RFR: 8073093: AARCH64: C2 generates poor code for ByteBuffer accesses

[Florian Weimer]

On 02/17/2015 11:22 AM, Andrew Haley wrote:
>> You'll still have to allocate a wrapping ByteBuffer object to use them.
>>  I expect that makes them unattractive in many cases.
> 
> Hmm.  I'm having a hard time trying to understand why.  If you need to
> do a lot of accesses the allocation of the ByteBuffer won't be
> significant; if you don't need to do a lot of accesses it won't
> matter either.

The typical use case I have in mind is exemplified by
com.sun.crypto.provider.GHASH(processBlock(byte[] data, int ofs):

 174     private void processBlock(byte[] data, int ofs) {
 175         if (data.length - ofs < AES_BLOCK_SIZE) {
 176             throw new RuntimeException("need complete block");
 177         }
 178         state0 ^= getLong(data, ofs);
 179         state1 ^= getLong(data, ofs + 8);
 180         blockMult(subkeyH0, subkeyH1);
 181     }

That is, the byte array is supplied by the caller, and if we wanted to
use a ByteBuffer, we would have to allocate a fresh one on every
iteration.  In this case, neither of the two alternatives you list apply.

-- 
Florian Weimer / Red Hat Product Security