RFR: Backout: Refactor evac-in-progress flag to more general gc-phase flag

[Roman Kennke]

Am 02.10.2017 um 16:17 schrieb Aleksey Shipilev:
> On 10/02/2017 04:06 PM, Roman Kennke wrote:
>> This is a clean backout of the previous change "Refactor evac-in-progress flag to more general
>> gc-phase flag". In discussions we came to the conclusion that we should leave that code as it was,
>> and instead make new experimental code check for existing flags.
>>
>> Ok to back out that change?
>>
>> http://cr.openjdk.java.net/~rkennke/backout-gcflags/webrev.00/
> *) This looks wrong, should be just cbz? If that was masked by the patch, it would be nice to fix it
> up in another change after this backout.
>
> (two places in current patch):
> -  tbz(rscratch1, ShenandoahHeap::EVACUATION_BITPOS, done);
> +  cbzw(rscratch1, done);
>
> Otherwise looks good. Thanks for doing this!

It's how it was before. It is not wrong, it's just not quite as 
beautiful. The preceding load loads a byte, and masks off the upper 
bits. cbzw compares the lower 32bits and ignores the upper 32bits. cbz 
would consider all 64bits. If I understand correctly. Shouldn't make a 
difference performance-wise or correctness-wise, but I agree that cbz 
would look better.

Ok to push? And fix this in a followup change?

Roman