No, reduction patterns won't help. 
As I said in vfwmul patch. You should make sure your environment is working then try again.

Thanks.



juzhe.zhong@rivai.ai
 
From: Jeff Law
Date: 2023-06-30 07:43
To: 钟居哲; gcc-patches
CC: kito.cheng; kito.cheng; palmer; palmer; rdapp.gcc
Subject: Re: [PATCH] RISC-V: Support vfwnmacc/vfwmsac/vfwnmsac combine lowering
 
 
On 6/28/23 16:56, 钟居哲 wrote:
> 
> 
> ------------------------------------------------------------------------
> juzhe.zhong@rivai.ai
> 
>     *From:* Jeff Law <mailto:jeffreyalaw@gmail.com>
>     *Date:* 2023-06-29 06:43
>     *To:* 钟居哲 <mailto:juzhe.zhong@rivai.ai>; gcc-patches
>     <mailto:gcc-patches@gcc.gnu.org>
>     *CC:* kito.cheng <mailto:kito.cheng@gmail.com>; kito.cheng
>     <mailto:kito.cheng@sifive.com>; palmer <mailto:palmer@dabbelt.com>;
>     palmer <mailto:palmer@rivosinc.com>; rdapp.gcc
>     <mailto:rdapp.gcc@gmail.com>
>     *Subject:* Re: [PATCH] RISC-V: Support vfwnmacc/vfwmsac/vfwnmsac
>     combine lowering
>     On 6/28/23 16:10, 钟居哲 wrot
>      > Sure.
>      >
>      > https://godbolt.org/z/8857KzTno <https://godbolt.org/z/8857KzTno>
>      >
>      > Failed to match this instruction:
>      > (set (reg:VNx2DF 134 [ vect__31.47 ])
>      >      (fma:VNx2DF (neg:VNx2DF (float_extend:VNx2DF (reg:VNx2SF 136 [
>      > vect__28.44 ])))
>      >          (reg:VNx2DF 150 [ vect__8.12 ])
>      >          (reg:VNx2DF 171 [ vect__29.45 ])))
>     Please attach the full dump.  I would expect to see additional attempts
>     with more operands replaced.
THanks for the dump.  I think this fundamentally the same issue as the 
widening problem.
 
Drop those intermediate patterns.  They're not needed/helpful.  You may 
need a dependency height reduction pattern to get the code you want, but 
I see no evidence those extra patterns will solve anything.
 
jeff