<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Jul 28, 2024, at 10:43 AM, Carl Shapiro <<a href="mailto:carl.shapiro@gmail.com" class="">carl.shapiro@gmail.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Sun, Jul 28, 2024 at 7:54 AM Tim McNerney <<a href="mailto:mc@media.mit.edu" target="_blank" class="">mc@media.mit.edu</a>> wrote:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="auto" class=""><div dir="ltr" class=""><div dir="ltr" class=""><div class=""><div class="">CCL already has 32-bit ARM support. There is no OS interfacing work to do here (only work to make up for the <i class="">lack</i> of OS). </div></div></div></div></div></blockquote><div class=""><br class=""></div><div class="">The Cortex-M processors execute Thumb-1 or Thumb-2 instructions which are different from 32-bit ARM instructions. The Cortex-A designs and older designs from ARM with a "T" in their name support both the 32-bit ARM and Thumb instructions.</div><div class=""><br class=""></div><div class="">On a Cortex-A and other processors that support both ISAs, code can switch between ISA states with the BX or BLX instruction setting the lower bit of the destination to 1 or 0 to specify either the Thumb or ARM ISA. If someone wants to add a backend to the Cortex-M, starting with a working ARM backend and switching the code generator to using Thumb would seem like a possible way to start.</div></div></div></div></blockquote><div><br class=""></div><div>Doesn't seem like it would be very hard. They are the same ISA, just different encodings.</div><div><br class=""></div><div><a href="https://stackoverflow.com/questions/28669905/what-is-the-difference-between-the-arm-thumb-and-thumb-2-instruction-encodings" class="">https://stackoverflow.com/questions/28669905/what-is-the-difference-between-the-arm-thumb-and-thumb-2-instruction-encodings</a></div><div><br class=""></div></div>rg<div class=""><br class=""></div></body></html>