RE: PATCH: Add XOP 128-bit and 256-bit support for upcoming AMD Orochi processor.

["rajagopal, dwarak" <dwarak dot rajagopal at amd dot com>]

Hi Honza,
I will be going to take over this patch from Harsha and wrap this up, so that I can check in this patch.

It would be great if you could answer the comments below from Harsha so that I will get more clarity.

Thanks,
Dwarak

Hi Honza,

I have gone through your feedback on the XOP patch and it makes sense and I will fix as per your suggestions.

However I am not entirely sure I understand the 2 comments below. Since Mike Meissner added these patterns, I mostly inherited them from him.
 
Can you please elaborate or provide some more guidance on what I need to do.
(Please see my comments below)

> +;; We don't have a straight 32-bit parallel multiply on XOP, so fake it with a
> +;; multiply/add.  In general, we expect the define_split to occur before
> +;; register allocation, so we have to handle the corner case where the target
> +;; is the same as one of the inputs.
> +(define_insn_and_split "*xop_mulv4si3"
> +  [(set (match_operand:V4SI 0 "register_operand" "=&x")
> +	(mult:V4SI (match_operand:V4SI 1 "register_operand" "%x")
> +		   (match_operand:V4SI 2 "nonimmediate_operand" "xm")))]
> > +  "TARGET_XOP"
> > +  "#"
> > +  "&& (reload_completed
> > +       || (!reg_mentioned_p (operands[0], operands[1])
> > +	   && !reg_mentioned_p (operands[0], operands[2])))"
> 
> WHat happens when regs are mentioned?
> There are other cases 2 memory operand multiply-add splitting testing
> these, are we somehow making sure this conditional will always hold and
> we won't ICE not being able to satisfy the conditions?

Actually I am not even sure this xop_mulv4si3 pattern is needed because XOP now implies SSE 4.2 and AVX and so we can just generate the mulv4si3 patterns for AVX or SSE 4.1 when -mxop is used. Can I just remove this xop_mulv4si3 pattern then?

As for your reference to "other cases 2 memory operand multiply-add splitting", I assume you are referring to the vpmac/d* define_splits.
 
In XOP vpmac/d* instructions, there is no restriction any more for the destination reg to be same as the third src operand unlike SSE5. And only the second source can be memory. Also I don't see anything in the manual that the destination reg is enforced to be different from source 1, source 2 or source 3 operands individually either.

Should I then remove below from the pmac/d* patterns?

(!reg_mentioned_p (operands[0], operands[1])
> > +	   && !reg_mentioned_p (operands[0], operands[2]))


> 
> > +;; The following are for the various unpack insns which doesn't need
> the first
> > +;; source operand, so we can just use the output operand for the first
> operand.
> > +;; This allows either of the other two operands to be a memory operand.
> We
> > +;; can't just use the first operand as an argument to the normal pperm
> because
> > +;; then an output only argument, suddenly becomes an input operand.
> > +(define_insn "xop_pperm_zero_v16qi_v8hi"
> > +  [(set (match_operand:V8HI 0 "register_operand" "=x,x")
> > +	(zero_extend:V8HI
> > +	 (vec_select:V8QI
> > +	  (match_operand:V16QI 1 "nonimmediate_operand" "xm,x")
> > +	  (match_operand 2 "" ""))))	;; parallel with const_int's
> > +   (use (match_operand:V16QI 3 "nonimmediate_operand" "x,xm"))]
> 
> Hmm, there is no unspec or omething that would make it clear that we can
> not ever somehow simplify into this form with operand 2 being something
> different than parallel with const_ints.  I think this needs new
> predicate.

I can define a new predicate for it in predicates.md, but I am not sure how exactly to represent the "parallel with const ints" part.

Any suggestions?

Thanks,
Harsha