Re: [PATCH] c++: simplify norm_cache manipulation

[Jason Merrill <jason@redhat.com>]

On 5/18/23 14:01, Patrick Palka wrote:
> Avoid performing two norm_cache lookups during normalization of a
> concept-id by allocating inserting a norm_entry* before rather than
> after the fact, which is simpler and faster.
> 
> Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for
> trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	* constraint.cc (normalize_concept_check): Avoid having to do
> 	two norm_cache lookups.  Remove unnecessary early exit for an
> 	ill-formed concept definition.
> ---
>   gcc/cp/constraint.cc | 31 +++++++++----------------------
>   1 file changed, 9 insertions(+), 22 deletions(-)
> 
> diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
> index c81e024e0e2..8cf0f2d0974 100644
> --- a/gcc/cp/constraint.cc
> +++ b/gcc/cp/constraint.cc
> @@ -774,38 +774,25 @@ normalize_concept_check (tree check, tree args, norm_info info)
>   
>     if (!norm_cache)
>       norm_cache = hash_table<norm_hasher>::create_ggc (31);
> -  norm_entry entry = {tmpl, targs, NULL_TREE};
> -  norm_entry **slot = nullptr;
> -  hashval_t hash = 0;
> -  bool insert = false;
> +  norm_entry *entry = nullptr;
>     if (!info.generate_diagnostics ())
>       {
>         /* Cache the normal form of the substituted concept-id (when not
>   	 diagnosing).  */
> -      hash = norm_hasher::hash (&entry);
> -      slot = norm_cache->find_slot_with_hash (&entry, hash, NO_INSERT);
> -      if (slot)
> +      norm_entry elt = {tmpl, targs, NULL_TREE};
> +      norm_entry **slot = norm_cache->find_slot (&elt, INSERT);
> +      if (*slot)
>   	return (*slot)->norm;
> -      insert = true;
> +      entry = ggc_alloc<norm_entry> ();
> +      *entry = elt;
> +      *slot = entry;
>       }
>   
> -  /* The concept may have been ill-formed.  */
>     tree def = get_concept_definition (DECL_TEMPLATE_RESULT (tmpl));
> -  if (def == error_mark_node)
> -    return error_mark_node;
> -
>     info.update_context (check, args);
>     tree norm = normalize_expression (def, targs, info);
> -  if (insert)
> -    {
> -      /* Recompute SLOT since norm_cache may have been expanded during
> -	 the recursive call.  */
> -      slot = norm_cache->find_slot_with_hash (&entry, hash, INSERT);
> -      gcc_checking_assert (!*slot);
> -      entry.norm = norm;
> -      *slot = ggc_alloc<norm_entry> ();
> -      **slot = entry;
> -    }
> +  if (entry)
> +    entry->norm = norm;
>     return norm;
>   }
>