ICE: `naked_asm!` unreachable

[matthiaskrgr]

auto-reduced (treereduce-rust):

//@compile-flags: -Zcodegen-backend=cranelift
#![feature(asm_const_ptr)]
use std::arch::{asm, global_asm, naked_asm};

#[unsafe(naked)]
extern "system" fn naked() {
    unsafe {
        naked_asm!("ret /* {} */", const &0);
    }
}

fn main() {
    naked();
}

original:

//@ only-x86_64

use std::arch::{asm, global_asm, naked_asm};

global_asm!("/* {} */", const &0);
//~^ ERROR using pointers in asm `const` operand is experimental

#[unsafe(naked)]
extern "system" fn naked() {
    unsafe {
        naked_asm!("ret /* {} */", const &0);
        //~^ ERROR using pointers in asm `const` operand is experimental
    }
}

fn main() {
    naked();
    unsafe {
        asm!("/* {} */", const &0);
        //~^ ERROR using pointers in asm `const` operand is experimental
    }
}

Version information

rustc 1.99.0-nightly (a04c7a037 2026-08-11)
binary: rustc
commit-hash: a04c7a037d59b6dedc9f921e84e391f13a257aa4
commit-date: 2026-08-11
host: x86_64-unknown-linux-gnu
release: 1.99.0-nightly
LLVM version: 23.1.0

Possibly related line of code:
https://github.com/rust-lang/rust/blob/a04c7a037d59b6dedc9f921e84e391f13a257aa4/compiler/rustc_codegen_cranelift/src/global_asm.rs#L140-L152

Command:
/home/matthias/.rustup/toolchains/master/bin/rustc -Zcodegen-backend=cranelift -Zcrate-attr=feature(asm_const_ptr)

Program output

warning: unused imports: `asm` and `global_asm`
 --> /tmp/icemaker_global_tempdir.KbBkuV4MJKpM/rustc_testrunner_tmpdir_reporting.EKgaEUGDTD6K/mvce.rs:1:17
  |
1 | use std::arch::{asm, global_asm, naked_asm};
  |                 ^^^  ^^^^^^^^^^
  |
  = note: `#[warn(unused_imports)]` (part of `#[warn(unused)]`) on by default

warning: unnecessary `unsafe` block
 --> /tmp/icemaker_global_tempdir.KbBkuV4MJKpM/rustc_testrunner_tmpdir_reporting.EKgaEUGDTD6K/mvce.rs:5:5
  |
5 |     unsafe {
  |     ^^^^^^ unnecessary `unsafe` block
  |
  = note: `#[warn(unused_unsafe)]` (part of `#[warn(unused)]`) on by default

error: asm! and global_asm! sym operands are not yet supported
 --> /tmp/icemaker_global_tempdir.KbBkuV4MJKpM/rustc_testrunner_tmpdir_reporting.EKgaEUGDTD6K/mvce.rs:6:28
  |
6 |         naked_asm!("ret /* {} */", const &0);
  |                            ^^


