[cfe-commits] [PATCH] CodeGen support for transparent_union

[Stefan Kristiansson]

Ping?

On Mon, Jul 9, 2012 at 6:28 AM, Stefan Kristiansson
<stefan.kristiansson at saunalahti.fi> wrote:
> Hi,
>
> This is a follow-up to the message I sent to cfe-dev about
> unexpected behaviour on transparent unions [1].
>
> As I mentioned there, currently when unions marked with the transparent_union
> attribute are used as function arguments, the declared function gets called
> with the union instead of the calling convention of the first field in
> the transparent union as is required by the description [2].
>
> Looking at the commit log, most of the current implementation of the
> transparent_union attribute support origins from r70419, which actually
> mentions the lack of proper CodeGen support [3].
>
> Attached is a patch that tries to improve the situation by converting the
> type to the first field of the union, but there are a couple of things I am
> not completely satisfied with, so feedback on this patch is most welcome.
> The thing that bugs me most is the conversion in classifyArgument in
> lib/CodeGen/TargetInfo.cpp. Since this is ABI specific, every ABI
> has to do the conversion, which seems sub-optimal to me.
>
> Stefan
>
> [1] http://lists.cs.uiuc.edu/pipermail/cfe-dev/2012-July/022672.html
> [2] http://gcc.gnu.org/onlinedocs/gcc/Type-Attributes.html
> [3] http://lists.cs.uiuc.edu/pipermail/cfe-commits/Week-of-Mon-20090427/016496.html