upstream rustc_codegen_ssa/rustc_middle changes for enzyme/autodiff

Author: ZuseZ4

Diff for: Cargo.lock

@@ -4121,6 +4121,7 @@ dependencies = [
 name = "rustc_monomorphize"
 version = "0.0.0"
 dependencies = [
+ "rustc_ast",
  "rustc_data_structures",
  "rustc_errors",
  "rustc_fluent_macro",
@@ -4129,6 +4130,7 @@ dependencies = [
  "rustc_middle",
  "rustc_session",
  "rustc_span",
+ "rustc_symbol_mangling",
  "rustc_target",
  "serde",
  "serde_json",

Diff for: compiler/rustc_ast/src/expand/autodiff_attrs.rs

@@ -6,7 +6,6 @@
 use std::fmt::{self, Display, Formatter};
 use std::str::FromStr;
 
-use crate::expand::typetree::TypeTree;
 use crate::expand::{Decodable, Encodable, HashStable_Generic};
 use crate::ptr::P;
 use crate::{Ty, TyKind};
@@ -79,10 +78,6 @@ pub struct AutoDiffItem {
     /// The name of the function being generated
     pub target: String,
     pub attrs: AutoDiffAttrs,
-    /// Describe the memory layout of input types
-    pub inputs: Vec<TypeTree>,
-    /// Describe the memory layout of the output type
-    pub output: TypeTree,
 }
 #[derive(Clone, Eq, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
 pub struct AutoDiffAttrs {
@@ -266,18 +261,14 @@ impl AutoDiffAttrs {
         self,
         source: String,
         target: String,
-        inputs: Vec<TypeTree>,
-        output: TypeTree,
     ) -> AutoDiffItem {
-        AutoDiffItem { source, target, inputs, output, attrs: self }
+        AutoDiffItem { source, target, attrs: self }
     }
 }
 
 impl fmt::Display for AutoDiffItem {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         write!(f, "Differentiating {} -> {}", self.source, self.target)?;
-        write!(f, " with attributes: {:?}", self.attrs)?;
-        write!(f, " with inputs: {:?}", self.inputs)?;
-        write!(f, " with output: {:?}", self.output)
+        write!(f, " with attributes: {:?}", self.attrs)
     }
 }

Diff for: compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -427,7 +427,7 @@ struct UsageSets<'tcx> {
 /// Prepare sets of definitions that are relevant to deciding whether something
 /// is an "unused function" for coverage purposes.
 fn prepare_usage_sets<'tcx>(tcx: TyCtxt<'tcx>) -> UsageSets<'tcx> {
-    let (all_mono_items, cgus) = tcx.collect_and_partition_mono_items(());
+    let (all_mono_items, _, cgus) = tcx.collect_and_partition_mono_items(());
 
     // Obtain a MIR body for each function participating in codegen, via an
     // arbitrary instance.

Diff for: compiler/rustc_codegen_ssa/messages.ftl

@@ -351,3 +351,6 @@ codegen_ssa_use_cargo_directive = use the `cargo:rustc-link-lib` directive to sp
 codegen_ssa_version_script_write_failure = failed to write version script: {$error}
 
 codegen_ssa_visual_studio_not_installed = you may need to install Visual Studio build tools with the "C++ build tools" workload
+
+codegen_ssa_autodiff_without_lto = using the autodiff feature requires using fat-lto
+

Diff for: compiler/rustc_codegen_ssa/src/assert_module_sources.rs

@@ -48,7 +48,7 @@ pub fn assert_module_sources(tcx: TyCtxt<'_>, set_reuse: &dyn Fn(&mut CguReuseTr
         }
 
         let available_cgus =
-            tcx.collect_and_partition_mono_items(()).1.iter().map(|cgu| cgu.name()).collect();
+            tcx.collect_and_partition_mono_items(()).2.iter().map(|cgu| cgu.name()).collect();
 
         let mut ams = AssertModuleSource {
             tcx,

Diff for: compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -293,7 +293,7 @@ fn exported_symbols_provider_local(
         // external linkage is enough for monomorphization to be linked to.
         let need_visibility = tcx.sess.target.dynamic_linking && !tcx.sess.target.only_cdylib;
 
-        let (_, cgus) = tcx.collect_and_partition_mono_items(());
+        let (_, _, cgus) = tcx.collect_and_partition_mono_items(());
 
         // The symbols created in this loop are sorted below it
         #[allow(rustc::potential_query_instability)]

