[PATCH] Fix for PR64081 in RTL loop unroller

[Jeff Law]

On 01/16/15 08:16, Zamyatin, Igor wrote:
>>> Not sure it's possible to merge DF_REG_DEF_CHAIN walk and
>> DF_REF_CHAIN walk...
>> OK.  Just use the same overall structure if we can't pull the test out into a
>> single function that could be called from both places.
>>
>
> Thanks, is updated patch ok for trunk?
>
> Igor
>
>
> Changelog:
>
> gcc
>
> 2015-01-16  Igor Zamyatin  <igor.zamyatin@intel.com>
>
> 	PR rtl-optimization/64081
> 	* loop-iv.c (def_pred_latch_p): New function.
> 	(latch_dominating_def): Allow specific cases with non-single
> 	definitions.
> 	(iv_get_reaching_def): Likewise.
> 	(check_complex_exit_p): New function.
> 	(check_simple_exit): Use check_complex_exit_p to allow certain cases
> 	with exits not executing on any iteration.
>
> testsuite
>
> 2014-01-16  Igor Zamyatin  <igor.zamyatin@intel.com>
>
> 	PR rtl-optimization/64081
> 	* gcc.dg/pr64081.c: New test.
Just a few nits below.  Approved with the nits fixed.


> +/* Checks that def is in an immediate predecessor of the latch block.  */
> +
> +static bool
> +def_pred_latch_p (df_ref d_ref)
Use the actual parameter name in the comment and put it in caps, mention 
the return values.  Something like this:

/* Return true if D_REF is defined in an immediate predecessor of the
    current loop's latch block.  Otherwise return false.  */

>
> +  /* If we have single definition it has to be excuted on each iteration.  */
s/excuted/executed/

> +/* Check whether exit is not simple but still good for further analysis.
> +   Looks like such loops mostly are a result of jump threading.  */
> +
> +static bool
> +check_complex_exit_p (struct loop* loop, basic_block bb)
/* Return true if LOOP has a complex exit, but is still good for further
    analysis.  Return false otherwise.  BB is LOOP's exit block.  */


With those comment fixes, this is OK for the trunk.

Thanks,
Jeff