#include "llvm/ADT/SetOperations.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/DenseSet.h"
+#include "llvm/ADT/SetVector.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/CallSite.h"
#include "llvm/IR/Dominators.h"
// Print the liveset found at the insert location
static cl::opt<bool> PrintLiveSet("spp-print-liveset", cl::Hidden,
cl::init(false));
-static cl::opt<bool> PrintLiveSetSize("spp-print-liveset-size",
- cl::Hidden, cl::init(false));
+static cl::opt<bool> PrintLiveSetSize("spp-print-liveset-size", cl::Hidden,
+ cl::init(false));
// Print out the base pointers for debugging
-static cl::opt<bool> PrintBasePointers("spp-print-base-pointers",
- cl::Hidden, cl::init(false));
+static cl::opt<bool> PrintBasePointers("spp-print-base-pointers", cl::Hidden,
+ cl::init(false));
+
+#ifdef XDEBUG
+static bool ClobberNonLive = true;
+#else
+static bool ClobberNonLive = false;
+#endif
+static cl::opt<bool, true> ClobberNonLiveOverride("rs4gc-clobber-non-live",
+ cl::location(ClobberNonLive),
+ cl::Hidden);
namespace {
struct RewriteStatepointsForGC : public FunctionPass {
"Make relocations explicit at statepoints", false, false)
namespace {
+struct GCPtrLivenessData {
+ /// Values defined in this block.
+ DenseMap<BasicBlock *, DenseSet<Value *>> KillSet;
+ /// Values used in this block (and thus live); does not included values
+ /// killed within this block.
+ DenseMap<BasicBlock *, DenseSet<Value *>> LiveSet;
+
+ /// Values live into this basic block (i.e. used by any
+ /// instruction in this basic block or ones reachable from here)
+ DenseMap<BasicBlock *, DenseSet<Value *>> LiveIn;
+
+ /// Values live out of this basic block (i.e. live into
+ /// any successor block)
+ DenseMap<BasicBlock *, DenseSet<Value *>> LiveOut;
+};
+
// The type of the internal cache used inside the findBasePointers family
// of functions. From the callers perspective, this is an opaque type and
// should not be inspected.
};
}
+/// Compute the live-in set for every basic block in the function
+static void computeLiveInValues(DominatorTree &DT, Function &F,
+ GCPtrLivenessData &Data);
+
+/// Given results from the dataflow liveness computation, find the set of live
+/// Values at a particular instruction.
+static void findLiveSetAtInst(Instruction *inst, GCPtrLivenessData &Data,
+ StatepointLiveSetTy &out);
+
// TODO: Once we can get to the GCStrategy, this becomes
// Optional<bool> isGCManagedPointer(const Value *V) const override {
// 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.)
+// is not encountered.)
static bool isHandledGCPointerType(Type *T) {
// We fully support gc pointers
if (isGCPointerType(T))
/// 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))
+ if (isGCPointerType(Ty))
return true;
if (VectorType *VT = dyn_cast<VectorType>(Ty))
return isGCPointerType(VT->getScalarType());
if (ArrayType *AT = dyn_cast<ArrayType>(Ty))
return containsGCPtrType(AT->getElementType());
if (StructType *ST = dyn_cast<StructType>(Ty))
- return std::any_of(ST->subtypes().begin(), ST->subtypes().end(),
- [](Type *SubType) {
- return containsGCPtrType(SubType);
- });
+ return std::any_of(
+ ST->subtypes().begin(), ST->subtypes().end(),
+ [](Type *SubType) { return containsGCPtrType(SubType); });
return false;
}
}
#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
-// live. Values used by that instruction are considered live.
-//
-// preconditions: valid IR graph, term is either a terminator instruction or
-// a call instruction, pred is the basic block of term, DT, LI are valid
-//
-// side effects: none, does not mutate IR
-//
-// postconditions: populates liveValues as discussed above
-static void findLiveGCValuesAtInst(Instruction *term, BasicBlock *pred,
- DominatorTree &DT, LoopInfo *LI,
- StatepointLiveSetTy &liveValues) {
- liveValues.clear();
-
- assert(isa<CallInst>(term) || isa<InvokeInst>(term) || term->isTerminator());
-
- Function *F = pred->getParent();
-
- auto is_live_gc_reference =
- [&](Value &V) { return isLiveGCReferenceAt(V, term, DT, LI); };
-
- // 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(!isUnhandledGCPointerType(arg.getType()) &&
- "support for FCA unimplemented");
-
- if (is_live_gc_reference(arg)) {
- liveValues.insert(&arg);
- }
- }
-
- // Walk through all dominating blocks - the ones which can contain
- // definitions used in this block - and check to see if any of the values
- // they define are used in locations potentially reachable from the
- // interesting instruction.
