Switch statement: extra out-of-bounds code emitted

[Dale Johannesen]

On Thursday, December 20, 2001, at 02:17 PM, Chris Sears wrote:

>
> Given a switch statement of the form:
>
>   unsigned char i;
>
>   switch ( i ) {
>     case 0: funct0(); break;
>     case 1: funct1(); break;
>     ...
>     case 255: funct255(); break;
>   }
>
> bounds checking the index variable is unnecessary.

Perhaps more usefully,

   switch ( i&7 ) {    /* or i%8 */
     case 0: case 1: case 2: case 3:  /* case bodies omitted */
     case 4: case 5: case 6: case 7:
   }

could omit the bounds checks.  This isn't dependent on the type of i.