rlib handling

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -15,6 +15,7 @@
 use rustc_middle::ty::layout::{FnAbiOf, HasTyCtxt, HasTypingEnv, LayoutOf};
 use rustc_middle::ty::{self, GenericArgsRef, Instance, SimdAlign, Ty, TyCtxt, TypingEnv};
 use rustc_middle::{bug, span_bug};
+use rustc_session::config::CrateType;
 use rustc_span::{Span, Symbol, sym};
 use rustc_symbol_mangling::{mangle_internal_symbol, symbol_name_for_instance_in_crate};
 use rustc_target::callconv::PassMode;
@@ -1136,8 +1137,17 @@ fn codegen_autodiff<'ll, 'tcx>(
     if !tcx.sess.opts.unstable_opts.autodiff.contains(&rustc_session::config::AutoDiff::Enable) {
         let _ = tcx.dcx().emit_almost_fatal(AutoDiffWithoutEnable);
     }
-    if tcx.sess.lto() != rustc_session::config::Lto::Fat {
-        let _ = tcx.dcx().emit_almost_fatal(AutoDiffWithoutLto);
+
+    let ct = tcx.crate_types();
+    let lto = tcx.sess.lto();
+    if ct.len() == 1 && ct.contains(&CrateType::Executable) {
+        if lto != rustc_session::config::Lto::Fat {
+            let _ = tcx.dcx().emit_almost_fatal(AutoDiffWithoutLto);
+        }
+    } else {
+        if lto != rustc_session::config::Lto::Fat && !tcx.sess.opts.cg.linker_plugin_lto.enabled() {
+            let _ = tcx.dcx().emit_almost_fatal(AutoDiffWithoutLto);
+        }
     }
 
     let fn_args = instance.args;

compiler/rustc_mir_transform/src/cross_crate_inline.rs

@@ -34,6 +34,14 @@ fn cross_crate_inlinable(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
         return true;
     }
 
+    // FIXME(autodiff): replace this as per discussion in https://github.com/rust-lang/rust/pull/149033#discussion_r2535465880
+    if tcx.has_attr(def_id, sym::autodiff_forward)
+        || tcx.has_attr(def_id, sym::autodiff_reverse)
+        || tcx.has_attr(def_id, sym::rustc_autodiff)
+    {
+        return true;
+    }
+
     if tcx.has_attr(def_id, sym::rustc_intrinsic) {
         // Intrinsic fallback bodies are always cross-crate inlineable.
         // To ensure that the MIR inliner doesn't cluelessly try to inline fallback

compiler/rustc_monomorphize/src/collector/autodiff.rs

@@ -7,6 +7,8 @@
 // mono so this does not interfere in `autodiff` intrinsics
 // codegen process. If they are unused, LLVM will remove them when
 // compiling with O3.
+// FIXME(autodiff): Remove this whole file, as per discussion in
+// https://github.com/rust-lang/rust/pull/149033#discussion_r2535465880
 pub(crate) fn collect_autodiff_fn<'tcx>(
     tcx: TyCtxt<'tcx>,
     instance: ty::Instance<'tcx>,