mirror of
https://github.com/rust-lang/rust.git
synced 2025-10-03 02:40:40 +00:00
ebef9d7f63
Set the dead_on_return attribute (added in LLVM 21) for arguments that are passed indirectly, but not byval. This indicates that the value of the argument on return does not matter, enabling additional dead store elimination.
34 lines
1.3 KiB
Rust
34 lines
1.3 KiB
Rust
//@ compile-flags: -C opt-level=3 -C no-prepopulate-passes
|
|
|
|
#![crate_type = "lib"]
|
|
|
|
// Test for the absence of `readonly` on the argument when it is mutated via `&raw const`.
|
|
// See <https://github.com/rust-lang/rust/issues/111502>.
|
|
|
|
// CHECK: i8 @foo(ptr{{( dead_on_return)?}} noalias{{( nocapture)?}} noundef align 1{{( captures\(none\))?}} dereferenceable(128) %x)
|
|
#[no_mangle]
|
|
pub fn foo(x: [u8; 128]) -> u8 {
|
|
let ptr = core::ptr::addr_of!(x).cast_mut();
|
|
unsafe {
|
|
(*ptr)[0] = 1;
|
|
}
|
|
x[0]
|
|
}
|
|
|
|
// CHECK: i1 @second(ptr{{( dead_on_return)?}} noalias{{( nocapture)?}} noundef align {{[0-9]+}}{{( captures\(none\))?}} dereferenceable({{[0-9]+}}) %a_ptr_and_b)
|
|
#[no_mangle]
|
|
pub unsafe fn second(a_ptr_and_b: (*mut (i32, bool), (i64, bool))) -> bool {
|
|
let b_bool_ptr = core::ptr::addr_of!(a_ptr_and_b.1.1).cast_mut();
|
|
(*b_bool_ptr) = true;
|
|
a_ptr_and_b.1.1
|
|
}
|
|
|
|
// If going through a deref (and there are no other mutating accesses), then `readonly` is fine.
|
|
// CHECK: i1 @third(ptr{{( dead_on_return)?}} noalias{{( nocapture)?}} noundef readonly align {{[0-9]+}}{{( captures\(none\))?}} dereferenceable({{[0-9]+}}) %a_ptr_and_b)
|
|
#[no_mangle]
|
|
pub unsafe fn third(a_ptr_and_b: (*mut (i32, bool), (i64, bool))) -> bool {
|
|
let b_bool_ptr = core::ptr::addr_of!((*a_ptr_and_b.0).1).cast_mut();
|
|
(*b_bool_ptr) = true;
|
|
a_ptr_and_b.1.1
|
|
}
|