/// Spill a value incoming to the statepoint. It might be either part of /// vmstate /// or gcstate. In both cases unconditionally spill it on the stack unless it /// is a null constant. Return pair with first element being frame index /// containing saved value and second element with outgoing chain from the /// emitted store static std::pair<SDValue, SDValue> spillIncomingStatepointValue(SDValue Incoming, SDValue Chain, SelectionDAGBuilder &Builder) { SDValue Loc = Builder.StatepointLowering.getLocation(Incoming); // Emit new store if we didn't do it for this ptr before if (!Loc.getNode()) { Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(), Builder); assert(isa<FrameIndexSDNode>(Loc)); int Index = cast<FrameIndexSDNode>(Loc)->getIndex(); // We use TargetFrameIndex so that isel will not select it into LEA Loc = Builder.DAG.getTargetFrameIndex(Index, Incoming.getValueType()); // TODO: We can create TokenFactor node instead of // 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), false, false, 0); Builder.StatepointLowering.setLocation(Incoming, Loc); } assert(Loc.getNode()); return std::make_pair(Loc, Chain); }
/// Remove any duplicate (as SDValues) from the derived pointer pairs. This /// is not required for correctness. It's purpose is to reduce the size of /// StackMap section. It has no effect on the number of spill slots required /// or the actual lowering. static void removeDuplicatesGCPtrs(SmallVectorImpl<const Value *> &Bases, SmallVectorImpl<const Value *> &Ptrs, SmallVectorImpl<const Value *> &Relocs, SelectionDAGBuilder &Builder) { // This is horribly ineffecient, but I don't care right now SmallSet<SDValue, 64> Seen; SmallVector<const Value *, 64> NewBases, NewPtrs, NewRelocs; for (size_t i = 0; i < Ptrs.size(); i++) { SDValue SD = Builder.getValue(Ptrs[i]); // Only add non-duplicates if (Seen.count(SD) == 0) { NewBases.push_back(Bases[i]); NewPtrs.push_back(Ptrs[i]); NewRelocs.push_back(Relocs[i]); } Seen.insert(SD); } assert(Bases.size() >= NewBases.size()); assert(Ptrs.size() >= NewPtrs.size()); assert(Relocs.size() >= NewRelocs.size()); Bases = NewBases; Ptrs = NewPtrs; Relocs = NewRelocs; assert(Ptrs.size() == Bases.size()); assert(Ptrs.size() == Relocs.size()); }
static void pushStackMapConstant(SmallVectorImpl<SDValue>& Ops, SelectionDAGBuilder &Builder, uint64_t Value) { SDLoc L = Builder.getCurSDLoc(); Ops.push_back(Builder.DAG.getTargetConstant(StackMaps::ConstantOp, L, MVT::i64)); Ops.push_back(Builder.DAG.getTargetConstant(Value, L, MVT::i64)); }
/// Lower a single value incoming to a statepoint node. This value can be /// either a deopt value or a gc value, the handling is the same. We special /// case constants and allocas, then fall back to spilling if required. static void lowerIncomingStatepointValue(SDValue Incoming, SmallVectorImpl<SDValue> &Ops, SelectionDAGBuilder &Builder) { SDValue Chain = Builder.getRoot(); if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) { // If the original value was a constant, make sure it gets recorded as // such in the stackmap. This is required so that the consumer can // parse any internal format to the deopt state. It also handles null // pointers and other constant pointers in GC states pushStackMapConstant(Ops, Builder, C->getSExtValue()); } else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) { // This handles allocas as arguments to the statepoint (this is only // really meaningful for a deopt value. For GC, we'd be trying to // relocate the address of the alloca itself?) Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(), Incoming.getValueType())); } else { // Otherwise, locate a spill slot and explicitly spill it so it // can be found by the runtime later. We currently do not support // tracking values through callee saved registers to their eventual // spill location. This would be a useful optimization, but would // need to be optional since it requires a lot of complexity on the // runtime side which not all would support. std::pair<SDValue, SDValue> Res = spillIncomingStatepointValue(Incoming, Chain, Builder); Ops.push_back(Res.first); Chain = Res.second; } Builder.DAG.setRoot(Chain); }
