[vlc-devel] [PATCH 01/16] block cipher: improve performance

[Jean-Baptiste Kempf]

LGTM.
Does this add a special requirement to the input, like alignment?
Does this add latency?

On 26 Jun, glenvt18 wrote :
> 1. Use a dvbcsa_bs_world_t x 8 scratch buffer between the output of sbox and the input of
> the permute logic. It reduces the dependency between sbox output and permute logic input.
> 2x speed-up of CSA on x86 with both uint64 and sse2.
> 
> 2. Lookup 4 values at a time (a, b, c, d) - reduces dependency on a read value.
> 
> 3. Use separate scratch buffers for reading and writing.
> 
> Changes 2 and 3 add about 5% depending on the architecture.
> ---
>  src/dvbcsa_bs_block.c | 96 +++++++++++++++++++++++++++++++++------------------
>  1 file changed, 63 insertions(+), 33 deletions(-)
> 
> diff --git a/src/dvbcsa_bs_block.c b/src/dvbcsa_bs_block.c
> index 58f6ca9..e4f532c 100644
> --- a/src/dvbcsa_bs_block.c
> +++ b/src/dvbcsa_bs_block.c
> @@ -31,32 +31,48 @@
>  DVBCSA_INLINE static inline void
>  dvbcsa_bs_block_decrypt_register (const dvbcsa_bs_word_t *block, dvbcsa_bs_word_t *r)
>  {
> -  int	i, j, g;
> +  dvbcsa_bs_word_t scratch1[8];
> +  dvbcsa_bs_word_t scratch2[8];
> +  int i, j, g;
>  
>    r += 8 * 56;
>  
> -  // loop over kk[55]..kk[0]
> +  /* loop over kk[55]..kk[0] */
>    for (i = 55; i >= 0; i--)
>      {
>        dvbcsa_bs_word_t *r6_N = r + 8 * 6;
>  
> -      r -= 8;	/* virtual shift of registers */
> +      r -= 8;   /* virtual shift of registers */
>  
>        for (g = 0; g < 8; g++)
> -	{
> -	  union {
> -	    dvbcsa_bs_word_t so;
> -	    uint8_t si[BS_BATCH_BYTES];
> -	  } u;
> +        scratch1[g] = BS_XOR(block[i], r6_N[g]);
> +
> +      /* sbox */
> +      {
> +      uint8_t *p1, *p2;
> +      uint8_t a, b, c, d;
> +
> +      p1 = (uint8_t *)scratch1;
> +      p2 = (uint8_t *)scratch2;
> +      for (j = 0; j < BS_BATCH_BYTES * 8; j += 4)
> +        {
> +          a = p1[j + 0];
> +          b = p1[j + 1];
> +          c = p1[j + 2];
> +          d = p1[j + 3];
> +          p2[j + 0] = dvbcsa_block_sbox[a];
> +          p2[j + 1] = dvbcsa_block_sbox[b];
> +          p2[j + 2] = dvbcsa_block_sbox[c];
> +          p2[j + 3] = dvbcsa_block_sbox[d];
> +        }
> +      }
>  
> -	  u.so = BS_XOR(block[i], r6_N[g]);
> -
> -	  for (j = 0; j < BS_BATCH_BYTES; j++)
> -	    u.si[j] = dvbcsa_block_sbox[u.si[j]];
> -
> -	  dvbcsa_bs_word_t sbox_out = u.so;
> +      for (g = 0; g < 8; g++)
> +        {
> +          dvbcsa_bs_word_t sbox_out = scratch2[g];
> +          dvbcsa_bs_word_t w;
>  
> -	  // bit permutation
> +          /* bit permutation */
>  
>  	  dvbcsa_bs_word_t in = BS_OR(
>  				      BS_OR(
> @@ -67,8 +83,7 @@ dvbcsa_bs_block_decrypt_register (const dvbcsa_bs_word_t *block, dvbcsa_bs_word_
