PING: PR/17236, improve long long multiply on x86 (middle-end)

[Ian Lance Taylor]

Paolo Bonzini <bonzini@gnu.org> writes:

>> I'm OK with making this sort of change without a clear argument, but
>> only if you're prepared to do performance testing on three or more
>> primary platforms.  I'm not OK with making this sort of change with
>> neither an argument nor performance testing.  Right now, as far as I
>> know, you just have a single test case which improves.
>
> I already had SPEC on x86 and it was neutral, except that half of
> SPECfp was perturbated by the machine load.  I should be able to rerun
> it sometime next week.  Running i386 and x86_64 would not be very
> different (the RA problems are the same -- %eax/%edx for MUL/DIV and
> %cl for shift counts) and I don't have access to other platforms.

I think you do need some performance results on other platforms.
There are people who can help you get them.

I'd also like to know if you can use the size of the register class as
a tie-breaker.  That kind of patch would be OK.

Ian