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Diffstat (limited to 'lib/CodeGen/SelectionDAG/StatepointLowering.cpp')
| -rw-r--r-- | lib/CodeGen/SelectionDAG/StatepointLowering.cpp | 679 |
1 files changed, 679 insertions, 0 deletions
diff --git a/lib/CodeGen/SelectionDAG/StatepointLowering.cpp b/lib/CodeGen/SelectionDAG/StatepointLowering.cpp new file mode 100644 index 0000000..1271f6b --- /dev/null +++ b/lib/CodeGen/SelectionDAG/StatepointLowering.cpp @@ -0,0 +1,679 @@ +//===-- 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, + 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); + + // Handle the return value of the call iff any. + const bool HasDef = !Tmp->getType()->isVoidTy(); + if (HasDef) { + // 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. + 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) { + CallEnd = CallEnd->getGluedNode(); + assert(CallEnd && "Can not find call node"); + 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 + const TargetLowering &TLI = Builder.DAG.getTargetLoweringInfo(); + Ops.push_back( + Builder.DAG.getTargetFrameIndex(FI->getIndex(), TLI.getPointerTy())); + } 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). + if (Builder.GFI) { + 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); + } +} + +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) { + // 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). + if (GFI) { + 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, *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 = dyn_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"); + + 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); +} |