On Thu, Jun 20, 2024 at 4:55 PM Daniel P. Berrangé <berra...@redhat.com> wrote:
> Any particular reason you chose to list various instructions individually
> rather than just ask GCC for the full ABI ? I'd think all of the above
> condences down to just
To avoid that the default ('1') forces a lower level than the compiler default.
Something like what you propose below could work by adding a 'default'
value to the x86_version option, that leaves the flags entirely alone
apart from -mcx16.
However, doing so would prevent QEMU from changing the default to
x86-64-v2 in meson_options.txt, because then even a compiler that
defaults to x86-64-v3 would build a QEMU with AVX2 disabled.
For AVX2 specifically this is not a huge deal because the decision to
use AVX2 code is mostly done at runtime; but it would be a problem for
future integer instruction set extensions---for example if the distro
compiler uses APX you don't want to disable it.
> # add flags for individual instruction set extensions
> if get_option('x86_version') >= '1'
> if host_arch == 'i386'
> qemu_common_flags = ['-mfpmath=sse'] + qemu_common_flags
Also -msse2 here, but yes.
Paolo
