tests/codegen-llvm/c-variadic-lifetime.rs

//@ add-minicore
//@ compile-flags: -Copt-level=3
#![crate_type = "lib"]

// Check that `%args` explicitly has its lifetime start and end. Being explicit can improve
// instruction and register selection, see e.g. https://github.com/rust-lang/rust/pull/144549

#[unsafe(no_mangle)]
unsafe extern "C" fn variadic(a: f64, mut args: ...) -> f64 {
    // CHECK: call void @llvm.lifetime.start.p0({{(i64 [0-9]+, )?}}ptr nonnull %args)
    // CHECK: call void @llvm.va_start.p0(ptr nonnull %args)

    let b = args.next_arg::<f64>();
    let c = args.next_arg::<f64>();

    a + b + c

    // We no longer call the LLVM va_end.
    // CHECK-NOT: call void @llvm.va_end

    // But we do still explicitly end the lifetime of the VaList.
    // CHECK: call void @llvm.lifetime.end.p0({{(i64 [0-9]+, )?}}ptr nonnull %args)
}