| //===-- StatepointLowering.cpp - SDAGBuilder's statepoint code -----------===// |
| // |
| // The LLVM Compiler Infrastructure |
| // |
| // This file is distributed under the University of Illinois Open Source |
| // License. See LICENSE.TXT for details. |
| // |
| //===----------------------------------------------------------------------===// |
| // |
| // 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/SmallSet.h" |
| #include "llvm/ADT/Statistic.h" |
| #include "llvm/CodeGen/FunctionLoweringInfo.h" |
| #include "llvm/CodeGen/GCMetadata.h" |
| #include "llvm/CodeGen/GCStrategy.h" |
| #include "llvm/CodeGen/SelectionDAG.h" |
| #include "llvm/CodeGen/StackMaps.h" |
| #include "llvm/IR/CallingConv.h" |
| #include "llvm/IR/Instructions.h" |
| #include "llvm/IR/IntrinsicInst.h" |
| #include "llvm/IR/Intrinsics.h" |
| #include "llvm/IR/Statepoint.h" |
| #include "llvm/Target/TargetLowering.h" |
| #include <algorithm> |
| 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"); |
| |
| void |
| StatepointLoweringState::startNewStatepoint(SelectionDAGBuilder &Builder) { |
| // Consistency check |
| assert(PendingGCRelocateCalls.empty() && |
| "Trying to visit statepoint before finished processing previous one"); |
| Locations.clear(); |
| RelocLocations.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. |
| AllocatedStackSlots.resize(Builder.FuncInfo.StatepointStackSlots.size()); |
| for (size_t i = 0; i < AllocatedStackSlots.size(); i++) { |
| AllocatedStackSlots[i] = false; |
| } |
| } |
| void StatepointLoweringState::clear() { |
| Locations.clear(); |
| RelocLocations.clear(); |
| AllocatedStackSlots.clear(); |
| assert(PendingGCRelocateCalls.empty() && |
| "cleared before statepoint sequence completed"); |
| } |
| |
| SDValue |
| StatepointLoweringState::allocateStackSlot(EVT ValueType, |
| SelectionDAGBuilder &Builder) { |
| |
| NumSlotsAllocatedForStatepoints++; |
| |
| // The basic scheme here is to 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. |
| |
| // If this doesn't succeed in 40000 iterations, something is seriously wrong |
| for (int i = 0; i < 40000; i++) { |
| assert(Builder.FuncInfo.StatepointStackSlots.size() == |
| AllocatedStackSlots.size() && |
| "broken invariant"); |
| const size_t NumSlots = AllocatedStackSlots.size(); |
| assert(NextSlotToAllocate <= NumSlots && "broken invariant"); |
| |
| if (NextSlotToAllocate >= NumSlots) { |
| assert(NextSlotToAllocate == NumSlots); |
| // record stats |
| if (NumSlots + 1 > StatepointMaxSlotsRequired) { |
| StatepointMaxSlotsRequired = NumSlots + 1; |
| } |
| |
| SDValue SpillSlot = Builder.DAG.CreateStackTemporary(ValueType); |
| const unsigned FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex(); |
| Builder.FuncInfo.StatepointStackSlots.push_back(FI); |
| AllocatedStackSlots.push_back(true); |
| return SpillSlot; |
| } |
| if (!AllocatedStackSlots[NextSlotToAllocate]) { |
| const int FI = Builder.FuncInfo.StatepointStackSlots[NextSlotToAllocate]; |
| AllocatedStackSlots[NextSlotToAllocate] = true; |
| 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 |
| // keep this code as simple as possible. |
| NextSlotToAllocate++; |
| } |
| llvm_unreachable("infinite loop?"); |
| } |
| |
| /// 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(SDValue Incoming, |
| SelectionDAGBuilder &Builder) { |
| |
| 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()) { |
| // 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()); |
| |
| Builder.StatepointLowering.setLocation(Incoming, Loc); |
| } |
| } |
| |
| // 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) |
| } |
| |
| /// 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()); |
| } |
| |
| /// 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 SDNode *lowerCallFromStatepoint(ImmutableStatepoint StatepointSite, |
| MachineBasicBlock *LandingPad, |
| SelectionDAGBuilder &Builder) { |
| |
| ImmutableCallSite CS(StatepointSite.getCallSite()); |
| |
| // Lower the actual call itself - This is a bit of a hack, but we want to |
