#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/CodeGen/FunctionLoweringInfo.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
#include "llvm/CodeGen/GCMetadata.h"
#include "llvm/CodeGen/GCStrategy.h"
#include "llvm/CodeGen/SelectionDAG.h"
SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType);
const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex();
+ auto *MFI = Builder.DAG.getMachineFunction().getFrameInfo();
+ MFI->markAsStatepointSpillSlotObjectIndex(FI);
+
Builder.FuncInfo.StatepointStackSlots.push_back(FI);
AllocatedStackSlots.push_back(true);
return SpillSlot;
return Builder.DAG.getFrameIndex(FI, ValueType);
}
// Note: We deliberately choose to advance this only on the failing path.
- // Doing so on the suceeding path involes a bit of complexity that caused a
- // minor bug previously. Unless performance shows this matters, please
+ // Doing so on the succeeding path involves a bit of complexity that caused
+ // a minor bug previously. Unless performance shows this matters, please
// keep this code as simple as possible.
NextSlotToAllocate++;
}
llvm_unreachable("infinite loop?");
}
+/// Utility function for reservePreviousStackSlotForValue. Tries to find
+/// stack slot index to which we have spilled value for previous statepoints.
+/// LookUpDepth specifies maximum DFS depth this function is allowed to look.
+static Optional<int> findPreviousSpillSlot(const Value *Val,
+ SelectionDAGBuilder &Builder,
+ int LookUpDepth) {
+ // Can not look any further - give up now
+ if (LookUpDepth <= 0)
+ return Optional<int>();
+
+ // Spill location is known for gc relocates
+ if (isGCRelocate(Val)) {
+ GCRelocateOperands RelocOps(cast<Instruction>(Val));
+
+ FunctionLoweringInfo::StatepointSpilledValueMapTy &SpillMap =
+ Builder.FuncInfo.StatepointRelocatedValues[RelocOps.getStatepoint()];
+
+ auto It = SpillMap.find(RelocOps.getDerivedPtr());
+ if (It == SpillMap.end())
+ return Optional<int>();
+
+ return It->second;
+ }
+
+ // Look through bitcast instructions.
+ if (const BitCastInst *Cast = dyn_cast<BitCastInst>(Val)) {
+ return findPreviousSpillSlot(Cast->getOperand(0), Builder, LookUpDepth - 1);
+ }
+
+ // Look through phi nodes
+ // All incoming values should have same known stack slot, otherwise result
+ // is unknown.
+ if (const PHINode *Phi = dyn_cast<PHINode>(Val)) {
+ Optional<int> MergedResult = None;
+
+ for (auto &IncomingValue : Phi->incoming_values()) {
+ Optional<int> SpillSlot =
+ findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth - 1);
+ if (!SpillSlot.hasValue())
+ return Optional<int>();
+
+ if (MergedResult.hasValue() && *MergedResult != *SpillSlot)
+ return Optional<int>();
+
+ MergedResult = SpillSlot;
+ }
+ return MergedResult;
+ }
+
+ // TODO: We can do better for PHI nodes. In cases like this:
+ // ptr = phi(relocated_pointer, not_relocated_pointer)
+ // statepoint(ptr)
+ // We will return that stack slot for ptr is unknown. And later we might
+ // assign different stack slots for ptr and relocated_pointer. This limits
+ // llvm's ability to remove redundant stores.
+ // Unfortunately it's hard to accomplish in current infrastructure.
+ // We use this function to eliminate spill store completely, while
+ // in example we still need to emit store, but instead of any location
+ // we need to use special "preferred" location.
+
+ // TODO: handle simple updates. If a value is modified and the original
+ // value is no longer live, it would be nice to put the modified value in the
+ // same slot. This allows folding of the memory accesses for some
+ // instructions types (like an increment).
