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+//===- 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/DenseMap.h"
+#include "llvm/ADT/None.h"
+#include "llvm/ADT/Optional.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/CodeGen/FunctionLoweringInfo.h"
+#include "llvm/CodeGen/GCMetadata.h"
+#include "llvm/CodeGen/GCStrategy.h"
+#include "llvm/CodeGen/ISDOpcodes.h"
+#include "llvm/CodeGen/MachineFrameInfo.h"
+#include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineMemOperand.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/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/MachineValueType.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");
+
+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) == ValueType.getSizeInBits() && "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 Optional<int> findPreviousSpillSlot(const Value *Val,
+ SelectionDAGBuilder &Builder,
+ int LookUpDepth) {
+ // Can not look any further - give up now
+ if (LookUpDepth <= 0)
+ return None;
+
+ // Spill location is known for gc relocates
+ if (const auto *Relocate = dyn_cast<GCRelocateInst>(Val)) {
+ const auto &SpillMap =
+ Builder.FuncInfo.StatepointSpillMaps[Relocate->getStatepoint()];
+
+ auto It = SpillMap.find(Relocate->getDerivedPtr());
+ if (It == SpillMap.end())
+ return None;
+
+ return It->second;
+ }
+
+ // Look through bitcast instructions.
+ if (const BitCastInst *Cast = dyn_cast<BitCastInst>(Val))
+ return findPreviousSpillSlot(Cast->getOperand(0), Builder, LookUpDepth - 1);
+
+ // Look through phi nodes
+ // All incoming values should have same known stack slot, otherwise result
+ // is unknown.
+ if (const PHINode *Phi = dyn_cast<PHINode>(Val)) {
+ Optional<int> MergedResult = None;
+
+ for (auto &IncomingValue : Phi->incoming_values()) {
+ Optional<int> SpillSlot =
+ findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth - 1);
+ if (!SpillSlot.hasValue())
+ return None;
+
+ if (MergedResult.hasValue() && *MergedResult != *SpillSlot)
+ return None;
+
+ 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 None;
+}
+
+/// 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 (isa<ConstantSDNode>(Incoming) || isa<FrameIndexSDNode>(Incoming)) {
+ // We won't need to spill this, so no need to check for previously
+ // allocated stack slots
+ return;
+ }
+
+ SDValue OldLocation = Builder.StatepointLowering.getLocation(Incoming);
+ if (OldLocation.getNode())
+ // Duplicates in input
+ return;
+
+ const int LookUpDepth = 6;
+ Optional<int> Index =
+ findPreviousSpillSlot(IncomingValue, Builder, LookUpDepth);
+ if (!Index.hasValue())
+ return;
+
+ 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);
+}
+
+/// Remove any duplicate (as SDValues) from the derived pointer pairs. This
+/// is not required for correctness. It's purpose is to reduce the size of
+/// StackMap section. It has no effect on the number of spill slots required
+/// or the actual lowering.
+static void
+removeDuplicateGCPtrs(SmallVectorImpl<const Value *> &Bases,
+ SmallVectorImpl<const Value *> &Ptrs,
+ SmallVectorImpl<const GCRelocateInst *> &Relocs,
+ SelectionDAGBuilder &Builder,
+ FunctionLoweringInfo::StatepointSpillMap &SSM) {
+ DenseMap<SDValue, const Value *> Seen;
+
+ SmallVector<const Value *, 64> NewBases, NewPtrs;
+ SmallVector<const GCRelocateInst *, 64> NewRelocs;
+ for (size_t i = 0, e = Ptrs.size(); i < e; i++) {
+ SDValue SD = Builder.getValue(Ptrs[i]);
+ auto SeenIt = Seen.find(SD);
+
+ if (SeenIt == Seen.end()) {
+ // Only add non-duplicates
+ NewBases.push_back(Bases[i]);
+ NewPtrs.push_back(Ptrs[i]);
+ NewRelocs.push_back(Relocs[i]);
+ Seen[SD] = Ptrs[i];
+ } else {
+ // Duplicate pointer found, note in SSM and move on:
+ SSM.DuplicateMap[Ptrs[i]] = SeenIt->second;
+ }
+ }
+ assert(Bases.size() >= NewBases.size());
+ assert(Ptrs.size() >= NewPtrs.size());
+ assert(Relocs.size() >= NewRelocs.size());
+ Bases = NewBases;
+ Ptrs = NewPtrs;
+ Relocs = NewRelocs;
+ assert(Ptrs.size() == Bases.size());
+ assert(Ptrs.size() == Relocs.size());
+}
+
+/// Extract call from statepoint, lower it and return pointer to the
+/// call node. Also update NodeMap so that getValue(statepoint) will
+/// reference lowered call result
+static std::pair<SDValue, SDNode *> lowerCallFromStatepointLoweringInfo(
+ SelectionDAGBuilder::StatepointLoweringInfo &SI,
+ SelectionDAGBuilder &Builder, SmallVectorImpl<SDValue> &PendingExports) {
+ SDValue ReturnValue, CallEndVal;
+ std::tie(ReturnValue, CallEndVal) =
+ Builder.lowerInvokable(SI.CLI, SI.EHPadBB);
+ SDNode *CallEnd = CallEndVal.getNode();
+
+ // Get a call instruction from the call sequence chain. Tail calls are not
+ // allowed. The following code is essentially reverse engineering X86's
+ // LowerCallTo.
