#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 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 std::any_of(
+ ST->subtypes().begin(), ST->subtypes().end(),
+ [](Type *SubType) { return containsGCPtrType(SubType); });
return false;
}
-#endif
-
-// 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(!isAggWhichContainsGCPtrType(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(!isAggWhichContainsGCPtrType(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();
- }
+// 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
static bool order_by_name(llvm::Value *a, llvm::Value *b) {
if (a->hasName() && b->hasName()) {
}
}
-/// 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
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");
- assert((!isa<Instruction>(I) || isa<InvokeInst>(I) ||
- !cast<Instruction>(I)->isTerminator()) &&
- "With the exception of invoke terminators don't define values");
- assert(!isa<StoreInst>(I) && !isa<FenceInst>(I) &&
- "Can't be definitions to start with");
- assert(!isa<ICmpInst>(I) && !isa<FCmpInst>(I) &&
- "Comparisons don't give ops");
- // There's a bunch of instructions which just don't make sense to apply to
- // a pointer. The only valid reason for this would be pointer bit
- // twiddling which we're just not going to support.
- assert((!isa<Instruction>(I) || !cast<Instruction>(I)->isBinaryOp()) &&
- "Binary ops on pointer values are meaningless. Unless your "
- "bit-twiddling which we don't support");
-
- if (Argument *Arg = dyn_cast<Argument>(I)) {
+ // 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
// We should have never reached here if this argument isn't an gc value
- assert(Arg->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return Arg;
- }
+ return I;
- if (GlobalVariable *global = dyn_cast<GlobalVariable>(I)) {
+ if (isa<GlobalVariable>(I))
// base case
- assert(global->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return global;
- }
+ return I;
// inlining could possibly introduce phi node that contains
// undef if callee has multiple returns
- if (UndefValue *undef = dyn_cast<UndefValue>(I)) {
- assert(undef->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return undef; // utterly meaningless, but useful for dealing with
- // partially optimized code.
- }
+ 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)) {
+ if (Constant *Con = dyn_cast<Constant>(I)) {
assert(!isa<GlobalVariable>(I) && !isa<UndefValue>(I) &&
"order of checks wrong!");
// Note: Finding a constant base for something marked for relocation
// 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");
- return con;
+ assert(isa<ConstantPointerNull>(Con) &&
+ "null is the only case which makes sense");
+ return Con;
}
if (CastInst *CI = dyn_cast<CastInst>(I)) {
- Value *def = CI->stripPointerCasts();
- assert(def->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
+ Value *Def = CI->stripPointerCasts();
// If we find a cast instruction here, it means we've found a cast which is
// not simply a pointer cast (i.e. an inttoptr). We don't know how to
// handle int->ptr conversion.
- assert(!isa<CastInst>(def) && "shouldn't find another cast here");
- return findBaseDefiningValue(def);
+ assert(!isa<CastInst>(Def) && "shouldn't find another cast here");
+ return findBaseDefiningValue(Def);
}
- if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
- if (LI->getType()->isPointerTy()) {
- Value *Op = LI->getOperand(0);
- (void)Op;
- // Has to be a pointer to an gc object, or possibly an array of such?
- assert(Op->getType()->isPointerTy());
- return LI; // The value loaded is an gc base itself
- }
- }
- if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
- Value *Op = GEP->getOperand(0);
- if (Op->getType()->isPointerTy()) {
- return findBaseDefiningValue(Op); // The base of this GEP is the base
- }
- }
+ if (isa<LoadInst>(I))
+ return I; // The value loaded is an gc base itself
- if (AllocaInst *alloc = dyn_cast<AllocaInst>(I)) {
- // An alloca represents a conceptual stack slot. It's the slot itself
- // that the GC needs to know about, not the value in the slot.
- assert(alloc->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return alloc;
- }
+ if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I))
+ // The base of this GEP is the base
+ return findBaseDefiningValue(GEP->getPointerOperand());
if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(I)) {
switch (II->getIntrinsicID()) {
+ case Intrinsic::experimental_gc_result_ptr:
default:
// fall through to general call handling
break;
case Intrinsic::experimental_gc_result_float:
case Intrinsic::experimental_gc_result_int:
llvm_unreachable("these don't produce pointers");
- case Intrinsic::experimental_gc_result_ptr:
- // This is just a special case of the CallInst check below to handle a
- // statepoint with deopt args which hasn't been rewritten for GC yet.
- // TODO: Assert that the statepoint isn't rewritten yet.
- return II;
case Intrinsic::experimental_gc_relocate: {
// Rerunning safepoint insertion after safepoints are already
// inserted is not supported. It could probably be made to work,
// We assume that functions in the source language only return base
// pointers. This should probably be generalized via attributes to support
// both source language and internal functions.
- if (CallInst *call = dyn_cast<CallInst>(I)) {
- assert(call->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return call;
- }
- if (InvokeInst *invoke = dyn_cast<InvokeInst>(I)) {
- assert(invoke->getType()->isPointerTy() &&
- "Base for pointer must be another pointer");
- return invoke;
- }
+ if (isa<CallInst>(I) || isa<InvokeInst>(I))
+ return I;
// I have absolutely no idea how to implement this part yet. It's not
// neccessarily hard, I just haven't really looked at it yet.
assert(!isa<LandingPadInst>(I) && "Landing Pad is unimplemented");
- if (AtomicCmpXchgInst *cas = dyn_cast<AtomicCmpXchgInst>(I)) {
+ if (isa<AtomicCmpXchgInst>(I))
// A CAS is effectively a atomic store and load combined under a
// predicate. From the perspective of base pointers, we just treat it
- // like a load. We loaded a pointer from a address in memory, that value
- // had better be a valid base pointer.
- return cas->getPointerOperand();
- }
- if (AtomicRMWInst *atomic = dyn_cast<AtomicRMWInst>(I)) {
- assert(AtomicRMWInst::Xchg == atomic->getOperation() &&
- "All others are binary ops which don't apply to base pointers");
- // semantically, a load, store pair. Treat it the same as a standard load
- return atomic->getPointerOperand();
- }
+ // like a load.
+ return I;
+
+ assert(!isa<AtomicRMWInst>(I) && "Xchg handled above, all others are "
+ "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,
// this is a defining definition of the base just like a load is.
- if (ExtractValueInst *ev = dyn_cast<ExtractValueInst>(I)) {
- return ev;
- }
+ if (isa<ExtractValueInst>(I))
+ return I;
// We should never see an insert vector since that would require we be
// tracing back a struct value not a pointer value.
// 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.
- if (SelectInst *select = dyn_cast<SelectInst>(I)) {
- return select;
- }
-
- return cast<PHINode>(I);
+ assert((isa<SelectInst>(I) || isa<PHINode>(I)) &&
+ "missing instruction case in findBaseDefiningValing");
+ return I;
}
/// 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;
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(!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.");
}
}
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;
- }
- }
-
- result.liveset = liveset;
- result.PointerToBase = PointerToBase;
-}
+/// 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);
-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
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
// 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) ||
- (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
}
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);
+ analyzeParsePointLiveness(DT, OriginalLivenessData, 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);
+/// 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);
+ }
+ }
- // 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;
- }
- assert(liveset.size() == PointerToBase.size());
+ // 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,
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
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];
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;
+}
+
+// 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