RFR: 8241077: x86_64: Minor Assembler improvements

[Vladimir Kozlov]

Good. I think it is trivial.

Thanks,
Vladimir

On 3/16/20 1:28 PM, Claes Redestad wrote:
> Hi,
> 
> a few small improvements extracted from 8241042 to keep that RFE
> more focused:
> 
> - make InstructionAttr more compact by reordering some bool and int
> fields leads to slightly better (and more compact) code generation.
> 
> - _is_managed only used on 32-bit
> 
> - code gen for *_needs_rex improve if replacing reg != (x)noreg
>    with reg->is_valid(), since the expression compiles down into a
>    range checks (fewer branches)
> 
> Bug:    https://bugs.openjdk.java.net/browse/JDK-8241077
> Webrev: http://cr.openjdk.java.net/~redestad/8241077/open.00/
> 
> Testing: tier1-5 (together with JDK-8241042)
> 
> /Claes