Re: [PATCH v2] Generalize get_most_common_single_value to return k_th value & count

[Martin Liška <mliska at suse dot cz>]

On 7/15/19 10:20 AM, Xiong Hu Luo wrote:
> Currently get_most_common_single_value could only return the max hist
> <value, count>, add qsort to enable this function return kth value.
> Rename it to get_kth_value_count.
> 
> gcc/ChangeLog:
> 
> 	2019-07-15  Xiong Hu Luo  <luoxhu@linux.ibm.com>
> 
> 	* ipa-profile.c (get_most_common_single_value): Use
> 	get_kth_value_count.
> 	* value-prof.c (struct value_count_t): New struct.
> 	(cmp_counts): New function.
> 	(get_most_common_single_value): Rename to ...
> 	get_kth_value_count.  Add input params k, return
> 	the k_th value and count.
> 	(gimple_divmod_fixed_value_transform): Use get_kth_value_count.
> 	(gimple_ic_transform): Likewise.
> 	(gimple_stringops_transform): Likewise.
> 	* value-prof.h (get_most_common_single_value): Add input params
> 	k, default to 0.
> ---
>  gcc/ipa-profile.c |  4 +--
>  gcc/value-prof.c  | 66 +++++++++++++++++++++++++++++++++--------------
>  gcc/value-prof.h  |  8 +++---
>  3 files changed, 52 insertions(+), 26 deletions(-)
> 
> diff --git a/gcc/ipa-profile.c b/gcc/ipa-profile.c
> index 1fb939b73d0..37a004c4ce4 100644
> --- a/gcc/ipa-profile.c
> +++ b/gcc/ipa-profile.c
> @@ -192,8 +192,8 @@ ipa_profile_generate_summary (void)
>  		  if (h)
>  		    {
>  		      gcov_type val, count, all;
> -		      if (get_most_common_single_value (NULL, "indirect call",
> -							h, &val, &count, &all))
> +		      if (get_kth_value_count (NULL, "indirect call", h, &val,
> +					       &count, &all))
>  			{
>  			  struct cgraph_edge * e = node->get_edge (stmt);
>  			  if (e && !e->indirect_unknown_callee)
> diff --git a/gcc/value-prof.c b/gcc/value-prof.c
> index 32e6ddd8165..9b7fb52dcd2 100644
> --- a/gcc/value-prof.c
> +++ b/gcc/value-prof.c
> @@ -713,19 +713,42 @@ gimple_divmod_fixed_value (gassign *stmt, tree value, profile_probability prob,
>    return tmp2;
>  }
>  
> -/* Return most common value of TOPN_VALUE histogram.  If
> -   there's a unique value, return true and set VALUE and COUNT
> +struct value_count_t {
> +  gcov_type value;
> +  gcov_type count;
> +};

I like introduction of the tuple, please fix GNU coding style: '{' shoud
be on the next line.

> +typedef struct value_count_t *value_count;
> +typedef const struct value_count_t *const_value_count;

We use C++, please do not come up with these defines.

> +
> +static int
> +cmp_counts (const void *v1, const void *v2)
> +{
> +  const_value_count h1 = (const_value_count) v1;
> +  const_value_count h2 = (const_value_count) v2;
> +  if (h1->count < h2->count)
> +    return 1;
> +  if (h1->count > h2->count)
> +    return -1;
> +  return 0;
> +}

In order to provide stable results, we want secondary comparison based on 'value'.

> +
> +/* Return the k-th value count of TOPN_VALUE histogram.  If
> +   there's a value, return true and set VALUE and COUNT
>     arguments.  */
>  
>  bool
> -get_most_common_single_value (gimple *stmt, const char *counter_type,
> -			      histogram_value hist,
> -			      gcov_type *value, gcov_type *count,
> -			      gcov_type *all)
> +get_kth_value_count (gimple *stmt, const char *counter_type,
> +		     histogram_value hist, gcov_type *value, gcov_type *count,
> +		     gcov_type *all, unsigned k)
>  {
> +  auto_vec<struct value_count_t, 4> value_vec;

Please replace '4' with GCOV_TOPN_VALUES.

> +  struct value_count_t temp;
> +
>    if (hist->hvalue.counters[2] == -1)
>      return false;
>  
> +  gcc_assert (k < GCOV_TOPN_VALUES);
> +
>    *count = 0;
>    *value = 0;
>  
> @@ -743,14 +766,21 @@ get_most_common_single_value (gimple *stmt, const char *counter_type,
>  
>        *all = read_all;
>  
> -      if (c > *count)
> -	{
> -	  *value = v;
> -	  *count = c;
> -	}
> -      else if (c == *count && v > *value)
> -	*value = v;
> +     temp.value = v;
> +     temp.count = c;
> +
> +     value_vec.safe_push (temp);
> +    }
> +
> +  value_vec.qsort (cmp_counts);

I don't like sorting that all the time. Please sort the values once when we load it from disk.

About the name, I would prefer:
get_nth_most_common_value instead.

Thanks,
Martin

> +
> +  if (k < value_vec.length ())
> +    {
> +      *value = value_vec[k].value;
> +      *count = value_vec[k].count;
>      }
> +  else
> +    return false;
>  
>    return true;
>  }
> @@ -784,8 +814,7 @@ gimple_divmod_fixed_value_transform (gimple_stmt_iterator *si)
>    if (!histogram)
>      return false;
>  
> -  if (!get_most_common_single_value (stmt, "divmod", histogram, &val, &count,
> -				     &all))
> +  if (!get_kth_value_count (stmt, "divmod", histogram, &val, &count, &all))
>      return false;
>  
>    value = histogram->hvalue.value;
> @@ -1439,8 +1468,8 @@ gimple_ic_transform (gimple_stmt_iterator *gsi)
>    if (!histogram)
>      return false;
>  
> -  if (!get_most_common_single_value (NULL, "indirect call", histogram, &val,
> -				     &count, &all))
> +  if (!get_kth_value_count (NULL, "indirect call", histogram, &val, &count,
> +			    &all))
>      return false;
>  
>    if (4 * count <= 3 * all)
> @@ -1658,8 +1687,7 @@ gimple_stringops_transform (gimple_stmt_iterator *gsi)
>    if (!histogram)
>      return false;
>  
> -  if (!get_most_common_single_value (stmt, "stringops", histogram, &val,
> -				     &count, &all))
> +  if (!get_kth_value_count (stmt, "stringops", histogram, &val, &count, &all))
>      return false;
>  
>    gimple_remove_histogram_value (cfun, stmt, histogram);
> diff --git a/gcc/value-prof.h b/gcc/value-prof.h
> index ca846d08cbd..228bd0f2f70 100644
> --- a/gcc/value-prof.h
> +++ b/gcc/value-prof.h
> @@ -89,11 +89,9 @@ void free_histograms (function *);
>  void stringop_block_profile (gimple *, unsigned int *, HOST_WIDE_INT *);
>  gcall *gimple_ic (gcall *, struct cgraph_node *, profile_probability);
>  bool check_ic_target (gcall *, struct cgraph_node *);
> -bool get_most_common_single_value (gimple *stmt, const char *counter_type,
> -				   histogram_value hist,
> -				   gcov_type *value, gcov_type *count,
> -				   gcov_type *all);
> -
> +bool get_kth_value_count (gimple *stmt, const char *counter_type,
> +			  histogram_value hist, gcov_type *value,
> +			  gcov_type *count, gcov_type *all, unsigned k = 0);
>  
>  /* In tree-profile.c.  */
>  extern void gimple_init_gcov_profiler (void);
>