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diff --git a/js/src/wasm/WasmFrameIter.h b/js/src/wasm/WasmFrameIter.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:
+ *
+ * Copyright 2014 Mozilla Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef wasm_frame_iter_h
+#define wasm_frame_iter_h
+
+#include "js/ProfilingFrameIterator.h"
+#include "js/TypeDecls.h"
+#include "wasm/WasmTypes.h"
+
+namespace js {
+
+namespace jit {
+class MacroAssembler;
+struct Register;
+class Label;
+enum class FrameType;
+}  // namespace jit
+
+namespace wasm {
+
+class Code;
+class CodeRange;
+class DebugFrame;
+class TypeIdDesc;
+class Instance;
+class ModuleSegment;
+
+struct CallableOffsets;
+struct FuncOffsets;
+class Frame;
+
+using RegisterState = JS::ProfilingFrameIterator::RegisterState;
+
+// Iterates over a linear group of wasm frames of a single wasm JitActivation,
+// called synchronously from C++ in the wasm thread. It will stop at the first
+// frame that is not of the same kind, or at the end of an activation.
+//
+// If you want to handle every kind of frames (including JS jit frames), use
+// JitFrameIter.
+
+class WasmFrameIter {
+ public:
+  enum class Unwind { True, False };
+  static constexpr uint32_t ColumnBit = 1u << 31;
+
+ private:
+  jit::JitActivation* activation_;
+  const Code* code_;
+  const CodeRange* codeRange_;
+  unsigned lineOrBytecode_;
+  Frame* fp_;
+  const TlsData* tls_;
+  uint8_t* unwoundIonCallerFP_;
+  jit::FrameType unwoundIonFrameType_;
+  Unwind unwind_;
+  void** unwoundAddressOfReturnAddress_;
+  uint8_t* resumePCinCurrentFrame_;
+
+  void popFrame();
+
+ public:
+  // See comment above this class definition.
+  explicit WasmFrameIter(jit::JitActivation* activation, Frame* fp = nullptr);
+  const jit::JitActivation* activation() const { return activation_; }
+  void setUnwind(Unwind unwind) { unwind_ = unwind; }
+  void operator++();
+  bool done() const;
+  const char* filename() const;
+  const char16_t* displayURL() const;
+  bool mutedErrors() const;
+  JSAtom* functionDisplayAtom() const;
+  unsigned lineOrBytecode() const;
+  uint32_t funcIndex() const;
+  unsigned computeLine(uint32_t* column) const;
+  const CodeRange* codeRange() const { return codeRange_; }
+  Instance* instance() const;
+  void** unwoundAddressOfReturnAddress() const;
+  bool debugEnabled() const;
+  DebugFrame* debugFrame() const;
+  jit::FrameType unwoundIonFrameType() const;
+  uint8_t* unwoundIonCallerFP() const { return unwoundIonCallerFP_; }
+  Frame* frame() const { return fp_; }
+  const TlsData* tls() const { return tls_; }
+
+  // Returns the address of the next instruction that will execute in this
+  // frame, once control returns to this frame.
+  uint8_t* resumePCinCurrentFrame() const;
+};
+
+enum class SymbolicAddress;
+
+// An ExitReason describes the possible reasons for leaving compiled wasm
+// code or the state of not having left compiled wasm code
+// (ExitReason::None). It is either a known reason, or a enumeration to a native
+// function that is used for better display in the profiler.
+class ExitReason {
+ public:
+  enum class Fixed : uint32_t {
+    None,             // default state, the pc is in wasm code
+    FakeInterpEntry,  // slow-path entry call from C++ WasmCall()
+    ImportJit,        // fast-path call directly into JIT code
+    ImportInterp,     // slow-path call into C++ Invoke()
+    BuiltinNative,    // fast-path call directly into native C++ code
+    Trap,             // call to trap handler
+    DebugTrap         // call to debug trap handler
+  };
+
+ private:
+  uint32_t payload_;
+
+  ExitReason() : ExitReason(Fixed::None) {}
+
+ public:
+  MOZ_IMPLICIT ExitReason(Fixed exitReason)
+      : payload_(0x0 | (uint32_t(exitReason) << 1)) {
+    MOZ_ASSERT(isFixed());
+    MOZ_ASSERT_IF(isNone(), payload_ == 0);
+  }
+
+  explicit ExitReason(SymbolicAddress sym)
+      : payload_(0x1 | (uint32_t(sym) << 1)) {
+    MOZ_ASSERT(uint32_t(sym) <= (UINT32_MAX << 1), "packing constraints");
+    MOZ_ASSERT(!isFixed());
+  }
+
+  static ExitReason Decode(uint32_t payload) {
+    ExitReason reason;
+    reason.payload_ = payload;
+    return reason;
+  }
+
+  static ExitReason None() { return ExitReason(ExitReason::Fixed::None); }
+
+  bool isFixed() const { return (payload_ & 0x1) == 0; }
+  bool isNone() const { return isFixed() && fixed() == Fixed::None; }
+  bool isNative() const {
+    return !isFixed() || fixed() == Fixed::BuiltinNative;
+  }
+  bool isInterpEntry() const {
+    return isFixed() && fixed() == Fixed::FakeInterpEntry;
+  }
+
+  uint32_t encode() const { return payload_; }
+  Fixed fixed() const {
+    MOZ_ASSERT(isFixed());
+    return Fixed(payload_ >> 1);
+  }
+  SymbolicAddress symbolic() const {
+    MOZ_ASSERT(!isFixed());
+    return SymbolicAddress(payload_ >> 1);
+  }
+};
+
+// Iterates over the frames of a single wasm JitActivation, given an
+// asynchronously-profiled thread's state.
