[cfe-dev] Conversions of ext_vector types

´╝│yoyo ´╝Žujita syoyofujita at gmail.com
Thu Apr 19 19:25:10 PDT 2012


I am no an cfe vector expr developer, so I also don't know the story behind this, but I guess this is a bug of cfe.

To add an information a bit, the code handles float4 + int4 arithmetic with conversion-free casting, whereas OpenCL keenel and gcc vector extension(and possibly AltiVec extension) does not allow float4 + int4 expression.

Also note, arithmetic operations and type casting is not C compatible for vector variables(see OpenCL spec for example)

--
Syoyo

On 2012/04/20, at 1:00, "Schoedel, Kevin P" <kevin.p.schoedel at intel.com> wrote:

> As a C programmer, I find the behaviour of ext_vector conversions
> surprising.
> 
> typedef float float4 __attribute__((ext_vector_type(4)));
> typedef int int4 __attribute__((ext_vector_type(4)));
> float4 f(float4 a, int4 b)
> {
>     return a + b;
> }
> 
> define <4 x float> @f(<4 x float> %a, <4 x i32> %b) nounwind uwtable readnone {
> entry:
>   %0 = bitcast <4 x i32> %b to <4 x float>
>   %add = fadd <4 x float> %0, %a
>   ret <4 x float> %add
> }
> 
> I've looked, but not found the story behind this. Would there be
> objections to having conversions, like other ext_vector operations,
> perform the corresponding scalar operation elementwise instead?
> 
> --
> Kevin Schoedel kevin.p.schoedel at intel.com +1-519-772-2580
> SSG-DPD-ECDL-DMP - Intel Dynamic Mobility and Parallelism
> 
> _______________________________________________
> cfe-dev mailing list
> cfe-dev at cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/cfe-dev




More information about the cfe-dev mailing list