Updated webrev: http://cr.openjdk.java.net/~luhenry/8250902/webrev.02
> Next code in inline_digestBase_implCompressMB should be reversed
> (get_long_*() should be called for long_state):
>
> if (long_state) {
> state = get_state_from_digestBase_object(digestBase_obj);
> } else {
> state = get_long_state_from_digestBase_object(digestBase_obj);
> }
Thanks for pointing that out. I tested everything with `hotspot:tier1` and
`jdk:tier1` in fastdebug on Windows-x86, Windows-x64 and Linux-x64.
> It seems that the algorithm can be optimized further using SSE/AVX
> instructions. I am not aware of any specific SSE/AVX implementation which
> leverages those instructions in the best possible way. Sandhya can chime in
> more on that.
I have done some research prior to implementing this intrinsic and the only
pointers I could find to vectorized MD5 is on computing _multiple_ MD5 hashes
in parallel but not a _single_ MD5 hash. Using vectors effectively parallelize
the computation of many MD5 hash, but it does not accelerate the computation of
a single MD5 hash. And looking at the algorithm, every step depends on the
previous step's result, which make it particularly hard to
parallelize/vectorize.
> As far as I know, I came across this which points to MD5 SSE/AVX
> implementation.
> https://software.intel.com/content/www/us/en/develop/articles/intel-isa-l-cryptographic-hashes-for-cloud-storage.html
That library points to computing many MD5 hashes in parallel. Quoting: "Intel®
ISA-L uses a novel technique called multi-buffer hashing, which [...] compute
several hashes at once within a single core." That is similar to what I found
in researching how to vectorize MD5. I also did not find any reference of an
ISA-level implementation of MD5, neither in x86 nor ARM.
If you can point me to a document describing how to vectorize MD5, I would be
more than happy to take a look and implement the algorithm. However, my
understanding is that MD5 is not vectorizable by-design.
> Add tests to verify intrinsic implementation. You can use
> test/hotspot/jtreg/compiler/intrinsics/sha/ as examples.
I looked at these tests and they already cover MD5. I am not sure what's the
best way to add tests here: 1. should I rename ` compiler/intrinsics/sha` to `
compiler/intrinsics/digest` and add the md5 tests there, 2. should I just add `
compiler/intrinsics/md5`, or 3. the name doesn't matter and I can just add it
in ` compiler/intrinsics/sha`?
> In vm_version_x86.cpp move UseMD5Intrinsics flag setting near UseSHA flag
> setting.
Fixed.
> In new file macroAssembler_x86_md5.cpp no need empty line after copyright
> line. There is also typo 'rrdistribute':
>
> * This code is free software; you can rrdistribute it and/or modify it
>
> Our validate-headers check failed. See GPL header template:
> ./make/templates/gpl-header
I updated the header, and added the license for the original code for the MD5
core algorithm.
> Did you test it on 32-bit x86?
I did run `hotspot:tier1` and `jdk:tier1` on Windows-x86, Windows-x64 and
Linux-x64.
> Would be interesting to see result of artificially switching off AVX and SSE:
> '-XX:UseSSE=0 -XX:UseAVX=0'. It will make sure that only general instructions
> are needed.
The results are below:
-XX:-UseMD5Intrinsics
Benchmark (digesterName) (length) (provider) Mode Cnt
Score Error Units
MessageDigests.digest md5 64 DEFAULT thrpt 10
3512.618 ± 9.384 ops/ms
MessageDigests.digest md5 1024 DEFAULT thrpt 10
450.037 ± 1.213 ops/ms
MessageDigests.digest md5 16384 DEFAULT thrpt 10
29.887 ± 0.057 ops/ms
MessageDigests.digest md5 1048576 DEFAULT thrpt 10
0.485 ± 0.002 ops/ms
-XX:+UseMD5Intrinsics
Benchmark (digesterName) (length) (provider) Mode Cnt
Score Error Units
MessageDigests.digest md5 64 DEFAULT thrpt 10
4212.156 ± 7.781 ops/ ms => 19% speedup
MessageDigests.digest md5 1024 DEFAULT thrpt 10
548.609 ± 1.374 ops/ ms => 22% speedup
MessageDigests.digest md5 16384 DEFAULT thrpt 10
37.961 ± 0.079 ops/ ms => 27% speedup
MessageDigests.digest md5 1048576 DEFAULT thrpt 10
0.596 ± 0.006 ops/ ms => 23% speedup
-XX:-UseMD5Intrinsics -XX:UseSSE=0 -XX:UseAVX=0
Benchmark (digesterName) (length) (provider) Mode Cnt
Score Error Units
MessageDigests.digest md5 64 DEFAULT thrpt 10
3462.769 ± 4.992 ops/ms
MessageDigests.digest md5 1024 DEFAULT thrpt 10
443.858 ± 0.576 ops/ms
MessageDigests.digest md5 16384 DEFAULT thrpt 10
29.723 ± 0.480 ops/ms
MessageDigests.digest md5 1048576 DEFAULT thrpt 10
0.470 ± 0.001 ops/ms
-XX:+UseMD5Intrinsics -XX:UseSSE=0 -XX:UseAVX=0
Benchmark (digesterName) (length) (provider) Mode Cnt
Score Error Units
MessageDigests.digest md5 64 DEFAULT thrpt 10
4237.219 ± 15.627 ops/ms => 22% speedup
MessageDigests.digest md5 1024 DEFAULT thrpt 10
564.625 ± 1.510 ops/ms => 27% speedup
MessageDigests.digest md5 16384 DEFAULT thrpt 10
38.004 ± 0.078 ops/ms => 28% speedup
MessageDigests.digest md5 1048576 DEFAULT thrpt 10
0.597 ± 0.002 ops/ms => 27% speedup
Thank you,
Ludovic
