Re: [Qemu-devel] 3 new x86 instructions

[Blue Swirl]

On Thu, Jan 10, 2013 at 1:46 PM, Torbjorn Granlund <address@hidden> wrote:
> There are 3 instructions, MULX, ADCX, and ADOX, which would be very
> useful to see in qemu.  I looked into putting them in myself, but the
> startup time for hacking qemu is longer than I can affort in this
> period.
>
> Apparently, MULX is implemented in Haswell, while ADCX and ADOX will
> appear in Broadwell (or so says the rumours).
>
> I need these instructions for hacking the GMP library (GNUs bignum
> library).
>
> Documentation for the instructions is available at
> http://software.intel.com/file/45088.
>
> Would some kind qemu hacker consider adding these instructions?

MULX implies a bunch of other instructions due to CPUID flag grouping.
ADCX and ADOX can be implemented separately. None of these and the
other instructions in the MULX group look very complex.

The other extensions like 256 bit float and extending existing SSE
instructions to use them would need much more work. FMA looks simple
except for the YMM variants. Random number instructions increase
demand of cryptographically secure random number supply from the host.

It would be nice if the implementer had access to the real HW which
implements the instructions for comparison tests.

> There is support in binutils 23.1 for these instructions, but I think it
> is there already in version 22.x.
>
> In the meantime, I'm using an inferior, comparatively slow emulator.
> :-)
>
> --
> Torbjörn
>