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diff --git a/js/public/ColumnNumber.h b/js/public/ColumnNumber.h
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+++ b/js/public/ColumnNumber.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// [SMDOC] Column numbers
+//
+// Inside SpiderMonkey, column numbers are represented as 1-origin 32-bit
+// unsigned integers. Some parts of the engine use the highest bit of a column
+// number as a tag to indicate Wasm frame.
+//
+// These classes help clarifying the origin of the column number, and also
+// figuring out whether the column number uses the wasm's tag or not, and also
+// help converting between them.
+//
+// Also these classes support converting from 0-origin column number.
+//
+// In a 0-origin context, column 0 is the first character of the line.
+// In a 1-origin context, column 1 is the first character of the line,
+// for example:
+//
+//           function foo() { ... }
+//           ^              ^
+// 0-origin: 0              15
+// 1-origin: 1              16
+
+#ifndef js_ColumnNumber_h
+#define js_ColumnNumber_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+#include "mozilla/Attributes.h"  // MOZ_IMPLICIT
+
+#include <limits>    // std::numeric_limits
+#include <stdint.h>  // uint32_t
+
+namespace JS {
+
+// Wasm function index.
+//
+// This class is used as parameter or return type of
+// TaggedColumnNumberOneOrigin class below.
+struct WasmFunctionIndex {
+  // TaggedColumnNumberOneOrigin uses the highest bit as a tag.
+  static constexpr uint32_t Limit = std::numeric_limits<int32_t>::max() / 2;
+
+  // For wasm frames, the function index is returned as the column with the
+  // high bit set. In paths that format error stacks into strings, this
+  // information can be used to synthesize a proper wasm frame. But when raw
+  // column numbers are handed out, we just fix them to the first column to
+  // avoid confusion.
+  static constexpr uint32_t DefaultBinarySourceColumnNumberOneOrigin = 1;
+
+ private:
+  uint32_t value_ = 0;
+
+ public:
+  constexpr WasmFunctionIndex() = default;
+  constexpr WasmFunctionIndex(const WasmFunctionIndex& other) = default;
+
+  inline explicit WasmFunctionIndex(uint32_t value) : value_(value) {
+    MOZ_ASSERT(valid());
+  }
+
+  uint32_t value() const { return value_; }
+
+  bool valid() const { return value_ <= Limit; }
+};
+
+// The offset between 2 column numbers.
+struct ColumnNumberOffset {
+ private:
+  int32_t value_ = 0;
+
+ public:
+  constexpr ColumnNumberOffset() = default;
+  constexpr ColumnNumberOffset(const ColumnNumberOffset& other) = default;
+
+  inline explicit ColumnNumberOffset(int32_t value) : value_(value) {}
+
+  static constexpr ColumnNumberOffset zero() { return ColumnNumberOffset(); }
+
+  bool operator==(const ColumnNumberOffset& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const ColumnNumberOffset& rhs) const {
+    return !(*this == rhs);
+  }
+
+  int32_t value() const { return value_; }
+};
+
+// The positive offset from certain column number.
+struct ColumnNumberUnsignedOffset {
+ private:
+  uint32_t value_ = 0;
+
+ public:
+  constexpr ColumnNumberUnsignedOffset() = default;
+  constexpr ColumnNumberUnsignedOffset(
+      const ColumnNumberUnsignedOffset& other) = default;
+
+  inline explicit ColumnNumberUnsignedOffset(uint32_t value) : value_(value) {}
+
+  static constexpr ColumnNumberUnsignedOffset zero() {
+    return ColumnNumberUnsignedOffset();
+  }
+
+  ColumnNumberUnsignedOffset operator+(
+      const ColumnNumberUnsignedOffset& offset) const {
+    return ColumnNumberUnsignedOffset(value_ + offset.value());
+  }
+
+  ColumnNumberUnsignedOffset& operator+=(
+      const ColumnNumberUnsignedOffset& offset) {
+    value_ += offset.value();
+    return *this;
+  }
+
+  bool operator==(const ColumnNumberUnsignedOffset& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const ColumnNumberUnsignedOffset& rhs) const {
+    return !(*this == rhs);
+  }
+
+  uint32_t value() const { return value_; }
+
+  uint32_t* addressOfValueForTranscode() { return &value_; }
+};
+
+struct TaggedColumnNumberOneOrigin;
+
+namespace detail {
+
+// Shared implementation of {,Limited}ColumnNumberOneOrigin classes.
+//
+// LimitValue being 0 means there's no limit.
