diff --git a/compiler/rustc_codegen_llvm/src/back/write.rs b/compiler/rustc_codegen_llvm/src/back/write.rs
index 657db58831c1b..f437e52355ef0 100644
--- a/compiler/rustc_codegen_llvm/src/back/write.rs
+++ b/compiler/rustc_codegen_llvm/src/back/write.rs
@@ -55,6 +55,7 @@ use llvm::{
     LLVMRustLLVMHasZlibCompressionForDebugSymbols, LLVMRustLLVMHasZstdCompressionForDebugSymbols, LLVMGetNextBasicBlock,
 };
 use rustc_ast::expand::autodiff_attrs::{AutoDiffItem, DiffActivity, DiffMode};
+use rustc_ast::expand::typetree::FncTree;
 use rustc_codegen_ssa::back::link::ensure_removed;
 use rustc_codegen_ssa::back::write::{
     BitcodeSection, CodegenContext, EmitObj, ModuleConfig, TargetMachineFactoryConfig,
@@ -1091,6 +1092,24 @@ pub(crate) unsafe fn differentiate(
         llvm::set_loose_types(true);
     }
 
+    // Before dumping the module, we want all the tt to become part of the module.
+    for item in &diff_items {
+        let llvm_data_layout = unsafe { llvm::LLVMGetDataLayoutStr(&*llmod) };
+        let llvm_data_layout =
+            std::str::from_utf8(unsafe { CStr::from_ptr(llvm_data_layout) }.to_bytes())
+                .expect("got a non-UTF8 data-layout from LLVM");
+        //let input_tts: Vec<TypeTree> =
+        //    item.inputs.iter().map(|x| to_enzyme_typetree(x.clone(), llvm_data_layout, llcx)).collect();
+        //let output_tt = to_enzyme_typetree(item.output, llvm_data_layout, llcx);
+        let tt: FncTree = FncTree {
+            args: item.inputs.clone(),
+            ret: item.output.clone(),
+        };
+        let name = CString::new(item.source.clone()).unwrap();
+        let fn_def: &llvm::Value = llvm::LLVMGetNamedFunction(llmod, name.as_ptr()).unwrap();
+        crate::builder::add_tt2(llmod, llcx, fn_def, tt);
+    }
+
     if std::env::var("ENZYME_PRINT_MOD_BEFORE").is_ok() {
         unsafe {
             LLVMDumpModule(llmod);
diff --git a/compiler/rustc_codegen_llvm/src/builder.rs b/compiler/rustc_codegen_llvm/src/builder.rs
index f7afe9cbefb7a..733dd76ed105c 100644
--- a/compiler/rustc_codegen_llvm/src/builder.rs
+++ b/compiler/rustc_codegen_llvm/src/builder.rs
@@ -136,6 +136,49 @@ macro_rules! builder_methods_for_value_instructions {
         })+
     }
 }
+pub fn add_tt2<'ll>(llmod: &'ll llvm::Module, llcx: &'ll llvm::Context, fn_def: &'ll Value, tt: FncTree) {
+    let inputs = tt.args;
+    let ret_tt: TypeTree = tt.ret;
+    let llvm_data_layout: *const c_char = unsafe { llvm::LLVMGetDataLayoutStr(&*llmod) };
+    let llvm_data_layout =
+        std::str::from_utf8(unsafe { std::ffi::CStr::from_ptr(llvm_data_layout) }.to_bytes())
+            .expect("got a non-UTF8 data-layout from LLVM");
+    let attr_name = "enzyme_type";
+    let c_attr_name = std::ffi::CString::new(attr_name).unwrap();
+    for (i, &ref input) in inputs.iter().enumerate() {
+        let c_tt = to_enzyme_typetree(input.clone(), llvm_data_layout, llcx);
+        let c_str = unsafe { llvm::EnzymeTypeTreeToString(c_tt.inner) };
+        let c_str = unsafe { std::ffi::CStr::from_ptr(c_str) };
+        unsafe {
+            let attr = llvm::LLVMCreateStringAttribute(
+                llcx,
+                c_attr_name.as_ptr(),
+                c_attr_name.as_bytes().len() as c_uint,
+                c_str.as_ptr(),
+                c_str.to_bytes().len() as c_uint,
+            );
+            llvm::LLVMRustAddFncParamAttr(fn_def, i as u32, attr);
+        }
+        unsafe { llvm::EnzymeTypeTreeToStringFree(c_str.as_ptr()) };
+    }
+    let ret_attr = unsafe {
+        let c_tt = to_enzyme_typetree(ret_tt, llvm_data_layout, llcx);
+        let c_str = llvm::EnzymeTypeTreeToString(c_tt.inner);
+        let c_str = std::ffi::CStr::from_ptr(c_str);
+        let attr = llvm::LLVMCreateStringAttribute(
+            llcx,
+            c_attr_name.as_ptr(),
+            c_attr_name.as_bytes().len() as c_uint,
+            c_str.as_ptr(),
+            c_str.to_bytes().len() as c_uint,
+        );
+        llvm::EnzymeTypeTreeToStringFree(c_str.as_ptr());
+        attr
+    };
+    unsafe {
+        llvm::LLVMRustAddRetFncAttr(fn_def, ret_attr);
+    }
+}
 
