RFR: 8241095: x86: Improve prefix handling in Assembler

[Claes Redestad]

On 2020-03-18 20:30, Vladimir Kozlov wrote:
> Looks good.

Thanks!

> 
> I checked that moved methods stay the same. You only modified 
> prefixq(Address adr) and prefixq(Address adr, Register src) as we 
> discussed. Good.

Yep.

Also: By passing in rax (or any other valid register constant in the 0-7
encoding range) I can reuse get_prefixq(Address adr, Register src)
from prefixq(Address adr) without any overhead in compiled code. I'll
add a short comment on that.

/Claes

> 
> Thanks,
> Vladimir
> 
> On 3/18/20 6:46 AM, Claes Redestad wrote:
>> Hej,
>>
>> this patch enable folding emitted prefixq bytes into multi-byte emitter
>> functions (emit_int16(int8, int8) etc).
>>
>> Only those functions where there is always a prefix being emitted have
>> been adjusted. Other variants could improve slightly by doing similar
>> tricks, but with a smaller payoff and more complexity.
>>
>> Webrev: http://cr.openjdk.java.net/~redestad/8241095/open.00
>> Bug:    https://bugs.openjdk.java.net/browse/JDK-8241095
>>
>> Testing: tier1-4 (ongoing)
>>
>> Thanks,
>>
>> /Claes