Fwd: RFR(S): 8248188 Add HotSpotIntrinsicCandidate and API for Base64 decoding (repost to correct mailing list)
cjashfor at linux.ibm.com
Mon Aug 10 21:00:57 UTC 2020
I had originally made two posts to the hotspot-compiler-dev and
ppc-aix-port-dev mailing lists, but since this RFR requires modifying
the core library code, it makes sense to post it to core-lib-devs instead.
The two original posts:
To recap the current state:
Currently in java.util.Base64, there is a HotSpotIntrinsicCandidate and
API for encodeBlock, but none for decoding. This means that only
encoding gets acceleration from the underlying CPU's vector or other
I'd like to propose adding a new intrinsic for decodeBlock. The
considerations I have for this new intrinsic's API:
* Don't make any assumptions about the underlying capability of the
hardware. For example, do not impose any specific block size granularity.
* Because of the difficulty of handling the isMIME=true option in a
vector-based accelerator, do not call this intrinsic when isMIME=true.
If desired, a new HotSpotIntrinsicCandidate can be introduced in the
future for this case.
* Any remaining data that is not processed by the intrinsic will be
processed by the pure Java implementation. This allows the intrinsic to
process whatever block sizes it's good at without the complexity of
handling the end fragments.
* If any illegal character is discovered in the decoding process, the
intrinsic can return 0, or any number of bytes produced, up to but not
including the byte containing the error. At this point, the pure-Java
algorithm will be called, which will discover the error and report it
via a thrown exception as usual.
I've tested the patch in the webrev with an actual intrinsic coded up
for Power9/Power10, but that runtime intrinsic and arch-specific patches
aren't in the webrev, because I want to get some consensus on the
library-level intrinsic API first.
I'm open to any comments about this.
Thanks for your consideration,
IBM Systems, LTC OpenJDK team
503-985-8699 Home office
cjashfor at us.ibm.com
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