+ // statepoint (i)
+ // i1 = i+1
+ // statepoint (i1)
+ // However we need to be careful for cases like this:
+ // statepoint(i)
+ // i1 = i+1
+ // statepoint(i, i1)
+ // Here we want to reserve spill slot for 'i', but not for 'i+1'. If we just
+ // put handling of simple modifications in this function like it's done
+ // for bitcasts we might end up reserving i's slot for 'i+1' because order in
+ // which we visit values is unspecified.
+
+ // Don't know any information about this instruction
+ return Optional<int>();
+}
+
/// Try to find existing copies of the incoming values in stack slots used for
/// statepoint spilling. If we can find a spill slot for the incoming value,
/// mark that slot as allocated, and reuse the same slot for this safepoint.
-/// This helps to avoid series of loads and stores that only serve to resuffle
+/// This helps to avoid series of loads and stores that only serve to reshuffle
/// values on the stack between calls.
-static void reservePreviousStackSlotForValue(SDValue Incoming,
+static void reservePreviousStackSlotForValue(const Value *IncomingValue,
SelectionDAGBuilder &Builder) {
+ SDValue Incoming = Builder.getValue(IncomingValue);
+
if (isa<ConstantSDNode>(Incoming) || isa<FrameIndexSDNode>(Incoming)) {
// We won't need to spill this, so no need to check for previously
// allocated stack slots
return;
}
- SDValue Loc = Builder.StatepointLowering.getLocation(Incoming);
- if (Loc.getNode()) {
+ SDValue OldLocation = Builder.StatepointLowering.getLocation(Incoming);
+ if (OldLocation.getNode())
// duplicates in input
return;
- }
-
- // Search back for the load from a stack slot pattern to find the original
- // slot we allocated for this value. We could extend this to deal with
- // simple modification patterns, but simple dealing with trivial load/store
- // sequences helps a lot already.
- if (LoadSDNode *Load = dyn_cast<LoadSDNode>(Incoming)) {
- if (auto *FI = dyn_cast<FrameIndexSDNode>(Load->getBasePtr())) {
- const int Index = FI->getIndex();
- auto Itr = std::find(Builder.FuncInfo.StatepointStackSlots.begin(),
- Builder.FuncInfo.StatepointStackSlots.end(), Index);
- if (Itr == Builder.FuncInfo.StatepointStackSlots.end()) {
- // not one of the lowering stack slots, can't reuse!
- // TODO: Actually, we probably could reuse the stack slot if the value
- // hasn't changed at all, but we'd need to look for intervening writes
- return;
- } else {
- // This is one of our dedicated lowering slots
- const int Offset =
- std::distance(Builder.FuncInfo.StatepointStackSlots.begin(), Itr);
- if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {
- // stack slot already assigned to someone else, can't use it!
- // TODO: currently we reserve space for gc arguments after doing
- // normal allocation for deopt arguments. We should reserve for
- // _all_ deopt and gc arguments, then start allocating. This
- // will prevent some moves being inserted when vm state changes,
- // but gc state doesn't between two calls.
- return;
- }
- // Reserve this stack slot
- Builder.StatepointLowering.reserveStackSlot(Offset);
- }
- // Cache this slot so we find it when going through the normal
- // assignment loop.
- SDValue Loc =
- Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType());
+ const int LookUpDepth = 6;
+ Optional<int> Index =
+ findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth);
+ if (!Index.hasValue())
+ return;
- Builder.StatepointLowering.setLocation(Incoming, Loc);
- }
+ auto Itr = std::find(Builder.FuncInfo.StatepointStackSlots.begin(),
+ Builder.FuncInfo.StatepointStackSlots.end(), *Index);
+ assert(Itr != Builder.FuncInfo.StatepointStackSlots.end() &&
+ "value spilled to the unknown stack slot");
+
+ // This is one of our dedicated lowering slots
+ const int Offset =
+ std::distance(Builder.FuncInfo.StatepointStackSlots.begin(), Itr);
+ if (Builder.StatepointLowering.isStackSlotAllocated(Offset)) {
+ // stack slot already assigned to someone else, can't use it!
