Re: [PATCH, Pointer Bounds Checker 23/x] Function split

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

2014-09-03 23:12 GMT+04:00 Jeff Law <law@redhat.com>:
> On 08/18/14 09:55, Ilya Enkovich wrote:
>>
>> On 04 Jun 01:15, Jeff Law wrote:
>>>
>>> On 06/03/14 01:10, Ilya Enkovich wrote:
>>>>
>>>> Hi,
>>>>
>>>> This patch does not allow splitting in case bounds are returned until
>>>> retutrned bounds are supported.  It also propagates instrumentation marks
>>>> for generated call and function.
>>>>
>>>> Bootstrapped and tested on linux-x86_64.
>>>>
>>>> Thanks,
>>>> Ilya
>>>> --
>>>> gcc/
>>>>
>>>> 2014-06-03  Ilya Enkovich  <ilya.enkovich@intel.com>
>>>>
>>>>         * ipa-split.c: Include tree-chkp.h.
>>>>         (consider_split): Do not split when return bounds.
>>>>         (split_function): Propagate Pointer Bounds Checker
>>>>         instrumentation marks.
>>>
>>> It's a hack.  There's no reason we can't support this.  So I'll
>>> approve on the condition that you do look at removing this
>>> limitation in the future.
>>>
>>> jeff
>>>
>>
>> I did some work for function splitting and now patch cover more cases.
>> Now returned bounds are supported but it is not allowed to split producers
>> of returned pointer and its bounds.  Is it OK?
>>
>> Thanks,
>> Ilya
>> --
>> 2014-08-15  Ilya Enkovich  <ilya.enkovich@intel.com>
>>
>>         * ipa-split.c: Include tree-chkp.h.
>>         (find_retbnd): New.
>>         (consider_split): Do not split retbnd and retval
>>         producers.
>>         (split_function): Propagate Pointer Bounds Checker
>>         instrumentation marks and handle returned bounds.
>
> I don't think it's sufficient to just look at the SSA_NAME_DEFSTMT and
> verify that it's not in the header.
>
> You could easily have the SSA_NAME_DEF_STMT be a PHI which is in the same
> partition as the RETURN statement.  One of the PHI arguments might be fed
> from a statement in the header, right?
>
> Don't you have to look at the entire set of definitions which directly and
> indirectly feed the return statement and verify that each and every one is
> in the same partition as the return statement?

A problem I'm trying to avoid is that bounds in return statement are
not taken into account when checking for data dependencies between
parts.  It means we may have a case when return statement with bounds
is put into split part but bounds producer is not.  If
SSA_NAME_DEFSTMT for returned bounds is in the same partition as a
return then I do not think I should care about the rest of definitions
chain because regular split point checks should make sure we have
everything required.

>
> And if so, that makes me start to think the original hack wasn't so bad
> after all :-)

It's always nice to have a backup plan! :)

Ilya

>
> jeff
>