autodiff rlib handling

compiler/rustc_codegen_llvm/src/intrinsic.rs

@@ -15,6 +15,7 @@ use rustc_middle::mir::BinOp;
 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 @@ use crate::collector::{MonoItems, create_fn_mono_item};
 // 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>,

tests/run-make/autodiff/rlib/dep.rs

@@ -0,0 +1,7 @@
+pub fn f(x: f64, y: f64) -> f64 {
+    2.0 * x + y
+}
+
+pub fn g(x: f64) -> f64 {
+    2.0 * x
+}

tests/run-make/autodiff/rlib/lib.rs

@@ -0,0 +1,13 @@
+#![feature(autodiff)]
+extern crate simple_dep;
+use std::autodiff::*;
+
+#[inline(never)]
+pub fn f2(x: f64) -> f64 {
+    x.sin()
+}
+
+#[autodiff_forward(df1_lib, Dual, Dual)]
+pub fn _f1(x: f64) -> f64 {
+    simple_dep::f(x, x) * f2(x)
+}

tests/run-make/autodiff/rlib/main.rs

@@ -0,0 +1,8 @@
+extern crate foo;
+
+fn main() {
+    //dbg!("Running main.rs");
+    let enzyme_y1_lib = foo::df1_lib(1.5, 1.0);
+    println!("output1: {:?}", enzyme_y1_lib.0);
+    println!("output2: {:?}", enzyme_y1_lib.1);
+}

tests/run-make/autodiff/rlib/rmake.rs

@@ -0,0 +1,66 @@
+//@ needs-enzyme
+//@ ignore-cross-compile
+
+use run_make_support::{cwd, run, rustc};
+
+fn main() {
+    // Build the dependency crate.
+    rustc()
+        .input("dep.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=simple_dep")
+        .arg("-Clinker-plugin-lto")
+        .arg("--crate-type=lib")
+        .emit("dep-info,metadata,link")
+        .run();
+
+    let cwd = cwd();
+    let cwd_str = cwd.to_string_lossy();
+
+    let mydep = format!("-Ldependency={cwd_str}");
+
+    let simple_dep_rlib =
+        format!("--extern=simple_dep={}", cwd.join("libsimple_dep.rlib").to_string_lossy());
+
+    // Build the main library that depends on `simple_dep`.
+    rustc()
+        .input("lib.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=foo")
+        .arg("-Clinker-plugin-lto")
+        .arg("--crate-type=lib")
+        .emit("dep-info,metadata,link")
+        .arg(&mydep)
+        .arg(&simple_dep_rlib)
+        .run();
+
+    let foo_rlib = format!("--extern=foo={}", cwd.join("libfoo.rlib").to_string_lossy());
+
+    // Build the final binary linking both rlibs.
+    rustc()
+        .input("main.rs")
+        .arg("-Zautodiff=Enable")
+        .arg("--edition=2024")
+        .arg("-Copt-level=3")
+        .arg("--crate-name=foo")
+        .arg("-Clto=fat")
+        .arg("--crate-type=bin")
+        .emit("dep-info,link")
+        .arg(&mydep)
+        .arg(&foo_rlib)
+        .arg(&simple_dep_rlib)
+        .run();
+
+    // Run the binary and check its output.
+    let binary = run("foo");
+    assert!(binary.status().success(), "binary failed to run");
+
+    let binary_out = binary.stdout();
+    let output = String::from_utf8_lossy(&binary_out);
+    assert!(output.contains("output1: 4.488727439718245"));
+    assert!(output.contains("output2: 3.3108023673168265"));
+}