+ // TODO: currently we reserve space for gc arguments after doing
+ // normal allocation for deopt arguments. We should reserve for
+ // _all_ deopt and gc arguments, then start allocating. This
+ // will prevent some moves being inserted when vm state changes,
+ // but gc state doesn't between two calls.
+ return;
}
+ // Reserve this stack slot
+ Builder.StatepointLowering.reserveStackSlot(Offset);
- // TODO: handle case where a reloaded value flows through a phi to
- // another safepoint. e.g.
- // bb1:
- // a' = relocated...
- // bb2: % pred: bb1, bb3, bb4, etc.
- // a_phi = phi(a', ...)
- // statepoint ... a_phi
- // NOTE: This will require reasoning about cross basic block values. This is
- // decidedly non trivial and this might not be the right place to do it. We
- // don't really have the information we need here...
-
- // TODO: handle simple updates. If a value is modified and the original
- // value is no longer live, it would be nice to put the modified value in the
- // same slot. This allows folding of the memory accesses for some
- // instructions types (like an increment).
- // statepoint (i)
- // i1 = i+1
- // statepoint (i1)
+ // Cache this slot so we find it when going through the normal
+ // assignment loop.
+ SDValue Loc = Builder.DAG.getTargetFrameIndex(*Index, Incoming.getValueType());
+ Builder.StatepointLowering.setLocation(Incoming, Loc);
}
/// Remove any duplicate (as SDValues) from the derived pointer pairs. This
SmallVectorImpl<const Value *> &Relocs,
SelectionDAGBuilder &Builder) {
- // This is horribly ineffecient, but I don't care right now
+ // This is horribly inefficient, but I don't care right now
SmallSet<SDValue, 64> Seen;
SmallVector<const Value *, 64> NewBases, NewPtrs, NewRelocs;
/// call node. Also update NodeMap so that getValue(statepoint) will
/// reference lowered call result
static SDNode *
-lowerCallFromStatepoint(ImmutableStatepoint ISP, MachineBasicBlock *LandingPad,
+lowerCallFromStatepoint(ImmutableStatepoint ISP, const BasicBlock *EHPadBB,
SelectionDAGBuilder &Builder,
SmallVectorImpl<SDValue> &PendingExports) {
ImmutableCallSite CS(ISP.getCallSite());
- SDValue ActualCallee = Builder.getValue(ISP.getActualCallee());
+ SDValue ActualCallee;
+
+ if (ISP.getNumPatchBytes() > 0) {
+ // If we've been asked to emit a nop sequence instead of a call instruction
+ // for this statepoint then don't lower the call target, but use a constant
+ // `null` instead. Not lowering the call target lets statepoint clients get
+ // away without providing a physical address for the symbolic call target at
+ // link time.
+
+ const auto &TLI = Builder.DAG.getTargetLoweringInfo();
+ const auto &DL = Builder.DAG.getDataLayout();
+
+ unsigned AS = ISP.getCalledValue()->getType()->getPointerAddressSpace();
+ ActualCallee = Builder.DAG.getConstant(0, Builder.getCurSDLoc(),
+ TLI.getPointerTy(DL, AS));
+ } else
+ ActualCallee = Builder.getValue(ISP.getCalledValue());
assert(CS.getCallingConv() != CallingConv::AnyReg &&
"anyregcc is not supported on statepoints!");
SDValue ReturnValue, CallEndVal;
std::tie(ReturnValue, CallEndVal) = Builder.lowerCallOperands(
ISP.getCallSite(), ImmutableStatepoint::CallArgsBeginPos,
- ISP.getNumCallArgs(), ActualCallee, DefTy, LandingPad,
+ ISP.getNumCallArgs(), ActualCallee, DefTy, EHPadBB,
false /* IsPatchPoint */);
SDNode *CallEnd = CallEndVal.getNode();
// ch, glue = callseq_end ch, glue
// get_return_value ch, glue
//
- // get_return_value can either be a CopyFromReg to grab the return value from
- // %RAX, or it can be a LOAD to load a value returned by reference via a stack
- // slot.
