RFR(S): 8193927: Optimize scanning code for oops.

[Volker Simonis]

Hi Goetz,

looks good now! Thanks for doing the change.

I'm pretty sure you could return 'false' on zero as well as zero
doesn't generate any code at all.

Regards,
Volker


On Thu, Dec 21, 2017 at 5:18 PM, Lindenmaier, Goetz
<goetz.lindenmaier at sap.com> wrote:
> Hi Volker,
>
> you are right, encapsulating it in a function is a better solution:
> http://cr.openjdk.java.net/~goetz/wr17/8193927-oopsInCode/webrev.02
>
> Making it switchable would require changes to x86, which is
> not my scope.
>
> Best regards,
>   Goetz.
>
>> -----Original Message-----
>> From: Volker Simonis [mailto:volker.simonis at gmail.com]
>> Sent: Donnerstag, 21. Dezember 2017 14:51
>> To: Lindenmaier, Goetz <goetz.lindenmaier at sap.com>
>> Cc: hotspot-compiler-dev at openjdk.java.net
>> Subject: Re: RFR(S): 8193927: Optimize scanning code for oops.
>>
>> Hi Goetz,
>>
>> this seems to be a little strange flag for me because it can not be
>> used for really controlling the emission of immediate oops. It only
>> records if a platform can emit immediate oops or not.
>>
>> So wouldn't it be better to either have a flag like
>> "EmitImmediateOops" which really controls the emission of immediate
>> oops. I.e. it could be used to switch the emission of immediate oops
>> off even on platforms which usually do that. Or if that's not
>> reasonable, don't introduce a new flag at all but just declare a
>> platform specific method instead which returns if immediate oops can
>> be emitted on that platform or not.
>>
>> Thanks,
>> Volker
>>
>> On Thu, Dec 21, 2017 at 9:30 AM, Lindenmaier, Goetz
>> <goetz.lindenmaier at sap.com> wrote:
>> > Hi,
>> >
>> > Some platforms don't emit immediate oops to the code. If so, scans
>> > of the code for oops can be skipped.
>> >
>> > Add flag ImmediateOopsEmitted to each platform specifying the behavior.
>> > Only search code for immediate oops if this flag is set. Make sure no
>> > oops are emitted to code if the flag is not set.
>> >
>> > @aarch people: should the flag set to 'false' on aarch/arm?  So far it
>> > is true, which defaults to the old behavior.
>> >
>> > Please review this change. I please need a sponsor.
>> > http://cr.openjdk.java.net/~goetz/wr17/8193927-oopsInCode/webrev.01/
>> >
>> > Best regards,
>> >   Goetz