Re: [PATCH] [RS6000] Change maddld match_operand from DI to GPR

["Kewen.Lin" <linkw@linux.ibm.com>]

Hi Segher,

on 2019/6/24 下午4:02, Segher Boessenkool wrote:
> Hi Kewen,
> 
> On Mon, Jun 24, 2019 at 03:43:26PM +0800, Kewen.Lin wrote:
>> on 2019/6/24 下午3:19, Segher Boessenkool wrote:
>>> Newer ISAs require 64-bit to be implemented.  There are no optional
>>> 64-bit categories anymore.  Since this instruction is enabled for P9
>>> (ISA 3.0) only (that's the TARGET_MODULO), it's fine.
>>>
>>> What you are saying is quite true for older CPUs/ISAs though: there you
>>> have to make sure you are targetting a CPU that supports the 64-bit
>>> categories, before using any 64-bit insns.
>>>
>>> But those days are gone :-)
>>
>> Good to know that, thanks a lot for the information!  It's fine then.
>>
>> It sounds like we can have a clean up for some others like 
>> TARGET_EXTSWSLI. :)
> 
> Yes, but be careful there!  The insn patterns for this use DImode, which
> does not mean the same thing without -mpowerpc64 (it's a register pair
> then, not what you want).
> 
> And it doesn't make much sense to allow this for SImode as well (using
> GPR, perhaps), because the insn just is a shift left for SImode, and we
> already have shift left instructions.
> 
> So we might want to just directly say "TARGET_MODULO && TARGET_POWERPC64"
> in those patterns (TARGET_MODULO is a funny way of saying "p9 or later").
> 

Thanks for further clarification!  Yes, I agree with you.  I just noticed
that extswsli isn't like maddld and not suitable for SImode.


Thanks,
Kewen

> 
> Segher
>