Brainwaves

Now that I have implemented the conditional long branch emulation, it’s inevitable that I need to work on the long branch call form. This, however, requires some side-tracking. Emulating the brl.call instruction requires stack unwinding because it needs to get the value of ar.ec as it was at the time of the trap. It’s also possible that the brl.call instruction writes to one of the preserved branch registers. In that case, we need to know if that branch register was saved and where. Luckily, the runtime architecture states that b0 is to be used to save the return address, so we may ignore writing to other branch registers at first. Nonetheless, stack unwinding is necessary. This, by all means, is a good thing, because we need it in other situations as well—situations we’re not correctly handling now. Maybe I should import the latest libuwx first…

This entry was posted on Friday, July 7th, 2006 at 5:08 am and is filed under FreeBSD. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.