[PATCH] Allow casts of mixed-size same-arity vectors

[Eli Friedman]

On Wed, Sep 11, 2013 at 3:34 PM, Hal Finkel <hfinkel at anl.gov> wrote:

> ----- Original Message -----
> > On Sep 11, 2013, at 3:29 PM, Hal Finkel < hfinkel at anl.gov > wrote:
> >
> >
> >
> >
> >
> > ----- Original Message -----
> >
> >
> > ----- Original Message -----
> >
> >
> > Hal —
> >
> > Am I understanding this correctly:
> >
> > vector4float x;
> > vector4int16 y = (vector4int16)x; // this is a conversion
> > vector4int32 z = (vector4int32)x; // this is a bitcast
> >
> > This seems confusing in the extreme.
> >
> > On the other hand, I don't really like the implied int-to-float
> > bitcast semantics. Maybe it would be better to just add a warning
> > for this case. What do you think?
> >
> > bitcast semantics for vector casts are an essential tool for SIMD
> > programming. Essentially all warnings generated would be false
> > positives.
>
> Do you specifically mean in OpenCL, or generally? (I've worked on SIMD
> special function implementations, so I understand the utility).
>
>
OpenCL doesn't allow writing casts like this at all, if that's what you're
asking; OpenCL requires using intrinsics.

-Eli
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