+ //
+ // We are expecting DAG to have the following form:
+ //
+ // ch = eh_label (only in case of invoke statepoint)
+ // ch, glue = callseq_start ch
+ // ch, glue = X86::Call ch, glue
+ // ch, glue = callseq_end ch, glue
+ // get_return_value ch, glue
+ //
+ // get_return_value can either be a sequence of CopyFromReg instructions
+ // to grab the return value from the return register(s), or it can be a LOAD
+ // to load a value returned by reference via a stack slot.
+
+ bool HasDef = !SI.CLI.RetTy->isVoidTy();
+ if (HasDef) {
+ if (CallEnd->getOpcode() == ISD::LOAD)
+ CallEnd = CallEnd->getOperand(0).getNode();
+ else
+ while (CallEnd->getOpcode() == ISD::CopyFromReg)
+ CallEnd = CallEnd->getOperand(0).getNode();
+ }
+
+ assert(CallEnd->getOpcode() == ISD::CALLSEQ_END && "expected!");
+ return std::make_pair(ReturnValue, CallEnd->getOperand(0).getNode());
+}
+
+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.getObjectAlignment(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());
+
+#ifndef NDEBUG
+ // Right now we always allocate spill slots that are of the same
+ // size as the value we're about to spill (the size of spillee can
+ // vary since we spill vectors of pointers too). At some point we
+ // can consider allowing spills of smaller values to larger slots
+ // (i.e. change the '==' in the assert below to a '>=').
+ MachineFrameInfo &MFI = Builder.DAG.getMachineFunction().getFrameInfo();
+ assert((MFI.getObjectSize(Index) * 8) == Incoming.getValueSizeInBits() &&
+ "Bad spill: stack slot does not match!");
+#endif
+
+ auto &MF = Builder.DAG.getMachineFunction();
+ auto PtrInfo = MachinePointerInfo::getFixedStack(MF, Index);
+ Chain = Builder.DAG.getStore(Chain, Builder.getCurSDLoc(), Incoming, Loc,
+ PtrInfo);
+
+ 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 LiveInOnly,
+ SmallVectorImpl<SDValue> &Ops,
+ SmallVectorImpl<MachineMemOperand*> &MemRefs,
+ SelectionDAGBuilder &Builder) {
+ // 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();
+
+ if (ConstantSDNode *C = dyn_cast<ConstantSDNode>(Incoming)) {
+ // If the original value was a constant, make sure it gets recorded as
+ // such in the stackmap. This is required so that the consumer can
+ // parse any internal format to the deopt state. It also handles null
+ // pointers and other constant pointers in GC states. Note the constant
+ // vectors do not appear to actually hit this path and that anything larger
+ // than an i64 value (not type!) will fail asserts here.
+ pushStackMapConstant(Ops, Builder, C->getSExtValue());
+ } else if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {
+ // This handles allocas as arguments to the statepoint (this is only
+ // really meaningful for a deopt value. For GC, we'd be trying to
+ // relocate the address of the alloca itself?)
