Re: Emulate if x86-64 on x86-64

[Peter Maydell]

On Tue, 13 Aug 2024 at 16:54, Jakob Bohm via <qemu-discuss@nongnu.org> wrote:
> Another approach that might be worth examining would be to build the TCG
> snippet collection for different host CPU generations (such as x86-64
> with only SSE2, x86-64 with SSE3 and x86-64 with AVX512), thereby
> providing fast emulation of the latest on the new on the new and medium
> CPU generations .  This would imply some table selection logic in the
> TCG initialization based on actual host and selected guest CPUs. This
> idea is mostly for Qemu binaries that will run on different hosts .

What "TCG snippet collection" ? QEMU generates code from IR
instruction-at-a-time, it doesn't do assembly of prebuilt
larger bits of code.

We do have some support for runtime detection of host
CPU features, so we can generate better code if some
things are available; notably we will check for and
use AVX1, AVX2, AVX512 if available.

thanks
-- PMM