shift subreg patch [was: gcc/Alpha]

[Richard Henderson]

The attached patch cleans up this untidiness.


r~


On Fri, Dec 12, 1997 at 10:31:26AM +0100, Robert Harley wrote:
> >Can you give an example of what you mean?
> 
> OK.  A 'zapnot' appears for code like this:
> 
> ------------------------------------------------------------------------------
> typedef unsigned long u64;
> 
> #define TAB_SIZE (16UL)
> #define TAB_MASK (TAB_SIZE-1UL)
> 
> u64 foo(u64 bh, u64 bl, u64 *p)
> {
>   u64 sh;
>   static const int tab[TAB_SIZE] = { 4,0,1,0,2,0,1,0,3,0,1,0,2,0,1,0 };
> 
>   do {
>     sh = (u64)tab[bl & TAB_MASK];
>     bl >>= sh; bh >>= sh;
>   } while (!(bl & 1UL));
> 
>   *p = bh;
>   return bl;
> } /* end foo */
> ------------------------------------------------------------------------------
> 
> But then it disappears mysteriously at the slightest change!
> For instance, if the second shift is commented out.
> 
> -- Rob.