rustc SIGSEGV compiling for thumbv7em with bad asm

[mqudsi]

mqudsi@Blitzkrieg /m/d/G/r/fullbuild> rustc --version
rustc 1.30.0-nightly (7e8ca9f8b 2018-08-03)
mqudsi@Blitzkrieg /m/d/G/r/fullbuild> rustc --target thumbv7em-none-eabi ./test.rs
fish: Job 2, “rustc --target thumbv7em-none-e…” terminated by signal SIGSEGV (Address boundary error)

test.rs:

#![feature(lang_items, start, asm)]
#![feature(panic_implementation)]
#![no_std]

use core::panic::PanicInfo;

fn rotr32(value: u32, mut shift: u8) -> u32 {
    shift = shift & 31;
    let result: u32;
    unsafe {
    asm!("ror $0, $1"
         : "=r"(result)
         : "r,0"(value), "r"(shift)
         );
    }

    return result;
}

#[start]
fn main(_argc: isize, _argv: *const *const u8) -> isize {
    return rotr32(14, 1) as isize;
}

#[panic_implementation]
fn panic(_: &PanicInfo) -> ! {
    loop {}
}

[nagisa]

That most likely is just a LLVM assertion.

[Amanieu]

This issue does not apply to the new asm! (RFC 2850) which properly validates operands.

The legacy llvm_asm! is deprecated and is no longer maintained.