Add LLVM codegen tests for new Rc implementation

Author: EFanZh

src/tools/miri/tests/fail/memleak_rc.stderr

@@ -5,9 +5,9 @@ LL |     let allocation_result = alloc.allocate(rc_layout.get());
    |                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    |
    = note: BACKTRACE:
-   = note: inside `alloc::raw_rc::allocate_uninit_raw_bytes::<std::alloc::Global>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
-   = note: inside `alloc::raw_rc::allocate_uninit_in::<std::alloc::Global, 1>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
-   = note: inside `alloc::raw_rc::allocate_uninit::<std::alloc::Global, 1>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
+   = note: inside `alloc::raw_rc::rc_alloc::allocate_uninit_raw_bytes::<std::alloc::Global>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
+   = note: inside `alloc::raw_rc::rc_alloc::allocate_uninit_in::<std::alloc::Global, 1>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
+   = note: inside `alloc::raw_rc::rc_alloc::allocate_uninit::<std::alloc::Global, 1>` at RUSTLIB/alloc/src/raw_rc/mod.rs:LL:CC
    = note: inside `alloc::raw_rc::raw_weak::RawWeak::<std::cell::RefCell<std::option::Option<Dummy>>, std::alloc::Global>::new_uninit::<TAG>` at RUSTLIB/alloc/src/raw_rc/raw_weak.rs:LL:CC
    = note: inside `alloc::raw_rc::raw_rc::RawRc::<std::cell::RefCell<std::option::Option<Dummy>>, std::alloc::Global>::new` at RUSTLIB/alloc/src/raw_rc/raw_rc.rs:LL:CC
    = note: inside `std::rc::Rc::<std::cell::RefCell<std::option::Option<Dummy>>>::new` at RUSTLIB/alloc/src/rc.rs:LL:CC

tests/codegen-llvm/lib-optimizations/rc-arc-optimizations.rs

@@ -0,0 +1,27 @@
+//@ compile-flags: -O -Z merge-functions=disabled
+
+#![crate_type = "lib"]
+
+use std::rc::{self, Rc};
+
+// Ensures that we can create array of `Weak`s using `memset`.
+
+#[no_mangle]
+pub fn array_of_rc_weak() -> [rc::Weak<u32>; 100] {
+    // CHECK-LABEL: @array_of_rc_weak(
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: call void @llvm.memset.
+    // CHECK-NEXT: ret void
+    [(); 100].map(|()| rc::Weak::new())
+}
+
+// Ensures that we convert `&Option<Rc<T>>` to `Option<&T>` without checking for `None`.
+
+#[no_mangle]
+pub fn option_rc_as_deref_no_cmp(rc: &Option<Rc<u32>>) -> Option<&u32> {
+    // CHECK-LABEL: @option_rc_as_deref_no_cmp(ptr
+    // CHECK-NEXT: start:
+    // CHECK-NEXT: %[[RC:.+]] = load ptr, ptr %rc
+    // CHECK-NEXT: ret ptr %[[RC]]
+    rc.as_deref()
+}