diff options
Diffstat (limited to 'contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp')
-rw-r--r-- | contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp | 1313 |
1 files changed, 1313 insertions, 0 deletions
diff --git a/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp b/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp new file mode 100644 index 000000000000..5afd05648772 --- /dev/null +++ b/contrib/llvm-project/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.cpp @@ -0,0 +1,1313 @@ +//===- StatepointLowering.cpp - SDAGBuilder's statepoint code -------------===// +// +// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. +// See https://llvm.org/LICENSE.txt for license information. +// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception +// +//===----------------------------------------------------------------------===// +// +// This file includes support code use by SelectionDAGBuilder when lowering a +// statepoint sequence in SelectionDAG IR. +// +//===----------------------------------------------------------------------===// + +#include "StatepointLowering.h" +#include "SelectionDAGBuilder.h" +#include "llvm/ADT/ArrayRef.h" +#include "llvm/ADT/STLExtras.h" +#include "llvm/ADT/SetVector.h" +#include "llvm/ADT/SmallBitVector.h" +#include "llvm/ADT/SmallSet.h" +#include "llvm/ADT/SmallVector.h" +#include "llvm/ADT/Statistic.h" +#include "llvm/CodeGen/FunctionLoweringInfo.h" +#include "llvm/CodeGen/GCMetadata.h" +#include "llvm/CodeGen/ISDOpcodes.h" +#include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunction.h" +#include "llvm/CodeGen/MachineMemOperand.h" +#include "llvm/CodeGen/MachineValueType.h" +#include "llvm/CodeGen/RuntimeLibcalls.h" +#include "llvm/CodeGen/SelectionDAG.h" +#include "llvm/CodeGen/SelectionDAGNodes.h" +#include "llvm/CodeGen/StackMaps.h" +#include "llvm/CodeGen/TargetLowering.h" +#include "llvm/CodeGen/TargetOpcodes.h" +#include "llvm/IR/CallingConv.h" +#include "llvm/IR/DerivedTypes.h" +#include "llvm/IR/GCStrategy.h" +#include "llvm/IR/Instruction.h" +#include "llvm/IR/Instructions.h" +#include "llvm/IR/LLVMContext.h" +#include "llvm/IR/Statepoint.h" +#include "llvm/IR/Type.h" +#include "llvm/Support/Casting.h" +#include "llvm/Support/CommandLine.h" +#include "llvm/Target/TargetMachine.h" +#include "llvm/Target/TargetOptions.h" +#include <cassert> +#include <cstddef> +#include <cstdint> +#include <iterator> +#include <tuple> +#include <utility> + +using namespace llvm; + +#define DEBUG_TYPE "statepoint-lowering" + +STATISTIC(NumSlotsAllocatedForStatepoints, + "Number of stack slots allocated for statepoints"); +STATISTIC(NumOfStatepoints, "Number of statepoint nodes encountered"); +STATISTIC(StatepointMaxSlotsRequired, + "Maximum number of stack slots required for a singe statepoint"); + +cl::opt<bool> UseRegistersForDeoptValues( + "use-registers-for-deopt-values", cl::Hidden, cl::init(false), + cl::desc("Allow using registers for non pointer deopt args")); + +cl::opt<bool> UseRegistersForGCPointersInLandingPad( + "use-registers-for-gc-values-in-landing-pad", cl::Hidden, cl::init(false), + cl::desc("Allow using registers for gc pointer in landing pad")); + +cl::opt<unsigned> MaxRegistersForGCPointers( + "max-registers-for-gc-values", cl::Hidden, cl::init(0), + cl::desc("Max number of VRegs allowed to pass GC pointer meta args in")); + +typedef FunctionLoweringInfo::StatepointRelocationRecord RecordType; + +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)); +} + +void StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) { + // Consistency check + assert(PendingGCRelocateCalls.empty() && + "Trying to visit statepoint before finished processing previous one"); + Locations.clear(); + NextSlotToAllocate = 0; + // Need to resize this on each safepoint - we need the two to stay in sync and + // the clear patterns of a SelectionDAGBuilder have no relation to + // FunctionLoweringInfo. Also need to ensure used bits get cleared. + AllocatedStackSlots.clear(); + AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size()); +} + +void StatepointLoweringState::clear() { + Locations.clear(); + AllocatedStackSlots.clear(); + assert(PendingGCRelocateCalls.empty() && + "cleared before statepoint sequence completed"); +} + +SDValue +StatepointLoweringState::allocateStackSlot(EVT ValueType, + SelectionDAGBuilder &Builder) { + NumSlotsAllocatedForStatepoints++; + MachineFrameInfo &MFI = Builder.DAG.getMachineFunction().getFrameInfo(); + + unsigned SpillSize = ValueType.getStoreSize(); + assert((SpillSize * 8) == + (-8u & (7 + ValueType.getSizeInBits())) && // Round up modulo 8. + "Size not in bytes?"); + + // First look for a previously created stack slot which is not in + // use (accounting for the fact arbitrary slots may already be + // reserved), or to create a new stack slot and use it. + + const size_t NumSlots = AllocatedStackSlots.size(); + assert(NextSlotToAllocate <= NumSlots && "Broken invariant"); + + assert(AllocatedStackSlots.size() == + Builder.FuncInfo.StatepointStackSlots.size() && + "Broken invariant"); + + for (; NextSlotToAllocate < NumSlots; NextSlotToAllocate++) { + if (!AllocatedStackSlots.test(NextSlotToAllocate)) { + const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate]; + if (MFI.getObjectSize(FI) == SpillSize) { + AllocatedStackSlots.set(NextSlotToAllocate); + // TODO: Is ValueType the right thing to use here? + return Builder.DAG.getFrameIndex(FI, ValueType); + } + } + } + + // Couldn't find a free slot, so create a new one: + + SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType); + const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex(); + MFI.markAsStatepointSpillSlotObjectIndex(FI); + + Builder.FuncInfo.StatepointStackSlots.push_back(FI); + AllocatedStackSlots.resize(AllocatedStackSlots.size()+1, true); + assert(AllocatedStackSlots.size() == + Builder.FuncInfo.StatepointStackSlots.size() && + "Broken invariant"); + + StatepointMaxSlotsRequired.updateMax( + Builder.FuncInfo.StatepointStackSlots.size()); + + return SpillSlot; +} + +/// 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 std::optional<int> findPreviousSpillSlot(const Value *Val, + SelectionDAGBuilder &Builder, + int LookUpDepth) { + // Can not look any further - give up now + if (LookUpDepth <= 0) + return std::nullopt; + + // Spill location is known for gc relocates + if (const auto *Relocate = dyn_cast<GCRelocateInst>(Val)) { + const Value *Statepoint = Relocate->getStatepoint(); + assert((isa<GCStatepointInst>(Statepoint) || isa<UndefValue>(Statepoint)) && + "GetStatepoint must return one of two types"); + if (isa<UndefValue>(Statepoint)) + return std::nullopt; + + const auto &RelocationMap = Builder.FuncInfo.StatepointRelocationMaps + [cast<GCStatepointInst>(Statepoint)]; + + auto It = RelocationMap.find(Relocate); + if (It == RelocationMap.end()) + return std::nullopt; + + auto &Record = It->second; + if (Record.type != RecordType::Spill) + return std::nullopt; + + return Record.payload.FI; + } + + // 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)) { + std::optional<int> MergedResult; + + for (const auto &IncomingValue : Phi->incoming_values()) { + std::optional<int> SpillSlot = + findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth - 1); + if (!SpillSlot) + return std::nullopt; + + if (MergedResult && *MergedResult != *SpillSlot) + return std::nullopt; + + 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 std::nullopt; +} + +/// Return true if-and-only-if the given SDValue can be lowered as either a +/// constant argument or a stack reference. The key point is that the value +/// doesn't need to be spilled or tracked as a vreg use. +static bool willLowerDirectly(SDValue Incoming) { + // We are making an unchecked assumption that the frame size <= 2^16 as that + // is the largest offset which can be encoded in the stackmap format. + if (isa<FrameIndexSDNode>(Incoming)) + return true; + + // The largest constant describeable in the StackMap format is 64 bits. + // Potential Optimization: Constants values are sign extended by consumer, + // and thus there are many constants of static type > 64 bits whose value + // happens to be sext(Con64) and could thus be lowered directly. + if (Incoming.getValueType().getSizeInBits() > 64) + return false; + + return isIntOrFPConstant(Incoming) || Incoming.isUndef(); +} + +/// 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 reshuffle +/// values on the stack between calls. +static void reservePreviousStackSlotForValue(const Value *IncomingValue, + SelectionDAGBuilder &Builder) { + SDValue Incoming = Builder.getValue(IncomingValue); + + // If we won't spill this, we don't need to check for previously allocated + // stack slots. + if (willLowerDirectly(Incoming)) + return; + + SDValue OldLocation = Builder.StatepointLowering.getLocation(Incoming); + if (OldLocation.getNode()) + // Duplicates in input + return; + + const int LookUpDepth = 6; + std::optional<int> Index = + findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth); + if (!Index) + return; + + const auto &StatepointSlots = Builder.FuncInfo.StatepointStackSlots; + + auto SlotIt = find(StatepointSlots, *Index); + assert(SlotIt != StatepointSlots.end() && + "Value spilled to the unknown stack slot"); + + // This is one of our dedicated lowering slots + const int Offset = std::distance(StatepointSlots.begin(), SlotIt); + 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, Builder.getFrameIndexTy()); + 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) { + 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()); +} + +static MachineMemOperand* getMachineMemOperand(MachineFunction &MF, + FrameIndexSDNode &FI) { + auto PtrInfo = MachinePointerInfo::getFixedStack(MF, FI.getIndex()); + auto MMOFlags = MachineMemOperand::MOStore | + MachineMemOperand::MOLoad | MachineMemOperand::MOVolatile; + auto &MFI = MF.getFrameInfo(); + return MF.getMachineMemOperand(PtrInfo, MMOFlags, + MFI.getObjectSize(FI.getIndex()), + MFI.getObjectAlign(FI.getIndex())); +} + +/// 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::tuple<SDValue, SDValue, MachineMemOperand*> +spillIncomingStatepointValue(SDValue Incoming, SDValue Chain, + SelectionDAGBuilder &Builder) { + SDValue Loc = Builder.StatepointLowering.getLocation(Incoming); + MachineMemOperand* MMO = nullptr; + + // 