+class ProfilingFrameIterator {
+  const Code* code_;
+  const CodeRange* codeRange_;
+  uint8_t* callerFP_;
+  void* callerPC_;
+  void* stackAddress_;
+  uint8_t* unwoundIonCallerFP_;
+  ExitReason exitReason_;
+
+  void initFromExitFP(const Frame* fp);
+
+ public:
+  ProfilingFrameIterator();
+
+  // Start unwinding at a non-innermost activation that has necessarily been
+  // exited from wasm code (and thus activation.hasWasmExitFP).
+  explicit ProfilingFrameIterator(const jit::JitActivation& activation);
+
+  // Start unwinding at a group of wasm frames after unwinding an inner group
+  // of JSJit frames.
+  explicit ProfilingFrameIterator(const Frame* fp);
+
+  // Start unwinding at the innermost activation given the register state when
+  // the thread was suspended.
+  ProfilingFrameIterator(const jit::JitActivation& activation,
+                         const RegisterState& state);
+
+  void operator++();
+  bool done() const { return !codeRange_ && exitReason_.isNone(); }
+
+  void* stackAddress() const {
+    MOZ_ASSERT(!done());
+    return stackAddress_;
+  }
+  uint8_t* unwoundIonCallerFP() const {
+    MOZ_ASSERT(done());
+    return unwoundIonCallerFP_;
+  }
+  const char* label() const;
+};
+
+// Prologue/epilogue code generation
+
+void SetExitFP(jit::MacroAssembler& masm, ExitReason reason,
+               jit::Register scratch);
+void ClearExitFP(jit::MacroAssembler& masm, jit::Register scratch);
+
+void GenerateExitPrologue(jit::MacroAssembler& masm, unsigned framePushed,
+                          ExitReason reason, CallableOffsets* offsets);
+void GenerateExitEpilogue(jit::MacroAssembler& masm, unsigned framePushed,
+                          ExitReason reason, CallableOffsets* offsets);
+
+void GenerateJitExitPrologue(jit::MacroAssembler& masm, unsigned framePushed,
+                             CallableOffsets* offsets);
+void GenerateJitExitEpilogue(jit::MacroAssembler& masm, unsigned framePushed,
+                             CallableOffsets* offsets);
+
+void GenerateJitEntryPrologue(jit::MacroAssembler& masm, Offsets* offsets);
+
+void GenerateFunctionPrologue(jit::MacroAssembler& masm,
+                              const TypeIdDesc& funcTypeId,
+                              const mozilla::Maybe<uint32_t>& tier1FuncIndex,
+                              FuncOffsets* offsets);
+void GenerateFunctionEpilogue(jit::MacroAssembler& masm, unsigned framePushed,
+                              FuncOffsets* offsets);
+
+// Iterates through frames for either possible cross-instance call or an entry
+// stub to obtain tls that corresponds to the passed fp.
+const TlsData* GetNearestEffectiveTls(const Frame* fp);
+TlsData* GetNearestEffectiveTls(Frame* fp);
+
+// Describes register state and associated code at a given call frame.
+
+struct UnwindState {
+  uint8_t* fp;
+  void* pc;
+  const Code* code;
+  const CodeRange* codeRange;
+  UnwindState() : fp(nullptr), pc(nullptr), code(nullptr), codeRange(nullptr) {}
+};
+
+// Ensures the register state at a call site is consistent: pc must be in the
+// code range of the code described by fp. This prevents issues when using
+// the values of pc/fp, especially at call sites boundaries, where the state
+// hasn't fully transitioned from the caller's to the callee's.
+//
+// unwoundCaller is set to true if we were in a transitional state and had to
+// rewind to the caller's frame instead of the current frame.
+//
+// Returns true if it was possible to get to a clear state, or false if the
+// frame should be ignored.
+
+bool StartUnwinding(const RegisterState& registers, UnwindState* unwindState,
+                    bool* unwoundCaller);
+
+}  // namespace wasm
+}  // namespace js
+
+#endif  // wasm_frame_iter_h