[aarch64-port-dev ] RFR: 8075930: AARCH64: Use FP Register in C2

Andrew Haley aph at redhat.com
Fri Apr 24 08:33:04 UTC 2015

On 23/04/15 20:01, Dean Long wrote:
> On 4/23/2015 9:46 AM, Andrew Haley wrote:
>> On 04/23/2015 04:13 PM, Edward Nevill wrote:
>>> I think that in order to do a GC root scan it must be at a safe
>>> point and I don't believe it can be at a safe point in native code.
>> Sure it can.  Native methods are always safepoints, as are calls to
>> the runtime to allocate objects, etc.  But all such calls have a
>> wrapper, and it pushes FP, it has an OopMap, so it should be fine.
> What happens at a safepoint polling point in a loop?  Will C2 try to 
> keep an oop value
> in R29 live across the safepoint?  If so, I assume the oopmap takes care 
> of that case as
> well.

I guess so.  Ed's argument that this is the same as EBP on x86 is quite
persuasive to me.


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