2 ms·

Why can't these older processors be supported via a software shim for unrecognised instructions? It is far better for software to run with a couple of percent

• snvzz 1y ago
  >Why can't these older processors be supported via a software shim for unrecognised instructions? It can. It's just this shim is out of scope for Ubuntu. Refer to opensbi instruction emulation. >It is far better for software to run with a couple of percent slowdown on old cpus only than not run at all. With features like vector instructions or pointer masking, we're talking a non-trivial slowdown.
• camel-cdr 1y ago
  > It is far better for software to run with a couple of percent slowdown on old cpus only than not run at all. The difference on geekbench is 2x and not every benchmark has been optimized for RVV yet: https://browser.geekbench.com/v6/cpu/compare/10681749?baseline=7313480 https://browser.geekbench.com/v6/cpu/compare/10681749?baseli... (same hardware, one using the newer geekbench version that can take advantage of RVA22+V)
• brucehoult 1y ago
  Because new instructions such as `c.lb{u}` and `c.sb` and `c.{s,z}ext.{b,h,w}` are going to be thoroughly mixed in all over the place. Probably the (kinda) conditional move `czero.eqz` and `czero.nez` too.