Diff for: compiler/rustc_codegen_ssa/src/back/write.rs

@@ -8,6 +8,7 @@ use std::{fs, io, mem, str, thread};
 
 use jobserver::{Acquired, Client};
 use rustc_ast::attr;
+use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::profiling::{SelfProfilerRef, VerboseTimingGuard};
@@ -41,7 +42,7 @@ use tracing::debug;
 use super::link::{self, ensure_removed};
 use super::lto::{self, SerializedModule};
 use super::symbol_export::symbol_name_for_instance_in_crate;
-use crate::errors::ErrorCreatingRemarkDir;
+use crate::errors::{AutodiffWithoutLto, ErrorCreatingRemarkDir};
 use crate::traits::*;
 use crate::{
     CachedModuleCodegen, CodegenResults, CompiledModule, CrateInfo, ModuleCodegen, ModuleKind,
@@ -120,6 +121,7 @@ pub struct ModuleConfig {
     pub merge_functions: bool,
     pub emit_lifetime_markers: bool,
     pub llvm_plugins: Vec<String>,
+    pub autodiff: Vec<config::AutoDiff>,
 }
 
 impl ModuleConfig {
@@ -280,6 +282,7 @@ impl ModuleConfig {
 
             emit_lifetime_markers: sess.emit_lifetime_markers(),
             llvm_plugins: if_regular!(sess.opts.unstable_opts.llvm_plugins.clone(), vec![]),
+            autodiff: if_regular!(sess.opts.unstable_opts.autodiff.clone(), vec![]),
         }
     }
 
@@ -401,6 +404,7 @@ impl<B: WriteBackendMethods> CodegenContext<B> {
 
 fn generate_lto_work<B: ExtraBackendMethods>(
     cgcx: &CodegenContext<B>,
+    autodiff: Vec<AutoDiffItem>,
     needs_fat_lto: Vec<FatLtoInput<B>>,
     needs_thin_lto: Vec<(String, B::ThinBuffer)>,
     import_only_modules: Vec<(SerializedModule<B::ModuleBuffer>, WorkProduct)>,
@@ -411,9 +415,18 @@ fn generate_lto_work<B: ExtraBackendMethods>(
         assert!(needs_thin_lto.is_empty());
         let module =
             B::run_fat_lto(cgcx, needs_fat_lto, import_only_modules).unwrap_or_else(|e| e.raise());
+        if cgcx.lto == Lto::Fat {
+            let _config = cgcx.config(ModuleKind::Regular);
+            todo!("fat LTO with autodiff is not yet implemented");
+            //module = unsafe { module.autodiff(cgcx, autodiff, config).unwrap() };
+        }
         // We are adding a single work item, so the cost doesn't matter.
         vec![(WorkItem::LTO(module), 0)]
     } else {
+        if !autodiff.is_empty() {
+            let dcx = cgcx.create_dcx();
+            dcx.handle().emit_fatal(AutodiffWithoutLto {});
+        }
         assert!(needs_fat_lto.is_empty());
         let (lto_modules, copy_jobs) = B::run_thin_lto(cgcx, needs_thin_lto, import_only_modules)
             .unwrap_or_else(|e| e.raise());
@@ -1041,6 +1054,9 @@ pub(crate) enum Message<B: WriteBackendMethods> {
     /// Sent from a backend worker thread.
     WorkItem { result: Result<WorkItemResult<B>, Option<WorkerFatalError>>, worker_id: usize },
 
+    /// A vector containing all the AutoDiff tasks that we have to pass to Enzyme.
+    AddAutoDiffItems(Vec<AutoDiffItem>),
+
     /// The frontend has finished generating something (backend IR or a
     /// post-LTO artifact) for a codegen unit, and it should be passed to the
     /// backend. Sent from the main thread.
@@ -1367,6 +1383,7 @@ fn start_executing_work<B: ExtraBackendMethods>(
 
         // This is where we collect codegen units that have gone all the way
         // through codegen and LLVM.
+        let mut autodiff_items = Vec::new();
         let mut compiled_modules = vec![];
         let mut compiled_allocator_module = None;
         let mut needs_link = Vec::new();
@@ -1478,9 +1495,13 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     let needs_thin_lto = mem::take(&mut needs_thin_lto);
                     let import_only_modules = mem::take(&mut lto_import_only_modules);
 
-                    for (work, cost) in
-                        generate_lto_work(&cgcx, needs_fat_lto, needs_thin_lto, import_only_modules)
-                    {
+                    for (work, cost) in generate_lto_work(
+                        &cgcx,
+                        autodiff_items.clone(),
+                        needs_fat_lto,
+                        needs_thin_lto,
+                        import_only_modules,
+                    ) {
                         let insertion_index = work_items
                             .binary_search_by_key(&cost, |&(_, cost)| cost)
                             .unwrap_or_else(|e| e);
@@ -1615,6 +1636,10 @@ fn start_executing_work<B: ExtraBackendMethods>(
                     main_thread_state = MainThreadState::Idle;
                 }
 
