addressing feedback, removing unused arg

Author: ZuseZ4

compiler/rustc_builtin_macros/src/autodiff.rs

@@ -233,20 +233,8 @@ mod llvm_enzyme {
  .filter(|a| **a == DiffActivity::Active || **a == DiffActivity::ActiveOnly)
  .count() as u32;
  let (d_sig, new_args, idents, errored) = gen_enzyme_decl(ecx, &sig, &x, span);
- let new_decl_span = d_sig.span;
  let d_body = gen_enzyme_body(
- ecx,
- &x,
- n_active,
- &sig,
- &d_sig,
- primal,
- &new_args,
- span,
- sig_span,
- new_decl_span,
- idents,
- errored,
+ ecx, &x, n_active, &sig, &d_sig, primal, &new_args, span, sig_span, idents, errored,
  );
  let d_ident = first_ident(&meta_item_vec[0]);
 
@@ -440,12 +428,10 @@ mod llvm_enzyme {
 
  /// 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 build something that should pass. We also add a inline_asm
- /// line, as one more barrier for rustc to prevent inlining of this function.
- /// FIXME(ZuseZ4): We still have cases of incorrect inlining across modules, see
- /// <https://github.com/EnzymeAD/rust/issues/173>, so this isn't sufficient.
- /// It also triggers an Enzyme crash if we due to a bug ever try to differentiate
- /// this function (which should never happen, since it is only a placeholder).
+ /// 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 accidentially 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(
@@ -458,7 +444,6 @@ mod llvm_enzyme {
  new_names: &[String],
  span: Span,
  sig_span: Span,
- _new_decl_span: Span,
  idents: Vec<Ident>,
  errored: bool,
  ) -> P<ast::Block> {