 fn add_tt<'ll>(llmod: &'ll llvm::Module, llcx: &'ll llvm::Context,val: &'ll Value, tt: FncTree) {
     let inputs = tt.args;
diff --git a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
index 260e66d2ce92a..0bf2eb5fb3a2f 100644
--- a/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
+++ b/compiler/rustc_codegen_llvm/src/llvm/ffi.rs
@@ -848,8 +848,8 @@ pub(crate) unsafe fn enzyme_rust_forward_diff(
     fnc: &Value,
     input_diffactivity: Vec<DiffActivity>,
     ret_diffactivity: DiffActivity,
-    input_tts: Vec<TypeTree>,
-    output_tt: TypeTree,
+    _input_tts: Vec<TypeTree>,
+    _output_tt: TypeTree,
     void_ret: bool,
 ) -> (&Value, Vec<usize>) {
     let ret_activity = cdiffe_from(ret_diffactivity);
@@ -878,13 +878,12 @@ pub(crate) unsafe fn enzyme_rust_forward_diff(
     };
     trace!("ret_primary_ret: {}", &ret_primary_ret);
 
-    let mut args_tree = input_tts.iter().map(|x| x.inner).collect::<Vec<_>>();
+    //let mut args_tree = input_tts.iter().map(|x| x.inner).collect::<Vec<_>>();
     //let mut args_tree = vec![TypeTree::new().inner; typetree.input_tt.len()];
 
     // We don't support volatile / extern / (global?) values.
     // Just because I didn't had time to test them, and it seems less urgent.
-    let args_uncacheable = vec![0; input_tts.len()];
-    assert!(args_uncacheable.len() == input_activity.len());
+    let args_uncacheable = vec![0; input_activity.len()];
     let num_fnc_args = LLVMCountParams(fnc);
     trace!("num_fnc_args: {}", num_fnc_args);
     trace!("input_activity.len(): {}", input_activity.len());
@@ -894,9 +893,16 @@ pub(crate) unsafe fn enzyme_rust_forward_diff(
 
     let mut known_values = vec![kv_tmp; input_activity.len()];
 
+    let tree_tmp = TypeTree::new();
+    let mut args_tree = vec![tree_tmp.inner; input_activity.len()];
+
+    //let mut args_tree = vec![std::ptr::null_mut(); input_activity.len()];
+    //let ret_tt = std::ptr::null_mut();
+    //let mut args_tree = vec![TypeTree::new().inner; input_tts.len()];
+    let ret_tt = TypeTree::new();
     let dummy_type = CFnTypeInfo {
         Arguments: args_tree.as_mut_ptr(),
-        Return: output_tt.inner.clone(),
+        Return: ret_tt.inner,
         KnownValues: known_values.as_mut_ptr(),
     };
 
