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;
}
-/// True iff this value is the null pointer constant (of any pointer type)
-static bool LLVM_ATTRIBUTE_UNUSED isNullConstant(Value *V) {
- return isa<Constant>(V) && isa<PointerType>(V->getType()) &&
- cast<Constant>(V)->isNullValue();
+/// 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)
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);
+ (void)VectorBase;
+ 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
// off a potentially null value and have proven it null. We also use
// null pointers in dead paths of relocation phis (which we might later
// want to find a base pointer for).
- assert(Con->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- assert(Con->isNullValue() && "null is the only case which makes sense");
+ assert(isa<ConstantPointerNull>(Con) &&
+ "null is the only case which makes sense");
return Con;
}
}
/// Returns the base defining value for this value.
-static Value *findBaseDefiningValueCached(Value *I, DefiningValueMapTy &cache) {
- Value *&Cached = cache[I];
+static Value *findBaseDefiningValueCached(Value *I, DefiningValueMapTy &Cache) {
+ Value *&Cached = Cache[I];
if (!Cached) {
Cached = findBaseDefiningValue(I);
}
- assert(cache[I] != nullptr);
+ assert(Cache[I] != nullptr);
if (TraceLSP) {
- errs() << "fBDV-cached: " << I->getName() << " -> " << Cached->getName()
+ dbgs() << "fBDV-cached: " << I->getName() << " -> " << Cached->getName()
<< "\n";
}
return Cached;
/// Return a base pointer for this value if known. Otherwise, return it's
/// base defining value.
-static Value *findBaseOrBDV(Value *I, DefiningValueMapTy &cache) {
- Value *def = findBaseDefiningValueCached(I, cache);
- auto Found = cache.find(def);
- if (Found != cache.end()) {
+static Value *findBaseOrBDV(Value *I, DefiningValueMapTy &Cache) {
+ Value *Def = findBaseDefiningValueCached(I, Cache);
+ auto Found = Cache.find(Def);
+ if (Found != Cache.end()) {
// Either a base-of relation, or a self reference. Caller must check.
return Found->second;
}
// Only a BDV available
- return def;
+ return Def;
}
/// Given the result of a call to findBaseDefiningValue, or findBaseOrBDV,
/// is it known to be a base pointer? Or do we need to continue searching.
-static bool isKnownBaseResult(Value *v) {
- if (!isa<PHINode>(v) && !isa<SelectInst>(v)) {
+static bool isKnownBaseResult(Value *V) {
+ if (!isa<PHINode>(V) && !isa<SelectInst>(V)) {
// no recursion possible
return true;
}
- if (cast<Instruction>(v)->getMetadata("is_base_value")) {
+ if (isa<Instruction>(V) &&
+ cast<Instruction>(V)->getMetadata("is_base_value")) {
// This is a previously inserted base phi or select. We know
// that this is a base value.
return true;
// If you see this trip and like to live really dangerously, the code should
// be correct, just with idioms the verifier can't handle. You can try
// disabling the verifier at your own substaintial risk.
- assert(!isNullConstant(base) && "the relocation code needs adjustment to "
- "handle the relocation of a null pointer "
- "constant without causing false positives "
- "in the safepoint ir verifier.");
+ assert(!isa<ConstantPointerNull>(base) &&
+ "the relocation code needs adjustment to handle the relocation of "
+ "a null pointer constant without causing false positives in the "
+ "safepoint ir verifier.");
}
}
Function &F, DominatorTree &DT, ArrayRef<Value *> live,
ArrayRef<struct PartiallyConstructedSafepointRecord> records) {
#ifndef NDEBUG
- int initialAllocaNum = 0;
-
- // record initial number of allocas
- for (inst_iterator itr = inst_begin(F), end = inst_end(F); itr != end;
- itr++) {
- if (isa<AllocaInst>(*itr))
- initialAllocaNum++;
- }
+ // record initial number of (static) allocas; we'll check we have the same
+ // number when we get done.
+ int InitialAllocaNum = 0;
+ for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end();
+ I != E; I++)
+ if (isa<AllocaInst>(*I))
+ InitialAllocaNum++;
#endif
// TODO-PERF: change data structures, reserve
}
} else {
assert((isa<Argument>(def) || isa<GlobalVariable>(def) ||
- (isa<Constant>(def) && cast<Constant>(def)->isNullValue())) &&
+ isa<ConstantPointerNull>(def)) &&
"Must be argument or global");
store->insertAfter(cast<Instruction>(alloca));
}
}
#ifndef NDEBUG
- for (inst_iterator itr = inst_begin(F), end = inst_end(F); itr != end;
- itr++) {
- if (isa<AllocaInst>(*itr))
- initialAllocaNum--;
- }
- assert(initialAllocaNum == 0 && "We must not introduce any extra allocas");
+ for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end();
+ I != E; I++)
+ if (isa<AllocaInst>(*I))
+ InitialAllocaNum--;
+ assert(InitialAllocaNum == 0 && "We must not introduce any extra allocas");
#endif
}
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
if (!shouldRewriteStatepointsIn(F))
return false;
- // Gather all the statepoints which need rewritten.
+ DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
+
+ // Gather all the statepoints which need rewritten. Be careful to only
+ // consider those in reachable code since we need to ask dominance queries
+ // when rewriting. We'll delete the unreachable ones in a moment.
SmallVector<CallSite, 64> ParsePointNeeded;
+ bool HasUnreachableStatepoint = false;
for (Instruction &I : inst_range(F)) {
// TODO: only the ones with the flag set!
- if (isStatepoint(I))
- ParsePointNeeded.push_back(CallSite(&I));
+ if (isStatepoint(I)) {
+ if (DT.isReachableFromEntry(I.getParent()))
+ ParsePointNeeded.push_back(CallSite(&I));
+ else
+ HasUnreachableStatepoint = true;
+ }
}
+ bool MadeChange = false;
+
+ // Delete any unreachable statepoints so that we don't have unrewritten
+ // statepoints surviving this pass. This makes testing easier and the
+ // resulting IR less confusing to human readers. Rather than be fancy, we
+ // just reuse a utility function which removes the unreachable blocks.
+ if (HasUnreachableStatepoint)
+ MadeChange |= removeUnreachableBlocks(F);
+
// Return early if no work to do.
if (ParsePointNeeded.empty())
- return false;
+ return MadeChange;
+
+ // As a prepass, go ahead and aggressively destroy single entry phi nodes.
+ // These are created by LCSSA. They have the effect of increasing the size
+ // of liveness sets for no good reason. It may be harder to do this post
+ // insertion since relocations and base phis can confuse things.
+ for (BasicBlock &BB : F)
+ if (BB.getUniquePredecessor()) {
+ MadeChange = true;
+ FoldSingleEntryPHINodes(&BB);
+ }
- DominatorTree &DT = getAnalysis<DominatorTreeWrapperPass>().getDomTree();
- return insertParsePoints(F, DT, this, ParsePointNeeded);
+ MadeChange |= insertParsePoints(F, DT, this, ParsePointNeeded);
+ return MadeChange;
}
projects / oota-llvm.git / blobdiff