTree &DT, Pass *P,
SmallVectorImpl<CallSite> &toUpdate) {
#ifndef NDEBUG
SmallVector<Value *, 64> DeoptValues;
for (Use &U : StatepointCS.vm_state_args()) {
Value *Arg = cast<Value>(&U);
- if (isGCPointerType(Arg->getType()))
+ assert(!isUnhandledGCPointerType(Arg->getType()) &&
+ "support for FCA unimplemented");
+ if (isHandledGCPointerType(Arg->getType()))
DeoptValues.push_back(Arg);
}
insertUseHolderAfter(CS, DeoptValues, holders);
// site.
findLiveReferences(F, DT, P, toUpdate, records);
+ // Do a limited scalarization of any live at safepoint vector values which
+ // contain pointers. This enables this pass to run after vectorization at
+ // the cost of some possible performance loss. TODO: it would be nice to
+ // natively support vectors all the way through the backend so we don't need
+ // to scalarize here.
+ for (size_t i = 0; i < records.size(); i++) {
+ struct PartiallyConstructedSafepointRecord &info = records[i];
+ Instruction *statepoint = toUpdate[i].getInstruction();
+ splitVectorValues(cast<Instruction>(statepoint), info.liveset, DT);
+ }
+
// B) Find the base pointers for each live pointer
/* scope for caching */ {
// Cache the 'defining value' relation used in the computation and
projects / oota-llvm.git / blobdiff