+                Message::AddAutoDiffItems(mut items) => {
+                    autodiff_items.append(&mut items);
+                }
+
                 Message::CodegenComplete => {
                     if codegen_state != Aborted {
                         codegen_state = Completed;
@@ -2092,6 +2117,10 @@ impl<B: ExtraBackendMethods> OngoingCodegen<B> {
         drop(self.coordinator.sender.send(Box::new(Message::CodegenComplete::<B>)));
     }
 
+    pub(crate) fn submit_autodiff_items(&self, items: Vec<AutoDiffItem>) {
+        drop(self.coordinator.sender.send(Box::new(Message::<B>::AddAutoDiffItems(items))));
+    }
+
     pub(crate) fn check_for_errors(&self, sess: &Session) {
         self.shared_emitter_main.check(sess, false);
     }

Diff for: compiler/rustc_codegen_ssa/src/base.rs

@@ -621,7 +621,8 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
 
     // Run the monomorphization collector and partition the collected items into
     // codegen units.
-    let codegen_units = tcx.collect_and_partition_mono_items(()).1;
+    let (_, autodiff_fncs, codegen_units) = tcx.collect_and_partition_mono_items(());
+    let autodiff_fncs = autodiff_fncs.to_vec();
 
     // Force all codegen_unit queries so they are already either red or green
     // when compile_codegen_unit accesses them. We are not able to re-execute
@@ -692,6 +693,10 @@ pub fn codegen_crate<B: ExtraBackendMethods>(
         );
     }
 
+    if !autodiff_fncs.is_empty() {
+        ongoing_codegen.submit_autodiff_items(autodiff_fncs);
+    }
+
     // For better throughput during parallel processing by LLVM, we used to sort
     // CGUs largest to smallest. This would lead to better thread utilization
     // by, for example, preventing a large CGU from being processed last and
@@ -1051,7 +1056,7 @@ pub(crate) fn provide(providers: &mut Providers) {
             config::OptLevel::SizeMin => config::OptLevel::Default,
         };
 
-        let (defids, _) = tcx.collect_and_partition_mono_items(cratenum);
+        let (defids, _, _) = tcx.collect_and_partition_mono_items(cratenum);
 
         let any_for_speed = defids.items().any(|id| {
             let CodegenFnAttrs { optimize, .. } = tcx.codegen_fn_attrs(*id);

Diff for: compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -1,4 +1,9 @@
-use rustc_ast::{MetaItemInner, MetaItemKind, ast, attr};
+use std::str::FromStr;
+
+use rustc_ast::expand::autodiff_attrs::{
+    AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ret_activity,
+};
+use rustc_ast::{MetaItem, MetaItemInner, MetaItemKind, ast, attr};
 use rustc_attr::{InlineAttr, InstructionSetAttr, OptimizeAttr, list_contains_name};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
@@ -779,6 +784,133 @@ fn check_link_name_xor_ordinal(
     }
 }
 
