Re: [PATCH V2] rs6000: Support to build constants by li/lis+oris/xoris

[Jiufu Guo <guojiufu@linux.ibm.com>]

Date: Thu, 01 Dec 2022 09:48:06 +0800
In-Reply-To: <20221128171950.GN25951@gate.crashing.org> (Segher Boessenkool's
	message of "Mon, 28 Nov 2022 11:19:50 -0600")
Message-ID: <7e4jufyjvt.fsf@pike.rch.stglabs.ibm.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.2 (gnu/linux)

Segher Boessenkool <segher@kernel.crashing.org> writes:

> On Mon, Nov 28, 2022 at 03:51:59PM +0800, Jiufu Guo wrote:
>> Jiufu Guo via Gcc-patches <gcc-patches@gcc.gnu.org> writes:
>> > Segher Boessenkool <segher@kernel.crashing.org> writes:
>> >>> > +      else
>> >>> > +	{
>> >>> > +	  emit_move_insn (temp,
>> >>> > +			  GEN_INT (((ud2 << 16) ^ 0x80000000) - 0x80000000));
>> >>> > +	  if (ud1 != 0)
>> >>> > +	    emit_move_insn (temp, gen_rtx_IOR (DImode, temp, GEN_INT (ud1)));
>> >>> > +	  emit_move_insn (dest,
>> >>> > +			  gen_rtx_ZERO_EXTEND (DImode,
>> >>> > +					       gen_lowpart (SImode, temp)));
>> >>> > +	}
>> >>
>> >> Why this?  Please just write it in DImode, do not go via SImode?
>> > Thanks for catch this. Yes, gen_lowpart with DImode would be ok.
>> Oh, Sorry. DImode can not be used here.  The genreated pattern with
>> DImode can not be recognized.  Using SImode is to match 'rlwxx'.
>
> There are patterns that accept DImode for rlwinm just fine.  Please use
>   (and:DI (const_int 0xffffffff) (x:DI))
> not the obfuscated
>   (zero_extend:DI (subreg:SI (x:DI) LOWBYTE))

I just submit a simple patch for this:
https://gcc.gnu.org/pipermail/gcc-patches/2022-December/607589.html

Thanks for comments!

BR,
Jeff (Jiufu)
>
>
> Segher