[Ffmpeg-cvslog] r7525 - trunk/libavutil/aes.c

[Michel Bardiaux]

michael wrote:
> Author: michael
> Date: Mon Jan 15 02:01:56 2007
> New Revision: 7525
> 
> Modified:
>    trunk/libavutil/aes.c
> 
> Log:
> replace / by >> this makes the .o ~150 bytes smaller

What are the version of gcc and the configure options? Its quite 
astonishing, I would have expected any halfway decent compiler to 
convert every division by a power of two, to shifts, so that this source 
change would have no effect.

> 
> 
> Modified: trunk/libavutil/aes.c
> ==============================================================================
> --- trunk/libavutil/aes.c	(original)
> +++ trunk/libavutil/aes.c	Mon Jan 15 02:01:56 2007
> @@ -101,7 +101,7 @@
>  static void init_multbl2(uint8_t tbl[1024], int c[4], uint8_t *log8, uint8_t *alog8, uint8_t *sbox){
>      int i, j;
>      for(i=0; i<1024; i++){
> -        int x= sbox[i/4];
> +        int x= sbox[i>>2];
>          if(x) tbl[i]= alog8[ log8[x] + log8[c[i&3]] ];
>      }
>  #ifndef CONFIG_SMALL
> @@ -116,7 +116,7 @@
>      AVAES *a;
>      int i, j, t, rconpointer = 0;
>      uint8_t tk[8][4];
> -    int KC= key_bits/32;
> +    int KC= key_bits>>5;
>      int rounds= KC + 6;
>      uint8_t  log8[256];
>      uint8_t alog8[512];
> @@ -158,7 +158,7 @@
>          tk[0][0] ^= rcon[rconpointer++];
>  
>          for(j = 1; j < KC; j++){
> -            if(KC != 8 || j != KC/2)
> +            if(KC != 8 || j != KC>>1)
>                  for(i = 0; i < 4; i++) tk[j][i] ^=      tk[j-1][i];
>              else
>                  for(i = 0; i < 4; i++) tk[j][i] ^= sbox[tk[j-1][i]];
> @@ -172,7 +172,7 @@
>              mix(a->round_key[i], dec_multbl);
>          }
>      }else{
> -        for(i=0; i<(rounds+1)/2; i++){
> +        for(i=0; i<(rounds+1)>>1; i++){
>              for(j=0; j<16; j++)
>                  FFSWAP(int, a->round_key[i][0][j], a->round_key[rounds-i][0][j]);
>          }


-- 
Michel Bardiaux
R&D Director
T +32 [0] 2 790 29 41
F +32 [0] 2 790 29 02
E mailto:mbardiaux at mediaxim.be

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