| 1 Aug 2025 |
 emily | "This is why LoongArch is better than RISC-V and also why the author of LoongArch does not like RISC-V and creates this new ISA." | 12:06:14 |
 K900 | But the actual opcodes are identical | 12:06:16 |
| emily | https://godbolt.org/z/ncGdnxqEf lol | 12:06:20 |
| emily | (this is the entire link the reddit post goes to) | 12:06:28 |
 dramforever | it's literally not the same instruction encodings | 12:07:41 |
| emily | RISC-V feels like the kind of architecture I would have produced as a teenager who was monomaniacally fixated on orthogonality and minimality in all things | 12:07:57 |
| emily | I guess this comparison is probably not using uhh RV32 or whatever though | 12:08:13 |
| emily | or whatever you're meant to be using now. the real architecture | 12:08:20 |
| K900 | It's literally like that | 12:08:26 |
| emily | yeah ok the reddit comments say as much | 12:08:34 |
| K900 | Their response to "why" is "just do more uop fusion lol" | 12:08:37 |
| emily | well, no | 12:09:02 |
| emily | https://godbolt.org/z/19jnvda7G | 12:09:03 |
| emily | it looks like rva23u64 beats MIPS there | 12:09:20 |
| emily | so it's just a dumb comparison | 12:09:27 |
| K900 | Well yeah I don't mean this specific case | 12:09:37 |
| K900 | I just mean in general | 12:09:39 |
| emily | although the fragmentation of the RISC-V instruction sets in general is its own kind of dumb I suppose | 12:09:39 |
| emily | but also the thing teenage me would have done | 12:09:45 |
| K900 | There's like | 12:09:46 |
| K900 | A List | 12:09:47 |
| K900 | Of like Officially Mandated Fusions You Must Do To Fast | 12:10:01 |
| K900 | That compilers also know | 12:10:07 |
| emily | I think x86 also involves known uop fusions that compilers take into account | 12:10:08 |
| emily | it's arguably better to write it down than not | 12:10:15 |
| K900 | Not really | 12:10:17 |
| K900 | (for x86) | 12:10:23 |
| K900 | x86 mostly just has scheduling fuckery because it's very wide | 12:10:37 |
| K900 | But then modern aarch64 is also very wide | 12:10:46 |
| K900 | So it's likely actually fast RISC-V will also be very wide | 12:10:55 |
