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diff --git a/lib/Target/AArch64/AArch64StackOffset.h b/lib/Target/AArch64/AArch64StackOffset.h
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index 000000000000..13f12a6c9c30
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+++ b/lib/Target/AArch64/AArch64StackOffset.h
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+//==--AArch64StackOffset.h ---------------------------------------*- 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 contains the declaration of the StackOffset class, which is used to
+// describe scalable and non-scalable offsets during frame lowering.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIB_TARGET_AARCH64_AARCH64STACKOFFSET_H
+#define LLVM_LIB_TARGET_AARCH64_AARCH64STACKOFFSET_H
+
+#include "llvm/Support/MachineValueType.h"
+
+namespace llvm {
+
+/// StackOffset is a wrapper around scalable and non-scalable offsets and is
+/// used in several functions such as 'isAArch64FrameOffsetLegal' and
+/// 'emitFrameOffset()'. StackOffsets are described by MVTs, e.g.
+//
+///   StackOffset(1, MVT::nxv16i8)
+//
+/// would describe an offset as being the size of a single SVE vector.
+///
+/// The class also implements simple arithmetic (addition/subtraction) on these
+/// offsets, e.g.
+//
+///   StackOffset(1, MVT::nxv16i8) + StackOffset(1, MVT::i64)
+//
+/// describes an offset that spans the combined storage required for an SVE
+/// vector and a 64bit GPR.
+class StackOffset {
+  int64_t Bytes;
+  int64_t ScalableBytes;
+
+  explicit operator int() const;
+
+public:
+  using Part = std::pair<int64_t, MVT>;
+
+  StackOffset() : Bytes(0), ScalableBytes(0) {}
+
+  StackOffset(int64_t Offset, MVT::SimpleValueType T) : StackOffset() {
+    assert(MVT(T).getSizeInBits() % 8 == 0 &&
+           "Offset type is not a multiple of bytes");
+    *this += Part(Offset, T);
+  }
+
+  StackOffset(const StackOffset &Other)
+      : Bytes(Other.Bytes), ScalableBytes(Other.ScalableBytes) {}
+
+  StackOffset &operator=(const StackOffset &) = default;
+
+  StackOffset &operator+=(const StackOffset::Part &Other) {
+    int64_t OffsetInBytes = Other.first * (Other.second.getSizeInBits() / 8);
+    if (Other.second.isScalableVector())
+      ScalableBytes += OffsetInBytes;
+    else
+      Bytes += OffsetInBytes;
+    return *this;
+  }
+
+  StackOffset &operator+=(const StackOffset &Other) {
+    Bytes += Other.Bytes;
+    ScalableBytes += Other.ScalableBytes;
+    return *this;
+  }
+
+  StackOffset operator+(const StackOffset &Other) const {
+    StackOffset Res(*this);
+    Res += Other;
+    return Res;
+  }
+
+  StackOffset &operator-=(const StackOffset &Other) {
+    Bytes -= Other.Bytes;
+    ScalableBytes -= Other.ScalableBytes;
+    return *this;
+  }
+
+  StackOffset operator-(const StackOffset &Other) const {
+    StackOffset Res(*this);
+    Res -= Other;
+    return Res;
+  }
+
+  StackOffset operator-() const {
+    StackOffset Res = {};
+    const StackOffset Other(*this);
+    Res -= Other;
+    return Res;
+  }
+
+  /// Returns the scalable part of the offset in bytes.
+  int64_t getScalableBytes() const { return ScalableBytes; }
+
+  /// Returns the non-scalable part of the offset in bytes.
+  int64_t getBytes() const { return Bytes; }
+
+  /// Returns the offset in parts to which this frame offset can be
+  /// decomposed for the purpose of describing a frame offset.
+  /// For non-scalable offsets this is simply its byte size.
+  void getForFrameOffset(int64_t &NumBytes, int64_t &NumPredicateVectors,
+                         int64_t &NumDataVectors) const {
+    assert(isValid() && "Invalid frame offset");
+
+    NumBytes = Bytes;
+    NumDataVectors = 0;
+    NumPredicateVectors = ScalableBytes / 2;
+    // This method is used to get the offsets to adjust the frame offset.
+    // If the function requires ADDPL to be used and needs more than two ADDPL
+    // instructions, part of the offset is folded into NumDataVectors so that it
+    // uses ADDVL for part of it, reducing the number of ADDPL instructions.
+    if (NumPredicateVectors % 8 == 0 || NumPredicateVectors < -64 ||
+        NumPredicateVectors > 62) {
+      NumDataVectors = NumPredicateVectors / 8;
+      NumPredicateVectors -= NumDataVectors * 8;
+    }
+  }
+
+  /// Returns whether the offset is known zero.
+  explicit operator bool() const { return Bytes || ScalableBytes; }
+
+  bool isValid() const {
+    // The smallest scalable element supported by scaled SVE addressing
+    // modes are predicates, which are 2 scalable bytes in size. So the scalable
+    // byte offset must always be a multiple of 2.
+    return ScalableBytes % 2 == 0;
+  }
+};
+
+} // end namespace llvm
+
+#endif