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()); + + // 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) == + (-8 & (7 + // Round up modulo 8. + (int64_t)Incoming.getValueSizeInBits())) && + "Bad spill: stack slot does not match!"); + + // Note: Using the alignment of the spill slot (rather than the abi or + // preferred alignment) is required for correctness when dealing with spill + // slots with preferred alignments larger than frame alignment.. + auto &MF = Builder.DAG.getMachineFunction(); + auto PtrInfo = MachinePointerInfo::getFixedStack(MF, Index); + auto *StoreMMO = MF.getMachineMemOperand( + PtrInfo, MachineMemOperand::MOStore, MFI.getObjectSize(Index), + MFI.getObjectAlign(Index)); + Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc, + StoreMMO); + + MMO = getMachineMemOperand(MF, *cast<FrameIndexSDNode>(Loc)); + + Builder.StatepointLowering.setLocation(Incoming, Loc); + } + + assert(Loc.getNode()); + return std::make_tuple(Loc, Chain, MMO); +} + +/// 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 RequireSpillSlot, + SmallVectorImpl<SDValue> &Ops, + SmallVectorImpl<MachineMemOperand *> &MemRefs, + SelectionDAGBuilder &Builder) { + + if (willLowerDirectly(Incoming)) { + 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())); + + auto &MF = Builder.DAG.getMachineFunction(); + auto *MMO = getMachineMemOperand(MF, *FI); + MemRefs.push_back(MMO); + return; + } + + assert(Incoming.getValueType().getSizeInBits() <= 64); + + if (Incoming.isUndef()) { + // Put an easily recognized constant that's unlikely to be a valid + // value so that uses of undef by the consumer of the stackmap is + // easily recognized. This is legal since the compiler is always + // allowed to chose an arbitrary value for undef. + pushStackMapConstant(Ops, Builder, 0xFEFEFEFE); + return; + } + + // 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. + if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) { + pushStackMapConstant(Ops, Builder, C->getSExtValue()); + return; + } else if (ConstantFPSDNode *C = dyn_cast<ConstantFPSDNode>(Incoming)) { + pushStackMapConstant(Ops, Builder, + C->getValueAPF().bitcastToAPInt().getZExtValue()); + return; + } + + llvm_unreachable("unhandled direct lowering case"); + } + + + + if (!RequireSpillSlot) { + // 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. For live-through + // fix-up pass should be executed to force spilling of such registers. + Ops.push_back(Incoming); + } else { + // Otherwise, locate a spill slot and explicitly spill it so it can be + // found by the runtime later. Note: We know all of these spills are + // independent, but don't bother to exploit that chain wise. DAGCombine + // will happily do so as needed, so doing it here would be a small compile + // time win at most. + SDValue Chain = Builder.getRoot(); + auto Res = spillIncomingStatepointValue(Incoming, Chain, Builder); + Ops.push_back(std::get<0>(Res)); + if (auto *MMO = std::get<2>(Res)) + MemRefs.push_back(MMO); + Chain = std::get<1>(Res); + Builder.DAG.setRoot(Chain); + } + +} + +/// Return true if value V represents the GC value. The behavior is conservative +/// in case it is not sure that value is not GC the function returns true. +static bool isGCValue(const Value *V, SelectionDAGBuilder &Builder) { + auto *Ty = V->getType(); + if (!Ty->isPtrOrPtrVectorTy()) + return false; + if (auto *GFI = Builder.GFI) + if (auto IsManaged = GFI->getStrategy().isGCManagedPointer(Ty)) + return *IsManaged; + return true; // conservative +} + +/// 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, + SmallVectorImpl<MachineMemOperand *> &MemRefs, + SmallVectorImpl<SDValue> &GCPtrs, + DenseMap<SDValue, int> &LowerAsVReg, + SelectionDAGBuilder::StatepointLoweringInfo &SI, + SelectionDAGBuilder &Builder) { + // Lower the deopt and gc arguments for this statepoint. Layout will be: + // deopt argument length, deopt arguments.., gc arguments... + + // 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; + + // Decide which deriver pointers will go on VRegs + unsigned MaxVRegPtrs = MaxRegistersForGCPointers.getValue(); + + // Pointers used on exceptional path of invoke statepoint. + // We cannot assing them to VRegs. + SmallSet<SDValue, 8> LPadPointers; + if (!UseRegistersForGCPointersInLandingPad) + if (const auto *StInvoke = + dyn_cast_or_null<InvokeInst>(SI.StatepointInstr)) { + LandingPadInst *LPI = StInvoke->getLandingPadInst(); + for (const auto *Relocate : SI.GCRelocates) + if (Relocate->getOperand(0) == LPI) { + LPadPointers.insert(Builder.getValue(Relocate->getBasePtr())); + LPadPointers.insert(Builder.getValue(Relocate->getDerivedPtr())); + } + } + + LLVM_DEBUG(dbgs() << "Deciding how to lower GC Pointers:\n"); + + // List of unique lowered GC Pointer values. + SmallSetVector<SDValue, 16> LoweredGCPtrs; + // Map lowered GC Pointer value to the index in above vector + DenseMap<SDValue, unsigned> GCPtrIndexMap; + + unsigned CurNumVRegs = 0; + + auto canPassGCPtrOnVReg = [&](SDValue SD) { + if (SD.getValueType().isVector()) + return false; + if (LPadPointers.count(SD)) + return false; + return !willLowerDirectly(SD); + }; + + auto processGCPtr = [&](const Value *V) { + SDValue PtrSD = Builder.getValue(V); + if (!LoweredGCPtrs.insert(PtrSD)) + return; // skip duplicates + GCPtrIndexMap[PtrSD] = LoweredGCPtrs.size() - 1; + + assert(!LowerAsVReg.count(PtrSD) && "must not have been seen"); + if (LowerAsVReg.size() == MaxVRegPtrs) + return; + assert(V->getType()->isVectorTy() == PtrSD.getValueType().isVector() && + "IR and SD types disagree"); + if (!canPassGCPtrOnVReg(PtrSD)) { + LLVM_DEBUG(dbgs() << "direct/spill "; PtrSD.dump(&Builder.DAG)); + return; + } + LLVM_DEBUG(dbgs() << "vreg "; PtrSD.dump(&Builder.DAG)); + LowerAsVReg[PtrSD] = CurNumVRegs++; + }; + + // Process derived pointers first to give them more chance to go on VReg. + for (const Value *V : SI.Ptrs) + processGCPtr(V); + for (const Value *V : SI.Bases) + processGCPtr(V); + + LLVM_DEBUG(dbgs() << LowerAsVReg.size() << " pointers will go in vregs\n"); + + auto requireSpillSlot = [&](const Value *V) { + if (!Builder.DAG.getTargetLoweringInfo().isTypeLegal( + Builder.getValue(V).getValueType())) + return true; + if (isGCValue(V, Builder)) + return !LowerAsVReg.count(Builder.getValue(V)); + return !(LiveInDeopt || UseRegistersForDeoptValues); + }; + + // 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 (requireSpillSlot(V)) + reservePreviousStackSlotForValue(V, Builder); + } + + for (const Value *V : SI.Ptrs) { + SDValue SDV = Builder.getValue(V); + if (!LowerAsVReg.count(SDV)) + reservePreviousStackSlotForValue(V, Builder); + } + + for (const Value *V : SI.Bases) { + SDValue SDV = Builder.getValue(V); + if (!LowerAsVReg.count(SDV)) + reservePreviousStackSlotForValue(V, 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. + LLVM_DEBUG(dbgs() << "Lowering deopt state\n"); + for (const Value *V : SI.DeoptState) { + SDValue Incoming; + // If this is a function argument at a static frame index, generate it as + // the frame index. + if (const Argument *Arg = dyn_cast<Argument>(V)) { + int FI = Builder.FuncInfo.getArgumentFrameIndex(Arg); + if (FI != INT_MAX) + Incoming = Builder.DAG.getFrameIndex(FI, Builder.getFrameIndexTy()); + } + if (!Incoming.getNode()) + Incoming = Builder.getValue(V); + LLVM_DEBUG(dbgs() << "Value " << *V + << " requireSpillSlot = " << requireSpillSlot(V) << "\n"); + lowerIncomingStatepointValue(Incoming, requireSpillSlot(V), Ops, MemRefs, + Builder); + } + + // Finally, go ahead and lower all the gc arguments. + pushStackMapConstant(Ops, Builder, LoweredGCPtrs.size()); + for (SDValue SDV : LoweredGCPtrs) + lowerIncomingStatepointValue(SDV, !LowerAsVReg.count(SDV), Ops, MemRefs, + Builder); + + // Copy to out vector. LoweredGCPtrs will be empty after this point. + GCPtrs = LoweredGCPtrs.takeVector(); + + // 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 + SmallVector<SDValue, 4> Allocas; + 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!"); + Allocas.push_back(Builder.DAG.getTargetFrameIndex( + FI->getIndex(), Builder.getFrameIndexTy())); + + auto &MF = Builder.DAG.getMachineFunction(); + auto *MMO = getMachineMemOperand(MF, *FI); + MemRefs.push_back(MMO); + } + } + pushStackMapConstant(Ops, Builder, Allocas.size()); + Ops.append(Allocas.begin(), Allocas.end()); + + // Now construct GC base/derived map; + pushStackMapConstant(Ops, Builder, SI.Ptrs.size()); + SDLoc L = Builder.getCurSDLoc(); + for (unsigned i = 0; i < SI.Ptrs.size(); ++i) { + SDValue Base = Builder.getValue(SI.Bases[i]); + assert(GCPtrIndexMap.count(Base) && "base not found in index map"); + Ops.push_back( + Builder.DAG.getTargetConstant(GCPtrIndexMap[Base], L, MVT::i64)); + SDValue Derived = Builder.getValue(SI.Ptrs[i]); + assert(GCPtrIndexMap.count(Derived) && "derived not found in index map"); + Ops.push_back( + Builder.DAG.getTargetConstant(GCPtrIndexMap[Derived], L, MVT::i64)); + } +} + +SDValue SelectionDAGBuilder::LowerAsSTATEPOINT( + SelectionDAGBuilder::StatepointLoweringInfo &SI) { + // 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. + + NumOfStatepoints++; + // Clear state + StatepointLowering.startNewStatepoint(*this); + assert(SI.Bases.size() == SI.Ptrs.size() && "Pointer without base!"); + assert((GFI || SI.Bases.empty()) && + "No gc specified, so cannot relocate pointers!"); + + LLVM_DEBUG(dbgs() << "Lowering statepoint " << *SI.StatepointInstr << "\n"); +#ifndef NDEBUG + for (const auto *Reloc : SI.GCRelocates) + if (Reloc->getParent() == SI.StatepointInstr->getParent()) + StatepointLowering.scheduleRelocCall(*Reloc); +#endif + + // Lower statepoint vmstate and gcstate arguments + + // All lowered meta args. + SmallVector<SDValue, 10> LoweredMetaArgs; + // Lowered GC pointers (subset of above). + SmallVector<SDValue, 16> LoweredGCArgs; + SmallVector<MachineMemOperand*, 16> MemRefs; + // Maps derived pointer SDValue to statepoint result of relocated pointer. + DenseMap<SDValue, int> LowerAsVReg; + lowerStatepointMetaArgs(LoweredMetaArgs, MemRefs, LoweredGCArgs, LowerAsVReg, + SI, *this); + + // Now that we've emitted the spills, we need to update the root so that the + // call sequence is ordered correctly. + SI.CLI.setChain(getRoot()); + + // Get call node, we will replace it later with statepoint + SDValue ReturnVal; + SDNode *CallNode; + std::tie(ReturnVal, CallNode) = lowerCallFromStatepointLoweringInfo(SI, *this); + + // Construct the actual GC_TRANSITION_START, STATEPOINT, and GC_TRANSITION_END + // nodes with all the appropriate arguments and return values. + + // Call Node: Chain, Target, {Args}, RegMask, [Glue] + SDValue Chain = CallNode->getOperand(0); + + SDValue Glue; + bool CallHasIncomingGlue = CallNode->getGluedNode(); + if (CallHasIncomingGlue) { + // Glue is always last operand + Glue = CallNode->getOperand(CallNode->getNumOperands() - 1); + } + + // Build the GC_TRANSITION_START node if necessary. + // + // The operands to the GC_TRANSITION_{START,END} nodes are laid out in the + // order in which they appear in the call to the statepoint intrinsic. If + // any of the operands is a pointer-typed, that operand is immediately + // followed by a SRCVALUE for the pointer that may be used during lowering + // (e.g. to form MachinePointerInfo values for loads/stores). + const bool IsGCTransition = + (SI.StatepointFlags & (uint64_t)StatepointFlags::GCTransition) == + (uint64_t)StatepointFlags::GCTransition; + if (IsGCTransition) { + SmallVector<SDValue, 8> TSOps; + + // Add chain + TSOps.push_back(Chain); + + // Add GC transition arguments + for (const Value *V : SI.GCTransitionArgs) { + TSOps.push_back(getValue(V)); + if (V->getType()->isPointerTy()) + TSOps.push_back(DAG.getSrcValue(V)); + } + + // Add glue if necessary + if (CallHasIncomingGlue) + TSOps.push_back(Glue); + + SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue); + + SDValue GCTransitionStart = + DAG.getNode(ISD::GC_TRANSITION_START, getCurSDLoc(), NodeTys, TSOps); + + Chain = GCTransitionStart.getValue(0); + Glue = GCTransitionStart.getValue(1); + } + + // TODO: Currently, all of these operands are being marked as read/write in + // PrologEpilougeInserter.cpp, we should special case the VMState arguments + // and flags to be read-only. + SmallVector<SDValue, 40> Ops; + + // Add the <id> and <numBytes> constants. + Ops.push_back(DAG.getTargetConstant(SI.ID, getCurSDLoc(), MVT::i64)); + Ops.push_back( + DAG.getTargetConstant(SI.NumPatchBytes, getCurSDLoc(), MVT::i32)); + + // Calculate and push starting position of vmstate arguments + // Get number of arguments incoming directly into call node + unsigned NumCallRegArgs = + CallNode->getNumOperands() - (CallHasIncomingGlue ? 4 : 3); + Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, getCurSDLoc(), MVT::i32)); + + // Add call target + SDValue CallTarget = SDValue(CallNode->getOperand(1).getNode(), 0); + Ops.push_back(CallTarget); + + // Add call arguments + // Get position of register mask in the call + SDNode::op_iterator RegMaskIt; + if (CallHasIncomingGlue) + RegMaskIt = CallNode->op_end() - 2; + else + RegMaskIt = CallNode->op_end() - 1; + Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt); + + // Add a constant argument for the calling convention + pushStackMapConstant(Ops, *this, SI.CLI.CallConv); + + // Add a constant argument for the flags + uint64_t Flags = SI.StatepointFlags; + assert(((Flags & ~(uint64_t)StatepointFlags::MaskAll) == 0) && + "Unknown flag used"); + pushStackMapConstant(Ops, *this, Flags); + + // Insert all vmstate and gcstate arguments + llvm::append_range(Ops, LoweredMetaArgs); + + // Add register mask from call node + Ops.push_back(*RegMaskIt); + + // Add chain + Ops.push_back(Chain); + + // Same for the glue, but we add it only if original call had it + if (Glue.getNode()) + Ops.push_back(Glue); + + // Compute return values. Provide a glue output since we consume one as + // input. This allows someone else to chain off us as needed. + SmallVector<EVT, 8> NodeTys; + for (auto SD : LoweredGCArgs) { + if (!LowerAsVReg.count(SD)) + continue; + NodeTys.push_back(SD.getValueType()); + } + LLVM_DEBUG(dbgs() << "Statepoint has " << NodeTys.size() << " results\n"); + assert(NodeTys.size() == LowerAsVReg.size() && "Inconsistent GC Ptr lowering"); + NodeTys.push_back(MVT::Other); + NodeTys.push_back(MVT::Glue); + + unsigned NumResults = NodeTys.size(); + MachineSDNode *StatepointMCNode = + DAG.getMachineNode(TargetOpcode::STATEPOINT, getCurSDLoc(), NodeTys, Ops); + DAG.setNodeMemRefs(StatepointMCNode, MemRefs); + + // For values lowered to tied-defs, create the virtual registers if used + // in other blocks. For local gc.relocate record appropriate statepoint + // result in StatepointLoweringState. + DenseMap<SDValue, Register> VirtRegs; + for (const auto *Relocate : SI.GCRelocates) { + Value *Derived = Relocate->getDerivedPtr(); + SDValue SD = getValue(Derived); + if (!LowerAsVReg.count(SD)) + continue; + + SDValue Relocated = SDValue(StatepointMCNode, LowerAsVReg[SD]); + + // Handle local relocate. Note that different relocates might + // map to the same SDValue. + if (SI.StatepointInstr->getParent() == Relocate->getParent()) { + SDValue Res = StatepointLowering.getLocation(SD); + if (Res) + assert(Res == Relocated); + else + StatepointLowering.setLocation(SD, Relocated); + continue; + } + + // Handle multiple gc.relocates of the same input efficiently. + if (VirtRegs.count(SD)) + continue; + + auto *RetTy = Relocate->getType(); + Register Reg = FuncInfo.CreateRegs(RetTy); + RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(), + DAG.getDataLayout(), Reg, RetTy, std::nullopt); + SDValue Chain = DAG.getRoot(); + RFV.getCopyToRegs(Relocated, DAG, getCurSDLoc(), Chain, nullptr); + PendingExports.push_back(Chain); + + VirtRegs[SD] = Reg; + } + + // Record for later use how each relocation was lowered. This is needed to + // allow later gc.relocates to mirror the lowering chosen. + const Instruction *StatepointInstr = SI.StatepointInstr; + auto &RelocationMap = FuncInfo.StatepointRelocationMaps[StatepointInstr]; + for (const GCRelocateInst *Relocate : SI.GCRelocates) { + const Value *V = Relocate->getDerivedPtr(); + SDValue SDV = getValue(V); + SDValue Loc = StatepointLowering.getLocation(SDV); + + bool IsLocal = (Relocate->getParent() == StatepointInstr->getParent()); + + RecordType Record; + if (IsLocal && LowerAsVReg.count(SDV)) { + // Result is already stored in StatepointLowering + Record.type = RecordType::SDValueNode; + } else if (LowerAsVReg.count(SDV)) { + Record.type = RecordType::VReg; + assert(VirtRegs.count(SDV)); + Record.payload.Reg = VirtRegs[SDV]; + } else if (Loc.getNode()) { + Record.type = RecordType::Spill; + Record.payload.FI = cast<FrameIndexSDNode>(Loc)->getIndex(); + } else { + Record.type = RecordType::NoRelocate; + // If we didn't relocate a value, we'll essentialy end up inserting an + // additional use of the original value when lowering the gc.relocate. + // We need to make sure the value is available at the new use, which + // might be in another block. + if (Relocate->getParent() != StatepointInstr->getParent()) + ExportFromCurrentBlock(V); + } + RelocationMap[Relocate] = Record; + } + + + + SDNode *SinkNode = StatepointMCNode; + + // Build the GC_TRANSITION_END node if necessary. + // + // See the comment above regarding GC_TRANSITION_START for the layout of + // the operands to the GC_TRANSITION_END node. + if (IsGCTransition) { + SmallVector<SDValue, 8> TEOps; + + // Add chain + TEOps.push_back(SDValue(StatepointMCNode, NumResults - 2)); + + // Add GC transition arguments + for (const Value *V : SI.GCTransitionArgs) { + TEOps.push_back(getValue(V)); + if (V->getType()->isPointerTy()) + TEOps.push_back(DAG.getSrcValue(V)); + } + + // Add glue + TEOps.push_back(SDValue(StatepointMCNode, NumResults - 1)); + + SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue); + + SDValue GCTransitionStart = + DAG.getNode(ISD::GC_TRANSITION_END, getCurSDLoc(), NodeTys, TEOps); + + SinkNode = GCTransitionStart.getNode(); + } + + // Replace original call + // Call: ch,glue = CALL ... + // Statepoint: [gc relocates],ch,glue = STATEPOINT ... + unsigned NumSinkValues = SinkNode->getNumValues(); + SDValue StatepointValues[2] = {SDValue(SinkNode, NumSinkValues - 2), + SDValue(SinkNode, NumSinkValues - 1)}; + DAG.ReplaceAllUsesWith(CallNode, StatepointValues); + // Remove original call node + DAG.DeleteNode(CallNode); + + // Since we always emit CopyToRegs (even for local relocates), we must + // update root, so that they are emitted before any local uses. + (void)getControlRoot(); + + // TODO: A better future implementation would be to emit a single variable + // argument, variable return value STATEPOINT node here and then hookup the + // return value of each gc.relocate to the respective output of the + // previously emitted STATEPOINT value. Unfortunately, this doesn't appear + // to actually be possible today. + + return ReturnVal; +} + +/// Return two gc.results if present. First result is a block local +/// gc.result, second result is a non-block local gc.result. Corresponding +/// entry will be nullptr if not present. +static std::pair<const GCResultInst*, const GCResultInst*> +getGCResultLocality(const GCStatepointInst &S) { + std::pair<const GCResultInst *, const GCResultInst*> Res(nullptr, nullptr); + for (const auto *U : S.users()) { + auto *GRI = dyn_cast<GCResultInst>(U); + if (!GRI) + continue; + if (GRI->getParent() == S.getParent()) + Res.first = GRI; + else + Res.second = GRI; + } + return Res; +} + +void +SelectionDAGBuilder::LowerStatepoint(const GCStatepointInst &I, + const BasicBlock *EHPadBB /*= nullptr*/) { + assert(I.getCallingConv() != CallingConv::AnyReg && + "anyregcc is not supported on statepoints!"); + +#ifndef NDEBUG + // Check that the associated GCStrategy expects to encounter statepoints. + assert(GFI->getStrategy().useStatepoints() && + "GCStrategy does not expect to encounter statepoints"); +#endif + + SDValue ActualCallee; + SDValue Callee = getValue(I.getActualCalledOperand()); + + if (I.