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Re: RFC: S/390 Transactional memory support - save/restore of FPRs
- From: Richard Henderson <rth at redhat dot com>
- To: Torvald Riegel <triegel at redhat dot com>
- Cc: Andreas Krebbel <krebbel at linux dot vnet dot ibm dot com>, gcc at gcc dot gnu dot org
- Date: Tue, 21 May 2013 11:03:25 -0700
- Subject: Re: RFC: S/390 Transactional memory support - save/restore of FPRs
- References: <20130521124056 dot GA16148 at bart> <1369146488 dot 8410 dot 1064 dot camel at triegel dot csb>
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~