Re: [PATCH 2/3]rs6000: NFC use sext_hwi to replace ((v&0xf..f)^0x80..0) - 0x80..0

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

On 2022-12-01 15:10, Jiufu Guo via Gcc-patches wrote:
> Hi Kewen,
> 
> 在 12/1/22 2:11 PM, Kewen.Lin 写道:
>> on 2022/12/1 13:35, Jiufu Guo wrote:
>>> Hi Kewen,
>>> 
>>> Thanks for your quick and insight review!
>>> 
>>> 在 12/1/22 1:17 PM, Kewen.Lin 写道:
>>>> Hi Jeff,
>>>> 
>>>> on 2022/12/1 09:36, Jiufu Guo wrote:
>>>>> Hi,
>>>>> 
>>>>> This patch just uses sext_hwi to replace the expression like:
>>>>> ((value & 0xf..f) ^ 0x80..0) - 0x80..0 for rs6000.cc and rs6000.md.
>>>>> 
>>>>> Bootstrap & regtest pass on ppc64{,le}.
>>>>> Is this ok for trunk?
>>>> 
>>>> You didn't say it clearly but I guessed you have grepped in the 
>>>> whole
>>>> config/rs6000 directory, right?  I noticed there are still two 
>>>> places
>>>> using this kind of expression in function 
>>>> constant_generates_xxspltiw,
>>>> but I assumed it's intentional as their types are not HOST_WIDE_INT.
>>>> 
>>>> gcc/config/rs6000/rs6000.cc:      short sign_h_word = ((h_word & 
>>>> 0xffff) ^ 0x8000) - 0x8000;
>>>> gcc/config/rs6000/rs6000.cc:  int sign_word = ((word & 0xffffffff) ^ 
>>>> 0x80000000) - 0x80000000;
>>>> 
>>>> If so, could you state it clearly in commit log like "with type
>>>> signed/unsigned HOST_WIDE_INT" or similar?
>>>> 
>>> Good question!
>>> 
>>> And as you said sext_hwi is more for "signed/unsigned HOST_WIDE_INT".
>>> For these two places, it seems sext_hwi is not needed actually!
>>> And I did see why these expressions are used, may be just an 
>>> assignment
>>> is ok.
>> 
>> ah, I see.  I agree using the assignment is quite enough.  Could you
>> please also simplify them together?  Since they are with the form
>> "((value & 0xf..f) ^ 0x80..0) - 0x80..0" too, and can be refactored
>> in a better way.  Thanks!
> 
> Sure, I believe just "short sign_h_word = vsx_const->half_words[0];"
> should be correct :-), and included in the updated patch.
> 
> Updated patch is attached,  bootstrap&regtest is on going.

Bootstrap and regtest pass on ppc64{,le}.

BR,
Jeff (Jiufu)
> 
> 
> BR,
> Jeff (Jiufu)
> 
>> 
>> BR,
>> Kewen
>>