Re: [PATCH 05/13] allow constructing a auto_vec with a preallocation, and a possibly larger actual allocation size

[Richard Sandiford <richard dot sandiford at linaro dot org>]

tbsaunde+gcc@tbsaunde.org writes:
> From: Trevor Saunders <tbsaunde+gcc@tbsaunde.org>
>
> This allows us to set the capacity of the vector when we construct it,
> and still use a stack buffer when the size is small enough.
>
> gcc/ChangeLog:
>
> 2017-05-09  Trevor Saunders  <tbsaunde+gcc@tbsaunde.org>
>
> 	* genrecog.c (int_set::int_set): Explicitly construct our
> auto_vec base class.
> 	* vec.h (auto_vec::auto_vec): New constructor.
> ---
>  gcc/genrecog.c |  8 +++++---
>  gcc/vec.h      | 12 ++++++++++++
>  2 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/genrecog.c b/gcc/genrecog.c
> index 6a9e610e7a0..b69043f0d02 100644
> --- a/gcc/genrecog.c
> +++ b/gcc/genrecog.c
> @@ -1407,14 +1407,16 @@ struct int_set : public auto_vec <uint64_t, 1>
>    iterator end ();
>  };
>  
> -int_set::int_set () {}
> +int_set::int_set () : auto_vec<uint64_t, 1> () {}
>  
> -int_set::int_set (uint64_t label)
> +int_set::int_set (uint64_t label) :
> +  auto_vec<uint64_t, 1> ()
>  {
>    safe_push (label);
>  }
>  
> -int_set::int_set (const int_set &other)
> +int_set::int_set (const int_set &other) :
> +  auto_vec<uint64_t, 1> ()
>  {
>    safe_splice (other);
>  }

Is this part of the patch necessary?  Won't the default constructor
be used anyway?

Thanks,
Richard

> diff --git a/gcc/vec.h b/gcc/vec.h
> index fee46164b01..914f89c350c 100644
> --- a/gcc/vec.h
> +++ b/gcc/vec.h
> @@ -1272,6 +1272,18 @@ public:
>      this->m_vec = &m_auto;
>    }
>  
> +  auto_vec (size_t s)
> +  {
> +    if (s > N)
> +      {
> +	this->create (s);
> +	return;
> +      }
> +
> +    m_auto.embedded_init (MAX (N, 2), 0, 1);
> +    this->m_vec = &m_auto;
> +  }
> +
>    ~auto_vec ()
>    {
>      this->release ();