void * JS_FASTCALL
stubs::CompileFunction(VMFrame &f, uint32 nactual)
{
    /*
     * We have a partially constructed frame. That's not really good enough to
     * compile though because we could throw, so get a full, adjusted frame.
     */
    JSContext *cx = f.cx;
    JSStackFrame *fp = f.fp();

    /*
     * Since we can only use members set by initCallFrameCallerHalf,
     * we must carefully extract the callee from the nactual.
     */
    JSObject &callee = fp->formalArgsEnd()[-(int(nactual) + 2)].toObject();
    JSFunction *fun = callee.getFunctionPrivate();
    JSScript *script = fun->script();

    /*
     * FixupArity/RemovePartialFrame expect to be called after the early
     * prologue.
     */
    fp->initCallFrameEarlyPrologue(fun, nactual);

    if (nactual != fp->numFormalArgs()) {
        fp = (JSStackFrame *)FixupArity(f, nactual);
        if (!fp)
            return NULL;
    }

    /* Finish frame initialization. */
    fp->initCallFrameLatePrologue();

    /* These would have been initialized by the prologue. */
    f.regs.fp = fp;
    f.regs.sp = fp->base();
    f.regs.pc = script->code;

    if (fun->isHeavyweight() && !js::CreateFunCallObject(cx, fp))
        THROWV(NULL);

    CompileStatus status = CanMethodJIT(cx, script, fp, CompileRequest_JIT);
    if (status == Compile_Okay)
        return script->getJIT(fp->isConstructing())->invokeEntry;

    /* Function did not compile... interpret it. */
    JSBool ok = Interpret(cx, fp);
    InlineReturn(f);

    if (!ok)
        THROWV(NULL);

    return NULL;
}
/*
 * This function must only be called after the early prologue, since it depends
 * on fp->exec.fun.
 */
void * JS_FASTCALL
stubs::FixupArity(VMFrame &f, uint32 nactual)
{
    JSContext *cx = f.cx;
    JSStackFrame *oldfp = f.fp();

    JS_ASSERT(nactual != oldfp->numFormalArgs());

    /*
     * Grossssss! *move* the stack frame. If this ends up being perf-critical,
     * we can figure out how to spot-optimize it. Be careful to touch only the
     * members that have been initialized by initCallFrameCallerHalf and the
     * early prologue.
     */
    uint32 flags         = oldfp->isConstructingFlag();
    JSFunction *fun      = oldfp->fun();
    void *ncode          = oldfp->nativeReturnAddress();

    /* Pop the inline frame. */
    f.fp() = oldfp->prev();
    f.regs.sp = (Value*) oldfp;

    /* Reserve enough space for a callee frame. */
    JSStackFrame *newfp = cx->stack().getInlineFrameWithinLimit(cx, (Value*) oldfp, nactual,
                                                                fun, fun->script(), &flags,
                                                                f.entryfp, &f.stackLimit);
    if (!newfp) {
        /*
         * The PC is not coherent with the current frame, so fix it up for
         * exception handling.
         */
        f.regs.pc = f.jit()->nativeToPC(ncode);
        THROWV(NULL);
    }

    /* Reset the part of the stack frame set by the caller. */
    newfp->initCallFrameCallerHalf(cx, flags, ncode);

    /* Reset the part of the stack frame set by the prologue up to now. */
    newfp->initCallFrameEarlyPrologue(fun, nactual);

    /* The caller takes care of assigning fp to regs. */
    return newfp;
}