Re: [PATCH, RFC, rs6000, v3] enable early gimple-folding of vec_splat

[Will Schmidt]

On Wed, 2018-09-12 at 08:23 -0500, Segher Boessenkool wrote: 
> Hi!

> > +   unsigned int n_elts = VECTOR_CST_NELTS (arg0);
> > +   if (TREE_CODE (arg1) != INTEGER_CST
> > +       || TREE_INT_CST_LOW (arg1) > (n_elts -1))
> > +     return false;
> 
> I think you should check lower bound 0 as well.  Maybe use IN_RANGE?

I'm comparing the IN_RANGE usage here with elsewhere in rs6000.c.
Do I need the sext_hwi() adjustment for arg1 within the IN_RANGE check?
As reference, this is for the vec_splat intrinsic, where arg1 is defined
as 'const int', and we want to return false if arg1 is outside the range
of 0..#elements . 
        vector bool char vec_splat (vector bool char, const int);

So.. this?
        unsigned int n_elts = VECTOR_CST_NELTS (arg0);
        if (TREE_CODE (arg1) != INTEGER_CST
            || !IN_RANGE (TREE_INT_CST_LOW (arg1), 0, (n_elts - 1))
          return false;

OR something like this with sext_hwi(...) ?:
        unsigned int n_elts = VECTOR_CST_NELTS (arg0);
        if (TREE_CODE (arg1) != INTEGER_CST
            || !IN_RANGE (sext_hwi (TREE_INT_CST_LOW (arg1), n_elts),
                          0, (n_elts - 1)))
          return false;


thanks
-Will


> 
> The rest looks fine, thanks!  Okay for trunk (with the trivialities fixed).
> 
> 
> Segher
>