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Date: Thu, 16 Jun 2011 07:39:00 -0000
Message-ID: <BANLkTikeXbH74+8hJsxYQmU2w9PsxC6oJw@mail.gmail.com>
Subject: Re: RFA (fold): PATCH for c++/49290 (folding *(T*)(ar+10))
From: Richard Guenther <richard.guenther@gmail.com>
To: Mike Stump <mikestump@comcast.net>
Cc: Richard Guenther <rguenther@suse.de>, Jason Merrill <jason@redhat.com>, 	gcc-patches List <gcc-patches@gcc.gnu.org>
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On Wed, Jun 15, 2011 at 7:46 PM, Mike Stump <mikestump@comcast.net> wrote:
> 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)
> {
> =A0switch (TREE_CODE (TREE_TYPE (expr)))
> =A0 =A0{
> =A0 =A0case INTEGER_TYPE:
> =A0 =A0case VECTOR_TYPE:
> =A0 =A0 =A0if (!tree_int_cst_equal (TYPE_SIZE (type), TYPE_SIZE (TREE_TYP=
E (expr))))
> =A0 =A0 =A0 =A0{
> =A0 =A0 =A0 =A0 =A0error ("can%'t convert between vector values of differ=
ent size");
> =A0 =A0 =A0 =A0 =A0return error_mark_node;
> =A0 =A0 =A0 =A0}
> =3D> =A0 =A0return build1 (VIEW_CONVERT_EXPR, type, expr);
>
> If people want to not create useless conversions in the first place, thou=
gh, I suspect there are lots of places that create useless conversions in t=
he compiler.

Yeah, the above looks it comes from the frontends - gimplification
should strip this conversion, if it doesn't that is a bug ;)

Richard.