+ assert(Incoming.getValueType() == Builder.getFrameIndexTy() &&
+ "Incoming value is a frame index!");
+ Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(),
+ Builder.getFrameIndexTy()));
+
+ auto &MF = Builder.DAG.getMachineFunction();
+ auto *MMO = getMachineMemOperand(MF, *FI);
+ MemRefs.push_back(MMO);
+
+ } else if (LiveInOnly) {
+ // If this value is live in (not live-on-return, or live-through), we can
+ // treat it the same way patchpoint treats it's "live in" values. We'll
+ // end up folding some of these into stack references, but they'll be
+ // handled by the register allocator. Note that we do not have the notion
+ // of a late use so these values might be placed in registers which are
+ // clobbered by the call. This is fine for live-in.
+ Ops.push_back(Incoming);
+ } else {
+ // Otherwise, locate a spill slot and explicitly spill it so it
+ // can be found by the runtime later. We currently do not support
+ // tracking values through callee saved registers to their eventual
+ // spill location. This would be a useful optimization, but would
+ // need to be optional since it requires a lot of complexity on the
+ // runtime side which not all would support.
+ auto Res = spillIncomingStatepointValue(Incoming, Chain, Builder);
+ Ops.push_back(std::get<0>(Res));
+ if (auto *MMO = std::get<2>(Res))
+ MemRefs.push_back(MMO);
+ Chain = std::get<1>(Res);;
+ }
+
+ 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,
+ SmallVectorImpl<MachineMemOperand*> &MemRefs, SelectionDAGBuilder::StatepointLoweringInfo &SI,
+ SelectionDAGBuilder &Builder) {
+ // Lower the deopt and gc arguments for this statepoint. Layout will be:
+ // deopt argument length, deopt arguments.., gc arguments...
+#ifndef NDEBUG
+ if (auto *GFI = Builder.GFI) {
+ // Check that each of the gc pointer and bases we've gotten out of the
+ // safepoint is something the strategy thinks might be a pointer (or vector
+ // of pointers) into the GC heap. This is basically just here to help catch
+ // errors during statepoint insertion. TODO: This should actually be in the
+ // Verifier, but we can't get to the GCStrategy from there (yet).
+ GCStrategy &S = GFI->getStrategy();
+ for (const Value *V : SI.Bases) {
+ auto Opt = S.isGCManagedPointer(V->getType()->getScalarType());
+ if (Opt.hasValue()) {
+ assert(Opt.getValue() &&
+ "non gc managed base pointer found in statepoint");
+ }
+ }
+ for (const Value *V : SI.Ptrs) {
+ auto Opt = S.isGCManagedPointer(V->getType()->getScalarType());
+ if (Opt.hasValue()) {
+ assert(Opt.getValue() &&
+ "non gc managed derived pointer found in statepoint");
+ }
+ }
+ assert(SI.Bases.size() == SI.Ptrs.size() && "Pointer without base!");
+ } else {
+ assert(SI.Bases.empty() && "No gc specified, so cannot relocate pointers!");
+ assert(SI.Ptrs.empty() && "No gc specified, so cannot relocate pointers!");
+ }
+#endif
+
+ // Figure out what lowering strategy we're going to use for each part
+ // Note: Is is conservatively correct to lower both "live-in" and "live-out"
+ // as "live-through". A "live-through" variable is one which is "live-in",
+ // "live-out", and live throughout the lifetime of the call (i.e. we can find
+ // it from any PC within the transitive callee of the statepoint). In
+ // particular, if the callee spills callee preserved registers we may not
+ // be able to find a value placed in that register during the call. This is
+ // fine for live-out, but not for live-through. If we were willing to make
+ // assumptions about the code generator producing the callee, we could
+ // potentially allow live-through values in callee saved registers.
+ const bool LiveInDeopt =
+ SI.StatepointFlags & (uint64_t)StatepointFlags::DeoptLiveIn;
+
+ auto isGCValue =[&](const Value *V) {
+ return is_contained(SI.Ptrs, V) || is_contained(SI.Bases, V);
+ };
+
+ // Before we actually start lowering (and allocating spill slots for values),
+ // reserve any stack slots which we judge to be profitable to reuse for a
+ // particular value. This is purely an optimization over the code below and
+ // doesn't change semantics at all. It is important for performance that we
+ // reserve slots for both deopt and gc values before lowering either.