- BasicBlock *BBI = pred;
- while (true) {
- if (TraceLSP) {
- errs() << "[LSP] Looking at dominating block " << pred->getName() << "\n";
- }
- assert(DT.dominates(BBI, pred));
- assert(isPotentiallyReachable(BBI, pred, &DT) &&
- "dominated block must be reachable");
-
- // Walk through the instructions in dominating blocks and keep any
- // that have a use potentially reachable from the block we're
- // considering putting the safepoint in
- for (Instruction &inst : *BBI) {
- if (TraceLSP) {
- errs() << "[LSP] Looking at instruction ";
- inst.dump();
- }
-
- if (pred == BBI && (&inst) == term) {
- if (TraceLSP) {
- errs() << "[LSP] stopped because we encountered the safepoint "
- "instruction.\n";
- }
-
- // If we're in the block which defines the interesting instruction,
- // we don't want to include any values as live which are defined
- // _after_ the interesting line or as part of the line itself
- // i.e. "term" is the call instruction for a call safepoint, the
- // results of the call should not be considered live in that stackmap
- break;
- }
-
- assert(!isUnhandledGCPointerType(inst.getType()) &&
- "support for FCA unimplemented");
-
- if (is_live_gc_reference(inst)) {
- if (TraceLSP) {
- errs() << "[LSP] found live value for this safepoint ";
- inst.dump();
- term->dump();
- }
- liveValues.insert(&inst);
- }
- }
- if (!DT.getNode(BBI)->getIDom()) {
- assert(BBI == &F->getEntryBlock() &&
- "failed to find a dominator for something other than "
- "the entry block");
- break;
- }
- BBI = DT.getNode(BBI)->getIDom()->getBlock();
- }
-}
-
static bool order_by_name(llvm::Value *a, llvm::Value *b) {
if (a->hasName() && b->hasName()) {
return -1 == a->getName().compare(b->getName());
}
}
-/// Find the initial live set. Note that due to base pointer
-/// insertion, the live set may be incomplete.
-static void
-analyzeParsePointLiveness(DominatorTree &DT, const CallSite &CS,
- PartiallyConstructedSafepointRecord &result) {
+// 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
+// live. Values used by that instruction are considered live.
+static void analyzeParsePointLiveness(
+ DominatorTree &DT, GCPtrLivenessData &OriginalLivenessData,
+ const CallSite &CS, PartiallyConstructedSafepointRecord &result) {
Instruction *inst = CS.getInstruction();
- BasicBlock *BB = inst->getParent();
StatepointLiveSetTy liveset;
- findLiveGCValuesAtInst(inst, BB, DT, nullptr, liveset);
+ findLiveSetAtInst(inst, OriginalLivenessData, liveset);
if (PrintLiveSet) {
// Note: This output is used by several of the test cases
}
/// If we can trivially determine that this vector contains only base pointers,
-/// return the base instruction.
+/// return the base instruction.
static Value *findBaseOfVector(Value *I) {
assert(I->getType()->isVectorTy() &&
cast<VectorType>(I->getType())->getElementType()->isPointerTy() &&
if (isa<UndefValue>(I))
// utterly meaningless, but useful for dealing with partially optimized
// code.
- return I;
+ return I;
// Due to inheritance, this must be _after_ the global variable and undef
// checks
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<UndefValue>(I))
// utterly meaningless, but useful for dealing with
// partially optimized code.
- return I;
+ return I;
// Due to inheritance, this must be _after_ the global variable and undef
// checks
// predicate. From the perspective of base pointers, we just treat it
// like a load.
return I;
-
+
assert(!isa<AtomicRMWInst>(I) && "Xchg handled above, all others are "
- "binary ops which don't apply to pointers");
+ "binary ops which don't apply to pointers");
// The aggregate ops. Aggregates can either be in the heap or on the
// stack, but in either case, this is simply a field load. As a result,
// return a value which dynamically selects from amoung several base
// derived pointers (each with it's own base potentially). It's the job of
// the caller to resolve these.
- assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&
+ assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&
"missing instruction case in findBaseDefiningValing");
return I;
}
done = true;
// Since we're adding elements to 'states' as we run, we can't keep
// iterators into the set.
- SmallVector<Value*, 16> Keys;
+ SmallVector<Value *, 16> Keys;
Keys.reserve(states.size());
for (auto Pair : states) {
Value *V = Pair.first;
// We want to keep naming deterministic in the loop that follows, so
// sort the keys before iteration. This is useful in allowing us to
// write stable tests. Note that there is no invalidation issue here.
