[macstl-dev] Integrating Linux changes, or that funny return type issue

[Glen Low]

Michael:

On 04/06/2005, at 12:37 AM, Glen Low wrote:

> Michael:
>
> I've integrated most of your changes but not having a YDL box handy  
> I can't really test. I'm definitely supporting only gcc >= 3.4.2 on  
> Linux because of the vector bool issues.
>
> I noticed one of the first changes you made related to mainline 3.3  
> ickiness with return values within templates. I'm wondering whether  
> it still holds for 3.4.2 and above; please try to compile:
>
> namespace macstl
>     {
>         namespace impl
>             {
>                 template <unsigned int v0, unsigned int v1,  
> unsigned int v2, unsigned int v3> struct generator
>                     {
>                         __vector unsigned int operator() () const
>                             {
>                                 #if defined(USE_C99_VEC_INIT_IN_TEMPL)
>
>                                 return (__vector unsigned int) {v0,  
> v1, v2, v3};
>
>                                 #elif defined 
> (USE_MOT_VEC_INIT_IN_TEMPL)
>
>                                 // most compilers choke on this,  
> not realizing v0 - v3 ARE constant expressions!!
>                                 return (__vector unsigned int) (v0,  
> v1, v2, v3);
>
>                                 #else
>
>                                 union union_type
>                                     {
>                                         unsigned int val [4];
>                                         __vector unsigned int vec;
>                                     };
>
>                                 static const union_type un = {v0,  
> v1, v2, v3};
>                                 return un.vec;
>
>                                 #endif
>
>                             }
>                     };
>             }
>     }
>
> On mainline 3.3, the "__vector unsigned int operator() () const"  
> line caused major unpleasantness IIRC.

I didn't get a reply from you. Based on the bug description back in  
our list in March 2005, and looking the gcc Bugzilla here http:// 
gcc.gnu.org/bugzilla/show_bug.cgi?id=8795, it seemed that returns  
with vector types in C++ cause a "sorry, unimplemented: `integer_cst'  
not supported by dump_type" error. It's claimed to be fixed in gcc  
3.4 and since that's the minimum version I'm going to support for  
Linux, I will leave the code as above. (It concerns me since there's  
a few more places where vector types are returned in macstl  
0.2.2.15/16).

Also based on the differences between the gcc 3.3 and 3.4 manuals at  
gcc.gnu.org, it seems 3.3 requires vec_splat_u32 to have a char, but  
3.4 requires vec_splat_u32 to have an int, so again I will leave the  
code written as "vec_splat_u32 (-16)".

Cheers, Glen Low


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