diff --git a/js/public/CallArgs.h b/js/public/CallArgs.h
index 153441d98ac0..04da7c731d10 100644
--- a/js/public/CallArgs.h
+++ b/js/public/CallArgs.h
@@ -42,29 +42,6 @@
 typedef bool
 (* JSNative)(JSContext *cx, unsigned argc, JS::Value *vp);
 
-/* Typedef for native functions that may be called in parallel. */
-typedef bool
-(* JSParallelNative)(js::ForkJoinContext *cx, unsigned argc, JS::Value *vp);
-
-/*
- * Typedef for native functions that may be called either in parallel or
- * sequential execution.
- */
-typedef bool
-(* JSThreadSafeNative)(js::ThreadSafeContext *cx, unsigned argc, JS::Value *vp);
-
-/*
- * Convenience wrappers for passing in ThreadSafeNative to places that expect
- * a JSNative or a JSParallelNative.
- */
-template <JSThreadSafeNative threadSafeNative>
-inline bool
-JSNativeThreadSafeWrapper(JSContext *cx, unsigned argc, JS::Value *vp);
-
-template <JSThreadSafeNative threadSafeNative>
-inline bool
-JSParallelNativeThreadSafeWrapper(js::ForkJoinContext *cx, unsigned argc, JS::Value *vp);
-
 /*
  * Compute |this| for the |vp| inside a JSNative, either boxing primitives or
  * replacing with the global object as necessary.
diff --git a/js/src/jscntxtinlines.h b/js/src/jscntxtinlines.h
index 99333f4b23e7..a5f3ab8633d1 100644
--- a/js/src/jscntxtinlines.h
+++ b/js/src/jscntxtinlines.h
@@ -485,24 +485,4 @@ JSContext::currentScript(jsbytecode **ppc,
     return script;
 }
 
-template <JSThreadSafeNative threadSafeNative>
-inline bool
-JSNativeThreadSafeWrapper(JSContext *cx, unsigned argc, JS::Value *vp)
-{
-    return threadSafeNative(cx, argc, vp);
-}
-
-template <JSThreadSafeNative threadSafeNative>
-inline bool
-JSParallelNativeThreadSafeWrapper(js::ForkJoinContext *cx, unsigned argc, JS::Value *vp)
-{
-    return threadSafeNative(cx, argc, vp);
-}
-
-/* static */ inline JSContext *
-js::ExecutionModeTraits<js::SequentialExecution>::toContextType(ExclusiveContext *cx)
-{
-    return cx->asJSContext();
-}
-
 #endif /* jscntxtinlines_h */
diff --git a/js/src/jsfriendapi.h b/js/src/jsfriendapi.h
index 388d2bfdb235..08d58bd91719 100644
--- a/js/src/jsfriendapi.h
+++ b/js/src/jsfriendapi.h
@@ -2165,7 +2165,6 @@ struct JSJitInfo {
         Getter,
         Setter,
         Method,
-        ParallelNative,
         StaticMethod,
         // Must be last
         OpTypeCount
@@ -2220,11 +2219,6 @@ struct JSJitInfo {
         AliasSetCount
     };
 
-    bool hasParallelNative() const
-    {
-        return type() == ParallelNative;
-    }
-
     bool needsOuterizedThisObject() const
     {
         return type() != Getter && type() != Setter;
@@ -2254,8 +2248,6 @@ struct JSJitInfo {
         JSJitGetterOp getter;
         JSJitSetterOp setter;
         JSJitMethodOp method;
-        /* An alternative native that's safe to call in parallel mode. */
-        JSParallelNative parallelNative;
         /* A DOM static method, used for Promise wrappers */
         JSNative staticMethod;
     };
@@ -2340,45 +2332,6 @@ struct JSTypedMethodJitInfo
                                                  have side-effects. */
 };
 