+ for (const Value *V : SI.DeoptState) {
+ if (!LiveInDeopt || isGCValue(V))
+ reservePreviousStackSlotForValue(V, Builder);
+ }
+ for (unsigned i = 0; i < SI.Bases.size(); ++i) {
+ reservePreviousStackSlotForValue(SI.Bases[i], Builder);
+ reservePreviousStackSlotForValue(SI.Ptrs[i], Builder);
+ }
+
+ // First, prefix the list with the number of unique values to be
+ // lowered. Note that this is the number of *Values* not the
+ // number of SDValues required to lower them.
+ const int NumVMSArgs = SI.DeoptState.size();
+ pushStackMapConstant(Ops, Builder, NumVMSArgs);
+
+ // The vm state arguments are lowered in an opaque manner. We do not know
+ // what type of values are contained within.
+ for (const Value *V : SI.DeoptState) {
+ SDValue Incoming;
+ // 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);
+ const bool LiveInValue = LiveInDeopt && !isGCValue(V);
+ lowerIncomingStatepointValue(Incoming, LiveInValue, Ops, MemRefs, Builder);
+ }
+
+ // Finally, go ahead and lower all the gc arguments. There's no prefixed
+ // length for this one. After lowering, we'll have the base and pointer
+ // arrays interwoven with each (lowered) base pointer immediately followed by
+ // it's (lowered) derived pointer. i.e
+ // (base[0], ptr[0], base[1], ptr[1], ...)
+ for (unsigned i = 0; i < SI.Bases.size(); ++i) {
+ const Value *Base = SI.Bases[i];
+ lowerIncomingStatepointValue(Builder.getValue(Base), /*LiveInOnly*/ false,
+ Ops, MemRefs, Builder);
+
+ const Value *Ptr = SI.Ptrs[i];
+ lowerIncomingStatepointValue(Builder.getValue(Ptr), /*LiveInOnly*/ false,
+ Ops, MemRefs, Builder);
+ }
+
+ // If there are any explicit spill slots passed to the statepoint, record
+ // them, but otherwise do not do anything special. These are user provided
+ // allocas and give control over placement to the consumer. In this case,
+ // it is the contents of the slot which may get updated, not the pointer to
+ // the alloca
+ for (Value *V : SI.GCArgs) {
+ SDValue Incoming = Builder.getValue(V);
+ if (FrameIndexSDNode *FI = dyn_cast<FrameIndexSDNode>(Incoming)) {
+ // This handles allocas as arguments to the statepoint
+ assert(Incoming.getValueType() == Builder.getFrameIndexTy() &&
+ "Incoming value is a frame index!");
+ Ops.push_back(Builder.DAG.getTargetFrameIndex(FI->getIndex(),
+ Builder.getFrameIndexTy()));
+
+ auto &MF = Builder.DAG.getMachineFunction();
+ auto *MMO = getMachineMemOperand(MF, *FI);
+ MemRefs.push_back(MMO);
+ }
+ }
+
+ // Record computed locations for all lowered values.
+ // This can not be embedded in lowering loops as we need to record *all*
+ // values, while previous loops account only values with unique SDValues.
+ const Instruction *StatepointInstr = SI.StatepointInstr;
+ auto &SpillMap = Builder.FuncInfo.StatepointSpillMaps[StatepointInstr];
+
+ for (const GCRelocateInst *Relocate : SI.GCRelocates) {
+ const Value *V = Relocate->getDerivedPtr();
+ SDValue SDV = Builder.getValue(V);
+ SDValue Loc = Builder.StatepointLowering.getLocation(SDV);
+
+ if (Loc.getNode()) {
+ SpillMap.SlotMap[V] = cast<FrameIndexSDNode>(Loc)->getIndex();
+ } else {
+ // Record value as visited, but not spilled. This is case for allocas
+ // and constants. For this values we can avoid emitting spill load while
+ // visiting corresponding gc_relocate.
+ // Actually we do not need to record them in this map at all.
+ // We do this only to check that we are not relocating any unvisited
+ // value.
+ SpillMap.SlotMap[V] = None;
+
+ // Default llvm mechanisms for exporting values which are used in
+ // different basic blocks does not work for gc relocates.
+ // Note that it would be incorrect to teach llvm that all relocates are
+ // uses of the corresponding values so that it would automatically
+ // export them. Relocates of the spilled values does not use original
+ // value.
+ if (Relocate->getParent() != StatepointInstr->getParent())
+ Builder.ExportFromCurrentBlock(V);
+ }
+ }
+}
+
+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);
+
+#ifndef NDEBUG
+ // We schedule gc relocates before removeDuplicateGCPtrs since we _will_
+ // encounter the duplicate gc relocates we elide in removeDuplicateGCPtrs.
