My First LLVM PR

Honestly, it&rsquo;s actually my second upstreamed PR, but I think it&rsquo;s worth writing a blog about and the title sounds better then &lsquo; My Second LLVM PR &rsquo;. It&rsquo;s also a revival of the work done by @huhu233, who implemented the feature of this PR for the ARM backend. I also received a lot of help from the PR reviewer, @RKSimon, to ensure the code is up to LLVM&rsquo;s…