-namespace JS {
-namespace detail {
-
-/* NEVER DEFINED, DON'T USE.  For use by JS_CAST_PARALLEL_NATIVE_TO only. */
-inline int CheckIsParallelNative(JSParallelNative parallelNative);
-
-} // namespace detail
-} // namespace JS
-
-#define JS_CAST_PARALLEL_NATIVE_TO(v, To) \
-    (static_cast<void>(sizeof(JS::detail::CheckIsParallelNative(v))), \
-     reinterpret_cast<To>(v))
-
-/*
- * You may ask yourself: why do we define a wrapper around a wrapper here?
- * The answer is that some compilers don't understand initializing a union
- * as we do below with a construct like:
- *
- * reinterpret_cast<JSJitGetterOp>(JSParallelNativeThreadSafeWrapper<op>)
- *
- * (We need the reinterpret_cast because we must initialize the union with
- * a datum of the type of the union's first member.)
- *
- * Presumably this has something to do with template instantiation.
- * Initializing with a normal function pointer seems to work fine. Hence
- * the ugliness that you see before you.
- */
-#define JS_JITINFO_NATIVE_PARALLEL(infoName, parallelOp)                \
-    const JSJitInfo infoName =                                          \
-        {{JS_CAST_PARALLEL_NATIVE_TO(parallelOp, JSJitGetterOp)},0,0,JSJitInfo::ParallelNative,JSJitInfo::AliasEverything,JSVAL_TYPE_MISSING,false,false,false,false,false,0}
-
-#define JS_JITINFO_NATIVE_PARALLEL_THREADSAFE(infoName, wrapperName, serialOp) \
-    bool wrapperName##_ParallelNativeThreadSafeWrapper(js::ForkJoinContext *cx, unsigned argc, \
-                                                       JS::Value *vp)   \
-    {                                                                   \
-        return JSParallelNativeThreadSafeWrapper<serialOp>(cx, argc, vp); \
-    }                                                                   \
-    JS_JITINFO_NATIVE_PARALLEL(infoName, wrapperName##_ParallelNativeThreadSafeWrapper)
-
 static MOZ_ALWAYS_INLINE const JSJitInfo *
 FUNCTION_VALUE_TO_JITINFO(const JS::Value& v)
 {
diff --git a/js/src/jsfun.h b/js/src/jsfun.h
index a1c84bfc26b0..702d0de25f03 100644
--- a/js/src/jsfun.h
+++ b/js/src/jsfun.h
@@ -19,8 +19,6 @@ namespace js {
 class FunctionExtended;
 
 typedef JSNative           Native;
-typedef JSParallelNative   ParallelNative;
-typedef JSThreadSafeNative ThreadSafeNative;
 }
 
 struct JSAtomState;
@@ -157,9 +155,6 @@ class JSFunction : public js::NativeObject
     bool isNamedLambda() const {
         return isLambda() && displayAtom() && !hasGuessedAtom();
     }
-    bool hasParallelNative() const {
-        return isNative() && jitInfo() && jitInfo()->hasParallelNative();
-    }
 
     bool isBuiltinFunctionConstructor();
 
@@ -402,15 +397,6 @@ class JSFunction : public js::NativeObject
         return isInterpreted() ? nullptr : native();
     }
 
-    JSParallelNative parallelNative() const {
-        MOZ_ASSERT(hasParallelNative());
-        return jitInfo()->parallelNative;
-    }
-
-    JSParallelNative maybeParallelNative() const {
-        return hasParallelNative() ? parallelNative() : nullptr;
-    }
-
     void initNative(js::Native native, const JSJitInfo *jitinfo) {
         MOZ_ASSERT(native);
         u.n.native = native;
diff --git a/js/src/jsinfer.h b/js/src/jsinfer.h
index c36dcd6aac48..9a2acf48f997 100644
--- a/js/src/jsinfer.h
+++ b/js/src/jsinfer.h
@@ -181,27 +181,6 @@ ExecutionModeString(ExecutionMode mode)
  */
 static const unsigned NumExecutionModes = ParallelExecution + 1;
 
-template <ExecutionMode mode>
-struct ExecutionModeTraits
-{
-};
-
-template <> struct ExecutionModeTraits<SequentialExecution>
-{
-    typedef JSContext * ContextType;
-    typedef ExclusiveContext * ExclusiveContextType;
-
-    static inline JSContext *toContextType(ExclusiveContext *cx);
-};
-
-template <> struct ExecutionModeTraits<ParallelExecution>
-{
-    typedef ForkJoinContext * ContextType;
-    typedef ForkJoinContext * ExclusiveContextType;
-
-    static inline ForkJoinContext *toContextType(ForkJoinContext *cx) { return cx; }
-};
-
 namespace jit {
     struct IonScript;
     class JitAllocPolicy;
diff --git a/js/src/vm/ForkJoin.cpp b/js/src/vm/ForkJoin.cpp
index fd3a61b9a79e..542b9c421727 100644
--- a/js/src/vm/ForkJoin.cpp
+++ b/js/src/vm/ForkJoin.cpp
@@ -2123,9 +2123,6 @@ intrinsic_SetForkJoinTargetRegionPar(ForkJoinContext *cx, unsigned argc, Value *
     return true;
 }
 
-JS_JITINFO_NATIVE_PARALLEL(js::intrinsic_SetForkJoinTargetRegionInfo,
-                           intrinsic_SetForkJoinTargetRegionPar);
-
 bool
 js::intrinsic_ClearThreadLocalArenas(JSContext *cx, unsigned argc, Value *vp)
 {
@@ -2138,6 +2135,3 @@ intrinsic_ClearThreadLocalArenasPar(ForkJoinContext *cx, unsigned argc, Value *v
     //cx->allocator()->arenas.wipeDuringParallelExecution(cx->runtime());
     return true;
 }
-
-JS_JITINFO_NATIVE_PARALLEL(js::intrinsic_ClearThreadLocalArenasInfo,
-                           intrinsic_ClearThreadLocalArenasPar);