signal: 4 (SIGILL) when testing virtual-function-elimination

Found when I trying to solve #123955 Here is the program, saved as tests/ui/codegen/vfe.rs:

//@ run-pass
//@ compile-flags: -C lto -Zvirtual-function-elimination
//@ no-prefer-dynamic

trait Empty {}
impl Empty for () {}

fn main() {
    _ = Box::new(()) as Box<dyn Empty>;
}

if I run rustc -C lto -Z virtual-function-elimination vfe.rs and run the produced binary, it runs perfectly.
if I run ./x test --stage 1 tests/ui/codegen/vfe.rs, if fails with the error:
```
running 1 tests
```

[ui] tests/ui/codegen/vfe.rs ... F

failures:

---- [ui] tests/ui/codegen/vfe.rs stdout ----

error: test run failed! status: signal: 4 (SIGILL) (core dumped) command: cd "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/test/ui/codegen/vfe" && RUSTC="/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/stage1/bin/rustc" RUST_TEST_THREADS="16" "/home/ray/Desktop/rust/build/x86_64-unknown-linux-gnu/test/ui/codegen/vfe/a" stdout: none stderr: none


I'm curious if this is about the `./x test` issue.

@rustbot label +C-bug +requires-nightly

rust-lang / rust

signal: 4 (SIGILL) when testing virtual-function-elimination #129267