@@ -935,7 +941,7 @@ pub(crate) unsafe fn enzyme_rust_reverse_diff(
     rust_input_activity: Vec<DiffActivity>,
     ret_activity: DiffActivity,
     input_tts: Vec<TypeTree>,
-    output_tt: TypeTree,
+    _output_tt: TypeTree,
 ) -> (&Value, Vec<usize>) {
     let (primary_ret, ret_activity) = match ret_activity {
         DiffActivity::Const => (true, CDIFFE_TYPE::DFT_CONSTANT),
@@ -961,16 +967,11 @@ pub(crate) unsafe fn enzyme_rust_reverse_diff(
         input_activity.push(cdiffe_from(x));
     }
 
-    let mut args_tree = input_tts.iter().map(|x| x.inner).collect::<Vec<_>>();
+    //let args_tree = input_tts.iter().map(|x| x.inner).collect::<Vec<_>>();
 
     // We don't support volatile / extern / (global?) values.
     // Just because I didn't had time to test them, and it seems less urgent.
-    let args_uncacheable = vec![0; input_tts.len()];
-    if args_uncacheable.len() != input_activity.len() {
-        dbg!("args_uncacheable.len(): {}", args_uncacheable.len());
-        dbg!("input_activity.len(): {}", input_activity.len());
-    }
-    assert!(args_uncacheable.len() == input_activity.len());
+    let args_uncacheable = vec![0; input_activity.len()];
     let num_fnc_args = LLVMCountParams(fnc);
     println!("num_fnc_args: {}", num_fnc_args);
     println!("input_activity.len(): {}", input_activity.len());
@@ -979,9 +980,15 @@ pub(crate) unsafe fn enzyme_rust_reverse_diff(
 
     let mut known_values = vec![kv_tmp; input_tts.len()];
 
+    let tree_tmp = TypeTree::new();
+    let mut args_tree = vec![tree_tmp.inner; input_tts.len()];
+    //let mut args_tree = vec![TypeTree::new().inner; input_tts.len()];
+    let ret_tt = TypeTree::new();
+    //let mut args_tree = vec![std::ptr::null_mut(); input_tts.len()];
+    //let ret_tt = std::ptr::null_mut();
     let dummy_type = CFnTypeInfo {
         Arguments: args_tree.as_mut_ptr(),
-        Return: output_tt.inner.clone(),
+        Return: ret_tt.inner,
         KnownValues: known_values.as_mut_ptr(),
     };
 
@@ -1023,12 +1030,12 @@ extern "C" {
     //pub fn LLVMEraseFromParent(BB: &BasicBlock) -> &Value;
     // Enzyme
     pub fn LLVMRustAddFncParamAttr<'a>(
-        Instr: &'a Value,
+        F: &'a Value,
         index: c_uint,
         Attr: &'a Attribute
     );
 
-    pub fn LLVMRustAddRetAttr(V: &Value, attr: AttributeKind);
+    pub fn LLVMRustAddRetFncAttr(F: &Value, attr: &Attribute);
     pub fn LLVMRustRemoveFncAttr(V: &Value, attr: AttributeKind);
     pub fn LLVMRustHasDbgMetadata(I: &Value) -> bool;
     pub fn LLVMRustHasMetadata(I: &Value, KindID: c_uint) -> bool;
diff --git a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
index 8f17c26f10177..43ed4c50613a3 100644
--- a/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
+++ b/compiler/rustc_llvm/llvm-wrapper/RustWrapper.cpp
@@ -865,9 +865,9 @@ extern "C" void LLVMRustAddFncParamAttr(LLVMValueRef F, unsigned i,
 }
 
 extern "C" void LLVMRustAddRetFncAttr(LLVMValueRef F,
-                                      LLVMRustAttribute RustAttr) {
+                                      LLVMAttributeRef RustAttr) {
   if (auto *Fn = dyn_cast<Function>(unwrap<Value>(F))) {
-    Fn->addRetAttr(fromRust(RustAttr));
+    Fn->addRetAttr(unwrap(RustAttr));
   }
 }