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 + // `undef` instead. Not lowering the call target lets statepoint clients + // get away without providing a physical address for the symbolic call + // target at link time. + ActualCallee = DAG.getUNDEF(Callee.getValueType()); + } else { + ActualCallee = Callee; + } + + StatepointLoweringInfo SI(DAG); + populateCallLoweringInfo(SI.CLI, &I, GCStatepointInst::CallArgsBeginPos, + I.getNumCallArgs(), ActualCallee, + I.getActualReturnType(), false /* IsPatchPoint */); + + // There may be duplication in the gc.relocate list; such as two copies of + // each relocation on normal and exceptional path for an invoke. We only + // need to spill once and record one copy in the stackmap, but we need to + // reload once per gc.relocate. (Dedupping gc.relocates is trickier and best + // handled as a CSE problem elsewhere.) + // TODO: There a couple of major stackmap size optimizations we could do + // here if we wished. + // 1) If we've encountered a derived pair {B, D}, we don't need to actually + // record {B,B} if it's seen later. + // 2) Due to rematerialization, actual derived pointers are somewhat rare; + // given that, we could change the format to record base pointer relocations + // separately with half the space. This would require a format rev and a + // fairly major rework of the STATEPOINT node though. + SmallSet<SDValue, 8> Seen; + for (const GCRelocateInst *Relocate : I.getGCRelocates()) { + SI.GCRelocates.push_back(Relocate); + + SDValue DerivedSD = getValue(Relocate->getDerivedPtr()); + if (Seen.insert(DerivedSD).second) { + SI.Bases.push_back(Relocate->getBasePtr()); + SI.Ptrs.push_back(Relocate->getDerivedPtr()); + } + } + + // If we find a deopt value which isn't explicitly added, we need to + // ensure it gets lowered such that gc cycles occurring before the + // deoptimization event during the lifetime of the call don't invalidate + // the pointer we're deopting with. Note that we assume that all + // pointers passed to deopt are base pointers; relaxing that assumption + // would require relatively large changes to how we represent relocations. + for (Value *V : I.deopt_operands()) { + if (!isGCValue(V, *this)) + continue; + if (Seen.insert(getValue(V)).second) { + SI.Bases.push_back(V); + SI.Ptrs.push_back(V); + } + } + + SI.GCArgs = ArrayRef<const Use>(I.gc_args_begin(), I.gc_args_end()); + SI.StatepointInstr = &I; + SI.ID = I.getID(); + + SI.DeoptState = ArrayRef<const Use>(I.deopt_begin(), I.deopt_end()); + SI.GCTransitionArgs = ArrayRef<const Use>(I.gc_transition_args_begin(), + I.gc_transition_args_end()); + + SI.StatepointFlags = I.getFlags(); + SI.NumPatchBytes = I.getNumPatchBytes(); + SI.EHPadBB = EHPadBB; + + SDValue ReturnValue = LowerAsSTATEPOINT(SI); + + // Export the result value if needed + const auto GCResultLocality = getGCResultLocality(I); + + if (!GCResultLocality.first && !GCResultLocality.second) { + // The return value is not needed, just generate a poison value. + // Note: This covers the void return case. + setValue(&I, DAG.getIntPtrConstant(-1, getCurSDLoc())); + return; + } + + if (GCResultLocality.first) { + // Result value will be used in a same basic block. Don't export it or + // perform any explicit register copies. The gc_result will simply grab + // this value. + setValue(&I, ReturnValue); + } + + if (!GCResultLocality.second) + return; + // 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 + // completely and make statepoint call to return a tuple. + Type *RetTy = GCResultLocality.second->getType(); + Register Reg = FuncInfo.CreateRegs(RetTy); + RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(), + DAG.getDataLayout(), Reg, RetTy, + I.getCallingConv()); + SDValue Chain = DAG.getEntryNode(); + + RFV.getCopyToRegs(ReturnValue, DAG, getCurSDLoc(), Chain, nullptr); + PendingExports.push_back(Chain); + FuncInfo.ValueMap[&I] = Reg; +} + +void SelectionDAGBuilder::LowerCallSiteWithDeoptBundleImpl( + const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB, + bool VarArgDisallowed, bool ForceVoidReturnTy) { + StatepointLoweringInfo SI(DAG); + unsigned ArgBeginIndex = Call->arg_begin() - Call->op_begin(); + populateCallLoweringInfo( + SI.CLI, Call, ArgBeginIndex, Call->arg_size(), Callee, + ForceVoidReturnTy ? Type::getVoidTy(*DAG.getContext()) : Call->getType(), + false); + if (!VarArgDisallowed) + SI.CLI.IsVarArg = Call->getFunctionType()->isVarArg(); + + auto DeoptBundle = *Call->getOperandBundle(LLVMContext::OB_deopt); + + unsigned DefaultID = StatepointDirectives::DeoptBundleStatepointID; + + auto SD = parseStatepointDirectivesFromAttrs(Call->getAttributes()); + SI.ID = SD.StatepointID.value_or(DefaultID); + SI.NumPatchBytes = SD.NumPatchBytes.value_or(0); + + SI.DeoptState = + ArrayRef<const Use>(DeoptBundle.Inputs.begin(), DeoptBundle.Inputs.end()); + SI.StatepointFlags = static_cast<uint64_t>(StatepointFlags::None); + SI.EHPadBB = EHPadBB; + + // NB! The GC arguments are deliberately left empty. + + if (SDValue ReturnVal = LowerAsSTATEPOINT(SI)) { + ReturnVal = lowerRangeToAssertZExt(DAG, *Call, ReturnVal); + setValue(Call, ReturnVal); + } +} + +void SelectionDAGBuilder::LowerCallSiteWithDeoptBundle( + const CallBase *Call, SDValue Callee, const BasicBlock *EHPadBB) { + LowerCallSiteWithDeoptBundleImpl(Call, Callee, EHPadBB, + /* VarArgDisallowed = */ false, + /* ForceVoidReturnTy = */ false); +} + +void SelectionDAGBuilder::visitGCResult(const GCResultInst &CI) { + // The result value of the gc_result is simply the result of the actual + // call. We've already emitted this, so just grab the value. + const Value *SI = CI.getStatepoint(); + assert((isa<GCStatepointInst>(SI) || isa<UndefValue>(SI)) && + "GetStatepoint must return one of two types"); + if (isa<UndefValue>(SI)) + return; + + if (cast<GCStatepointInst>(SI)->getParent() == CI.getParent()) { + setValue(&CI, getValue(SI)); + return; + } + // 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 actual call return types can be + // different, and getValue() will use CopyFromReg of the wrong type, + // which is always i32 in our case. + Type *RetTy = CI.getType(); + SDValue CopyFromReg = getCopyFromRegs(SI, RetTy); + + assert(CopyFromReg.getNode()); + setValue(&CI, CopyFromReg); +} + +void SelectionDAGBuilder::visitGCRelocate(const GCRelocateInst &Relocate) { + const Value *Statepoint = Relocate.getStatepoint(); +#ifndef NDEBUG + // Consistency check + // We skip this check for relocates not in the same basic block as their + // statepoint. It would be too expensive to preserve validation info through + // different basic blocks. + assert((isa<GCStatepointInst>(Statepoint) || isa<UndefValue>(Statepoint)) && + "GetStatepoint must return one of two types"); + if (isa<UndefValue>(Statepoint)) + return; + + if (cast<GCStatepointInst>(Statepoint)->getParent() == Relocate.getParent()) + StatepointLowering.relocCallVisited(Relocate); +#endif + + const Value *DerivedPtr = Relocate.getDerivedPtr(); + auto &RelocationMap = + FuncInfo.StatepointRelocationMaps[cast<GCStatepointInst>(Statepoint)]; + auto SlotIt = RelocationMap.find(&Relocate); + assert(SlotIt != RelocationMap.end() && "Relocating not lowered gc value"); + const RecordType &Record = SlotIt->second; + + // If relocation was done via virtual register.. + if (Record.type == RecordType::SDValueNode) { + assert(cast<GCStatepointInst>(Statepoint)->getParent() == + Relocate.getParent() && + "Nonlocal gc.relocate mapped via SDValue"); + SDValue SDV = StatepointLowering.getLocation(getValue(DerivedPtr)); + assert(SDV.getNode() && "empty SDValue"); + setValue(&Relocate, SDV); + return; + } + if (Record.type == RecordType::VReg) { + Register InReg = Record.payload.Reg; + RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(), + DAG.getDataLayout(), InReg, Relocate.getType(), + std::nullopt); // This is not an ABI copy. + // We generate copy to/from regs even for local uses, hence we must + // chain with current root to ensure proper ordering of copies w.r.t. + // statepoint. + SDValue Chain = DAG.getRoot(); + SDValue Relocation = RFV.getCopyFromRegs(DAG, FuncInfo, getCurSDLoc(), + Chain, nullptr, nullptr); + setValue(&Relocate, Relocation); + return; + } + + if (Record.type == RecordType::Spill) { + unsigned Index = Record.payload.FI; + SDValue SpillSlot = DAG.getTargetFrameIndex(Index, getFrameIndexTy()); + + // All the reloads are independent and are reading memory only modified by + // statepoints (i.e. no other aliasing stores); informing SelectionDAG of + // this lets CSE kick in for free and allows reordering of + // instructions if possible. The lowering for statepoint sets the root, + // so this is ordering all reloads with the either + // a) the statepoint node itself, or + // b) the entry of the current block for an invoke statepoint. + const SDValue Chain = DAG.getRoot(); // != Builder.getRoot() + + auto &MF = DAG.getMachineFunction(); + auto &MFI = MF.getFrameInfo(); + auto PtrInfo = MachinePointerInfo::getFixedStack(MF, Index); + auto *LoadMMO = MF.getMachineMemOperand(PtrInfo, MachineMemOperand::MOLoad, + MFI.getObjectSize(Index), + MFI.getObjectAlign(Index)); + + auto LoadVT = DAG.getTargetLoweringInfo().getValueType(DAG.getDataLayout(), + Relocate.getType()); + + SDValue SpillLoad = + DAG.getLoad(LoadVT, getCurSDLoc(), Chain, SpillSlot, LoadMMO); + PendingLoads.push_back(SpillLoad.getValue(1)); + + assert(SpillLoad.getNode()); + setValue(&Relocate, SpillLoad); + return; + } + + assert(Record.type == RecordType::NoRelocate); + SDValue SD = getValue(DerivedPtr); + + if (SD.isUndef() && SD.getValueType().getSizeInBits() <= 64) { + // Lowering relocate(undef) as arbitrary constant. Current constant value + // is chosen such that it's unlikely to be a valid pointer. + setValue(&Relocate, DAG.getTargetConstant(0xFEFEFEFE, SDLoc(SD), MVT::i64)); + return; + } + + // We didn't need to spill these special cases (constants and allocas). + // See the handling in spillIncomingValueForStatepoint for detail. + setValue(&Relocate, SD); +} + +void SelectionDAGBuilder::LowerDeoptimizeCall(const CallInst *CI) { + const auto &TLI = DAG.getTargetLoweringInfo(); + SDValue Callee = DAG.getExternalSymbol(TLI.getLibcallName(RTLIB::DEOPTIMIZE), + TLI.getPointerTy(DAG.getDataLayout())); + + // We don't lower calls to __llvm_deoptimize as varargs, but as a regular + // call. We also do not lower the return value to any virtual register, and + // change the immediately following return to a trap instruction. + LowerCallSiteWithDeoptBundleImpl(CI, Callee, /* EHPadBB = */ nullptr, + /* VarArgDisallowed = */ true, + /* ForceVoidReturnTy = */ true); +} + +void SelectionDAGBuilder::LowerDeoptimizingReturn() { + // We do not lower the return value from llvm.deoptimize to any virtual + // register, and change the immediately following return to a trap + // instruction. + if (DAG.getTarget().Options.TrapUnreachable) + DAG.setRoot( + DAG.getNode(ISD::TRAP, getCurSDLoc(), MVT::Other, DAG.getRoot())); +} |