- SmallVector<Value*, 16> Keys;
+ SmallVector<Value *, 16> Keys;
Keys.reserve(states.size());
for (auto Pair : states) {
Value *V = Pair.first;
assert(!state.isUnknown() && "Optimistic algorithm didn't complete!");
if (!state.isConflict())
continue;
-
+
if (isa<PHINode>(v)) {
int num_preds =
std::distance(pred_begin(v->getParent()), pred_end(v->getParent()));
assert(!state.isUnknown() && "Optimistic algorithm didn't complete!");
if (!state.isConflict())
continue;
-
+
if (PHINode *basephi = dyn_cast<PHINode>(state.getBase())) {
PHINode *phi = cast<PHINode>(v);
unsigned NumPHIValues = phi->getNumIncomingValues();
// post condition: PointerToBase contains one (derived, base) pair for every
// pointer in live. Note that derived can be equal to base if the original
// pointer was a base pointer.
-static void findBasePointers(const StatepointLiveSetTy &live,
- DenseMap<llvm::Value *, llvm::Value *> &PointerToBase,
- DominatorTree *DT, DefiningValueMapTy &DVCache,
- DenseSet<llvm::Value *> &NewInsertedDefs) {
+static void
+findBasePointers(const StatepointLiveSetTy &live,
+ DenseMap<llvm::Value *, llvm::Value *> &PointerToBase,
+ DominatorTree *DT, DefiningValueMapTy &DVCache,
+ DenseSet<llvm::Value *> &NewInsertedDefs) {
// For the naming of values inserted to be deterministic - which makes for
// much cleaner and more stable tests - we need to assign an order to the
// live values. DenseSets do not provide a deterministic order across runs.
- SmallVector<Value*, 64> Temp;
+ SmallVector<Value *, 64> Temp;
Temp.insert(Temp.end(), live.begin(), live.end());
std::sort(Temp.begin(), Temp.end(), order_by_name);
for (Value *ptr : Temp) {
// 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(!isa<ConstantPointerNull>(base) &&
+ 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.");
PartiallyConstructedSafepointRecord &result) {
DenseMap<llvm::Value *, llvm::Value *> PointerToBase;
DenseSet<llvm::Value *> NewInsertedDefs;
- findBasePointers(result.liveset, PointerToBase, &DT, DVCache, NewInsertedDefs);
+ findBasePointers(result.liveset, PointerToBase, &DT, DVCache,
+ NewInsertedDefs);
if (PrintBasePointers) {
// Note: Need to print these in a stable order since this is checked in
// some tests.
errs() << "Base Pairs (w/o Relocation):\n";
- SmallVector<Value*, 64> Temp;
+ SmallVector<Value *, 64> Temp;
Temp.reserve(PointerToBase.size());
for (auto Pair : PointerToBase) {
Temp.push_back(Pair.first);
std::sort(Temp.begin(), Temp.end(), order_by_name);
for (Value *Ptr : Temp) {
Value *Base = PointerToBase[Ptr];
- errs() << " derived %" << Ptr->getName() << " base %"
- << Base->getName() << "\n";
+ errs() << " derived %" << Ptr->getName() << " base %" << Base->getName()
+ << "\n";
}
}
result.NewInsertedDefs = NewInsertedDefs;
}
-/// Check for liveness of items in the insert defs and add them to the live
-/// and base pointer sets
-static void fixupLiveness(DominatorTree &DT, const CallSite &CS,
- const DenseSet<Value *> &allInsertedDefs,
- PartiallyConstructedSafepointRecord &result) {
- Instruction *inst = CS.getInstruction();
-
- auto liveset = result.liveset;
- auto PointerToBase = result.PointerToBase;
-
- auto is_live_gc_reference =
- [&](Value &V) { return isLiveGCReferenceAt(V, inst, DT, nullptr); };
-
- // For each new definition, check to see if a) the definition dominates the
- // instruction we're interested in, and b) one of the uses of that definition
- // is edge-reachable from the instruction we're interested in. This is the
- // same definition of liveness we used in the intial liveness analysis
- for (Value *newDef : allInsertedDefs) {
- if (liveset.count(newDef)) {
- // already live, no action needed
- continue;
- }
-
- // PERF: Use DT to check instruction domination might not be good for
- // compilation time, and we could change to optimal solution if this
- // turn to be a issue
- if (!DT.dominates(cast<Instruction>(newDef), inst)) {
- // can't possibly be live at inst
- continue;
- }
-
- if (is_live_gc_reference(*newDef)) {
- // Add the live new defs into liveset and PointerToBase
- liveset.insert(newDef);
- PointerToBase[newDef] = newDef;
- }
- }
+/// Given an updated version of the dataflow liveness results, update the
+/// liveset and base pointer maps for the call site CS.
