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Subject: [Bug tree-optimization/55162] Loop ivopts cuts off top bits of loop counter
Date: Thu, 01 Nov 2012 10:12:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55162

--- Comment #1 from Oleg Endo <olegendo at gcc dot gnu.org> 2012-11-01 10:11:46 UTC ---
(In reply to comment #0)
> The same could be done on SH, too (comparing against the end address instead of
> using a loop counter), but it would add a loop setup overhead.  In the optimal
> case the above function would result in the following SH code:
> 
>         tst     r5,r5
>         bt/s    .L6
>         mov     #0,r0
> .L3:
>         mov.l   @r4+,r1
>         dt      r5
>         bf/s    .L3
>         add     r1,r0
> .L6:
>         rts
>         nop
> 

... which is the case if '*x++' is used instead of 'x[i]':

int test (int* x, unsigned int c)
{
  int s = 0;
  unsigned int i;
  for (i = 0; i < c; ++i)
    s += *x++;
  return s;
}