+ for (auto *Reloc : SI.GCRelocates)
+ if (Reloc->getParent() == SI.StatepointInstr->getParent())
+ StatepointLowering.scheduleRelocCall(*Reloc);
+#endif
+
+ // 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.
+ removeDuplicateGCPtrs(SI.Bases, SI.Ptrs, SI.GCRelocates, *this,
+ FuncInfo.StatepointSpillMaps[SI.StatepointInstr]);
+ assert(SI.Bases.size() == SI.Ptrs.size() &&
+ SI.Ptrs.size() == SI.GCRelocates.size());
+
+ // Lower statepoint vmstate and gcstate arguments
+ SmallVector<SDValue, 10> LoweredMetaArgs;
+ SmallVector<MachineMemOperand*, 16> MemRefs;
+ lowerStatepointMetaArgs(LoweredMetaArgs, MemRefs, 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, PendingExports);
+
+ // 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
+ Ops.insert(Ops.end(), LoweredMetaArgs.begin(), LoweredMetaArgs.end());
+
+ // 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.
+ SDVTList NodeTys = DAG.getVTList(MVT::Other, MVT::Glue);
+
+ MachineSDNode *StatepointMCNode =
+ DAG.getMachineNode(TargetOpcode::STATEPOINT, getCurSDLoc(), NodeTys, Ops);
+ DAG.setNodeMemRefs(StatepointMCNode, MemRefs);
+
+ 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, 0));
+
+ // 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, 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
+ DAG.ReplaceAllUsesWith(CallNode, SinkNode); // This may update Root
+ // Remove original 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.
+
+ return ReturnVal;
+}
+
+void
+SelectionDAGBuilder::LowerStatepoint(ImmutableStatepoint ISP,
+ const BasicBlock *EHPadBB /*= nullptr*/) {
+ assert(ISP.getCall()->getCallingConv() != CallingConv::AnyReg &&
+ "anyregcc is not supported on statepoints!");
+
+#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.
+ assert(GFI->getStrategy().useStatepoints() &&
+ "GCStrategy does not expect to encounter statepoints");
+#endif
+
+ SDValue ActualCallee;
+
+ if (ISP.getNumPatchBytes() > 0) {
+ // If we've been asked to emit a nop sequence instead of a call instruction
+ // for this statepoint then don't lower the call target, but use a constant
+ // `null` instead. Not lowering the call target lets statepoint clients get
+ // away without providing a physical address for the symbolic call target at
+ // link time.
+
+ const auto &TLI = DAG.getTargetLoweringInfo();
+ const auto &DL = DAG.getDataLayout();
+
+ unsigned AS = ISP.getCalledValue()->getType()->getPointerAddressSpace();
+ ActualCallee = DAG.getConstant(0, getCurSDLoc(), TLI.getPointerTy(DL, AS));
+ } else {
+ ActualCallee = getValue(ISP.getCalledValue());
+ }
+
+ StatepointLoweringInfo SI(DAG);
+ populateCallLoweringInfo(SI.CLI, ISP.getCall(),
+ ImmutableStatepoint::CallArgsBeginPos,
+ ISP.getNumCallArgs(), ActualCallee,
+ ISP.getActualReturnType(), false /* IsPatchPoint */);
+
+ for (const GCRelocateInst *Relocate : ISP.getRelocates()) {
+ SI.GCRelocates.push_back(Relocate);
+ SI.Bases.push_back(Relocate->getBasePtr());
+ SI.Ptrs.push_back(Relocate->getDerivedPtr());
+ }
+
+ SI.GCArgs = ArrayRef<const Use>(ISP.gc_args_begin(), ISP.gc_args_end());
+ SI.StatepointInstr = ISP.getInstruction();
+ SI.GCTransitionArgs =
+ ArrayRef<const Use>(ISP.gc_args_begin(), ISP.gc_args_end());
+ SI.ID = ISP.getID();
+ SI.DeoptState = ArrayRef<const Use>(ISP.deopt_begin(), ISP.deopt_end());
+ SI.StatepointFlags = ISP.getFlags();
+ SI.NumPatchBytes = ISP.getNumPatchBytes();
+ SI.EHPadBB = EHPadBB;
+
+ SDValue ReturnValue = LowerAsSTATEPOINT(SI);
+
+ // Export the result value if needed
+ const GCResultInst *GCResult = ISP.getGCResult();
+ Type *RetTy = ISP.getActualReturnType();
+ if (!RetTy->isVoidTy() && GCResult) {
+ if (GCResult->getParent() != ISP.getCall()->getParent()) {
+ // Result value will be used in a different basic block so we need to
+ // export it now. Default exporting mechanism will not work here because
+ // statepoint call has a different type than the actual call. It means
+ // that by default llvm will create export register of the wrong type
+ // (always i32 in our case). So instead we need to create export register
+ // with correct type manually.
