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diff --git a/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.h b/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.h
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+++ b/llvm/lib/CodeGen/SelectionDAG/StatepointLowering.h
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+//===- StatepointLowering.h - SDAGBuilder's statepoint code ---*- C++ -*---===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H
+#define LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallBitVector.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/CodeGen/SelectionDAGNodes.h"
+#include "llvm/CodeGen/ValueTypes.h"
+#include <cassert>
+
+namespace llvm {
+
+class CallInst;
+class SelectionDAGBuilder;
+
+/// This class tracks both per-statepoint and per-selectiondag information.
+/// For each statepoint it tracks locations of it's gc valuess (incoming and
+/// relocated) and list of gcreloc calls scheduled for visiting (this is
+/// used for a debug mode consistency check only).  The spill slot tracking
+/// works in concert with information in FunctionLoweringInfo.
+class StatepointLoweringState {
+public:
+  StatepointLoweringState() = default;
+
+  /// Reset all state tracking for a newly encountered safepoint.  Also
+  /// performs some consistency checking.
+  void startNewStatepoint(SelectionDAGBuilder &Builder);
+
+  /// Clear the memory usage of this object.  This is called from
+  /// SelectionDAGBuilder::clear.  We require this is never called in the
+  /// midst of processing a statepoint sequence.
+  void clear();
+
+  /// Returns the spill location of a value incoming to the current
+  /// statepoint.  Will return SDValue() if this value hasn't been
+  /// spilled.  Otherwise, the value has already been spilled and no
+  /// further action is required by the caller.
+  SDValue getLocation(SDValue Val) {
+    auto I = Locations.find(Val);
+    if (I == Locations.end())
+      return SDValue();
+    return I->second;
+  }
+
+  void setLocation(SDValue Val, SDValue Location) {
+    assert(!Locations.count(Val) &&
+           "Trying to allocate already allocated location");
+    Locations[Val] = Location;
+  }
+
+  /// Record the fact that we expect to encounter a given gc_relocate
+  /// before the next statepoint.  If we don't see it, we'll report
+  /// an assertion.
+  void scheduleRelocCall(const CallInst &RelocCall) {
+    // We are not interested in lowering dead instructions.
+    if (!RelocCall.use_empty())
+      PendingGCRelocateCalls.push_back(&RelocCall);
+  }
+
+  /// Remove this gc_relocate from the list we're expecting to see
+  /// before the next statepoint.  If we weren't expecting to see
+  /// it, we'll report an assertion.
+  void relocCallVisited(const CallInst &RelocCall) {
+    // We are not interested in lowering dead instructions.
+    if (RelocCall.use_empty())
+      return;
+    auto I = llvm::find(PendingGCRelocateCalls, &RelocCall);
+    assert(I != PendingGCRelocateCalls.end() &&
+           "Visited unexpected gcrelocate call");
+    PendingGCRelocateCalls.erase(I);
+  }
+
+  // TODO: Should add consistency tracking to ensure we encounter
+  // expected gc_result calls too.
+
+  /// Get a stack slot we can use to store an value of type ValueType.  This
+  /// will hopefully be a recylced slot from another statepoint.
+  SDValue allocateStackSlot(EVT ValueType, SelectionDAGBuilder &Builder);
+
+  void reserveStackSlot(int Offset) {
+    assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
+           "out of bounds");
+    assert(!AllocatedStackSlots.test(Offset) && "already reserved!");
+    assert(NextSlotToAllocate <= (unsigned)Offset && "consistency!");
+    AllocatedStackSlots.set(Offset);
+  }
+
+  bool isStackSlotAllocated(int Offset) {
+    assert(Offset >= 0 && Offset < (int)AllocatedStackSlots.size() &&
+           "out of bounds");
+    return AllocatedStackSlots.test(Offset);
+  }
+
+private:
+  /// Maps pre-relocation value (gc pointer directly incoming into statepoint)
+  /// into it's location (currently only stack slots)
+  DenseMap<SDValue, SDValue> Locations;
+
+  /// A boolean indicator for each slot listed in the FunctionInfo as to
+  /// whether it has been used in the current statepoint.  Since we try to
+  /// preserve stack slots across safepoints, there can be gaps in which
+  /// slots have been allocated.
+  SmallBitVector AllocatedStackSlots;
+
+  /// Points just beyond the last slot known to have been allocated
+  unsigned NextSlotToAllocate = 0;
+
+  /// Keep track of pending gcrelocate calls for consistency check
+  SmallVector<const CallInst *, 10> PendingGCRelocateCalls;
+};
+
+} // end namespace llvm
+
+#endif // LLVM_LIB_CODEGEN_SELECTIONDAG_STATEPOINTLOWERING_H