I just checked LLVM: https://godbolt.org/z/nMa6qnEeT
This patch generally is reasonable so LGTM. juzhe.zh...@rivai.ai From: Robin Dapp Date: 2023-08-03 02:49 To: 钟居哲; gcc-patches; palmer; kito.cheng; Jeff Law CC: rdapp.gcc Subject: Re: [PATCH] RISC-V: Implement vector "average" autovec pattern. > 1. How do you model round to +Inf (avg_floor) and round to -Inf (avg_ceil) ? That's just specified by the +1 or the lack of it in the original pattern. Actually the IFN is just a detour because we would create perfect code if not for the fallback. But as there is currently now way to check for the existence of a narrowing shift we cannot circumvent the fallback. > 2. Is it possible we could use vaadd[u] to model avg ? In principle yes (I first read it wrong that overflow must not happen but the specs actually say that it does not happen). However, we would need to set a rounding mode before vaadd or check its current value and provide a fallback. Off the spot I can't imagine a workaround like two vaadds or so. Regards Robin
