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

[Trevor Saunders <tbsaunde@tbsaunde.org>]

On Wed, May 10, 2017 at 07:54:13AM +0100, Richard Sandiford wrote:
> 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?

Well, without the change to the copy constructor we get this bootstrap
warning.

/src/gcc/gcc/genrecog.c: In copy constructor ‘int_set::int_set(const int_set&)’:
/src/gcc/gcc/genrecog.c:1417:1: error: base class ‘class auto_vec<long
unsigned int, 1>’ should be explicitly initialized in the copy
constructor [-Werror=extra]
 int_set::int_set (const int_set &other)
  ^~~~~~~

>
So we need to do something about that.  I'm not sure the other cases are
necessary, but I was there, and being explicit seemed better than
leaving it implicit.

Thanks

Trev

> 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 ();