Re: [PATCH, Pointer Bounds Checker 14/x] Passes [15/n] Optimize redundant checks

[Ilya Enkovich <enkovich dot gnu at gmail dot com>]

2014-10-09 21:41 GMT+04:00 Jeff Law <law@redhat.com>:
> On 10/08/14 13:22, Ilya Enkovich wrote:
>>
>> Hi,
>>
>> This patch adds removal of redundant (covered by other) checks into
>> checker optimization.
>>
>> Thanks,
>> Ilya
>> --
>> 2014-10-08  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         * tree-chkp.c (chkp_compare_checks): New.
>>         (chkp_remove_redundant_checks): New.
>>         (chkp_opt_execute): Run redundant checks removal
>>         algorithm.
>
>
> Wouldn't pure removal be better modeled in existing optimizers?  DOM would
> seem to be a natural fit?
>
> Similarly, isn't the swapping very similar to a reverse DOM walk DSE-like
> optimizer?
>
> Deferring further review until those questions are answered?
>
> jeff
>
>

Checks and and intersection removal code was added as a simple pass
catching trivial cases.  I'm sure there are optimizations having
common elements with what checker optimizer does.  But initially we
didn't want to adopt existing optimizers because GIMPLE representation
of instrumentation was not stable and also we still don't know what
are important targets for optimizations.

The plan is to have stable version first.  After enabling we want to
make performance analysis and determine which optimizations are most
required (it may appear checks removal doesn't give any significant
performance gain at all), determine which of current infrastructure
may be re-used (if any) and implement proper checker optimization.

Current optimizer is a simple code cleanup.  I do not think we should
make any significant rework of it as a part of enabling.  If current
approach seems to require significant changes to go to trunk then it
should be probably delayed and go separately from instrumentation
pass.

Thanks,
Ilya