Hi,
> Doloop optimization fails to be applied on the following inner loop
> when compiling for PowerPC (GCC -r162294) due to:
>
> Doloop: number of iterations too costly to compute.
strength reduction is performed in ivopts, introducing new variable:
for (p = inptr; p < something; p += 3)
...
So the number of iterations is (something - p) / 3, which doloop considers
too costly to compute.
Zdenek
> I do not understand why as the number of iterations is max_cols and I
> appreciate an explanation.
>
> Thanks,
> Revital
>
> 11 while (--max_rows >= 0)
> 12 {
> 13 inptr = *inbuf++;
> 14 outp = outbuf[0][rows];
> 15 rows++;
> 16
> 17 for (y = 0; y < max_cols; y++)
> 18 {
> 19 k = ((int) (inptr[0]));
> 20 inptr += 3;
> 21
> 22 outp[y] = (unsigned char) ((inarr[k]) >> 16);
> 23 }
> 24 }
>
>
> >From Doloop dump:
>
> Analyzing operand (reg/f:DI 246 [ D.2082 ]) of insn (insn 118 116 119 5
> test1.c:17 (set (reg:CC 272)
> (compare:CC (reg/v/f:DI 199 [ inptr ])
> (reg/f:DI 246 [ D.2082 ]))) 535 {*cmpdi_internal1}
> (expr_list:REG_DEAD (reg/f:DI 246 [ D.2082 ])
> (nil)))
> invariant (reg/f:DI 246 [ D.2082 ]) (in DI)
> Loop 2 is simple:
> simple exit 5 -> 6
> number of iterations: (mult:DI (plus:DI (minus:DI (reg/f:DI 246
> [ D.2082 ])
> (reg/v/f:DI 199 [ inptr ]))
> (const_int -3 [0xfffffffffffffffd]))
> (const_int -6148914691236517205 [0xaaaaaaaaaaaaaaab]))
> upper bound: -1
> Doloop: number of iterations too costly to compute.
>
>
> (See attached file: test1.c)