+template <uint32_t LimitValue = 0>
+struct MaybeLimitedColumnNumber {
+ public:
+  static constexpr uint32_t OriginValue = 1;
+
+ protected:
+  uint32_t value_ = OriginValue;
+
+  friend struct ::JS::TaggedColumnNumberOneOrigin;
+
+ public:
+  constexpr MaybeLimitedColumnNumber() = default;
+  MaybeLimitedColumnNumber(const MaybeLimitedColumnNumber& other) = default;
+  MaybeLimitedColumnNumber& operator=(const MaybeLimitedColumnNumber& other) =
+      default;
+
+  explicit MaybeLimitedColumnNumber(uint32_t value) : value_(value) {
+    MOZ_ASSERT(valid());
+  }
+
+  bool operator==(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    return !(*this == rhs);
+  }
+
+  MaybeLimitedColumnNumber<LimitValue> operator+(
+      const ColumnNumberOffset& offset) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(ptrdiff_t(value_) + offset.value() >= 0);
+    return MaybeLimitedColumnNumber<LimitValue>(value_ + offset.value());
+  }
+
+  MaybeLimitedColumnNumber<LimitValue> operator+(
+      const ColumnNumberUnsignedOffset& offset) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(ptrdiff_t(value_) + offset.value() >= 0);
+    return MaybeLimitedColumnNumber<LimitValue>(value_ + offset.value());
+  }
+
+  MaybeLimitedColumnNumber<LimitValue> operator-(
+      const ColumnNumberOffset& offset) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(ptrdiff_t(value_) - offset.value() >= 0);
+    return MaybeLimitedColumnNumber<LimitValue>(value_ - offset.value());
+  }
+  ColumnNumberOffset operator-(
+      const MaybeLimitedColumnNumber<LimitValue>& other) const {
+    MOZ_ASSERT(valid());
+    return ColumnNumberOffset(int32_t(value_) - int32_t(other.value_));
+  }
+
+  MaybeLimitedColumnNumber<LimitValue>& operator+=(
+      const ColumnNumberOffset& offset) {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(ptrdiff_t(value_) + offset.value() >= 0);
+    value_ += offset.value();
+    MOZ_ASSERT(valid());
+    return *this;
+  }
+  MaybeLimitedColumnNumber<LimitValue>& operator-=(
+      const ColumnNumberOffset& offset) {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(ptrdiff_t(value_) - offset.value() >= 0);
+    value_ -= offset.value();
+    MOZ_ASSERT(valid());
+    return *this;
+  }
+
+  bool operator<(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ < rhs.value_;
+  }
+  bool operator<=(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ <= rhs.value_;
+  }
+  bool operator>(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ > rhs.value_;
+  }
+  bool operator>=(const MaybeLimitedColumnNumber<LimitValue>& rhs) const {
+    MOZ_ASSERT(valid());
+    MOZ_ASSERT(rhs.valid());
+    return value_ >= rhs.value_;
+  }
+
+  uint32_t oneOriginValue() const {
+    MOZ_ASSERT(valid());
+
+    return value_;
+  }
+
+  uint32_t* addressOfValueForTranscode() { return &value_; }
+
+  bool valid() const {
+    if constexpr (LimitValue == 0) {
+      return true;
+    }
+
+    MOZ_ASSERT(value_ != 0);
+
+    return value_ <= LimitValue;
+  }
+};
+
+// See the comment for LimitedColumnNumberOneOrigin below
+static constexpr uint32_t ColumnNumberOneOriginLimit =
+    std::numeric_limits<int32_t>::max() / 2;
+
+}  // namespace detail
+
+// Column number in 1-origin with 31-bit limit.
+//
+// Various parts of the engine requires the column number be represented in
+// 31 bits.
+//
+// See:
+//  * TaggedColumnNumberOneOrigin
+//  * TokenStreamAnyChars::checkOptions
+//  * SourceNotes::isRepresentable
+//  * WasmFrameIter::computeLine
+struct LimitedColumnNumberOneOrigin : public detail::MaybeLimitedColumnNumber<
+                                          detail::ColumnNumberOneOriginLimit> {
+ private:
+  using Base =
+      detail::MaybeLimitedColumnNumber<detail::ColumnNumberOneOriginLimit>;
+
+ public:
+  static constexpr uint32_t Limit = detail::ColumnNumberOneOriginLimit;
+
+  static_assert(uint32_t(Limit + Limit) > Limit,
+                "Adding Limit should not overflow");
+
+  using Base::Base;
+
+  LimitedColumnNumberOneOrigin() = default;
+  LimitedColumnNumberOneOrigin(const LimitedColumnNumberOneOrigin& other) =
+      default;
+  MOZ_IMPLICIT LimitedColumnNumberOneOrigin(const Base& other) : Base(other) {}
+
+  static LimitedColumnNumberOneOrigin limit() {
+    return LimitedColumnNumberOneOrigin(Limit);
+  }
+
+  static LimitedColumnNumberOneOrigin fromUnlimited(uint32_t value) {
+    if (value > Limit) {
+      return LimitedColumnNumberOneOrigin(Limit);
+    }
+    return LimitedColumnNumberOneOrigin(value);
+  }
+  static LimitedColumnNumberOneOrigin fromUnlimited(
+      const MaybeLimitedColumnNumber<0>& value) {
+    return fromUnlimited(value.oneOriginValue());
+  }
+
+  static LimitedColumnNumberOneOrigin fromZeroOrigin(uint32_t value) {
+    return LimitedColumnNumberOneOrigin(value + 1);
+  }
+};
+
+// Column number in 1-origin.
