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diff --git a/js/src/frontend/DoWhileEmitter.h b/js/src/frontend/DoWhileEmitter.h
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+++ b/js/src/frontend/DoWhileEmitter.h
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+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * 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/. */
+
+#ifndef frontend_DoWhileEmitter_h
+#define frontend_DoWhileEmitter_h
+
+#include "mozilla/Attributes.h"
+#include "mozilla/Maybe.h"
+
+#include <stdint.h>
+
+#include "frontend/BytecodeControlStructures.h"
+
+namespace js {
+namespace frontend {
+
+struct BytecodeEmitter;
+
+// Class for emitting bytecode for do-while loop.
+//
+// Usage: (check for the return value is omitted for simplicity)
+//
+//   `do body while (cond);`
+//     DoWhileEmitter doWhile(this);
+//     doWhile.emitBody(offset_of_do, offset_of_body);
+//     emit(body);
+//     doWhile.emitCond();
+//     emit(cond);
+//     doWhile.emitEnd();
+//
+class MOZ_STACK_CLASS DoWhileEmitter {
+  BytecodeEmitter* bce_;
+
+  mozilla::Maybe<LoopControl> loopInfo_;
+
+#ifdef DEBUG
+  // The state of this emitter.
+  //
+  // +-------+ emitBody +------+ emitCond +------+ emitEnd  +-----+
+  // | Start |--------->| Body |--------->| Cond |--------->| End |
+  // +-------+          +------+          +------+          +-----+
+  enum class State {
+    // The initial state.
+    Start,
+
+    // After calling emitBody.
+    Body,
+
+    // After calling emitCond.
+    Cond,
+
+    // After calling emitEnd.
+    End
+  };
+  State state_ = State::Start;
+#endif
+
+ public:
+  explicit DoWhileEmitter(BytecodeEmitter* bce);
+
+  // Parameters are the offset in the source code for each character below:
+  //
+  //   do { ... } while ( x < 20 );
+  //   ^  ^
+  //   |  |
+  //   |  bodyPos
+  //   |
+  //   doPos
+  [[nodiscard]] bool emitBody(uint32_t doPos, uint32_t bodyPos);
+  [[nodiscard]] bool emitCond();
+  [[nodiscard]] bool emitEnd();
+};
+
+} /* namespace frontend */
+} /* namespace js */
+
+#endif /* frontend_DoWhileEmitter_h */