[llvm] [BPF] Support wrapping BPF map structs into nested, single field structs (PR #144097)

[Michal Rostecki via llvm-commits]

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@@ -0,0 +1,609 @@
+; RUN: llc -mtriple=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK-SHORT %s
+; RUN: llc -mtriple=bpfel -filetype=asm -o - %s | FileCheck -check-prefixes=CHECK %s
+
+; Source code:
+;   #![no_std]
+;   #![no_main]
+;   #![allow(dead_code)]
+;
+;   pub const BPF_MAP_TYPE_HASH: usize = 1;
+;
+;   // The real map definition.
+;   pub struct HashMapDef<K, V, const M: usize, const F: usize> {
+;       r#type: *const [i32; BPF_MAP_TYPE_HASH],
+;       key: *const K,
+;       value: *const V,
+;       max_entries: *const [i32; M],
+;       map_flags: *const [i32; F],
+;   }
+;   impl<K, V, const M: usize, const F: usize> HashMapDef<K, V, M, F> {
+;       pub const fn new() -> Self {
+;           Self {
+;               r#type: &[0i32; BPF_MAP_TYPE_HASH],
+;               key: ::core::ptr::null(),
+;               value: ::core::ptr::null(),
+;               max_entries: &[0i32; M],
+;               map_flags: &[0i32; F],
+;           }
+;       }
+;   }
+;   // Use `UnsafeCell` to allow mutability by multiple threads.
+;   pub struct HashMap<K, V, const M: usize, const F: usize = 0>(
+;       core::cell::UnsafeCell<HashMapDef<K, V, M, F>>,
+;   );
+;   impl<K, V, const M: usize, const F: usize> HashMap<K, V, M, F> {
+;       pub const fn new() -> Self {
+;           Self(core::cell::UnsafeCell::new(HashMapDef::new()))
+;       }
+;   }
+;   // Mark `HashMap` as thread-safe.
+;   unsafe impl<K: Sync, V: Sync, const M: usize, const F: usize> Sync for HashMap<K, V, M, F> {}
+;
+;   // Define custom structs for key and values.
+;   pub struct MyKey(u32);
+;   pub struct MyValue(u32);
+;
+;   #[link_section = ".maps"]
+;   #[export_name = "HASH_MAP"]
+;   pub static HASH_MAP: HashMap<MyKey, MyValue, 10> = HashMap::new();
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vadorovsky wrote:

Not really, it's just an arbitrary max size of the map.

https://github.com/llvm/llvm-project/pull/144097