Re: [PATCH 7/7] lto: partition specific lto_clone_numbers

[Jan Hubicka <hubicka@ucw.cz>]

> Replaces "lto_priv.$clone_number" by
> "lto_priv.$partition_hash.$partition_specific_clone_number".
> To reduce divergence for incremental LTO.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu
OK,
thanks!
Honza
> 
> gcc/lto/ChangeLog:
> 
> 	* lto-partition.cc (set_clone_partition_name_checksum): New.
> 	(CHECKSUM_STRING): New.
> 	(privatize_symbol_name_1): Use partition hash for lto_priv.
> 	(lto_promote_cross_file_statics): Use set_clone_partition_name_checksum.
> 	(lto_promote_statics_nonwpa): Changed clone_map type.
> ---
>  gcc/lto/lto-partition.cc | 49 +++++++++++++++++++++++++++++++++++-----
>  1 file changed, 43 insertions(+), 6 deletions(-)
> 
> diff --git a/gcc/lto/lto-partition.cc b/gcc/lto/lto-partition.cc
> index eb31ecba0d3..a2ce24eea23 100644
> --- a/gcc/lto/lto-partition.cc
> +++ b/gcc/lto/lto-partition.cc
> @@ -35,6 +35,7 @@ along with GCC; see the file COPYING3.  If not see
>  #include "ipa-fnsummary.h"
>  #include "lto-partition.h"
>  #include "sreal.h"
> +#include "md5.h"
>  
>  #include <limits>
>  #include <vector>
> @@ -1516,8 +1517,36 @@ validize_symbol_for_target (symtab_node *node)
>      }
>  }
>  
> -/* Maps symbol names to unique lto clone counters.  */
> -static hash_map<const char *, unsigned> *lto_clone_numbers;
> +/* Maps symbol names with partition checksum to unique lto clone counters.  */
> +using clone_map = hash_map<pair_hash<nofree_string_hash,
> +				     int_hash_base<uint64_t>>, unsigned>;
> +static clone_map *lto_clone_numbers;
> +uint64_t current_partition_checksum = 0;
> +
> +/* Computes a quick checksum to distinguish partitions of clone numbers.  */
> +void
> +set_clone_partition_name_checksum (ltrans_partition part)
> +{
> +#define CHECKSUM_STRING(FOO) md5_process_bytes ((FOO), strlen (FOO), &ctx)
> +  struct md5_ctx ctx;
> +  md5_init_ctx (&ctx);
> +
> +  CHECKSUM_STRING (part->name);
> +
> +  lto_symtab_encoder_iterator lsei;
> +  lto_symtab_encoder_t encoder = part->encoder;
> +
> +  for (lsei = lsei_start (encoder); !lsei_end_p (lsei); lsei_next (&lsei))
> +    {
> +      symtab_node *node = lsei_node (lsei);
> +      CHECKSUM_STRING (node->name ());
> +    }
> +
> +  uint64_t checksum[2];
> +  md5_finish_ctx (&ctx, checksum);
> +  current_partition_checksum = checksum[0];
> +#undef CHECKSUM_STRING
> +}
>  
>  /* Helper for privatize_symbol_name.  Mangle NODE symbol name
>     represented by DECL.  */
> @@ -1531,10 +1560,16 @@ privatize_symbol_name_1 (symtab_node *node, tree decl)
>      return false;
>  
>    const char *name = maybe_rewrite_identifier (name0);
> -  unsigned &clone_number = lto_clone_numbers->get_or_insert (name);
> +
> +  unsigned &clone_number = lto_clone_numbers->get_or_insert (
> +    std::pair<const char*, uint64_t> {name, current_partition_checksum});
> +
> +  char lto_priv[32];
> +  sprintf (lto_priv, "lto_priv.%lu", current_partition_checksum);
> +
>    symtab->change_decl_assembler_name (decl,
>  				      clone_function_name (
> -					  name, "lto_priv", clone_number));
> +					  name, lto_priv, clone_number));
>    clone_number++;
>  
>    if (node->lto_file_data)
> @@ -1735,11 +1770,13 @@ lto_promote_cross_file_statics (void)
>        part->encoder = compute_ltrans_boundary (part->encoder);
>      }
>  
> -  lto_clone_numbers = new hash_map<const char *, unsigned>;
> +  lto_clone_numbers = new clone_map;
>  
>    /* Look at boundaries and promote symbols as needed.  */
>    for (i = 0; i < n_sets; i++)
>      {
> +      set_clone_partition_name_checksum (ltrans_partitions[i]);
> +
>        lto_symtab_encoder_iterator lsei;
>        lto_symtab_encoder_t encoder = ltrans_partitions[i]->encoder;
>  
> @@ -1778,7 +1815,7 @@ lto_promote_statics_nonwpa (void)
>  {
>    symtab_node *node;
>  
> -  lto_clone_numbers = new hash_map<const char *, unsigned>;
> +  lto_clone_numbers = new clone_map;
>    FOR_EACH_SYMBOL (node)
>      {
>        rename_statics (NULL, node);
> -- 
> 2.42.1
>