/// Remove any duplicate (as SDValues) from the derived pointer pairs. This /// is not required for correctness. It's purpose is to reduce the size of /// StackMap section. It has no effect on the number of spill slots required /// or the actual lowering. static void removeDuplicateGCPtrs(SmallVectorImpl<const Value *> &Bases, SmallVectorImpl<const Value *> &Ptrs, SmallVectorImpl<const GCRelocateInst *> &Relocs, SelectionDAGBuilder &Builder, FunctionLoweringInfo::StatepointSpillMap &SSM) { DenseMap<SDValue, const Value *> Seen; SmallVector<const Value *, 64> NewBases, NewPtrs; SmallVector<const GCRelocateInst *, 64> NewRelocs; for (size_t i = 0, e = Ptrs.size(); i < e; i++) { SDValue SD = Builder.getValue(Ptrs[i]); auto SeenIt = Seen.find(SD); if (SeenIt == Seen.end()) { // Only add non-duplicates NewBases.push_back(Bases[i]); NewPtrs.push_back(Ptrs[i]); NewRelocs.push_back(Relocs[i]); Seen[SD] = Ptrs[i]; } else { // Duplicate pointer found, note in SSM and move on: SSM.DuplicateMap[Ptrs[i]] = SeenIt->second; } } assert(Bases.size() >= NewBases.size()); assert(Ptrs.size() >= NewPtrs.size()); assert(Relocs.size() >= NewRelocs.size()); Bases = NewBases; Ptrs = NewPtrs; Relocs = NewRelocs; assert(Ptrs.size() == Bases.size()); assert(Ptrs.size() == Relocs.size()); }
/// Lower a single value incoming to a statepoint node. This value can be /// either a deopt value or a gc value, the handling is the same. We special /// case constants and allocas, then fall back to spilling if required. static void lowerIncomingStatepointValue(SDValue Incoming, bool LiveInOnly, SmallVectorImpl<SDValue> &Ops, SelectionDAGBuilder &Builder) { SDValue Chain = Builder.getRoot(); if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) { // If the original value was a constant, make sure it gets recorded as // such in the stackmap. This is required so that the consumer can // parse any internal format to the deopt state. It also handles null // pointers and other constant pointers in GC states. Note the constant // vectors do not appear to actually hit this path and that anything larger // than an i64 value (not type!) will fail asserts here. pushStackMapConstant(Ops, Builder, C->getSExtValue()); } else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) { // This handles allocas as arguments to the statepoint (this is only // really meaningful for a deopt value. For GC, we'd be trying to // relocate the address of the alloca itself?) assert(Incoming.getValueType() == Builder.getFrameIndexTy() && "Incoming value is a frame index!"); Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(), Builder.getFrameIndexTy())); } else if (LiveInOnly) { // If this value is live in (not live-on-return, or live-through), we can // treat it the same way patchpoint treats it's "live in" values. We'll // end up folding some of these into stack references, but they'll be // handled by the register allocator. Note that we do not have the notion // of a late use so these values might be placed in registers which are // clobbered by the call. This is fine for live-in. Ops.push_back(Incoming); } else { // Otherwise, locate a spill slot and explicitly spill it so it // can be found by the runtime later. We currently do not support // tracking values through callee saved registers to their eventual // spill location. This would be a useful optimization, but would // need to be optional since it requires a lot of complexity on the // runtime side which not all would support. auto Res = spillIncomingStatepointValue(Incoming, Chain, Builder); Ops.push_back(Res.first); Chain = Res.second; } Builder.DAG.setRoot(Chain); }
/// Spill a value incoming to the statepoint. It might be either part of /// vmstate /// or gcstate. In both cases unconditionally spill it on the stack unless it /// is a null constant. Return pair with first element being frame index /// containing saved value and second element with outgoing chain from the /// emitted store static std::pair<SDValue, SDValue> spillIncomingStatepointValue(SDValue Incoming, SDValue Chain, SelectionDAGBuilder &Builder) { SDValue Loc = Builder.StatepointLowering.getLocation(Incoming); // Emit new store if we didn't do it for this ptr before if (!Loc.getNode()) { Loc = Builder.StatepointLowering.allocateStackSlot(Incoming.getValueType(), Builder); int Index = cast<FrameIndexSDNode>(Loc)->getIndex(); // We use TargetFrameIndex so that isel will not select it into LEA Loc = Builder.DAG.getTargetFrameIndex(Index, Builder.getFrameIndexTy()); // TODO: We can create TokenFactor node instead of // chaining stores one after another, this may allow // a bit more optimal scheduling for them #ifndef NDEBUG // Right now we always allocate spill slots that are of the same // size as