+static void recomputeLiveInValues(GCPtrLivenessData &RevisedLivenessData,
+ const CallSite &CS,
+ PartiallyConstructedSafepointRecord &result);
- result.liveset = liveset;
- result.PointerToBase = PointerToBase;
-}
-
-static void fixupLiveReferences(
- Function &F, DominatorTree &DT, Pass *P,
- const DenseSet<llvm::Value *> &allInsertedDefs,
- ArrayRef<CallSite> toUpdate,
+static void recomputeLiveInValues(
+ Function &F, DominatorTree &DT, Pass *P, ArrayRef<CallSite> toUpdate,
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
+ // TODO-PERF: reuse the original liveness, then simply run the dataflow
+ // again. The old values are still live and will help it stablize quickly.
+ GCPtrLivenessData RevisedLivenessData;
+ computeLiveInValues(DT, F, RevisedLivenessData);
for (size_t i = 0; i < records.size(); i++) {
struct PartiallyConstructedSafepointRecord &info = records[i];
const CallSite &CS = toUpdate[i];
- fixupLiveness(DT, CS, allInsertedDefs, info);
+ recomputeLiveInValues(RevisedLivenessData, CS, info);
}
}
// combination. This results is some blow up the function declarations in
// the IR, but removes the need for argument bitcasts which shrinks the IR
// greatly and makes it much more readable.
- SmallVector<Type *, 1> types; // one per 'any' type
+ SmallVector<Type *, 1> types; // one per 'any' type
types.push_back(liveVariables[i]->getType()); // result type
Value *gc_relocate_decl = Intrinsic::getDeclaration(
M, Intrinsic::experimental_gc_relocate, types);
// Take the name of the original value call if it had one.
token->takeName(CS.getInstruction());
- // The GCResult is already inserted, we just need to find it
+// The GCResult is already inserted, we just need to find it
#ifndef NDEBUG
Instruction *toReplace = CS.getInstruction();
assert((toReplace->hasNUses(0) || toReplace->hasNUses(1)) &&
// Second, create a gc.relocate for every live variable
CreateGCRelocates(liveVariables, live_start, basePtrs, token, Builder);
-
}
namespace {
// Replace an existing gc.statepoint with a new one and a set of gc.relocates
// which make the relocations happening at this safepoint explicit.
-//
+//
// WARNING: Does not do any fixup to adjust users of the original live
// values. That's the callers responsibility.
static void
// 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++)
+ for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end(); I != E;
+ I++)
if (isa<AllocaInst>(*I))
InitialAllocaNum++;
#endif
// In case if it was invoke statepoint
// we will insert stores for exceptional path gc relocates.
if (isa<InvokeInst>(Statepoint)) {
- insertRelocationStores(info.UnwindToken->users(),
- allocaMap, visitedLiveValues);
+ insertRelocationStores(info.UnwindToken->users(), allocaMap,
+ visitedLiveValues);
}
-#ifndef NDEBUG
- // As a debuging aid, pretend that an unrelocated pointer becomes null at
- // the gc.statepoint. This will turn some subtle GC problems into slightly
- // easier to debug SEGVs
- SmallVector<AllocaInst *, 64> ToClobber;
- for (auto Pair : allocaMap) {
- Value *Def = Pair.first;
- AllocaInst *Alloca = cast<AllocaInst>(Pair.second);
-
- // This value was relocated
- if (visitedLiveValues.count(Def)) {
- continue;
+ if (ClobberNonLive) {
+ // As a debuging aid, pretend that an unrelocated pointer becomes null at
+ // the gc.statepoint. This will turn some subtle GC problems into
+ // slightly easier to debug SEGVs. Note that on large IR files with
+ // lots of gc.statepoints this is extremely costly both memory and time
+ // wise.
