Re: [PATCH] ifcvt/vect: Emit COND_ADD for conditional scalar reduction.

[Robin Dapp <rdapp.gcc@gmail.com>]

Hi Tamar,

> So in the
> 
>   if (slp_node)
>     {
> 
> Add something like:
> 
> If (is_cond_op)
>     {
>       if (dump_enabled_p ())
> 	dump_printf_loc (MSG_MISSED_OPTIMIZATION, vect_location,
> 			 "left fold reduction on SLP not supported.\n");
>       return false;
>     }

Yes, seems reasonable, added.

> The only comment I have is whether you actually need this helper function?
> It looks like all the uses of it are in cases you have, or will call conditional_internal_fn_code
> directly.
> 
> e.g. in vect_transform_reduction you can replace it by 
> 
> bool cond_fn_p = cond_fn != ERROR_MARK;
> 
> and in 
> 
>   if (cond_fn_p (orig_code))
>       orig_code = conditional_internal_fn_code (internal_fn(orig_code));
> 
> just 
> 
> internal_fn new_fn = conditional_internal_fn_code (internal_fn(orig_code));
> if (new_fn != ERROR_MARK)
>   orig_code = new_fn;
> 
> which would save the repeated testing of the condition.

I see what you mean.  One complication is that we want to disambiguate
(among others):

 (1) code = IFN_COND_ADD, cond_fn = IFN_LAST.   (new case)
 (2) code = IFN_MAX, cond_fn = IFN_COND_MAX.
 (3) code = IFN_SOMETHING, cond_fn = IFN_LAST.

So just checking cond_fn is not enough (even if we made
get_conditional_internal_fn (IFN_COND_ADD) return IFN_COND_ADD).
We need to know if the initial code already was an IFN_COND.

It's a bit of a mess but I didn't dare untangling.  Well, actually, I
tried but made it worse ;)  The cond_fn_p check seemed least
intrusive to me.  Maybe you have another idea?

Regards
 Robin