[RFC] Vectorization of indexed elements

Vidya Praveen vidyapraveen@arm.com
Fri Sep 27 15:19:00 GMT 2013


On Fri, Sep 27, 2013 at 03:50:08PM +0100, Vidya Praveen wrote:
[...]
> > > I can't really insist on the single lane load.. something like:
> > > 
> > > vc:V4SI[0] = c
> > > vt:V4SI = vec_duplicate:V4SI (vec_select:SI vc:V4SI 0)
> > > va:V4SI = vb:V4SI <op> vt:V4SI
> > > 
> > > Or is there any other way to do this?
> > 
> > Can you elaborate on "I can't really insist on the single lane load"?
> > What's the single lane load in your example? 
> 
> Loading just one lane of the vector like this:
> 
> vc:V4SI[0] = c // from the above scalar example
> 
> or 
> 
> vc:V4SI[0] = c[2] 
> 
> is what I meant by single lane load. In this example:
> 
> t = c[2] 
> ...
> vb:v4si = b[0:3] 
> vc:v4si = { t, t, t, t }
> va:v4si = vb:v4si <op> vc:v4si 
> 
> If we are expanding the CONSTRUCTOR as vec_duplicate at vec_init, I cannot
> insist 't' to be vector and t = c[2] to be vect_t[0] = c[2] (which could be 
> seen as vec_select:SI (vect_t 0) ). 
> 
> > I'd expect the instruction
> > pattern as quoted to just work (and I hope we expand an uniform
> > constructor { a, a, a, a } properly using vec_duplicate).
> 
> As much as I went through the code, this is only done using vect_init. It is
> not expanded as vec_duplicate from, for example, store_constructor() of expr.c

Do you see any issues if we expand such constructor as vec_duplicate directly 
instead of going through vect_init way? 

VP




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