This patch adds a x86_64/avx assembler implementation of the Twofish block
cipher. The implementation processes eight blocks in parallel (two 4 block
chunk AVX operations). The table-lookups are done in general-purpose registers.
For small blocksizes the 3way-parallel functions from the twofish-x86_64-3way
module are called. A good performance increase is provided for blocksizes
greater or equal to 128B.

Patch has been tested with tcrypt and automated filesystem tests.

Tcrypt benchmark results:

Intel Core i5-2500 CPU (fam:6, model:42, step:7)

twofish-avx-x86_64 vs. twofish-x86_64-3way
128bit key:                                             (lrw:256bit)    (xts:256bit)
size    ecb-enc ecb-dec cbc-enc cbc-dec ctr-enc ctr-dec lrw-enc lrw-dec xts-enc xts-dec
16B     0.96x   0.97x   1.00x   0.95x   0.97x   0.97x   0.96x   0.95x   0.95x   0.98x
64B     0.99x   0.99x   1.00x   0.99x   0.98x   0.98x   0.99x   0.98x   0.99x   0.98x
256B    1.20x   1.21x   1.00x   1.19x   1.15x   1.14x   1.19x   1.20x   1.18x   1.19x
1024B   1.29x   1.30x   1.00x   1.28x   1.23x   1.24x   1.26x   1.28x   1.26x   1.27x
8192B   1.31x   1.32x   1.00x   1.31x   1.25x   1.25x   1.28x   1.29x   1.28x   1.30x

256bit key:                                             (lrw:384bit)    (xts:512bit)
size    ecb-enc ecb-dec cbc-enc cbc-dec ctr-enc ctr-dec lrw-enc lrw-dec xts-enc xts-dec
16B     0.96x   0.96x   1.00x   0.96x   0.97x   0.98x   0.95x   0.95x   0.95x   0.96x
64B     1.00x   0.99x   1.00x   0.98x   0.98x   1.01x   0.98x   0.98x   0.98x   0.98x
256B    1.20x   1.21x   1.00x   1.21x   1.15x   1.15x   1.19x   1.20x   1.18x   1.19x
1024B   1.29x   1.30x   1.00x   1.28x   1.23x   1.23x   1.26x   1.27x   1.26x   1.27x
8192B   1.31x   1.33x   1.00x   1.31x   1.26x   1.26x   1.29x   1.29x   1.28x   1.30x

twofish-avx-x86_64 vs aes-asm (8kB block):
         128bit  256bit
ecb-enc  1.19x   1.63x
ecb-dec  1.18x   1.62x
cbc-enc  0.75x   1.03x
cbc-dec  1.23x   1.67x
ctr-enc  1.24x   1.65x
ctr-dec  1.24x   1.65x
lrw-enc  1.15x   1.53x
lrw-dec  1.14x   1.52x
xts-enc  1.16x   1.56x
xts-dec  1.16x   1.56x

Signed-off-by: Johannes Goetzfried <Johannes.Goetzfried@informatik.stud.uni-erlangen.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>