+ SmallVector<AllocaInst *, 64> ToClobber;
+ for (auto Pair : allocaMap) {
+ Value *Def = Pair.first;
+ AllocaInst *Alloca = cast<AllocaInst>(Pair.second);
+
+ // This value was relocated
+ if (visitedLiveValues.count(Def)) {
+ continue;
+ }
+ ToClobber.push_back(Alloca);
}
- ToClobber.push_back(Alloca);
- }
- auto InsertClobbersAt = [&](Instruction *IP) {
- for (auto *AI : ToClobber) {
- auto AIType = cast<PointerType>(AI->getType());
- auto PT = cast<PointerType>(AIType->getElementType());
- Constant *CPN = ConstantPointerNull::get(PT);
- StoreInst *store = new StoreInst(CPN, AI);
- store->insertBefore(IP);
- }
- };
+ auto InsertClobbersAt = [&](Instruction *IP) {
+ for (auto *AI : ToClobber) {
+
auto AIType = cast<PointerType>(AI->getType());
+
auto PT = cast<PointerType>(AIType->getElementType());
+ Constant *CPN = ConstantPointerNull::get(PT);
+ StoreInst *store = new StoreInst(CPN, AI);
+ store->insertBefore(IP);
+ }
+ };
- // Insert the clobbering stores. These may get intermixed with the
- // gc.results and gc.relocates, but that's fine.
- if (auto II = dyn_cast<InvokeInst>(Statepoint)) {
- InsertClobbersAt(II->getNormalDest()->getFirstInsertionPt());
- InsertClobbersAt(II->getUnwindDest()->getFirstInsertionPt());
- } else {
- BasicBlock::iterator Next(cast<CallInst>(Statepoint));
- Next++;
- InsertClobbersAt(Next);
+ // Insert the clobbering stores. These may get intermixed with the
+ // gc.results and gc.relocates, but that's fine.
+ if (auto II = dyn_cast<InvokeInst>(Statepoint)) {
+ InsertClobbersAt(II->getNormalDest()->getFirstInsertionPt());
+ InsertClobbersAt(II->getUnwindDest()->getFirstInsertionPt());
+ } else {
+ BasicBlock::iterator Next(cast<CallInst>(Statepoint));
+ Next++;
+ InsertClobbersAt(Next);
+ }
}
-#endif
}
// update use with load allocas and add store for gc_relocated
for (auto Pair : allocaMap) {
assert(!inst->isTerminator() &&
"The only TerminatorInst that can produce a value is "
"InvokeInst which is handled above.");
- store->insertAfter(inst);
+ store->insertAfter(inst);
}
} else {
assert((isa<Argument>(def) || isa<GlobalVariable>(def) ||
}
#ifndef NDEBUG
- for (auto I = F.getEntryBlock().begin(), E = F.getEntryBlock().end();
- I != E; I++)
+ 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");
static void findLiveReferences(
Function &F, DominatorTree &DT, Pass *P, ArrayRef<CallSite> toUpdate,
MutableArrayRef<struct PartiallyConstructedSafepointRecord> records) {
+ GCPtrLivenessData OriginalLivenessData;
+ computeLiveInValues(DT, F, OriginalLivenessData);
for (size_t i = 0; i < records.size(); i++) {
struct PartiallyConstructedSafepointRecord &info = records[i];
const CallSite &CS = toUpdate[i];
- analyzeParsePointLiveness(DT, CS, info);
- }
-}
-
-static void addBasesAsLiveValues(StatepointLiveSetTy &liveset,
- DenseMap<Value *, Value *> &PointerToBase) {
- // Identify any base pointers which are used in this safepoint, but not
- // themselves relocated. We need to relocate them so that later inserted
- // safepoints can get the properly relocated base register.
- DenseSet<Value *> missing;
- for (Value *L : liveset) {
- assert(PointerToBase.find(L) != PointerToBase.end());
- Value *base = PointerToBase[L];
- assert(base);
- if (liveset.find(base) == liveset.end()) {
- assert(PointerToBase.find(base) == PointerToBase.end());
- // uniqued by set insert
- missing.insert(base);
- }
- }
-
- // Note that we want these at the end of the list, otherwise
- // register placement gets screwed up once we lower to STATEPOINT
- // instructions. This is an utter hack, but there doesn't seem to be a
- // better one.
