On Tue, Jan 9, 2024 at 4:59 PM Kito Cheng <kito.ch...@sifive.com> wrote: > > Oops, I should leave more context here: > > Actually we discussed that years ago, and most people agree with that, but I > guess we are just missing that, and also the ISA string isn't so terribly > long yet at that moment, however...the number of extensions are growth so > fast in last year, so I think it's time to moving this forward. > > Also we (SiFive) will send patches for clang/LLVM to relax that as well :) > > https://github.com/riscv-non-isa/riscv-toolchain-conventions/pull/14 > > On Wed, Jan 10, 2024 at 2:31 AM Jeff Law <jeffreya...@gmail.com> wrote: >> >> >> >> On 1/8/24 06:47, Kito Cheng wrote: >> > >> > Do you know how to build a ISA string with following extension? >> > - g >> > - c >> > - zba >> > - zbs >> > - svnapot >> > - zve64d >> > - zvl128b >> > >> > Don't trial and error with your gcc and don't read RISC-V ISA spec! OK, I >> > believe it's impossible for most people, even I work for RISC-V so many >> > years, I remember most of the rule of the the canonical order, it's still >> > hard to order that right in short time... >> > >> > So I think it's time to relax that for the -march string inputs, since we >> > have so many extension today, but we still keep the canonicalization >> > within the compiler, because we need that to handle multi-lib and also >> > it's easier to compare different ISA string. >> > >> > This patch break into serveral part: >> > 1) Small refactor patch >> > 2) Change the way of parsing ISA string. >> > 3) Remove unused functions >> > 4) Update test cases >> > 5) Update document >> Just because something is hard doesn't necessarily mean we should avoid it. >> >> A great example would be strict aliasing. I'd bet that 90% of C/C++ >> developers would get something wrong in this space. Similarly for >> oddities of FP arithmetic. >> >> My biggest worry is consistency across various tools. It's rather lame >> if GCC were on an island by itself either in being too strict or too loose. >> >> So where are the other key tools in this regard? Are we an outlier >> right now or will this patch make us an outlier? >> >> jeff
If we had fewer extensions, ensuring a canonical order is better as a code search of a fixed string will retrieve the relevant results, and I'd wish that we did not lose the strictness. Now that there are a hundred extensions, I agree that enforcing a strict order has lost its goodness... -- 宋方睿
