aarch64/macOS: error: invalid asm template string: expected `}`, found `.` + unsupported architectural extension: dit

[Nicceboy]

There are couple issues when compiling crate rustls-graviola, which utilises a lot of inline assembly.

Compiled on aarch64/macOS with latest Nightly/cranelift.

   Compiling graviola v0.2.1
error: invalid asm template string: expected `}`, found `.`
   Compiling rustls-graviola v0.2.1
    --> <anon>:5041:15
     |
5041 |        st1 {q0.16b}, [x0]
     |            -  ^ expected `}` in asm template string
     |            |
     |            because of this opening brace
     |
     = note: if you intended to print `{`, you can escape it using `{{`

error: aborting due to 1 previous error

error: unsupported architectural extension: dit
  |
note: instantiated into assembly here
 --> <inline asm>:8:17
  |
8 | .arch_extension dit
  |                 ^

error: unsupported architectural extension: dit
   |
note: instantiated into assembly here
  --> <inline asm>:10:17
   |
10 | .arch_extension nodit

See minimal example here to reproduce: https://github.com/Nicceboy/cranelift-graviola/.

[bjorn3]

There are two issues:

• I didn't escape { and } before passing the generated global_asm!() to cg_llvm.
• Graviola expects a register name like v0 to be used for out(vreg) to combine with .16b to form v0.16b, cg_clif however uses q0 as it enables the q modifier by default since Fix usage of vector registers in inline asm on arm64 #1564. It seems like I was a bit too eager using the q modifier everywhere though. I think it is only necessary for the loads/stores that cg_clif inserts for clobbered registers. Not for user references to vector registers.
• Enabling support for the dit feature using .arch_extension isn't supported by LLVM for whatever reason. That is going to be an issue for #[naked] functions too as those also use .arch_extension. cc @folkertdev In any case removing #[target_feature(enable = "dit")] in graviola doesn't work either as the DIT msr is not accessible.

Opened #1587 for the first two issues.

[folkertdev]

Fun. I guess I'll open an LLVM error for that one and hope for the best?

[folkertdev]

this works apparently https://godbolt.org/z/jWvxGKjPG

#[unsafe(no_mangle)]
#[unsafe(naked)]
//#[target_feature(enable = "dit")]
unsafe extern "C" fn write() {
    core::arch::naked_asm!(
        ".arch armv8.4-a",
        "msr DIT, #0",
        "ret"
    ) 
}

Still that seems really inconsistent

[folkertdev]

I believe this is related to rust-lang/rust#113221. Also arm's target features are just an absolute mess, and the above isn't really workable because there is no way to "pop" the .arch to go back to the previous state.