sha3.c: neon backend now twice the speed of scalar backend (~50% fewer cyles, see commit message)

made the following changes:
- row_t contents are now 3 uint64x2_t instead of uin64x2x3_t (so they
  are stored as registers instead of memory)
- fetch round constants 2 at a time
- round loop unrolled once
- drop convoluted ext/trn store (hard to read, doesn't help)

bench results
-------------
scalar backend:
  > make clean all SHA3_BACKEND=1
  ...
  > ./bench 10000
  info: cpucycles: version=20240318 implementation=arm64-vct persecond=2400000000
  info: backend=scalar num_trials=10000 src_lens=64,256,1024,4096,16384 dst_lens=32
  function,dst_len,64,256,1024,4096,16384
  sha3_224,28,20.2,10.3,10.3,9.3,9.2
  sha3_256,32,20.2,10.3,10.3,9.9,9.7
  sha3_384,48,20.9,15.3,12.8,12.7,12.7
  sha3_512,64,20.2,20.2,18.9,17.9,18.1
  shake128,32,20.2,10.3,9.0,8.1,7.9
  shake256,32,20.2,10.1,10.3,9.9,9.7

neon backend:
  > make clean all SHA3_BACKEND=3
  ...
  > ./bench 10000
  info: cpucycles: version=20240318 implementation=arm64-vct persecond=2400000000
  info: backend=neon num_trials=10000 src_lens=64,256,1024,4096,16384 dst_lens=32
  function,dst_len,64,256,1024,4096,16384
  sha3_224,28,9.7,5.0,5.0,4.6,4.5
  sha3_256,32,9.7,5.0,5.0,4.9,4.8
  sha3_384,48,9.7,7.3,6.2,6.2,6.1
  sha3_512,64,9.7,9.7,9.1,8.7,8.7
  shake128,32,9.7,5.0,4.5,4.0,4.0
  shake256,32,9.7,5.0,5.1,4.9,4.8

0 files changed, 0 insertions, 0 deletions