sparc ABI issue - structure returning from function is returned in 64bit registers

[psumbera]

Fixes: #52638

[rust-highfive]

r? @cramertj

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[nagisa]

r? @nagisa

@psumbera do you want to try and write up a test, or should I do it?

[nagisa]

It should be a codegen test, something along the lines of

// license here
// compile-flags: --target=sparc64-unknown-linux-gnu
#![feature(no_core, lang_items)]
#![no_core]

#[lang="sized"]
trait Sized { }
#[lang="freeze"]
trait Freeze { }
#[lang="copy"]
trait Copy { }
#[repr(C)]
pub struct Bool {
    b: bool,
}
#[no_mangle]
// CHECK: define i64 @structbool()
// CHECK-NEXT: start:
// CHECK-NEXT: ret i64 72057594037927936
pub extern "C" fn structbool() -> Bool {
    Bool { b: true }
}

[psumbera]

Can you please do tests for me? I'm afraid that tests on Solaris are not at good conditions. Plus I'm still fighting to get build of Rust 1.27 on sparc.

[nagisa]

I added a tests and put up a PR with the tests included at #52734.