+ // TODO: To eliminate this problem we can remove gc.result intrinsics
+ // completely and make statepoint call to return a tuple.
+ unsigned Reg = FuncInfo.CreateRegs(RetTy);
+ RegsForValue RFV(*DAG.getContext(), DAG.getTargetLoweringInfo(),
+ DAG.getDataLayout(), Reg, RetTy,
+ ISP.getCall()->getCallingConv());
+ SDValue Chain = DAG.getEntryNode();
+
+ RFV.getCopyToRegs(ReturnValue, DAG, getCurSDLoc(), Chain, nullptr);
+ PendingExports.push_back(Chain);
+ FuncInfo.ValueMap[ISP.getInstruction()] = Reg;
+ } else {
+ // Result value will be used in a same basic block. Don't export it or
+ // perform any explicit register copies.
+ // We'll replace the actuall call node shortly. gc_result will grab
+ // this value.
+ setValue(ISP.getInstruction(), ReturnValue);
+ }
+ } else {
+ // The token value is never used from here on, just generate a poison value
+ setValue(ISP.getInstruction(), DAG.getIntPtrConstant(-1, getCurSDLoc()));
+ }
+}
+
+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->getNumArgOperands(), 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.getValueOr(DefaultID);
+ SI.NumPatchBytes = SD.NumPatchBytes.getValueOr(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 Instruction *I = CI.getStatepoint();
+
+ if (I->getParent() != CI.getParent()) {
+ // Statepoint is in different basic block so we should have stored call
+ // result in a virtual register.
+ // We can not use default getValue() functionality to copy value from this
+ // register because statepoint and actual 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).getCalledValue()->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 GCRelocateInst &Relocate) {
+#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.
+ if (Relocate.getStatepoint()->getParent() == Relocate.getParent())
+ StatepointLowering.relocCallVisited(Relocate);
+
+ auto *Ty = Relocate.getType()->getScalarType();
+ if (auto IsManaged = GFI->getStrategy().isGCManagedPointer(Ty))
+ assert(*IsManaged && "Non gc managed pointer relocated!");
+#endif
+
+ const Value *DerivedPtr = Relocate.getDerivedPtr();
+ SDValue SD = getValue(DerivedPtr);
+
+ auto &SpillMap = FuncInfo.StatepointSpillMaps[Relocate.getStatepoint()];
+ auto SlotIt = SpillMap.find(DerivedPtr);
+ assert(SlotIt != SpillMap.end() && "Relocating not lowered gc value");
+ Optional<int> DerivedPtrLocation = SlotIt->second;
+
+ // We didn't need to spill these special cases (constants and allocas).
+ // See the handling in spillIncomingValueForStatepoint for detail.
+ if (!DerivedPtrLocation) {
+ setValue(&Relocate, SD);
+ return;
+ }
+
+ SDValue SpillSlot =
+ DAG.getTargetFrameIndex(*DerivedPtrLocation, getFrameIndexTy());
+
+ // Note: We know all of these reloads 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 = getRoot();
+
+ SDValue SpillLoad =
+ DAG.getLoad(DAG.getTargetLoweringInfo().getValueType(DAG.getDataLayout(),
+ Relocate.getType()),
+ getCurSDLoc(), Chain, SpillSlot,
+ MachinePointerInfo::getFixedStack(DAG.getMachineFunction(),
+ *DerivedPtrLocation));
+
+ DAG.setRoot(SpillLoad.getValue(1));
+
+ assert(SpillLoad.getNode());
+ setValue(&Relocate, SpillLoad);
+}
+
+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()));
+}
generated by cgit v1.2.3 (git 2.25.1) at 2025-10-09 13:48:11 +0000