[PATCH 3/4] spellcheck.h: add best_match template; implement early-reject

[Jeff Law]

On 06/14/2016 09:15 AM, David Malcolm wrote:
> There's a lot of repetition between find_closest_string and
> find_closest_identifier, and the next patch adds more, so this
> patch moves the logic into a new template class "best_match"
> for locating the closest string from a sequence of candidates.
>
> The patch also introduces a pair of early-reject optimizations
> that weren't present in the older implementations, reducing the
> number of calls to levenshtein_distance.
> Introducing class best_match allows for these optimizations to be
> in one place (best_match::consider), rather than having to implement
> them twice.
>
> Successfully bootstrapped&regrtested in combination with the rest of
> the kit on x86_64-pc-linux-gnu
> Successful -fself-test of stage1 on powerpc-ibm-aix7.1.3.0 of
> just this patch (on top of patches 1 and 2).
>
> OK for trunk if it passes individual bootstrap&regrtest?
>
> gcc/c/ChangeLog:
> 	* c-typeck.c: Include spellcheck-tree.h rather than spellcheck.h.
>
> gcc/cp/ChangeLog:
> 	* search.c: Include spellcheck-tree.h rather than spellcheck.h.
>
> gcc/ChangeLog:
> 	* spellcheck-tree.c: Include spellcheck-tree.h rather than
> 	spellcheck.h.
> 	(find_closest_identifier): Reimplement in terms of
> 	best_match<tree,tree>.
> 	* spellcheck-tree.h: New file.
> 	* spellcheck.c (struct edit_distance_traits<const char *>): New
> 	struct.
> 	(find_closest_string): Reimplement in terms of
> 	best_match<const char *, const char *>.
> 	* spellcheck.h (levenshtein_distance): Move prototype of tree-based
> 	overload to spellcheck-tree.h.
> 	(find_closest_identifier): Likewise.
> 	(struct edit_distance_traits<T>): New template.
> 	(class best_match): New class.
OK.
jeff