Re: [PATCH] Stream profile summary histogram through LTO files (issue6782131)

[Teresa Johnson <tejohnson@google.com>]

On Thu, Nov 29, 2012 at 8:17 AM, Jan Hubicka <hubicka@ucw.cz> wrote:
>> This patch ensures that the histograms from the profile summary are streamed
>> through the LTO files so that the working set can be computed for use in
>> downstream optimizations.
>>
>> Bootstrapped and tested on x86_64-unknown-linux-gnu. Ok for trunk?
>>
>> Thanks,
>> Teresa
>>
>> 2012-11-28  Teresa Johnson  <tejohnson@google.com>
>>
>>       * lto-cgraph.c (output_profile_summary): Stream out sum_all
>>         and histogram.
>>       (input_profile_summary): Stream in sum_all and histogram.
>>       (merge_profile_summaries): Merge sum_all and histogram.
>>       (input_symtab): Call compute_working_sets after merging
>>         summaries.
>>       * gcov-io.c (gcov_histo_index): Make extern for compiler.
>>       * gcov-io.h (gcov_histo_index): Ditto.
>>       * profile.c (compute_working_sets): Remove static keyword.
>>       * profile.h (compute_working_sets): Ditto.
>
> OK.
>>
>> Index: lto-cgraph.c
>> ===================================================================
>> --- lto-cgraph.c      (revision 193909)
>> +++ lto-cgraph.c      (working copy)
>> @@ -46,6 +46,7 @@ along with GCC; see the file COPYING3.  If not see
>>  #include "tree-streamer.h"
>>  #include "gcov-io.h"
>>  #include "tree-pass.h"
>> +#include "profile.h"
>
> Please update dependencies in Makefile.in

ok.

>> +      /* Count number of non-zero histogram entries, and fill in a bit vector
>> +         of non-zero indices.  */
>> +         counters.  */
>> +      for (bv_ix = 0; bv_ix < GCOV_HISTOGRAM_BITVECTOR_SIZE; bv_ix++)
>> +        histo_bitvector[bv_ix] = 0;
>> +      for (h_ix = 0; h_ix < GCOV_HISTOGRAM_SIZE; h_ix++)
>> +        {
>> +          if (profile_info->histogram[h_ix].num_counters > 0)
>> +            {
>> +              histo_bitvector[h_ix / 32] |= 1 << (h_ix % 32);
>> +              h_cnt++;
>> +            }
>
> I think this would be more readable if you just produced a bitpack instead of doing it
> by hand, like into gcov-io.

I assume you mean use the bitpack streaming functionality used other
places in lto-cgraph.c, and not change the way it is done in gcov-io.c
where this was cloned from? I will change the lto-cgraph.c code to use
the bitpacking.

>> +     lto_gcov_summary.sum_all = MAX (lto_gcov_summary.sum_all,
>> +                                     (file_data->profile_info.sum_all
>> +                                      * scale
>> +                                      + REG_BR_PROB_BASE / 2)
>> +                                     / REG_BR_PROB_BASE);
>
> Use RDIV for the scaling.

ok. This was cloned from the way we do other scalings in the same
function, I will change them all to use RDIV.

>> -#if IN_LIBGCOV || !IN_GCOV
>> +#if !IN_GCOV
>>  /* Determine the index into histogram for VALUE. */
>>
>> -static unsigned
>> +GCOV_LINKAGE unsigned
> I would probably go around the trouble of declaring this static in GCOV,
> so it is inlined at we do not bload libgcov more than needed.

Do you mean leave it static when IN_LIBGCOV? It isn't included when
IN_GCOV. I just need it extern when in the compiler. So do you mean
make it static when IN_LIBGCOV and GCOV_LINKAGE (i.e. extern) when
!IN_LIBGCOV?

Thanks,
Teresa

>
> Thanks,
> Honza



--
Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413