the value we're about to spill (the size of spillee can // vary since we spill vectors of pointers too). At some point we // can consider allowing spills of smaller values to larger slots // (i.e. change the '==' in the assert below to a '>='). MachineFrameInfo &MFI = Builder.DAG.getMachineFunction().getFrameInfo(); assert((MFI.getObjectSize(Index) * 8) == Incoming.getValueSizeInBits() && "Bad spill: stack slot does not match!"); #endif Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc, MachinePointerInfo::getFixedStack( Builder.DAG.getMachineFunction(), Index)); Builder.StatepointLowering.setLocation(Incoming, Loc); } assert(Loc.getNode()); return std::make_pair(Loc, Chain); }
/// 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 /// values on the stack between calls. 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 OldLocation = Builder.StatepointLowering.getLocation(Incoming); if (OldLocation.getNode()) // duplicates in input return; const int LookUpDepth = 6; Optional<int> Index = findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth); if (!Index.hasValue()) return; 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); // 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); }
/// Extract call from statepoint, lower it and return pointer to the /// call node. Also update NodeMap so that getValue(statepoint) will /// reference lowered call result static std::pair<SDValue, SDNode *> lowerCallFromStatepointLoweringInfo( SelectionDAGBuilder::StatepointLoweringInfo &SI, SelectionDAGBuilder &Builder, SmallVectorImpl<SDValue> &PendingExports) { SDValue ReturnValue, CallEndVal; std::tie(ReturnValue, CallEndVal) = Builder.lowerInvokable(SI.CLI, SI.EHPadBB); SDNode *CallEnd = CallEndVal.getNode(); // Get a call instruction from the call sequence chain. Tail calls are not // allowed. The following code is essentially reverse engineering X86's // LowerCallTo. // // We are expecting DAG to have the following form: // // ch = eh_label (only in case of invoke statepoint) // ch, glue = callseq_start ch // ch, glue = X86::Call ch, glue // ch, glue = callseq_end ch, glue // get_return_value ch, glue // // 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. bool HasDef = !SI.CLI.RetTy->isVoidTy(); 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!"); return std::make_pair(ReturnValue, CallEnd->getOperand(0).getNode()); }
/// Lower deopt state and gc pointer arguments of the statepoint. The actual /// lowering is described in lowerIncomingStatepointValue. This function is /// responsible for lowering everything in the right position and playing some /// tricks to avoid redundant stack manipulation where possible. On /// completion, 'Ops' will contain ready to use operands for machine code /// statepoint. The chain nodes will have already been created and the DAG root /// will be set to the last value spilled (if any were). static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops, ImmutableStatepoint StatepointSite, SelectionDAGBuilder &Builder) { // Lower the deopt and gc arguments for this statepoint. Layout will // be: deopt argument length, deopt arguments.., gc arguments... SmallVector<const Value *, 64> Bases, Ptrs, Relocations; getIncomingStatepointGCValues(Bases, Ptrs, Relocations, StatepointSite, Builder); #ifndef NDEBUG // Check that each of the gc pointer and bases we've gotten out of the // safepoint is something the strategy thinks might be a pointer into the GC // heap. This is basically just here to help catch errors during statepoint // insertion. TODO: This should actually be in the Verifier, but we can't get // to the GCStrategy from there (yet). GCStrategy &S = Builder.GFI->getStrategy(); for (const Value *V : Bases) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed base pointer found in statepoint"); } } for (const Value *V : Ptrs) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed derived pointer found in statepoint"); } } for (const Value *V : Relocations) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed pointer relocated"); } } #endif // Before we actually start lowering (and allocating spill slots for values), // reserve any stack slots which we judge to be profitable to reuse for a // particular value. This is purely an optimization over the code below and // 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()) { reservePreviousStackSlotForValue(V, Builder); } for (unsigned i = 0; i < Bases.size(); ++i) { reservePreviousStackSlotForValue(Bases[i], Builder); reservePreviousStackSlotForValue(Ptrs[i], Builder); } // First, prefix the list with the number of unique values to be // lowered. Note that this is the number of *Values* not the // number of SDValues required to lower them. const int NumVMSArgs = StatepointSite.getNumTotalVMSArgs(); pushStackMapConstant(Ops, Builder, NumVMSArgs); assert(NumVMSArgs == std::distance(StatepointSite.vm_state_begin(), StatepointSite.vm_state_end())); // The vm state arguments are lowered in an opaque manner. We do // not know what type of values are contained within. We skip the // first one since that happens to be the total number we lowered // explicitly just above. We could have left it in the loop and // not done it explicitly, but it's far easier to understand this // way. for (const Value *V : StatepointSite.vm_state_args()) { SDValue Incoming = Builder.getValue(V); lowerIncomingStatepointValue(Incoming, Ops, Builder); } // Finally, go ahead and lower all the gc arguments. There's no prefixed // length for this one. After lowering, we'll have the base and pointer // arrays interwoven with each (lowered) base pointer immediately followed by // it's (lowered) derived pointer. i.e // (base[0], ptr[0], base[1], ptr[1], ...) for (unsigned i = 0; i < Bases.size(); ++i) { const Value *Base = Bases[i]; lowerIncomingStatepointValue(Builder.getValue(Base), Ops, Builder); const Value *Ptr = Ptrs[i]; lowerIncomingStatepointValue(Builder.getValue(Ptr), Ops, Builder); } // If there are any explicit spill slots passed to the statepoint, record // them, but otherwise do not do anything special. These are user provided // allocas and give control over placement to the consumer. In this case, // it is the contents of the slot which may get updated, not the pointer to // the alloca for (Value *V : StatepointSite.gc_args()) { SDValue Incoming = Builder.getValue(V); if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) { // This handles allocas as arguments to the statepoint Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(), Incoming.getValueType())); } } // Record computed locations for all lowered values. // This can not be embedded in lowering loops as we need to record *all* // values, while previous loops account only values with unique SDValues. const Instruction *StatepointInstr = StatepointSite.getCallSite().getInstruction(); FunctionLoweringInfo::StatepointSpilledValueMapTy &SpillMap = Builder.FuncInfo.StatepointRelocatedValues[StatepointInstr]; for (GCRelocateOperands RelocateOpers : StatepointSite.getRelocates()) { const Value *V = RelocateOpers.getDerivedPtr(); SDValue SDV = Builder.getValue(V); SDValue Loc = Builder.StatepointLowering.getLocation(SDV); if (Loc.getNode()) { 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 // 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. 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 // export them. Relocates of the spilled values does not use original // value. if (StatepointSite.getCallSite().isInvoke()) Builder.ExportFromCurrentBlock(V); } } }
/// Lower deopt state and gc pointer arguments of the statepoint. The actual /// lowering is described in lowerIncomingStatepointValue. This function is /// responsible for lowering everything in the right position and playing some /// tricks to avoid redundant stack manipulation where possible. On /// completion, 'Ops' will contain ready to use operands for machine code /// statepoint. The chain nodes will have already been created and the DAG root /// will be set to the last value spilled (if any were). static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops, ImmutableStatepoint StatepointSite, SelectionDAGBuilder &Builder) { // Lower the deopt and gc arguments for this statepoint. Layout will // be: deopt argument length, deopt arguments.., gc arguments... SmallVector<const Value *, 64> Bases, Ptrs, Relocations; getIncomingStatepointGCValues(Bases, Ptrs, Relocations, StatepointSite, Builder); #ifndef NDEBUG // Check that each of the gc pointer and bases we've gotten out of the // safepoint is something the strategy thinks might be a pointer into the GC // heap. This is basically just here to help catch errors during statepoint // insertion. TODO: This should actually be in the Verifier, but we can't get // to the GCStrategy from there (yet). GCStrategy &S = Builder.GFI->getStrategy(); for (const Value *V : Bases) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed base pointer found in statepoint"); } } for (const Value *V : Ptrs) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed derived pointer found in statepoint"); } } for (const Value *V : Relocations) { auto Opt = S.isGCManagedPointer(V); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed pointer relocated"); } } #endif // Before we actually start lowering (and allocating spill slots for values), // reserve any stack slots which we judge to be profitable to reuse for a // particular value. This is purely an optimization over the code below and // 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); } 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); } // First, prefix the list with the number of unique values to be // lowered. Note that this is the number of *Values* not the // number of SDValues required to lower them. const int NumVMSArgs = StatepointSite.getNumTotalVMSArgs(); pushStackMapConstant(Ops, Builder, NumVMSArgs); assert(NumVMSArgs == std::distance(StatepointSite.vm_state_begin(), StatepointSite.vm_state_end())); // The vm state arguments are lowered in an opaque manner. We do // not know what type of values are contained within. We skip the // first one since that happens to be the total number we lowered // explicitly just above. We could have left it in the loop and // not done it explicitly, but it's far easier to understand this // way. for (const Value *V : StatepointSite.vm_state_args()) { SDValue Incoming = Builder.getValue(V); lowerIncomingStatepointValue(Incoming, Ops, Builder); } // Finally, go ahead and lower all the gc arguments. There's no prefixed // length for this one. After lowering, we'll have the base and pointer // arrays interwoven with each (lowered) base pointer immediately followed by // it's (lowered) derived pointer. i.e // (base[0], ptr[0], base[1], ptr[1], ...) for (unsigned i = 0; i < Bases.size(); ++i) { const Value *Base = Bases[i]; lowerIncomingStatepointValue(Builder.getValue(Base), Ops, Builder); const Value *Ptr = Ptrs[i]; lowerIncomingStatepointValue(Builder.getValue(Ptr), Ops, Builder); } // If there are any explicit spill slots passed to the statepoint, record // them, but otherwise do not do anything special. These are user provided // allocas and give control over placement to the consumer. In this case, // it is the contents of the slot which may get updated, not the pointer to // the alloca for (Value *V : StatepointSite.gc_args()) { SDValue Incoming = Builder.getValue(V); if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) { // This handles allocas as arguments to the statepoint Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(), Incoming.getValueType())); } } }
/// Lower deopt state and gc pointer arguments of the statepoint. The actual /// lowering is described in lowerIncomingStatepointValue. This function is /// responsible for lowering everything in the right position and playing some /// tricks to avoid redundant stack manipulation where possible. On /// completion, 'Ops' will contain ready to use operands for machine code /// statepoint. The chain nodes will have already been created and the DAG root /// will be set to the last value spilled (if any were). static void lowerStatepointMetaArgs(SmallVectorImpl<SDValue> &Ops, SelectionDAGBuilder::StatepointLoweringInfo &SI, SelectionDAGBuilder &Builder) { // Lower the deopt and gc arguments for this statepoint. Layout will be: // deopt argument length, deopt arguments.., gc arguments... #ifndef NDEBUG if (auto *GFI = Builder.GFI) { // Check that each of the gc pointer and bases we've gotten out of the // safepoint is something the strategy thinks might be a pointer (or vector // of pointers) into the GC heap. This is basically just here to help catch // errors during statepoint insertion. TODO: This should actually be in the // Verifier, but we can't get to the GCStrategy from there (yet). GCStrategy &S = GFI->getStrategy(); for (const Value *V : SI.Bases) { auto Opt = S.isGCManagedPointer(V->getType()->getScalarType()); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed base pointer found in statepoint"); } } for (const Value *V : SI.Ptrs) { auto Opt = S.isGCManagedPointer(V->getType()->getScalarType()); if (Opt.hasValue()) { assert(Opt.getValue() && "non gc managed derived pointer found in statepoint"); } } assert(SI.Bases.size() == SI.Ptrs.size() && "Pointer without base!"); } else { assert(SI.Bases.empty() && "No