Re: [PATCH 2/2] vec: Add array_slice::bsearch

[Martin Jambor <mjambor@suse.cz>]

Hi,

On Fri, Aug 26 2022, Richard Biener wrote:
>> Am 26.08.2022 um 18:40 schrieb Martin Jambor <mjambor@suse.cz>:
>> 
>> Hi,
>> 
>> This adds a method to binary search in a sorted array_slice.
>> 
>> The implementation is direct copy of vec:bsearch.  Moreover, to only
>> copy it once and not twice, I used const_cast in the non-const
>> variants to be able to use the const variants.  I hope that is
>> acceptable abuse of const_cast but I'll be happy to change that if
>> not.
>> 
>> Bootstrapped and tested along code that actually uses it on
>> x86_64-linux.  OK for trunk?
>
> Can you avoid the copying by using array slice bsearch from the vec<> bsearch?

I would be easy to just move the implementation to array_slice and then
implement vec<...>::bsearch by calling into that.

But I still think I need more constructors for that ;-)

Martin

>> 
>> 
>> gcc/ChangeLog:
>> 
>> 2022-08-08  Martin Jambor  <mjambor@suse.cz>
>> 
>>    * vec.h (array_slice::bsearch): New methods.
>> ---
>> gcc/vec.h | 94 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
>> 1 file changed, 94 insertions(+)
>> 
>> diff --git a/gcc/vec.h b/gcc/vec.h
>> index b0477e1044c..61ebdc4ca13 100644
>> --- a/gcc/vec.h
>> +++ b/gcc/vec.h
>> @@ -2301,6 +2301,14 @@ public:
>>   // True if the array is valid, false if it is an array like INVALID.
>>   bool is_valid () const { return m_base || m_size == 0; }
>> 
>> +  /* Methods for binary search in sorted array_slice.  */
>> +  const T *bsearch (const void *key, int (*compar)(const void *,
>> +                           const void *)) const;
>> +  T *bsearch (const void *key, int (*compar)(const void *, const void *));
>> +  const T *bsearch (const void *key,
>> +          int (*compar)(const void *, const void *, void *), void *) const;
>> +  T *bsearch (const void *key,
>> +          int (*compar)(const void *, const void *, void *), void *);
>> private:
>>   iterator m_base;
>>   unsigned int m_size;
>> @@ -2361,6 +2369,92 @@ make_array_slice (T *base, unsigned int size)
>>   return array_slice<T> (base, size);
>> }
>> 
>> +/* Search the contents of the sorted array_slice with a binary search.  CMP is
>> +   the comparison function to pass to bsearch.  */
>> +
>> +template<typename T>
>> +inline const T *
>> +array_slice<T>::bsearch (const void *key,
>> +             int (*compar) (const void *, const void *)) const
>> +{
>> +  const void *base = this->m_base;
>> +  size_t nmemb = this->size ();
>> +  size_t size = sizeof (T);
>> +  /* The following is a copy of glibc stdlib-bsearch.h.  */
>> +  size_t l, u, idx;
>> +  const void *p;
>> +  int comparison;
>> +
>> +  l = 0;
>> +  u = nmemb;
>> +  while (l < u)
>> +    {
>> +      idx = (l + u) / 2;
>> +      p = (const void *) (((const char *) base) + (idx * size));
>> +      comparison = (*compar) (key, p);
>> +      if (comparison < 0)
>> +    u = idx;
>> +      else if (comparison > 0)
>> +    l = idx + 1;
>> +      else
>> +    return (T *)const_cast<void *>(p);
>> +    }
>> +
>> +  return NULL;
>> +}
>> +
>> +template<typename T>
>> +inline T *
>> +array_slice<T>::bsearch (const void *key,
>> +             int (*compar) (const void *, const void *))
>> +{
>> +  return const_cast<T>(bsearch (key, compar));
>> +}
>> +
>> +/* Search the contents of the sorted array_slice with a binary search.  CMP is
>> +   the comparison function to pass to bsearch.  */
>> +
>> +template<typename T>
>> +inline const T *
>> +array_slice<T>::bsearch (const void *key,
>> +             int (*compar) (const void *, const void *, void *),
>> +             void *data) const
>> +{
>> +  const void *base = this->m_base;
>> +  size_t nmemb = this->size ();
>> +  size_t size = sizeof (T);
>> +  /* The following is a copy of glibc stdlib-bsearch.h.  */
>> +  size_t l, u, idx;
>> +  const void *p;
>> +  int comparison;
>> +
>> +  l = 0;
>> +  u = nmemb;
>> +  while (l < u)
>> +    {
>> +      idx = (l + u) / 2;
>> +      p = (const void *) (((const char *) base) + (idx * size));
>> +      comparison = (*compar) (key, p, data);
>> +      if (comparison < 0)
>> +    u = idx;
>> +      else if (comparison > 0)
>> +    l = idx + 1;
>> +      else
>> +    return (T *)const_cast<void *>(p);
>> +    }
>> +
>> +  return NULL;
>> +}
>> +
>> +template<typename T>
>> +inline T *
>> +array_slice<T>::bsearch (const void *key,
>> +             int (*compar) (const void *, const void *, void *),
>> +             void *data)
>> +{
>> +  return const_cast<T> (bsearch (key, compar, data));
>> +}
>> +
>> #if (GCC_VERSION >= 3000)
>> # pragma GCC poison m_vec m_vecpfx m_vecdata
>> #endif
>> -- 
>> 2.37.2
>>