Baremetal rpi target fails to build on new rust versions

[alloncm]

Example from rust 1.77.2:

error: <inline asm>:83:13: invalid operand for instruction
    msr     ELR_hyp, r0             // save the address in ELR_hyp

[alloncm]

It seems to break in version 1.77 (in 1.77.0 and 1.77.1 it does not build some dep and in 1.77.2 outputs the error above) meaning version 1.76.0 (nightly 2024.02.08) should work

[alloncm]

Trying to create a minimal reproduce-able example, this is still working though:

# rust-toolchain.toml
[toolchain]
channel = "nightly-2024-05-02" # first nightly version to now work
profile = "minimal"

# .cargo/config.toml
[target.armv7a-none-eabihf]
rustflags = [
    "-Ctarget-feature=+virtualization"
]

// main.rs
#![no_std]
#![no_main]

use core::{arch::global_asm, panic::PanicInfo};

global_asm!("
    msr     ELR_hyp, r0             // save the address in ELR_hyp
    eret                            // apply the mode change (Exception return)                            
");

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

build command: cargo b --target armv7a-none-eabihf -Z build-std=core

[alloncm]

This command builds the asm code without rustc arm-none-eabi-as -mcpu=cortex-a72 -mfpu=vfpv2 boot_armv7a.s

[alloncm]

It looks like with or without hard floats (eabi vs eabihf) both magenboy and the code above compiles on debug mode and fails to compile on release mode (after version 1.76 of course).

[alloncm]

rust-lang/rust#127269