Usage of curly braces in ARM assembly considered invalid

[mahircg-aws]

ARM multi load/store instructions require curly braces to specify the target register range: https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architecture/The-Instruction-Sets/Load-store-multiple-instructions?lang=en#:~:text=Load%20Multiple%20instructions%20load%20a,are%20consecutive%20word%2Daligned%20words.

The following inline assembly instruction requires curly braces as part of specifying the register range.

unsafe { asm!("stmib sp, {x0 - x15}",) }

During compilation, I get the following error.

error: invalid asm template string: expected `}`, found `-`
   --> firecrab/src/main.rs:386:34
    |
386 |     unsafe { asm!("stmib sp, {x0 - x15}",) }
    |                              -   ^ expected `}` in asm template string
    |                              |
    |                              because of this opening brace
    |
    = note: if you intended to print `{`, you can escape it using `{{`

Reading https://rust-lang.github.io/rfcs/2873-inline-asm.html#use-of-double-braces-in-the-template-string, it looks like the only usage for curly braces was for AVX extension in x86.

Same error is reported on assembly that is included in Rust world with core::arch::global_asm!(include_str!("asm.s"));

.macro asm_test
    stmib sp, {x0 - x15}

Is that a bug in the way the assembly blobs are parsed?

Meta

rustc --version --verbose:

rustc 1.84.0-nightly (b19329a37 2024-11-21)
binary: rustc
commit-hash: b19329a37cedf2027517ae22c87cf201f93d776e
commit-date: 2024-11-21
host: aarch64-apple-darwin
release: 1.84.0-nightly
LLVM version: 19.1.4

[taiki-e]

You have to use {{x0 - x15}} (double { and }) or raw option.

[mahircg-aws]

I tried that, and it causes the following error. I think it interprets the instruction as a vector operation and expects vector registers.

error: <instantiation>:2:16: vector register expected
    stmib sp, {x0 - x15}
               ^

error: could not compile `bin` (bin "bin")

[taiki-e]

Ah, you are trying to use the A32/T32 instruction with A64. In other words, it is an instruction for 32-bit Arm (AArch32) and therefore not available for AArch64.

See also ISA documentation; stmib is included only in AArch32's:

• AArch64 https://developer.arm.com/documentation/ddi0602/2025-03/Base-Instructions
• AArch32 https://developer.arm.com/documentation/ddi0597/2025-03/Base-Instructions

[mahircg-aws]

Yes, I've noticed that later on. I didn't realize it wasn't available until I used options(raw).

Closing this one, thanks for the pointers.