+struct ColumnNumberOneOrigin : public detail::MaybeLimitedColumnNumber<0> {
+ private:
+  using Base = detail::MaybeLimitedColumnNumber<0>;
+
+ public:
+  using Base::Base;
+  using Base::operator=;
+
+  ColumnNumberOneOrigin() = default;
+  ColumnNumberOneOrigin(const ColumnNumberOneOrigin& other) = default;
+  ColumnNumberOneOrigin& operator=(ColumnNumberOneOrigin&) = default;
+
+  MOZ_IMPLICIT ColumnNumberOneOrigin(const Base& other) : Base(other) {}
+
+  explicit ColumnNumberOneOrigin(const LimitedColumnNumberOneOrigin& other)
+      : Base(other.oneOriginValue()) {}
+
+  static ColumnNumberOneOrigin fromZeroOrigin(uint32_t value) {
+    return ColumnNumberOneOrigin(value + 1);
+  }
+};
+
+// Either LimitedColumnNumberOneOrigin, or WasmFunctionIndex.
+//
+// In order to pass the Wasm frame's (url, bytecode-offset, func-index) tuple
+// through the existing (url, line, column) tuple, it tags the highest bit of
+// the column to indicate "this is a wasm frame".
+//
+// When knowing clients see this bit, they shall render the tuple
+// (url, line, column|bit) as "url:wasm-function[column]:0xline" according
+// to the WebAssembly Web API's Developer-Facing Display Conventions.
+//   https://webassembly.github.io/spec/web-api/index.html#conventions
+// The wasm bytecode offset continues to be passed as the JS line to avoid
+// breaking existing devtools code written when this used to be the case.
+//
+// 0b0YYYYYYY_YYYYYYYY_YYYYYYYY_YYYYYYYY LimitedColumnNumberOneOrigin
+// 0b1YYYYYYY_YYYYYYYY_YYYYYYYY_YYYYYYYY WasmFunctionIndex
+//
+// The tagged colum number shouldn't escape the JS engine except for the
+// following places:
+//   * SavedFrame API which can directly access WASM frame's info
+//   * ubi::Node API which can also directly access WASM frame's info
+struct TaggedColumnNumberOneOrigin {
+  static constexpr uint32_t WasmFunctionTag = 1u << 31;
+
+  static_assert((WasmFunctionIndex::Limit & WasmFunctionTag) == 0);
+  static_assert((LimitedColumnNumberOneOrigin::Limit & WasmFunctionTag) == 0);
+
+ protected:
+  uint32_t value_ = LimitedColumnNumberOneOrigin::OriginValue;
+
+  explicit TaggedColumnNumberOneOrigin(uint32_t value) : value_(value) {}
+
+ public:
+  constexpr TaggedColumnNumberOneOrigin() = default;
+  TaggedColumnNumberOneOrigin(const TaggedColumnNumberOneOrigin& other) =
+      default;
+
+  explicit TaggedColumnNumberOneOrigin(
+      const LimitedColumnNumberOneOrigin& other)
+      : value_(other.value_) {
+    MOZ_ASSERT(isLimitedColumnNumber());
+  }
+  explicit TaggedColumnNumberOneOrigin(const WasmFunctionIndex& other)
+      : value_(other.value() | WasmFunctionTag) {
+    MOZ_ASSERT(isWasmFunctionIndex());
+  }
+
+  static TaggedColumnNumberOneOrigin fromRaw(uint32_t value) {
+    return TaggedColumnNumberOneOrigin(value);
+  }
+
+  static TaggedColumnNumberOneOrigin forDifferentialTesting() {
+    return TaggedColumnNumberOneOrigin(LimitedColumnNumberOneOrigin());
+  }
+
+  bool operator==(const TaggedColumnNumberOneOrigin& rhs) const {
+    return value_ == rhs.value_;
+  }
+
+  bool operator!=(const TaggedColumnNumberOneOrigin& rhs) const {
+    return !(*this == rhs);
+  }
+
+  bool isLimitedColumnNumber() const { return !isWasmFunctionIndex(); }
+
+  bool isWasmFunctionIndex() const { return !!(value_ & WasmFunctionTag); }
+
+  LimitedColumnNumberOneOrigin toLimitedColumnNumber() const {
+    MOZ_ASSERT(isLimitedColumnNumber());
+    return LimitedColumnNumberOneOrigin(value_);
+  }
+
+  WasmFunctionIndex toWasmFunctionIndex() const {
+    MOZ_ASSERT(isWasmFunctionIndex());
+    return WasmFunctionIndex(value_ & ~WasmFunctionTag);
+  }
+
+  uint32_t oneOriginValue() const {
+    return isWasmFunctionIndex()
+               ? WasmFunctionIndex::DefaultBinarySourceColumnNumberOneOrigin
+               : toLimitedColumnNumber().oneOriginValue();
+  }
+
+  uint32_t rawValue() const { return value_; }
+
+  uint32_t* addressOfValueForTranscode() { return &value_; }
+};
+
+}  // namespace JS
+
+#endif /* js_ColumnNumber_h */