+ // get_return_value can either be a sequence of CopyFromReg instructions
+ // to grab the return value from the return register(s), or it can be a LOAD
+ // to load a value returned by reference via a stack slot.
- if (HasDef && (CallEnd->getOpcode() == ISD::CopyFromReg ||
- CallEnd->getOpcode() == ISD::LOAD))
- CallEnd = CallEnd->getOperand(0).getNode();
+ if (HasDef) {
+ if (CallEnd->getOpcode() == ISD::LOAD)
+ CallEnd = CallEnd->getOperand(0).getNode();
+ else
+ while (CallEnd->getOpcode() == ISD::CopyFromReg)
+ CallEnd = CallEnd->getOperand(0).getNode();
+ }
assert(CallEnd->getOpcode() == ISD::CALLSEQ_END && "expected!");
- if (HasDef) {
- if (CS.isInvoke()) {
- // Result value will be used in different basic block for invokes
- // so we need to export it now. But statepoint call has a different type
- // than the actuall call. It means that standart exporting mechanism will
- // create register of the wrong type. So instead we need to create
- // register with correct type and save value into it manually.
+ // Export the result value if needed
+ const Instruction *GCResult = ISP.getGCResult();
+ if (HasDef && GCResult) {
+ if (GCResult->getParent() != CS.getParent()) {
+ // Result value will be used in a different basic block so we need to
+ // export it now.
+ // Default exporting mechanism will not work here because statepoint call
+ // has a different type than the actual call. It means that by default
+ // llvm will create export register of the wrong type (always i32 in our
+ // case). So instead we need to create export register with correct type
+ // manually.
// TODO: To eliminate this problem we can remove gc.result intrinsics
- // completelly and make statepoint call to return a tuple.
+ // completely and make statepoint call to return a tuple.
unsigned Reg = Builder.FuncInfo.CreateRegs(ISP.getActualReturnType());
- RegsForValue RFV(*Builder.DAG.getContext(),
- Builder.DAG.getTargetLoweringInfo(), Reg,
- ISP.getActualReturnType());
+ RegsForValue RFV(
+ *Builder.DAG.getContext(), Builder.DAG.getTargetLoweringInfo(),
+ Builder.DAG.getDataLayout(), Reg, ISP.getActualReturnType());
SDValue Chain = Builder.DAG.getEntryNode();
RFV.getCopyToRegs(ReturnValue, Builder.DAG, Builder.getCurSDLoc(), Chain,
PendingExports.push_back(Chain);
Builder.FuncInfo.ValueMap[CS.getInstruction()] = Reg;
} else {
- // The value of the statepoint itself will be the value of call itself.
- // We'll replace the actually call node shortly. gc_result will grab
+ // Result value will be used in a same basic block. Don't export it or
+ // perform any explicit register copies.
+ // We'll replace the actuall call node shortly. gc_result will grab
// this value.
Builder.setValue(CS.getInstruction(), ReturnValue);
}
SmallVectorImpl<const Value *> &Bases, SmallVectorImpl<const Value *> &Ptrs,
SmallVectorImpl<const Value *> &Relocs, ImmutableStatepoint StatepointSite,
SelectionDAGBuilder &Builder) {
- for (GCRelocateOperands relocateOpers :
- StatepointSite.getRelocates(StatepointSite)) {
+ for (GCRelocateOperands relocateOpers : StatepointSite.getRelocates()) {
Relocs.push_back(relocateOpers.getUnderlyingCallSite().getInstruction());
Bases.push_back(relocateOpers.getBasePtr());
Ptrs.push_back(relocateOpers.getDerivedPtr());
// chaining stores one after another, this may allow
// a bit more optimal scheduling for them
Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,
- MachinePointerInfo::getFixedStack(Index),
+ MachinePointerInfo::getFixedStack(
+ Builder.DAG.getMachineFunction(), Index),
false, false, 0);
Builder.StatepointLowering.setLocation(Incoming, Loc);
// to the GCStrategy from there (yet).