thread 'rustc' (632816) panicked at /rustc-dev/a04c7a037d59b6dedc9f921e84e391f13a257aa4/compiler/rustc_codegen_cranelift/src/global_asm.rs:146:69:
internal error: entered unreachable code
stack backtrace:
   0:     0x7f3037a76ae6 - <<std[448a6b8f3c6421af]::sys::backtrace::BacktraceLock>::print::DisplayBacktrace as core[faf7ed943a4f8e4f]::fmt::Display>::fmt
   1:     0x7f303800b823 - core[faf7ed943a4f8e4f]::fmt::write
   2:     0x7f3037a8ba0c - <std[448a6b8f3c6421af]::sys::stdio::unix::Stderr as core[faf7ed943a4f8e4f]::io::write::Write>::write_fmt
   3:     0x7f3037a49a4a - std[448a6b8f3c6421af]::panicking::default_hook::{closure#0}
   4:     0x7f3037a6a873 - std[448a6b8f3c6421af]::panicking::default_hook
   5:     0x7f30369fc7ea - std[448a6b8f3c6421af]::panicking::update_hook::<alloc[a52cb92b36bbf767]::boxed::Box<rustc_driver_impl[a86674e468a5c934]::install_ice_hook::{closure#1}>>::{closure#0}
   6:     0x7f3037a6ad12 - std[448a6b8f3c6421af]::panicking::panic_with_hook
   7:     0x7f3037a49b34 - std[448a6b8f3c6421af]::panicking::panic_handler::{closure#0}
   8:     0x7f3037a409e9 - std[448a6b8f3c6421af]::sys::backtrace::__rust_end_short_backtrace::<std[448a6b8f3c6421af]::panicking::panic_handler::{closure#0}, !>
   9:     0x7f3037a4b4dd - __rustc[ea1e64b7bd730d00]::rust_begin_unwind
  10:     0x7f30346c0a0c - core[faf7ed943a4f8e4f]::panicking::panic_fmt
  11:     0x7f3034cc98a2 - core[faf7ed943a4f8e4f]::panicking::panic
  12:     0x7f3024b11e6d - <rustc_codegen_cranelift[905dadbfd70718c8]::global_asm::GlobalAsmContext as rustc_codegen_ssa[2d44ee88eee97c4d]::traits::asm::AsmCodegenMethods>::codegen_global_asm
  13:     0x7f3024b03e6a - rustc_codegen_cranelift[905dadbfd70718c8]::driver::aot::codegen_cgu
  14:     0x7f3024aaa1fe - <rustc_codegen_cranelift[905dadbfd70718c8]::driver::aot::AotDriver as rustc_codegen_ssa[2d44ee88eee97c4d]::traits::backend::ExtraBackendMethods>::compile_codegen_unit::{closure#0}
  15:     0x7f3024b141ce - <rustc_codegen_cranelift[905dadbfd70718c8]::driver::aot::AotDriver as rustc_codegen_ssa[2d44ee88eee97c4d]::traits::backend::ExtraBackendMethods>::compile_codegen_unit
  16:     0x7f3024a77f62 - rustc_codegen_ssa[2d44ee88eee97c4d]::base::codegen_crate::<rustc_codegen_cranelift[905dadbfd70718c8]::driver::aot::AotDriver, rustc_codegen_cranelift[905dadbfd70718c8]::driver::aot::AotModule>
  17:     0x7f3024b2317f - <rustc_codegen_cranelift[905dadbfd70718c8]::CraneliftCodegenBackend as rustc_codegen_ssa[2d44ee88eee97c4d]::traits::backend::CodegenBackend>::codegen_crate
  18:     0x7f30392b16e5 - <rustc_interface[3209358e9030f33]::queries::Linker>::codegen_and_build_linker
  19:     0x7f30392a9097 - rustc_interface[3209358e9030f33]::interface::run_compiler::<(), rustc_driver_impl[a86674e468a5c934]::run_compiler::{closure#0}>::{closure#2}
  20:     0x7f30392784a4 - std[448a6b8f3c6421af]::sys::backtrace::__rust_begin_short_backtrace::<rustc_interface[3209358e9030f33]::util::run_in_thread_with_globals<rustc_interface[3209358e9030f33]::util::run_in_thread_pool_with_globals<rustc_interface[3209358e9030f33]::interface::run_compiler<(), rustc_driver_impl[a86674e468a5c934]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>
  21:     0x7f303927826d - <std[448a6b8f3c6421af]::thread::lifecycle::spawn_unchecked<rustc_interface[3209358e9030f33]::util::run_in_thread_with_globals<rustc_interface[3209358e9030f33]::util::run_in_thread_pool_with_globals<rustc_interface[3209358e9030f33]::interface::run_compiler<(), rustc_driver_impl[a86674e468a5c934]::run_compiler::{closure#0}>::{closure#2}, ()>::{closure#0}, ()>::{closure#0}::{closure#0}, ()>::{closure#1} as core[faf7ed943a4f8e4f]::ops::function::FnOnce<()>>::call_once::{shim:vtable#0}
  22:     0x7f30393093ba - <std[448a6b8f3c6421af]::sys::thread::unix::Thread>::new::thread_start
  23:     0x7f3032897739 - <unknown>
  24:     0x7f303291bedc - <unknown>
  25:                0x0 - <unknown>

error: the compiler unexpectedly panicked. This is a bug

note: we would appreciate a bug report: https://github.com/rust-lang/rust/issues/new?labels=C-bug%2C+I-ICE%2C+T-compiler&template=ice.md

note: please make sure that you have updated to the latest nightly

note: rustc 1.99.0-nightly (a04c7a037 2026-08-11) running on x86_64-unknown-linux-gnu

note: compiler flags: -Z codegen-backend=cranelift -Z crate-attr=feature(asm_const_ptr) -Z dump-mir-dir=dir

query stack during panic:
end of query stack
error: aborting due to 1 previous error; 2 warnings emitted

@rustbot label +F-asm_const_ptr

[rustbot]

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[matthiaskrgr]

#![feature(asm_const_ptr)]
use std::arch::naked_asm;
#[unsafe(naked)]
extern "C" fn naked() {
    naked_asm !("ret /* {} */", const & 0)
}
fn main() {
    naked()
}