rust/tests/codegen/c-variadic-opt.rs

// compile-flags: -C opt-level=3

#![crate_type = "lib"]
#![feature(c_variadic)]
#![no_std]
use core::ffi::VaList;

extern "C" {
    fn vprintf(fmt: *const i8, ap: VaList) -> i32;
}

// Ensure that `va_start` and `va_end` are properly injected even
// when the "spoofed" `VaListImpl` is not used.
#[no_mangle]
pub unsafe extern "C" fn c_variadic_no_use(fmt: *const i8, mut ap: ...) -> i32 {
    // CHECK: call void @llvm.va_start
    vprintf(fmt, ap.as_va_list())
    // CHECK: call void @llvm.va_end
}

// Check that `VaListImpl::clone` gets inlined into a direct call to `llvm.va_copy`
#[no_mangle]
pub unsafe extern "C" fn c_variadic_clone(fmt: *const i8, mut ap: ...) -> i32 {
    // CHECK: call void @llvm.va_start
    let mut ap2 = ap.clone();
    // CHECK: call void @llvm.va_copy
    let res = vprintf(fmt, ap2.as_va_list());
    res
    // CHECK: call void @llvm.va_end
}