+/// We now check the #[rustc_autodiff] attributes which we generated from the #[autodiff(...)]
+/// macros. There are two forms. The pure one without args to mark primal functions (the functions
+/// being differentiated). The other form is #[rustc_autodiff(Mode, ActivityList)] on top of the
+/// placeholder functions. We wrote the rustc_autodiff attributes ourself, so this should never
+/// panic, unless we introduced a bug when parsing the autodiff macro.
+fn autodiff_attrs(tcx: TyCtxt<'_>, id: DefId) -> AutoDiffAttrs {
+    let attrs = tcx.get_attrs(id, sym::rustc_autodiff);
+
+    let attrs =
+        attrs.filter(|attr| attr.name_or_empty() == sym::rustc_autodiff).collect::<Vec<_>>();
+
+    // check for exactly one autodiff attribute on placeholder functions.
+    // There should only be one, since we generate a new placeholder per ad macro.
+    // TODO: re-enable this. We should fix that rustc_autodiff isn't applied multiple times to the
+    // source function.
+    let msg_once = "cg_ssa: implementation bug. Autodiff attribute can only be applied once";
+    let attr = match attrs.len() {
+        0 => return AutoDiffAttrs::error(),
+        1 => attrs.get(0).unwrap(),
+        _ => {
+            attrs.get(0).unwrap()
+            //tcx.dcx().struct_span_err(attrs[1].span, msg_once).with_note("more than one").emit();
+            //return AutoDiffAttrs::error();
+        }
+    };
+
+    let list = attr.meta_item_list().unwrap_or_default();
+
+    // empty autodiff attribute macros (i.e. `#[autodiff]`) are used to mark source functions
+    if list.len() == 0 {
+        return AutoDiffAttrs::source();
+    }
+
+    let [mode, input_activities @ .., ret_activity] = &list[..] else {
+        tcx.dcx()
+            .struct_span_err(attr.span, msg_once)
+            .with_note("Implementation bug in autodiff_attrs. Please report this!")
+            .emit();
+        return AutoDiffAttrs::error();
+    };
+    let mode = if let MetaItemInner::MetaItem(MetaItem { path: ref p1, .. }) = mode {
+        p1.segments.first().unwrap().ident
+    } else {
+        let msg = "autodiff attribute must contain autodiff mode";
+        tcx.dcx().struct_span_err(attr.span, msg).with_note("empty argument list").emit();
+        return AutoDiffAttrs::error();
+    };
+
+    // parse mode
+    let msg_mode = "mode should be either forward or reverse";
+    let mode = match mode.as_str() {
+        "Forward" => DiffMode::Forward,
+        "Reverse" => DiffMode::Reverse,
+        "ForwardFirst" => DiffMode::ForwardFirst,
+        "ReverseFirst" => DiffMode::ReverseFirst,
+        _ => {
+            tcx.dcx().struct_span_err(attr.span, msg_mode).with_note("invalid mode").emit();
+            return AutoDiffAttrs::error();
+        }
+    };
+
+    // First read the ret symbol from the attribute
+    let ret_symbol = if let MetaItemInner::MetaItem(MetaItem { path: ref p1, .. }) = ret_activity {
+        p1.segments.first().unwrap().ident
+    } else {
+        let msg = "autodiff attribute must contain the return activity";
+        tcx.dcx().struct_span_err(attr.span, msg).with_note("missing return activity").emit();
+        return AutoDiffAttrs::error();
+    };
+
+    // Then parse it into an actual DiffActivity
+    let msg_unknown_ret_activity = "unknown return activity";
+    let ret_activity = match DiffActivity::from_str(ret_symbol.as_str()) {
+        Ok(x) => x,
+        Err(_) => {
+            tcx.dcx()
+                .struct_span_err(attr.span, msg_unknown_ret_activity)
+                .with_note("invalid return activity")
+                .emit();
+            return AutoDiffAttrs::error();
+        }
+    };
+
+    // Now parse all the intermediate (input) activities
+    let msg_arg_activity = "autodiff attribute must contain the return activity";
+    let mut arg_activities: Vec<DiffActivity> = vec![];
+    for arg in input_activities {
+        let arg_symbol = if let MetaItemInner::MetaItem(MetaItem { path: ref p2, .. }) = arg {
+            p2.segments.first().unwrap().ident
+        } else {
+            tcx.dcx()
+                .struct_span_err(attr.span, msg_arg_activity)
+                .with_note("Implementation bug, please report this!")
+                .emit();
+            return AutoDiffAttrs::error();
+        };
+
+        match DiffActivity::from_str(arg_symbol.as_str()) {
+            Ok(arg_activity) => arg_activities.push(arg_activity),
+            Err(_) => {
+                tcx.dcx()
+                    .struct_span_err(attr.span, msg_unknown_ret_activity)
+                    .with_note("invalid input activity")
+                    .emit();
+                return AutoDiffAttrs::error();
+            }
+        }
+    }
+
+    let mut msg = "".to_string();
+    for &input in &arg_activities {
+        if !valid_input_activity(mode, input) {
+            msg = format!("Invalid input activity {} for {} mode", input, mode);
+        }
+    }
+    if !valid_ret_activity(mode, ret_activity) {
+        msg = format!("Invalid return activity {} for {} mode", ret_activity, mode);
+    }
+    if msg != "".to_string() {
+        tcx.dcx().struct_span_err(attr.span, msg).with_note("invalid activity").emit();
+        return AutoDiffAttrs::error();
+    }
+
+    AutoDiffAttrs { mode, ret_activity, input_activity: arg_activities }
+}
+
 pub(crate) fn provide(providers: &mut Providers) {
-    *providers = Providers { codegen_fn_attrs, should_inherit_track_caller, ..*providers };
+    *providers =
+        Providers { codegen_fn_attrs, should_inherit_track_caller, autodiff_attrs, ..*providers };
 }

Diff for: compiler/rustc_codegen_ssa/src/errors.rs

@@ -37,6 +37,10 @@ pub(crate) struct CguNotRecorded<'a> {
     pub cgu_name: &'a str,
 }
 
+#[derive(Diagnostic)]
+#[diag(codegen_ssa_autodiff_without_lto)]
+pub struct AutodiffWithoutLto;
+
 #[derive(Diagnostic)]
 #[diag(codegen_ssa_unknown_reuse_kind)]
 pub(crate) struct UnknownReuseKind {