[Bug middle-end/34400] [4.3 regression] bad interaction between DF and SJLJ exceptions

["zadeck at naturalbridge dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #53 from zadeck at naturalbridge dot com  2008-01-17 22:37 -------
Subject: Re:  [4.3 regression] bad interaction between
 DF and SJLJ exceptions

seongbae dot park at gmail dot com wrote:
> ------- Comment #52 from seongbae dot park at gmail dot com  2008-01-17 22:31 -------
> Subject: Re:  [4.3 regression] bad interaction between DF and SJLJ exceptions
>
> I just talked to Kenny on the phone, and my suggestion is wrong
> since it changes the return value - doing my naive suggestion
> would lead to infinite loop, as the transfer function will almost always
> return true, even when the out set didn't change.
> Can you add a comment to that effect there ?
> Also please add a comment above df_live_scratch definition
> that this is an optimization to reduce memory allocation overhead
> for the scratch.
>
>   
will do.

> Can you explain why the hunk in df_live_bb_local_compute() is correct ?
> As this seems to change what DF_REF_AT_TOP means for artificial defs...
>
>   
In the old code we went thru the artificial defs twice, once for the
defs at the bottom and once for the defs at the top.  This is a waste of
time.  we only need to go thru them once since, for this problem, the
processing is order independent.


> Seongbae
>
> On Jan 17, 2008 1:31 PM, Seongbae Park (¹Ú¼º¹è, ÚÓà÷ÛÆ)
> <seongbae.park@gmail.com> wrote:
>   
>> In df_live_transfer_function:
>>
>> Doesn't look like we need df_live_scratch - can't we do:
>>
>> bitmap_and (out, gen, bb_lr_info->out);
>> bitmap_and_into (in, bb_lr_info->in);
>> return bitmap_ior_and_compl_into (out, in, kill);
>>
>> ?
>>
>> Seongbae
>>
>>
>> On Jan 17, 2008 1:05 PM, Kenneth Zadeck <zadeck@naturalbridge.com> wrote:
>>     
>>> This is the second of three patches to fix 34400.  This patch also makes
>>> some progress on 26854 but more work is required that is not going to be
>>> done in 4.3 to fix the problems here.
>>>
>>> This patch uses the output of the df_lr problem to make the df_live
>>> problem converge faster.
>>> This not only saves time but also space since the size of the df_live
>>> bitmaps never grows and the space of our bitmaps is proportional to the
>>> number of 1 bits.
>>>
>>> This has been tested on several platforms and along with the patch just
>>> committed cuts the time on the 34400 problems significantly.  I believe
>>> that this patch also has some modest improvement on bootstrap time, i.e
>>> regular programs.
>>>
>>> The change to df_live_reset is a slightly related latent bug fix.
>>>
>>> Ok to commit?
>>>
>>> Kenny
>>>
>>>
>>> 2008-01-17  Kenneth Zadeck  <zadeck@naturalbridge.com>
>>>         Steven Bosscher  <stevenb.gcc@gmail.com>
>>>
>>>     PR rtl-optimization/26854
>>>     PR rtl-optimization/34400
>>>     * df-problems.c (df_live_scratch): New scratch bitmap.
>>>     (df_live_alloc): Allocate df_live_scratch when doing df_live.
>>>     (df_live_reset): Clear the proper bitmaps.
>>>     (df_live_bb_local_compute): Only process the artificial defs once
>>>     since the order is not important.
>>>     (df_live_init): Init the df_live sets only with the variables
>>>     found live by df_lr.
>>>     (df_live_transfer_function): Use the df_lr sets to prune the
>>>     df_live sets as they are being computed.
>>>     (df_live_free): Free df_live_scratch.
>>>
>>>
>>>       
>>
>> --
>> #pragma ident "Seongbae Park, compiler, http://seongbae.blogspot.com";
>>
>>     
>
>
>   


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=34400