GCStrategy &S = Builder.GFI->getStrategy();
for (const Value *V : Bases) {
- auto Opt = S.isGCManagedPointer(V);
+ auto Opt = S.isGCManagedPointer(V->getType());
if (Opt.hasValue()) {
assert(Opt.getValue() &&
"non gc managed base pointer found in statepoint");
}
}
for (const Value *V : Ptrs) {
- auto Opt = S.isGCManagedPointer(V);
+ auto Opt = S.isGCManagedPointer(V->getType());
if (Opt.hasValue()) {
assert(Opt.getValue() &&
"non gc managed derived pointer found in statepoint");
}
}
for (const Value *V : Relocations) {
- auto Opt = S.isGCManagedPointer(V);
+ auto Opt = S.isGCManagedPointer(V->getType());
if (Opt.hasValue()) {
assert(Opt.getValue() && "non gc managed pointer relocated");
}
// doesn't change semantics at all. It is important for performance that we
// reserve slots for both deopt and gc values before lowering either.
for (const Value *V : StatepointSite.vm_state_args()) {
- SDValue Incoming = Builder.getValue(V);
- reservePreviousStackSlotForValue(Incoming, Builder);
+ reservePreviousStackSlotForValue(V, Builder);
}
for (unsigned i = 0; i < Bases.size(); ++i) {
- const Value *Base = Bases[i];
- reservePreviousStackSlotForValue(Builder.getValue(Base), Builder);
-
- const Value *Ptr = Ptrs[i];
- reservePreviousStackSlotForValue(Builder.getValue(Ptr), Builder);
+ reservePreviousStackSlotForValue(Bases[i], Builder);
+ reservePreviousStackSlotForValue(Ptrs[i], Builder);
}
// First, prefix the list with the number of unique values to be
FunctionLoweringInfo::StatepointSpilledValueMapTy &SpillMap =
Builder.FuncInfo.StatepointRelocatedValues[StatepointInstr];
- for (GCRelocateOperands RelocateOpers :
- StatepointSite.getRelocates(StatepointSite)) {
+ for (GCRelocateOperands RelocateOpers : StatepointSite.getRelocates()) {
const Value *V = RelocateOpers.getDerivedPtr();
SDValue SDV = Builder.getValue(V);
SDValue Loc = Builder.StatepointLowering.getLocation(SDV);
SpillMap[V] = cast<FrameIndexSDNode>(Loc)->getIndex();
} else {
// Record value as visited, but not spilled. This is case for allocas
- // and constants. For this values we can avoid emiting spill load while
+ // and constants. For this values we can avoid emitting spill load while
// visiting corresponding gc_relocate.
// Actually we do not need to record them in this map at all.
- // We do this only to check that we are not relocating any unvisited value.
+ // We do this only to check that we are not relocating any unvisited
+ // value.
SpillMap[V] = None;
// Default llvm mechanisms for exporting values which are used in
// different basic blocks does not work for gc relocates.
// Note that it would be incorrect to teach llvm that all relocates are
- // uses of the corresponging values so that it would automatically
+ // uses of the corresponding values so that it would automatically
// export them. Relocates of the spilled values does not use original
// value.
- if (StatepointSite.getCallSite().isInvoke())
+ if (RelocateOpers.getUnderlyingCallSite().getParent() !=
+ StatepointInstr->getParent())
Builder.ExportFromCurrentBlock(V);
}
}
}
void SelectionDAGBuilder::LowerStatepoint(
- ImmutableStatepoint ISP, MachineBasicBlock *LandingPad /*=nullptr*/) {
+ ImmutableStatepoint ISP, const BasicBlock *EHPadBB /*= nullptr*/) {
// The basic scheme here is that information about both the original call and
// the safepoint is encoded in the CallInst. We create a temporary call and
// lower it, then reverse engineer the calling sequence.