| // avoid modifying the actual lowering code. This is similiar in intent to |
| // the LowerCallOperands mechanism used by PATCHPOINT, but is structured |
| // differently. Hopefully, this is slightly more robust w.r.t. calling |
| // convention, return values, and other function attributes. |
| Value *ActualCallee = const_cast<Value *>(StatepointSite.actualCallee()); |
| |
| std::vector<Value *> Args; |
| CallInst::const_op_iterator arg_begin = StatepointSite.call_args_begin(); |
| CallInst::const_op_iterator arg_end = StatepointSite.call_args_end(); |
| Args.insert(Args.end(), arg_begin, arg_end); |
| // TODO: remove the creation of a new instruction! We should not be |
| // modifying the IR (even temporarily) at this point. |
| CallInst *Tmp = CallInst::Create(ActualCallee, Args); |
| Tmp->setTailCall(CS.isTailCall()); |
| Tmp->setCallingConv(CS.getCallingConv()); |
| Tmp->setAttributes(CS.getAttributes()); |
| Builder.LowerCallTo(Tmp, Builder.getValue(ActualCallee), false, LandingPad); |
| |
| // Handle the return value of the call iff any. |
| const bool HasDef = !Tmp->getType()->isVoidTy(); |
| 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. |
| // TODO: To eliminate this problem we can remove gc.result intrinsics |
| // completelly and make statepoint call to return a tuple. |
| unsigned reg = Builder.FuncInfo.CreateRegs(Tmp->getType()); |
| Builder.CopyValueToVirtualRegister(Tmp, reg); |
| 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 |
| // this value. |
| Builder.setValue(CS.getInstruction(), Builder.getValue(Tmp)); |
| } |
| } else { |
| // The token value is never used from here on, just generate a poison value |
| Builder.setValue(CS.getInstruction(), Builder.DAG.getIntPtrConstant(-1)); |
| } |
| // Remove the fake entry we created so we don't have a hanging reference |
| // after we delete this node. |
| Builder.removeValue(Tmp); |
| delete Tmp; |
| Tmp = nullptr; |
| |
| // Search for the call node |
| // 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 |
| // ch = eh_label ch (only in case of invoke statepoint) |
| // |
| // DAG root will be either last eh_label or callseq_end. |
| |
| SDNode *CallNode = nullptr; |
| |
| // We just emitted a call, so it should be last thing generated |
| SDValue Chain = Builder.DAG.getRoot(); |
| |
| // Find closest CALLSEQ_END walking back through lowered nodes if needed |
| SDNode *CallEnd = Chain.getNode(); |
| int Sanity = 0; |
| while (CallEnd->getOpcode() != ISD::CALLSEQ_END) { |
| assert(CallEnd->getNumOperands() >= 1 && |
| CallEnd->getOperand(0).getValueType() == MVT::Other); |
| |
| CallEnd = CallEnd->getOperand(0).getNode(); |
| |
| assert(Sanity < 20 && "should have found call end already"); |
| Sanity++; |
| } |
| assert(CallEnd->getOpcode() == ISD::CALLSEQ_END && |
| "Expected a callseq node."); |
| assert(CallEnd->getGluedNode()); |
| |
| // Step back inside the CALLSEQ |
| CallNode = CallEnd->getGluedNode(); |
| return CallNode; |
| } |
| |
| /// Callect all gc pointers coming into statepoint intrinsic, clean them up, |
| /// and return two arrays: |
| /// Bases - base pointers incoming to this statepoint |
| /// Ptrs - derived pointers incoming to this statepoint |
| /// Relocs - the gc_relocate corresponding to each base/ptr pair |
| /// Elements of this arrays should be in one-to-one correspondence with each |
| /// other i.e Bases[i], Ptrs[i] are from the same gcrelocate call |
| static void |
| getIncomingStatepointGCValues(SmallVectorImpl<const Value *> &Bases, |
| SmallVectorImpl<const Value *> &Ptrs, |
| SmallVectorImpl<const Value *> &Relocs, |
| ImmutableStatepoint StatepointSite, |
| SelectionDAGBuilder &Builder) { |
| for (GCRelocateOperands relocateOpers : |
| StatepointSite.getRelocates(StatepointSite)) { |
| Relocs.push_back(relocateOpers.getUnderlyingCallSite().getInstruction()); |
| Bases.push_back(relocateOpers.basePtr()); |
| Ptrs.push_back(relocateOpers.derivedPtr()); |
| } |
| |
