RFC: S/390 Transactional memory support - save/restore of FPRs

[Richard Henderson]

On 05/21/2013 07:28 AM, Torvald Riegel wrote:
>> > The additional prologue/epilogue FPR backups for TXs can only be
>> > avoided if the transaction is fully contained in the function body
>> > (and does not use the FPRs).  I call these non-escaping transactions.
> That's what __transaction_atomic etc. give you.  I believe we already
> check whether we need to save/restore vector registers, but I guess
> we're not checking for FPRs.
> 

No, we have bits reserved for optimizing the vector/fpr register save/restore
case, but we never actually set them.  We don't have enough feedback from the
register allocator in order to get those bits set.


r~