>  				      BS_OR(       BS_SHR (BS_AND (sbox_out, BS_VAL8(40)), 6),
>  					           BS_SHR (BS_AND (sbox_out, BS_VAL8(80)), 4)));
>  
> -	  dvbcsa_bs_word_t w = BS_XOR(r[8 * 8 + g], sbox_out);
> -
> +          w = BS_XOR(r[8 * 8 + g], sbox_out);
>  	  r[8 * 0 + g] = w;
>  	  BS_XOREQ(r[8 * 2 + g], w);
>  	  BS_XOREQ(r[8 * 3 + g], w);
> @@ -116,30 +131,46 @@ void dvbcsa_bs_block_decrypt_batch(const struct dvbcsa_bs_key_s *key,
>  DVBCSA_INLINE static inline void
>  dvbcsa_bs_block_encrypt_register (const dvbcsa_bs_word_t *block, dvbcsa_bs_word_t *r)
>  {
> -  int	i, j, g;
> +  dvbcsa_bs_word_t scratch1[8];
> +  dvbcsa_bs_word_t scratch2[8];
> +  int i, j, g;
>  
> -  // loop over kk[55]..kk[0]
> +  /* loop over kk[55]..kk[0] */
>    for (i = 0; i < 56; i++)
>      {
>        dvbcsa_bs_word_t *r7_N = r + 8 * 7;
>  
> -      r += 8;	/* virtual shift of registers */
> +      r += 8;   /* virtual shift of registers */
>  
>        for (g = 0; g < 8; g++)
> -	{
> -	  union {
> -	    dvbcsa_bs_word_t so;
> -	    uint8_t si[BS_BATCH_BYTES];
> -	  } u;
> +          scratch1[g] = BS_XOR(block[i], r7_N[g]);
> +
> +      /* sbox */
> +      {
> +      uint8_t *p1, *p2;
> +      uint8_t a, b, c, d;
> +
> +      p1 = (uint8_t *)scratch1;
> +      p2 = (uint8_t *)scratch2;
> +      for (j = 0; j < BS_BATCH_BYTES * 8; j += 4)
> +        {
> +          a = p1[j + 0];
> +          b = p1[j + 1];
> +          c = p1[j + 2];
> +          d = p1[j + 3];
> +          p2[j + 0] = dvbcsa_block_sbox[a];
> +          p2[j + 1] = dvbcsa_block_sbox[b];
> +          p2[j + 2] = dvbcsa_block_sbox[c];
> +          p2[j + 3] = dvbcsa_block_sbox[d];
> +        }
> +      }
>  
> -	  u.so = BS_XOR(block[i], r7_N[g]);
> -
> -	  for (j = 0; j < BS_BATCH_BYTES; j++)
> -	    u.si[j] = dvbcsa_block_sbox[u.si[j]];
> -
> -	  dvbcsa_bs_word_t sbox_out = u.so;
> +      for (g = 0; g < 8; g++)
> +        {
> +          dvbcsa_bs_word_t sbox_out = scratch2[g];
> +          dvbcsa_bs_word_t w = r[-8 * 1 + g];
>  
> -	  // bit permutation
> +          /* bit permutation */
>  
>  	  dvbcsa_bs_word_t in = BS_OR(
>  				      BS_OR(
> @@ -150,7 +181,6 @@ dvbcsa_bs_block_encrypt_register (const dvbcsa_bs_word_t *block, dvbcsa_bs_word_
>  				      BS_OR(       BS_SHR (BS_AND (sbox_out, BS_VAL8(40)), 6),
>  					           BS_SHR (BS_AND (sbox_out, BS_VAL8(80)), 4)));
>  
> -	  dvbcsa_bs_word_t w = r[-8 * 1 + g];
>  
>  	  r[8 * 7 + g] = BS_XOR(w, sbox_out);
>  	  BS_XOREQ(r[8 * 1 + g], w);
> -- 
> 1.9.1
> 
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-- 
With my kindest regards,

-- 
Jean-Baptiste Kempf
http://www.jbkempf.com/ - +33 672 704 734
Sent from my Electronic Device