| // Remove any redundant llvm::Values which map to the same SDValue as another |
| // input. Also has the effect of removing duplicates in the original |
| // llvm::Value input list as well. This is a useful optimization for |
| // reducing the size of the StackMap section. It has no other impact. |
| removeDuplicatesGCPtrs(Bases, Ptrs, Relocs, Builder); |
| |
| assert(Bases.size() == Ptrs.size() && Ptrs.size() == Relocs.size()); |
| } |
| |
| /// 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); |
| } |
| |
| /// 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 |
| Ops.push_back( |
| Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64)); |
| Ops.push_back(Builder.DAG.getTargetConstant(C->getSExtValue(), MVT::i64)); |
| } 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); |
| } |
| |
| /// 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 (auto I = StatepointSite.vm_state_begin() + 1, |
| E = StatepointSite.vm_state_end(); |
| I != E; ++I) { |
| Value *V = *I; |
| SDValue Incoming = Builder.getValue(V); |
| reservePreviousStackSlotForValue(Incoming, Builder); |
| } |
| for (unsigned i = 0; i < Bases.size() * 2; ++i) { |
| // Even elements will contain base, odd elements - derived ptr |
| const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2]; |
| SDValue Incoming = Builder.getValue(V); |
| reservePreviousStackSlotForValue(Incoming, 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.numTotalVMSArgs(); |
| Ops.push_back( |
| Builder.DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64)); |
| Ops.push_back(Builder.DAG.getTargetConstant(NumVMSArgs, MVT::i64)); |
| |
| assert(NumVMSArgs + 1 == 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 (auto I = StatepointSite.vm_state_begin() + 1, |
| E = StatepointSite.vm_state_end(); |
| I != E; ++I) { |
| const Value *V = *I; |
| 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() * 2; ++i) { |
| // Even elements will contain base, odd elements - derived ptr |
| const Value *V = i % 2 ? Bases[i / 2] : Ptrs[i / 2]; |
| SDValue Incoming = Builder.getValue(V); |
| lowerIncomingStatepointValue(Incoming, 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())); |
| |
| } |
| } |
| } |
| |
| void SelectionDAGBuilder::visitStatepoint(const CallInst &CI) { |
| // Check some preconditions for sanity |
| assert(isStatepoint(&CI) && |
| "function called must be the statepoint function"); |
| |
| LowerStatepoint(ImmutableStatepoint(&CI)); |
| } |
| |
| void |
| SelectionDAGBuilder::LowerStatepoint(ImmutableStatepoint ISP, |
| MachineBasicBlock *LandingPad/*=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. |
| |
| NumOfStatepoints++; |
| // Clear state |
| StatepointLowering.startNewStatepoint(*this); |
| |
| ImmutableCallSite CS(ISP.getCallSite()); |
| |
| #ifndef NDEBUG |
| // Consistency check |
| for (const User *U : CS->users()) { |
| const CallInst *Call = cast<CallInst>(U); |
| if (isGCRelocate(Call)) |
| StatepointLowering.scheduleRelocCall(*Call); |
| } |
| #endif |
| |
| #ifndef NDEBUG |
| // If this is a malformed statepoint, report it early to simplify debugging. |
| // This should catch any IR level mistake that's made when constructing or |
| // transforming statepoints. |
| ISP.verify(); |
| |
| // Check that the associated GCStrategy expects to encounter statepoints. |
| // TODO: This if should become an assert. For now, we allow the GCStrategy |
| // to be optional for backwards compatibility. This will only last a short |
| // period (i.e. a couple of weeks). |
| assert(GFI->getStrategy().useStatepoints() && |
| "GCStrategy does not expect to encounter statepoints"); |
| #endif |
| |
| // Lower statepoint vmstate and gcstate arguments |
| SmallVector<SDValue, 10> LoweredArgs; |
| lowerStatepointMetaArgs(LoweredArgs, ISP, *this); |
| |
| // Get call node, we will replace it later with statepoint |
| SDNode *CallNode = lowerCallFromStatepoint(ISP, LandingPad, *this); |
| |
| // Construct the actual STATEPOINT node with all the appropriate arguments |
