Re: PATH: Replace UNITS_PER_SIMD_WORD with GET_MODE_SIZE (TYPE_MODE (vectype))

[Paolo Bonzini <bonzini at gnu dot org>]

> > My first patch doesn't change
> > UNITS_PER_SIMD_WORD at all. It just removes
> > the hardcoded UNITS_PER_SIMD_WORD usage.
> > The only one left is in get_vectype_for_scalar_type.
>
> I like this approach the most.  As for get_vectype_for_scalar_type, this
> probably should be a target hook (effectively taking the place of
> UNITS_PER_SIMD_WORD).

Maybe.  However, the target hook would be implemented, depending on the 
architecture, either like this:

  nbytes = GET_MODE_SIZE (TYPE_MODE (scalar_type));
  nunits = UNITS_PER_SIMD_WORD / nbytes;
  vectype = build_vector_type (scalar_type, nunits);
  if (!VECTOR_MODE_P (TYPE_MODE (vectype))
      && !INTEGRAL_MODE_P (TYPE_MODE (vectype)))
    return NULL_TREE;

or like this:

  switch (TYPE_MODE (scalar_type))
    {
    case QImode: return build_vector_type_for_mode (scalar_type, 
V16QImode);
    case HImode: return build_vector_type_for_mode (scalar_type, V8HImode);
    case SImode: return build_vector_type_for_mode (scalar_type, V4SImode);
    ...
    }

in all the targets.  All the dumping stuff would stay in 
tree-vectorizer.c, and even if you added a new 
build_vector_type_for_size function, it would add more code duplication 
than value.

I think that H.J.'s patch to only use UNITS_PER_SIMD_WORD in 
get_vectype_for_scalar_type, plus his patch to add an argument to the 
target macro, is the simplest thing to do and it works.

Paolo