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Subject: Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10))
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Date: Wed, 15 Jun 2011 18:57:00 -0000
Cc: Richard Guenther <richard.guenther@gmail.com>, Jason Merrill <jason@redhat.com>, gcc-patches List <gcc-patches@gcc.gnu.org>
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To: Richard Guenther <rguenther@suse.de>
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On Jun 15, 2011, at 2:04 AM, Richard Guenther wrote:
> This VIEW_CONVERT_EXPR looks useless - in fact useless_type_conversion_p
> will tell you that, so you can omit it.

So, I tracked down who created it:

tree
convert_to_vector (tree type, tree expr)
{
  switch (TREE_CODE (TREE_TYPE (expr)))
    {
    case INTEGER_TYPE:
    case VECTOR_TYPE:
      if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYPE (expr=
))))
        {
          error ("can%'t convert between vector values of different size");
          return error_mark_node;
        }
=3D>    return build1 (VIEW_CONVERT_EXPR, type, expr);

If people want to not create useless conversions in the first place, though=
, I suspect there are lots of places that create useless conversions in the=
 compiler.