- for (Value *base : missing) {
- assert(base);
- liveset.insert(base);
- PointerToBase[base] = base;
+ analyzeParsePointLiveness(DT, OriginalLivenessData, CS, info);
}
- assert(liveset.size() == PointerToBase.size());
}
/// Remove any vector of pointers from the liveset by scalarizing them over the
/// 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) {
+ StatepointLiveSetTy &LiveSet, DominatorTree &DT) {
SmallVector<Value *, 16> ToSplit;
for (Value *V : LiveSet)
if (isa<VectorType>(V->getType()))
Function &F = *(StatepointInst->getParent()->getParent());
- DenseMap<Value*, AllocaInst*> AllocaMap;
+ DenseMap<Value *, AllocaInst *> AllocaMap;
// First is normal return, second is exceptional return (invoke only)
- DenseMap<Value*, std::pair<Value*,Value*>> Replacements;
+ DenseMap<Value *, std::pair<Value *, Value *>> Replacements;
for (Value *V : ToSplit) {
LiveSet.erase(V);
- AllocaInst *Alloca = new AllocaInst(V->getType(), "",
- F.getEntryBlock().getFirstNonPHI());
+ 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;
+ 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());
} else {
InvokeInst *Invoke = cast<InvokeInst>(StatepointInst);
// We've already normalized - check that we don't have shared destination
- // blocks
+ // blocks
BasicBlock *NormalDest = Invoke->getNormalDest();
assert(!isa<PHINode>(NormalDest->begin()));
BasicBlock *UnwindDest = Invoke->getUnwindDest();
AllocaInst *Alloca = AllocaMap[V];
// Capture all users before we start mutating use lists
- SmallVector<Instruction*, 16> Users;
+ SmallVector<Instruction *, 16> Users;
for (User *U : V->users())
Users.push_back(cast<Instruction>(U));
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());
+ LoadInst *Load = new LoadInst(
+ Alloca, "", Phi->getIncomingBlock(i)->getTerminator());
Phi->setIncomingValue(i, Load);
}
} else {
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);
}
// apply mem2reg to promote alloca to SSA
- SmallVector<AllocaInst*, 16> Allocas;
+ SmallVector<AllocaInst *, 16> Allocas;
for (Value *V : ToSplit)
Allocas.push_back(AllocaMap[V]);
PromoteMemToReg(Allocas, DT);
insertUseHolderAfter(CS, Bases, holders);
}
- // Add the bases explicitly to the live vector set. This may result in a few
- // extra relocations, but the base has to be available whenever a pointer
- // derived from it is used. Thus, we need it to be part of the statepoint's
- // gc arguments list. TODO: Introduce an explicit notion (in the following
- // code) of the GC argument list as seperate from the live Values at a
- // given statepoint.
- for (size_t i = 0; i < records.size(); i++) {
- struct PartiallyConstructedSafepointRecord &info = records[i];
- addBasesAsLiveValues(info.liveset, info.PointerToBase);
- }
+ // By selecting base pointers, we've effectively inserted new uses. Thus, we
+ // need to rerun liveness. We may *also* have inserted new defs, but that's
+ // not the key issue.
+ recomputeLiveInValues(F, DT, P, toUpdate, records);
- // If we inserted any new values, we need to adjust our notion of what is
- // live at a particular safepoint.
- if (!allInsertedDefs.empty()) {
- fixupLiveReferences(F, DT, P, allInsertedDefs, toUpdate, records);
- }
if (PrintBasePointers) {
for (size_t i = 0; i < records.size(); i++) {
struct PartiallyConstructedSafepointRecord &info = records[i];
return false;
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;
- SmallVector<CallSite, 16> UnreachableStatepoints;
+ bool HasUnreachableStatepoint = false;
for (Instruction &I : inst_range(F)) {
// TODO: only the ones with the flag set!
if (isStatepoint(I)) {
if (DT.isReachableFromEntry(I.getParent()))
ParsePointNeeded.push_back(CallSite(&I));
else
- UnreachableStatepoints.push_back(CallSite(&I));
+ 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 (!UnreachableStatepoints.empty())
+ if (HasUnreachableStatepoint)
MadeChange |= removeUnreachableBlocks(F);
// Return early if no work to do.
MadeChange |= insertParsePoints(F, DT, this, ParsePointNeeded);
return MadeChange;
}
+
+// liveness computation via standard dataflow
+// -------------------------------------------------------------------
+
+// TODO: Consider using bitvectors for liveness, the set of potentially
+// interesting values should be small and easy to pre-compute.
+
+/// Is this value a constant consisting of entirely null values?
+static bool isConstantNull(Value *V) {
+ return isa<Constant>(V) && cast<Constant>(V)->isNullValue();
+}
+
+/// Compute the live-in set for the location rbegin starting from
+/// the live-out set of the basic block
+static void computeLiveInValues(BasicBlock::reverse_iterator rbegin,
+ BasicBlock::reverse_iterator rend,
+ DenseSet<Value *> &LiveTmp) {
+
+ for (BasicBlock::reverse_iterator ritr = rbegin; ritr != rend; ritr++) {
+ Instruction *I = &*ritr;
+
+ // KILL/Def - Remove this definition from LiveIn
+ LiveTmp.erase(I);
+
+ // Don't consider *uses* in PHI nodes, we handle their contribution to
+ // predecessor blocks when we seed the LiveOut sets
+ if (isa<PHINode>(I))
+ continue;
+
+ // USE - Add to the LiveIn set for this instruction
+ for (Value *V : I->operands()) {
+ assert(!isUnhandledGCPointerType(V->getType()) &&
+ "support for FCA unimplemented");
+ if (isHandledGCPointerType(V->getType()) && !isConstantNull(V) &&
+ !isa<UndefValue>(V)) {
+ // The choice to exclude null and undef is arbitrary here. Reconsider?
