Rollup merge of #140697 - Sa4dUs:split-autodiff, r=ZuseZ4

Split `autodiff` into `autodiff_forward` and `autodiff_reverse`

This PR splits `#[autodiff]` macro so `#[autodiff(df, Reverse, args)]` would become `#[autodiff_reverse(df, args)]` and `#[autodiff(df, Forward, args)]` would become `#[autodiff_forwad(df, args)]`.

3 files changed, 39 insertions, 14 deletions

diff --git a/library/core/src/lib.rs b/library/core/src/lib.rs
index c49513f7a6d..989ab80b77d 100644
--- a/library/core/src/lib.rs
+++ b/library/core/src/lib.rs
@@ -225,10 +225,11 @@ pub mod assert_matches {
 
 // We don't export this through #[macro_export] for now, to avoid breakage.
 #[unstable(feature = "autodiff", issue = "124509")]
+#[cfg(not(bootstrap))]
 /// Unstable module containing the unstable `autodiff` macro.
 pub mod autodiff {
     #[unstable(feature = "autodiff", issue = "124509")]
-    pub use crate::macros::builtin::autodiff;
+    pub use crate::macros::builtin::{autodiff_forward, autodiff_reverse};
 }
 
 #[unstable(feature = "contracts", issue = "128044")]
diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 4742add0957..e70a1dab6e9 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -1519,20 +1519,41 @@ pub(crate) mod builtin {
         ($file:expr $(,)?) => {{ /* compiler built-in */ }};
     }
 
-    /// Automatic Differentiation macro which allows generating a new function to compute
-    /// the derivative of a given function. It may only be applied to a function.
-    /// The expected usage syntax is
-    /// `#[autodiff(NAME, MODE, INPUT_ACTIVITIES, OUTPUT_ACTIVITY)]`
-    /// where:
-    /// NAME is a string that represents a valid function name.
-    /// MODE is any of Forward, Reverse, ForwardFirst, ReverseFirst.
-    /// INPUT_ACTIVITIES consists of one valid activity for each input parameter.
-    /// OUTPUT_ACTIVITY must not be set if we implicitly return nothing (or explicitly return
-    /// `-> ()`). Otherwise it must be set to one of the allowed activities.
+    /// This macro uses forward-mode automatic differentiation to generate a new function.
+    /// It may only be applied to a function. The new function will compute the derivative
+    /// of the function to which the macro was applied.
+    ///
+    /// The expected usage syntax is:
+    /// `#[autodiff_forward(NAME, INPUT_ACTIVITIES, OUTPUT_ACTIVITY)]`
+    ///
+    /// - `NAME`: A string that represents a valid function name.
+    /// - `INPUT_ACTIVITIES`: Specifies one valid activity for each input parameter.
+    /// - `OUTPUT_ACTIVITY`: Must not be set if the function implicitly returns nothing
+    ///   (or explicitly returns `-> ()`). Otherwise, it must be set to one of the allowed activities.
+    #[unstable(feature = "autodiff", issue = "124509")]
+    #[allow_internal_unstable(rustc_attrs)]
+    #[rustc_builtin_macro]
+    #[cfg(not(bootstrap))]
+    pub macro autodiff_forward($item:item) {
+        /* compiler built-in */
+    }
+
+    /// This macro uses reverse-mode automatic differentiation to generate a new function.
+    /// It may only be applied to a function. The new function will compute the derivative
+    /// of the function to which the macro was applied.
+    ///
+    /// The expected usage syntax is:
+    /// `#[autodiff_reverse(NAME, INPUT_ACTIVITIES, OUTPUT_ACTIVITY)]`
+    ///
+    /// - `NAME`: A string that represents a valid function name.
+    /// - `INPUT_ACTIVITIES`: Specifies one valid activity for each input parameter.
+    /// - `OUTPUT_ACTIVITY`: Must not be set if the function implicitly returns nothing
+    ///   (or explicitly returns `-> ()`). Otherwise, it must be set to one of the allowed activities.
     #[unstable(feature = "autodiff", issue = "124509")]
     #[allow_internal_unstable(rustc_attrs)]
     #[rustc_builtin_macro]
-    pub macro autodiff($item:item) {
+    #[cfg(not(bootstrap))]
+    pub macro autodiff_reverse($item:item) {
         /* compiler built-in */
     }
 
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 4d984617739..4b2418a4985 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -276,12 +276,12 @@
 // tidy-alphabetical-start
 
 // stabilization was reverted after it hit beta
+#![cfg_attr(not(bootstrap), feature(autodiff))]
 #![feature(alloc_error_handler)]
 #![feature(allocator_internals)]
 #![feature(allow_internal_unsafe)]
 #![feature(allow_internal_unstable)]
 #![feature(asm_experimental_arch)]
-#![feature(autodiff)]
 #![feature(cfg_sanitizer_cfi)]
 #![feature(cfg_target_thread_local)]
 #![feature(cfi_encoding)]
@@ -636,12 +636,15 @@ pub mod simd {
     #[doc(inline)]
     pub use crate::std_float::StdFloat;
 }
+
 #[unstable(feature = "autodiff", issue = "124509")]
+#[cfg(not(bootstrap))]
 /// This module provides support for automatic differentiation.
 pub mod autodiff {
     /// This macro handles automatic differentiation.
-    pub use core::autodiff::autodiff;
+    pub use core::autodiff::{autodiff_forward, autodiff_reverse};
 }
+
 #[stable(feature = "futures_api", since = "1.36.0")]
 pub mod task {
     //! Types and Traits for working with asynchronous tasks.