gc specified, so cannot relocate pointers!"); assert(SI.Ptrs.empty() && "No gc specified, so cannot relocate pointers!"); } #endif // Figure out what lowering strategy we're going to use for each part // Note: Is is conservatively correct to lower both "live-in" and "live-out" // as "live-through". A "live-through" variable is one which is "live-in", // "live-out", and live throughout the lifetime of the call (i.e. we can find // it from any PC within the transitive callee of the statepoint). In // particular, if the callee spills callee preserved registers we may not // be able to find a value placed in that register during the call. This is // fine for live-out, but not for live-through. If we were willing to make // assumptions about the code generator producing the callee, we could // potentially allow live-through values in callee saved registers. const bool LiveInDeopt = SI.StatepointFlags & (uint64_t)StatepointFlags::DeoptLiveIn; auto isGCValue =[&](const Value *V) { return is_contained(SI.Ptrs, V) || is_contained(SI.Bases, V); }; // Before we actually start lowering (and allocating spill slots for values), // reserve any stack slots which we judge to be profitable to reuse for a // particular value. This is purely an optimization over the code below and // 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 : SI.DeoptState) { if (!LiveInDeopt || isGCValue(V)) reservePreviousStackSlotForValue(V, Builder); } for (unsigned i = 0; i < SI.Bases.size(); ++i) { reservePreviousStackSlotForValue(SI.Bases[i], Builder); reservePreviousStackSlotForValue(SI.Ptrs[i], Builder); } // First, prefix the list with the number of unique values to be // lowered. Note that this is the number of *Values* not the // number of SDValues required to lower them. const int NumVMSArgs = SI.DeoptState.size(); pushStackMapConstant(Ops, Builder, NumVMSArgs); // The vm state arguments are lowered in an opaque manner. We do not know // what type of values are contained within. for (const Value *V : SI.DeoptState) { SDValue Incoming = Builder.getValue(V); const bool LiveInValue = LiveInDeopt && !isGCValue(V); lowerIncomingStatepointValue(Incoming, LiveInValue, Ops, Builder); } // Finally, go ahead and lower all the gc arguments. There's no prefixed // length for this one. After lowering, we'll have the base and pointer // arrays interwoven with each (lowered) base pointer immediately followed by // it's (lowered) derived pointer. i.e // (base[0], ptr[0], base[1], ptr[1], ...) for (unsigned i = 0; i < SI.Bases.size(); ++i) { const Value *Base = SI.Bases[i]; lowerIncomingStatepointValue(Builder.getValue(Base), /*LiveInOnly*/ false, Ops, Builder); const Value *Ptr = SI.Ptrs[i]; lowerIncomingStatepointValue(Builder.getValue(Ptr), /*LiveInOnly*/ false, Ops, Builder); } // If there are any explicit spill slots passed to the statepoint, record // them, but otherwise do not do anything special. These are user provided // allocas and give control over placement to the consumer. In this case, // it is the contents of the slot which may get updated, not the pointer to // the alloca for (Value *V : SI.GCArgs) { SDValue Incoming = Builder.getValue(V); if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) { // This handles allocas as arguments to the statepoint assert(Incoming.getValueType() == Builder.getFrameIndexTy() && "Incoming value is a frame index!"); Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(), Builder.getFrameIndexTy())); } } // Record computed locations for all lowered values. // This can not be embedded in lowering loops as we need to record *all* // values, while previous loops account only values with unique SDValues. const Instruction *StatepointInstr = SI.StatepointInstr; auto &SpillMap = Builder.FuncInfo.StatepointSpillMaps[StatepointInstr]; for (const GCRelocateInst *Relocate : SI.GCRelocates) { const Value *V = Relocate->getDerivedPtr(); SDValue SDV = Builder.getValue(V); SDValue Loc = Builder.StatepointLowering.getLocation(SDV); if (Loc.getNode()) { SpillMap.SlotMap[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 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. SpillMap.SlotMap[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 corresponding values so that it would automatically // export them. Relocates of the spilled values does not use original // value. if (Relocate->getParent() != StatepointInstr->getParent()) Builder.ExportFromCurrentBlock(V); } } }