Bug 834919 – dev-lang/rust-1.59.0: unknown directive error on RISC-V

• Product: Gentoo Linux
• Status: RESOLVED UPSTREAM

[Description Yixun Lan 2022-03-10 14:23:57 UTC]

   |
62 - pub(crate) struct IterMut<'a, T: 'a, C: cfg::Config + 'a>(slice::IterMut<'a, Ptr<T, C>>);
62 + pub(crate) struct IterMut<'a, T, C: cfg::Config>(slice::IterMut<'a, Ptr<T, C>>);
   |

error: unknown directive
   |
note: instantiated into assembly here
  --> <inline asm>:1:2
   |
1  |     .insn i 0x0F, 0, x0, x0, 0x010
   |     ^

[Comment 1 Yixun Lan 2022-03-10 14:25:36 UTC]

Created attachment 766743 [details]
full build log

[Comment 2 Alex Fan 2022-03-14 10:29:51 UTC]

It is an issue with llvm MC support of .insn directive that is only included in llvm-14 (https://reviews.llvm.org/D108602?id=369214). Although the llvm version shipped with rust-1.59 has backported the .insn patch, the bootstrap rust compiler also needs to be compiled with llvm supporting .insn because std library in stage0 (specifically stdarch) uses .insn.

Upstream accepts fixes that use .word instead of .insn as a temporal workaround, but I asked people who opened the issue linked, it seems to be going to take some time. And once upgraded to llvm 14, upstream will eventually use .insn

So I guess a better solution is patch llvm with .insn support () until llvm-14 becomes stable in gentoo.

I applied the patch to portage llvm locally and compiles rust-1.58 with USE=system-llvm as a bootstrap compiler. Then with the bootstrap compiler, I compile rust-1.59 with USE=system-llvm,system-bootstrap successfully.

[Comment 3 Sam James 2022-03-14 10:36:14 UTC]

Am I missing why we can't just mask USE=system-llvm on riscv for now?

[Comment 4 Alex Fan 2022-03-14 10:43:16 UTC]

(In reply to Sam James from comment #3)
> Am I missing why we can't just mask USE=system-llvm on riscv for now?

Yeah, it should work once the bootstrap compiler is compiled with llvm supporting .insn, but atm, it seems the one they provide doesn't(otherwise, this bug won't exist).

[Comment 5 Alex Fan 2022-03-14 10:46:49 UTC]

>>otherwise, this bug won't exist

sorry, won't be discovered so quickly because by default USE=system-llvm and system-boostrap are disabled.

[Comment 6 Yixun Lan 2022-04-12 06:00:19 UTC]

tested, the problem is fixed in version 1.60.0

I'm closing this as wontfix