fix: aarch64-gnu-llvm-20-1

Author: sgasho

compiler/rustc_codegen_llvm/Cargo.toml

@@ -14,7 +14,7 @@ bitflags = "2.4.1"
 gimli = "0.31"
 itertools = "0.12"
 libc = "0.2"
-libloading = "0.9.0"
+libloading = { version = "0.9.0", optional = true }
 measureme = "12.0.1"
 object = { version = "0.37.0", default-features = false, features = ["std", "read"] }
 rustc-demangle = "0.1.21"
@@ -47,6 +47,6 @@ tracing = "0.1"
 [features]
 # tidy-alphabetical-start
 check_only = ["rustc_llvm/check_only"]
-llvm_enzyme = []
+llvm_enzyme = ["dep:libloading"]
 # tidy-alphabetical-end
 

compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs

@@ -451,6 +451,7 @@ pub(crate) use self::Fallback_AD::*;
 pub(crate) mod Fallback_AD {
     #![allow(unused_variables)]
 
+    use std::ffi::c_void;
     use std::sync::Mutex;
 
     use libc::c_char;
@@ -459,7 +460,9 @@ pub(crate) mod Fallback_AD {
 
     use super::{CConcreteType, CTypeTreeRef, Context, EnzymeTypeTree};
 
-    pub(crate) struct EnzymeWrapper;
+    pub(crate) struct EnzymeWrapper {
+        pub registerEnzymeAndPassPipeline: *const c_void,
+    }
 
     impl EnzymeWrapper {
         pub(crate) fn init<'a, B: WriteBackendMethods>(