| // and return values. |
| |
| // 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; |
| |
| // Calculate and push starting position of vmstate arguments |
| // Call Node: Chain, Target, {Args}, RegMask, [Glue] |
| SDValue Glue; |
| if (CallNode->getGluedNode()) { |
| // Glue is always last operand |
| Glue = CallNode->getOperand(CallNode->getNumOperands() - 1); |
| } |
| // Get number of arguments incoming directly into call node |
| unsigned NumCallRegArgs = |
| CallNode->getNumOperands() - (Glue.getNode() ? 4 : 3); |
| Ops.push_back(DAG.getTargetConstant(NumCallRegArgs, 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 (Glue.getNode()) |
| RegMaskIt = CallNode->op_end() - 2; |
| else |
| RegMaskIt = CallNode->op_end() - 1; |
| Ops.insert(Ops.end(), CallNode->op_begin() + 2, RegMaskIt); |
| |
| // Add a leading constant argument with the Flags and the calling convention |
| // masked together |
| CallingConv::ID CallConv = CS.getCallingConv(); |
| int Flags = cast<ConstantInt>(CS.getArgument(2))->getZExtValue(); |
| assert(Flags == 0 && "not expected to be used"); |
| Ops.push_back(DAG.getTargetConstant(StackMaps::ConstantOp, MVT::i64)); |
| Ops.push_back( |
| DAG.getTargetConstant(Flags | ((unsigned)CallConv << 1), MVT::i64)); |
| |
| // Insert all vmstate and gcstate arguments |
| Ops.insert(Ops.end(), LoweredArgs.begin(), LoweredArgs.end()); |
| |
| // Add register mask from call node |
| Ops.push_back(*RegMaskIt); |
| |
| // Add chain |
| Ops.push_back(CallNode->getOperand(0)); |
| |
| // 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. |
| SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue); |
| |
| SDNode *StatepointMCNode = DAG.getMachineNode(TargetOpcode::STATEPOINT, |
| getCurSDLoc(), NodeTys, Ops); |
| |
| // Replace original call |
| DAG.ReplaceAllUsesWith(CallNode, StatepointMCNode); // This may update Root |
| // Remove originall call node |
| DAG.DeleteNode(CallNode); |
| |
| // DON'T set the root - under the assumption that it's already set past the |
| // inserted node we created. |
| |
| // 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. |
| } |
| |
| void SelectionDAGBuilder::visitGCResult(const CallInst &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. |
| 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. |
| // 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).actualCallee()->getType()); |
| Type *RetTy = cast<FunctionType>( |
| CalleeType->getElementType())->getReturnType(); |
| SDValue CopyFromReg = getCopyFromRegs(I, RetTy); |
| |
| assert(CopyFromReg.getNode()); |
| setValue(&CI, CopyFromReg); |
| } |
| else { |
| setValue(&CI, getValue(I)); |
| } |
| } |
| |
| void SelectionDAGBuilder::visitGCRelocate(const CallInst &CI) { |
| #ifndef NDEBUG |
| // Consistency check |
| StatepointLowering.relocCallVisited(CI); |
| #endif |
| |
| GCRelocateOperands relocateOpers(&CI); |
| SDValue SD = getValue(relocateOpers.derivedPtr()); |
| |
| if (isa<ConstantSDNode>(SD) || isa<FrameIndexSDNode>(SD)) { |
| // We didn't need to spill these special cases (constants and allocas). |
| // See the handling in spillIncomingValueForStatepoint for detail. |
| setValue(&CI, SD); |
| return; |
| } |
| |
| SDValue Loc = StatepointLowering.getRelocLocation(SD); |
| // Emit new load if we did not emit it before |
| if (!Loc.getNode()) { |
| SDValue SpillSlot = StatepointLowering.getLocation(SD); |
| int FI = cast<FrameIndexSDNode>(SpillSlot)->getIndex(); |
| |
| // Be conservative: flush all pending loads |
| // TODO: Probably we can be less restrictive on this, |
| // it may allow more scheduling opprtunities |
| SDValue Chain = getRoot(); |
| |
| Loc = DAG.getLoad(SpillSlot.getValueType(), getCurSDLoc(), Chain, |
| SpillSlot, MachinePointerInfo::getFixedStack(FI), false, |
| false, false, 0); |
| |
| StatepointLowering.setRelocLocation(SD, Loc); |
| |
| // Again, be conservative, don't emit pending loads |
| DAG.setRoot(Loc.getValue(1)); |
| } |
| |
| assert(Loc.getNode()); |
| setValue(&CI, Loc); |
| } |
