Re: [PATCH 2/4] [ifcvt] if convert x=c ? y+z : y by RISC-V Zicond like insns

[Jeff Law <jeffreyalaw@gmail.com>]

On 11/27/23 19:46, Fei Gao wrote:
> On 2023-11-20 14:46  Jeff Law <jeffreyalaw@gmail.com> wrote:
>>
>>
>>
>> On 10/30/23 21:35, Fei Gao wrote:
>>
>>>> So just a few notes to further illustrate why I'm currently looking to
>>>> take the VRULL+Ventana implementation.  The code above would be much
>>>> better handled by just calling noce_emit_cmove.  noce_emit_cmove will go
>>>> through the conditional move expander.  So any improvement we make in
>>>> the expander "just work" when called from the if-converter.
>>> noce_emit_czero is used here to make sure czero insns are emited.
>>> noce_emit_cmove includes SFB and Thead movcc, which will take precedence
>>> over zicond in RISCV if enabled. Unfortunately we have products with SFB and Zicond
>>> both available and saw such conflict.
>>> And that is also the reason to add hook TARGET_HAVE_COND_ZERO
>>> in [PATCH 1/4] to disallow ineffient code emited by SFB enable and Zicond disabled case.
>> I understand what you're trying to do, but I would consider the
>> TARGET_HAVE_COND_ZERO fundamentally the wrong approach.
> Hi Jeff
> 
> Thanks for your review. I just post the new series.
> https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg327148.html
> https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg327151.html
> https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg327149.html
> https://www.mail-archive.com/gcc-patches@gcc.gnu.org/msg327150.html
> 
> TARGET_HAVE_COND_ZERO has been deleted.
THanks for the V2.  I'll see what I can do with them this week.  The 
series was posted prior to close of stage1, so it can still be 
integrated into gcc-14 if we get it cleaned up.

Jeff