On Tue, Aug 16, 2011 at 11:12 PM, Artem Shinkarov
<artyom.shinkar...@gmail.com> wrote:
> Hi, here is a new version of the patch with the adjustments.
>
> Two important comments.
> 1) At the moment when I expand expression mask ? vec0 : vec1, I
> replace mask with (mask == {-1,-1,..}). The first reason is that
> expand_vec_cond_expr requires first operand to be a comparison. Second
> reason is that a mask {3, 4, -1, 5} should be transformed into
> {0,0,-1,0} in order to simulate vcond as ((vec0 & mask) | (vec1 &
> ~mask)). So in both cases we need this adjustment.
Well. From a middle-end view I'd say that mask ? vec0 : vec1
should return (vec0 & mask) | (vec1 & ~mask) which is what
the XOP vcond instructions do, btw. Only by defining
v1 < v2 to return a mask constrained to {-1|0, -1|0, ...} the
combination v1 < v2 ? vec0 : vec1 gets it's vector element
selection semantic (instead of being just a bitwise selection,
which it really is).
So no, I don't think we need to convert {3, 4, -1, 5} to {0,0,-1,0}
(that would surprise my anyway, I'd have expected {-1,-1,-1,-1} ;)).
Does OpenCL somehow support you here?
> 2) Vector comparison through optab.
> As far as I just have adjusted expand_vector_operation in
> tree-vect-generic.c, it would be called only when there is no
> sufficient optab. I is being checked in expand_vector_operations_1. So
> the only place where I try to find an optab for the comparison is
> expand_vec_cond_expr_piecewise, which I adjusted.
>
> As for the vector hook, it will be triggered only when we don't have
> an appropriate optab.
>
> bootstrapped and tested on x86_64-unknown-linux-gnu.
> Anything else?
I didn't yet look at the updated patch, I'll wait for another update that
eventually follows my comments to your earlier mail.
Richard.
>
> Artem.
>
