no_mangle causes compilation errors with async-await on armv7-linux-androideabi and aarch64-linux-android targets

[jeswin]

Adding the no_mangle attribute to a function which contains an await results in a compilation error for armv7-linux-androideabi and aarch64-linux-android targets. Removing the attribute fixes the issue (though that's not a solution). There are no problems with x86_64-linux-android and i686-linux-android targets.

#![cfg(target_os = "android")]
#![allow(non_snake_case)]

use tokio::{runtime::Runtime };

#[no_mangle]
pub fn Java_blah_blah_func() -> &'static str {
    Runtime::new().unwrap().block_on(async {
        myfunc().await
    })
}

async fn myfunc() -> &'static str {
    "hello"
}

I expected to see this happen: library should get compiled successfully.

Instead, I get the following error:

Function return type does not match operand type of return inst!
  ret i32 undef
 { i8*, i32 }in function _ZN80_$LT$std..future..GenFuture$LT$T$GT$$u20$as$u20$core..future..future..Future$GT$4poll17h2e6af84f5e832d75E
LLVM ERROR: Broken function found, compilation aborted!

Meta

The error exists in the beta and nightly versions. RUST_BACKTRACE=1 doesn't seem to add additional information.

[jeswin]

Hi @jonas-schievink, Not sure if this is minimal enough, but I've created a repo to demonstrate the issue at https://github.com/jeswin/rust-lang-issue-70098-mcve

Please note that build.sh requires cargo-ndk to build.

[Centril]

@rustbot ping llvm

[rustbot]

Hey LLVM ICE-breakers! This bug has been identified as a good
"LLVM ICE-breaking candidate". In case it's useful, here are some
instructions for tackling these sorts of bugs. Maybe take a look?
Thanks! <3

cc @comex @cuviper @DutchGhost @hanna-kruppe @hdhoang @heyrutvik @JOE1994 @jryans @mmilenko @nagisa @nikic @Noah-Kennedy @SiavoshZarrasvand @spastorino @vertexclique @vgxbj

[Centril]

@rustbot ping cleanup