Remove gen_enzyme_body and call it in place instead

Author: Sa4dUs

compiler/rustc_builtin_macros/src/autodiff.rs

@@ -323,14 +323,17 @@ mod llvm_enzyme {
 
         let d_sig = gen_enzyme_decl(ecx, &sig, &x, span);
 
-        let d_body = gen_enzyme_body(
-            ecx,
-            &d_sig,
-            primal,
+        let d_body = ecx.block(
             span,
-            first_ident(&meta_item_vec[0]),
-            &generics,
-            impl_of_trait,
+            thin_vec![call_autodiff(
+                ecx,
+                primal,
+                first_ident(&meta_item_vec[0]),
+                span,
+                &d_sig,
+                &generics,
+                impl_of_trait,
+            )],
         );
 
         // The first element of it is the name of the function to be generated
@@ -584,43 +587,6 @@ mod llvm_enzyme {
         ecx.expr_path(path)
     }
 
-    /// We only want this function to type-check, since we will replace the body
-    /// later on llvm level. Using `loop {}` does not cover all return types anymore,
-    /// so instead we manually build something that should pass the type checker.
-    /// We also add a inline_asm line, as one more barrier for rustc to prevent inlining
-    /// or const propagation. inline_asm will also triggers an Enzyme crash if due to another
-    /// bug would ever try to accidentally differentiate this placeholder function body.
-    /// Finally, we also add back_box usages of all input arguments, to prevent rustc
-    /// from optimizing any arguments away.
-    fn gen_enzyme_body(
-        ecx: &ExtCtxt<'_>,
-        d_sig: &ast::FnSig,
-        primal: Ident,
-        span: Span,
-        diff_ident: Ident,
-        generics: &Generics,
-        is_impl: bool,
-    ) -> Box<ast::Block> {
-        let new_decl_span = d_sig.span;
-
-        // Add a call to the primal function to prevent it from being inlined
-        // and call `autodiff` intrinsic (this also covers the return type)
-        let body = ecx.block(
-            span,
-            thin_vec![call_autodiff(
-                ecx,
-                primal,
-                diff_ident,
-                new_decl_span,
-                d_sig,
-                generics,
-                is_impl,
-            )],
-        );
-
-        body
-    }
-
     // Generate the new function declaration. Const arguments are kept as is. Duplicated arguments must
     // be pointers or references. Those receive a shadow argument, which is a mutable reference/pointer.
     // Active arguments must be scalars. Their shadow argument is added to the return type (and will be