+ LiveTmp.insert(V);
+ }
+ }
+ }
+}
+
+static void computeLiveOutSeed(BasicBlock *BB, DenseSet<Value *> &LiveTmp) {
+
+ for (BasicBlock *Succ : successors(BB)) {
+ const BasicBlock::iterator E(Succ->getFirstNonPHI());
+ for (BasicBlock::iterator I = Succ->begin(); I != E; I++) {
+ PHINode *Phi = cast<PHINode>(&*I);
+ Value *V = Phi->getIncomingValueForBlock(BB);
+ assert(!isUnhandledGCPointerType(V->getType()) &&
+ "support for FCA unimplemented");
+ if (isHandledGCPointerType(V->getType()) && !isConstantNull(V) &&
+ !isa<UndefValue>(V)) {
+ // The choice to exclude null and undef is arbitrary here. Reconsider?
+ LiveTmp.insert(V);
+ }
+ }
+ }
+}
+
+static DenseSet<Value *> computeKillSet(BasicBlock *BB) {
+ DenseSet<Value *> KillSet;
+ for (Instruction &I : *BB)
+ if (isHandledGCPointerType(I.getType()))
+ KillSet.insert(&I);
+ return KillSet;
+}
+
+#ifndef NDEBUG
+/// Check that the items in 'Live' dominate 'TI'. This is used as a basic
+/// sanity check for the liveness computation.
+static void checkBasicSSA(DominatorTree &DT, DenseSet<Value *> &Live,
+ TerminatorInst *TI, bool TermOkay = false) {
+ for (Value *V : Live) {
+ if (auto *I = dyn_cast<Instruction>(V)) {
+ // The terminator can be a member of the LiveOut set. LLVM's definition
+ // of instruction dominance states that V does not dominate itself. As
+ // such, we need to special case this to allow it.
+ if (TermOkay && TI == I)
+ continue;
+ assert(DT.dominates(I, TI) &&
+ "basic SSA liveness expectation violated by liveness analysis");
+ }
+ }
+}
+
+/// Check that all the liveness sets used during the computation of liveness
+/// obey basic SSA properties. This is useful for finding cases where we miss
+/// a def.
+static void checkBasicSSA(DominatorTree &DT, GCPtrLivenessData &Data,
+ BasicBlock &BB) {
+ checkBasicSSA(DT, Data.LiveSet[&BB], BB.getTerminator());
+ checkBasicSSA(DT, Data.LiveOut[&BB], BB.getTerminator(), true);
+ checkBasicSSA(DT, Data.LiveIn[&BB], BB.getTerminator());
+}
+#endif
+
+static void computeLiveInValues(DominatorTree &DT, Function &F,
+ GCPtrLivenessData &Data) {
+
+ SmallSetVector<BasicBlock *, 200> Worklist;
+ auto AddPredsToWorklist = [&](BasicBlock *BB) {
+ // We use a SetVector so that we don't have duplicates in the worklist.
+ Worklist.insert(pred_begin(BB), pred_end(BB));
+ };
+ auto NextItem = [&]() {
+ BasicBlock *BB = Worklist.back();
+ Worklist.pop_back();
+ return BB;
+ };
+
+ // Seed the liveness for each individual block
+ for (BasicBlock &BB : F) {
+ Data.KillSet[&BB] = computeKillSet(&BB);
+ Data.LiveSet[&BB].clear();
+ computeLiveInValues(BB.rbegin(), BB.rend(), Data.LiveSet[&BB]);
+
+#ifndef NDEBUG
+ for (Value *Kill : Data.KillSet[&BB])
+ assert(!Data.LiveSet[&BB].count(Kill) && "live set contains kill");
+#endif
+
+ Data.LiveOut[&BB] = DenseSet<Value *>();
+ computeLiveOutSeed(&BB, Data.LiveOut[&BB]);
+ Data.LiveIn[&BB] = Data.LiveSet[&BB];
+ set_union(Data.LiveIn[&BB], Data.LiveOut[&BB]);
+ set_subtract(Data.LiveIn[&BB], Data.KillSet[&BB]);
+ if (!Data.LiveIn[&BB].empty())
+ AddPredsToWorklist(&BB);
+ }
+
+ // Propagate that liveness until stable
+ while (!Worklist.empty()) {
+ BasicBlock *BB = NextItem();
+
+ // Compute our new liveout set, then exit early if it hasn't changed
+ // despite the contribution of our successor.