ImmutableCallSite CS(ISP.getCallSite());
#ifndef NDEBUG
- // Consistency check. Don't do this for invokes. It would be too
- // expensive to preserve this information across different basic blocks
- if (!CS.isInvoke()) {
- for (const User *U : CS->users()) {
- const CallInst *Call = cast<CallInst>(U);
- if (isGCRelocate(Call))
- StatepointLowering.scheduleRelocCall(*Call);
- }
+ // Consistency check. Check only relocates in the same basic block as thier
+ // statepoint.
+ for (const User *U : CS->users()) {
+ const CallInst *Call = cast<CallInst>(U);
+ if (isGCRelocate(Call) && Call->getParent() == CS.getParent())
+ StatepointLowering.scheduleRelocCall(*Call);
}
#endif
// Get call node, we will replace it later with statepoint
SDNode *CallNode =
- lowerCallFromStatepoint(ISP, LandingPad, *this, PendingExports);
+ lowerCallFromStatepoint(ISP, EHPadBB, *this, PendingExports);
// Construct the actual GC_TRANSITION_START, STATEPOINT, and GC_TRANSITION_END
// nodes with all the appropriate arguments and return values.
// Replace original call
DAG.ReplaceAllUsesWith(CallNode, SinkNode); // This may update Root
- // Remove originall call node
+ // Remove original call node
DAG.DeleteNode(CallNode);
// DON'T set the root - under the assumption that it's already set past the
Instruction *I = cast<Instruction>(CI.getArgOperand(0));
assert(isStatepoint(I) && "first argument must be a statepoint token");
- if (isa<InvokeInst>(I)) {
- // For invokes we should have stored call result in a virtual register.
+ if (I->getParent() != CI.getParent()) {
+ // Statepoint is in different basic block so we should have stored call
+ // result in a virtual register.
// We can not use default getValue() functionality to copy value from this
// register because statepoint and actuall call return types can be
// different, and getValue() will use CopyFromReg of the wrong type,
// which is always i32 in our case.
- PointerType *CalleeType =
- cast<PointerType>(ImmutableStatepoint(I).getActualCallee()->getType());
+ PointerType *CalleeType = cast<PointerType>(
+ ImmutableStatepoint(I).getCalledValue()->getType());
Type *RetTy =
cast<FunctionType>(CalleeType->getElementType())->getReturnType();
SDValue CopyFromReg = getCopyFromRegs(I, RetTy);
#ifndef NDEBUG
// Consistency check
- // We skip this check for invoke statepoints. It would be too expensive to
- // preserve validation info through different basic blocks.
- if (!RelocateOpers.isTiedToInvoke()) {
+ // We skip this check for relocates not in the same basic block as thier
+ // statepoint. It would be too expensive to preserve validation info through
+ // different basic blocks.
+ if (RelocateOpers.getStatepoint()->getParent() == CI.getParent()) {
StatepointLowering.relocCallVisited(CI);
}
#endif
// Be conservative: flush all pending loads
// TODO: Probably we can be less restrictive on this,
- // it may allow more scheduling opprtunities
+ // it may allow more scheduling opportunities.
SDValue Chain = getRoot();
SDValue SpillLoad =
- DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain, SpillSlot,
- MachinePointerInfo::getFixedStack(*DerivedPtrLocation),
- false, false, false, 0);
+ DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain, SpillSlot,
+ MachinePointerInfo::getFixedStack(DAG.getMachineFunction(),
+ *DerivedPtrLocation),
+ false, false, false, 0);
// Again, be conservative, don't emit pending loads
DAG.setRoot(SpillLoad.getValue(1));
projects / oota-llvm.git / blobdiff