+ DenseSet<Value *> LiveOut = Data.LiveOut[BB];
+ const auto OldLiveOutSize = LiveOut.size();
+ for (BasicBlock *Succ : successors(BB)) {
+ assert(Data.LiveIn.count(Succ));
+ set_union(LiveOut, Data.LiveIn[Succ]);
+ }
+ // assert OutLiveOut is a subset of LiveOut
+ if (OldLiveOutSize == LiveOut.size()) {
+ // If the sets are the same size, then we didn't actually add anything
+ // when unioning our successors LiveIn Thus, the LiveIn of this block
+ // hasn't changed.
+ continue;
+ }
+ Data.LiveOut[BB] = LiveOut;
+
+ // Apply the effects of this basic block
+ DenseSet<Value *> LiveTmp = LiveOut;
+ set_union(LiveTmp, Data.LiveSet[BB]);
+ set_subtract(LiveTmp, Data.KillSet[BB]);
+
+ assert(Data.LiveIn.count(BB));
+ const DenseSet<Value *> &OldLiveIn = Data.LiveIn[BB];
+ // assert: OldLiveIn is a subset of LiveTmp
+ if (OldLiveIn.size() != LiveTmp.size()) {
+ Data.LiveIn[BB] = LiveTmp;
+ AddPredsToWorklist(BB);
+ }
+ } // while( !worklist.empty() )
+
+#ifndef NDEBUG
+ // Sanity check our ouput against SSA properties. This helps catch any
+ // missing kills during the above iteration.
+ for (BasicBlock &BB : F) {
+ checkBasicSSA(DT, Data, BB);
+ }
+#endif
+}
+
+static void findLiveSetAtInst(Instruction *Inst, GCPtrLivenessData &Data,
+ StatepointLiveSetTy &Out) {
+
+ BasicBlock *BB = Inst->getParent();
+
+ // Note: The copy is intentional and required
+ assert(Data.LiveOut.count(BB));
+ DenseSet<Value *> LiveOut = Data.LiveOut[BB];
+
+ // We want to handle the statepoint itself oddly. It's
+ // call result is not live (normal), nor are it's arguments
+ // (unless they're used again later). This adjustment is
+ // specifically what we need to relocate
+ BasicBlock::reverse_iterator rend(Inst);
+ computeLiveInValues(BB->rbegin(), rend, LiveOut);
+ LiveOut.erase(Inst);
+ Out.insert(LiveOut.begin(), LiveOut.end());
+}
+
+static void recomputeLiveInValues(GCPtrLivenessData &RevisedLivenessData,
+ const CallSite &CS,
+ PartiallyConstructedSafepointRecord &Info) {
+ Instruction *Inst = CS.getInstruction();
+ StatepointLiveSetTy Updated;
+ findLiveSetAtInst(Inst, RevisedLivenessData, Updated);
+
+#ifndef NDEBUG
+ DenseSet<Value *> Bases;
+ for (auto KVPair : Info.PointerToBase) {
+ Bases.insert(KVPair.second);
+ }
+#endif
+ // We may have base pointers which are now live that weren't before. We need
+ // to update the PointerToBase structure to reflect this.
+ for (auto V : Updated)
+ if (!Info.PointerToBase.count(V)) {
+ assert(Bases.count(V) && "can't find base for unexpected live value");
+ Info.PointerToBase[V] = V;
+ continue;
+ }
+
+#ifndef NDEBUG
+ for (auto V : Updated) {
+ assert(Info.PointerToBase.count(V) &&
+ "must be able to find base for live value");
+ }
+#endif
+
+ // Remove any stale base mappings - this can happen since our liveness is
+ // more precise then the one inherent in the base pointer analysis
+ DenseSet<Value *> ToErase;
+ for (auto KVPair : Info.PointerToBase)
+ if (!Updated.count(KVPair.first))
+ ToErase.insert(KVPair.first);
+ for (auto V : ToErase)
+ Info.PointerToBase.erase(V);
+
+#ifndef NDEBUG
+ for (auto KVPair : Info.PointerToBase)
+ assert(Updated.count(KVPair.first) && "record for non-live value");
+#endif
+
+ Info.liveset = Updated;
+}
projects / oota-llvm.git / blobdiff