Autodiff Upstreaming - rustc_codegen_ssa, rustc_middle

Cargo.lock

@@ -4234,6 +4234,7 @@ name = "rustc_monomorphize"
 version = "0.0.0"
 dependencies = [
  "rustc_abi",
+ "rustc_ast",
  "rustc_attr_parsing",
  "rustc_data_structures",
  "rustc_errors",
@@ -4243,6 +4244,7 @@ dependencies = [
  "rustc_middle",
  "rustc_session",
  "rustc_span",
+ "rustc_symbol_mangling",
  "rustc_target",
  "serde",
  "serde_json",

compiler/rustc_ast/src/expand/autodiff_attrs.rs

@@ -79,6 +79,7 @@ pub struct AutoDiffItem {
     pub target: String,
     pub attrs: AutoDiffAttrs,
 }
+
 #[derive(Clone, Eq, PartialEq, Encodable, Decodable, Debug, HashStable_Generic)]
 pub struct AutoDiffAttrs {
     /// Conceptually either forward or reverse mode AD, as described in various autodiff papers and
@@ -231,7 +232,7 @@ impl AutoDiffAttrs {
         self.ret_activity == DiffActivity::ActiveOnly
     }
 
-    pub fn error() -> Self {
+    pub const fn error() -> Self {
         AutoDiffAttrs {
             mode: DiffMode::Error,
             ret_activity: DiffActivity::None,

compiler/rustc_codegen_llvm/src/builder/autodiff.rs

@@ -62,8 +62,8 @@ fn generate_enzyme_call<'ll>(
     // add outer_fn name to ad_name to make it unique, in case users apply autodiff to multiple
     // functions. Unwrap will only panic, if LLVM gave us an invalid string.
     let name = llvm::get_value_name(outer_fn);
-    let outer_fn_name = std::ffi::CStr::from_bytes_with_nul(name).unwrap().to_str().unwrap();
-    ad_name.push_str(outer_fn_name.to_string().as_str());
+    let outer_fn_name = std::str::from_utf8(name).unwrap();
+    ad_name.push_str(outer_fn_name);
 
     // Let us assume the user wrote the following function square:
     //
@@ -255,14 +255,14 @@ fn generate_enzyme_call<'ll>(
             // have no debug info to copy, which would then be ok.
             trace!("no dbg info");
         }
+
         // Now that we copied the metadata, get rid of dummy code.
-        llvm::LLVMRustEraseInstBefore(entry, last_inst);
-        llvm::LLVMRustEraseInstFromParent(last_inst);
+        llvm::LLVMRustEraseInstUntilInclusive(entry, last_inst);
 
-        if cx.val_ty(outer_fn) != cx.type_void() {
-            builder.ret(call);
-        } else {
+        if cx.val_ty(call) == cx.type_void() {
             builder.ret_void();
+        } else {
+            builder.ret(call);
         }
 
         // Let's crash in case that we messed something up above and generated invalid IR.

compiler/rustc_codegen_llvm/src/coverageinfo/mapgen.rs

@@ -298,7 +298,7 @@ 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 MonoItemPartitions { all_mono_items, codegen_units } =
+    let MonoItemPartitions { all_mono_items, codegen_units, .. } =
         tcx.collect_and_partition_mono_items(());
 
     // Obtain a MIR body for each function participating in codegen, via an

compiler/rustc_codegen_llvm/src/llvm/enzyme_ffi.rs

@@ -7,11 +7,13 @@ use crate::llvm::Bool;
 extern "C" {
     // Enzyme
     pub fn LLVMRustHasMetadata(I: &Value, KindID: c_uint) -> bool;
-    pub fn LLVMRustEraseInstBefore(BB: &BasicBlock, I: &Value);
+    pub fn LLVMRustEraseInstUntilInclusive(BB: &BasicBlock, I: &Value);
     pub fn LLVMRustGetLastInstruction<'a>(BB: &BasicBlock) -> Option<&'a Value>;
     pub fn LLVMRustDIGetInstMetadata(I: &Value) -> Option<&Metadata>;
     pub fn LLVMRustEraseInstFromParent(V: &Value);
     pub fn LLVMRustGetTerminator<'a>(B: &BasicBlock) -> &'a Value;
+    pub fn LLVMDumpModule(M: &Module);
+    pub fn LLVMDumpValue(V: &Value);
     pub fn LLVMRustVerifyFunction(V: &Value, action: LLVMRustVerifierFailureAction) -> Bool;
 
     pub fn LLVMGetFunctionCallConv(F: &Value) -> c_uint;

compiler/rustc_codegen_ssa/messages.ftl

@@ -16,6 +16,8 @@ codegen_ssa_archive_build_failure = failed to build archive at `{$path}`: {$erro
 
 codegen_ssa_atomic_compare_exchange = Atomic compare-exchange intrinsic missing failure memory ordering
 
+codegen_ssa_autodiff_without_lto = using the autodiff feature requires using fat-lto
+
 codegen_ssa_binary_output_to_tty = option `-o` or `--emit` is used to write binary output type `{$shorthand}` to stdout, but stdout is a tty
 
 codegen_ssa_cgu_not_recorded =

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -7,6 +7,7 @@ use std::sync::mpsc::{Receiver, Sender, channel};
 use std::{fs, io, mem, str, thread};
 
 use rustc_ast::attr;
+use rustc_ast::expand::autodiff_attrs::AutoDiffItem;
 use rustc_data_structures::fx::{FxHashMap, FxIndexMap};
 use rustc_data_structures::jobserver::{self, Acquired};
 use rustc_data_structures::memmap::Mmap;
@@ -40,7 +41,7 @@ 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,
@@ -118,6 +119,7 @@ pub struct ModuleConfig {
     pub merge_functions: bool,
     pub emit_lifetime_markers: bool,
     pub llvm_plugins: Vec<String>,
+    pub autodiff: Vec<config::AutoDiff>,
 }
 
 impl ModuleConfig {
@@ -266,6 +268,7 @@ 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![]),
         }
     }
 
@@ -389,6 +392,7 @@ 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)>,
@@ -397,11 +401,19 @@ fn generate_lto_work<B: ExtraBackendMethods>(
 
     if !needs_fat_lto.is_empty() {
         assert!(needs_thin_lto.is_empty());
-        let module =
+        let mut 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);
+            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());
@@ -1021,6 +1033,9 @@ 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.
@@ -1348,6 +1363,7 @@ 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();
@@ -1459,9 +1475,13 @@ 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);
@@ -1596,6 +1616,10 @@ 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;
@@ -2070,6 +2094,10 @@ 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);
     }

compiler/rustc_codegen_ssa/src/base.rs

@@ -18,7 +18,7 @@ use rustc_middle::middle::debugger_visualizer::{DebuggerVisualizerFile, Debugger
 use rustc_middle::middle::exported_symbols::SymbolExportKind;
 use rustc_middle::middle::{exported_symbols, lang_items};
 use rustc_middle::mir::BinOp;
-use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem};
+use rustc_middle::mir::mono::{CodegenUnit, CodegenUnitNameBuilder, MonoItem, MonoItemPartitions};
 use rustc_middle::query::Providers;
 use rustc_middle::ty::layout::{HasTyCtxt, HasTypingEnv, LayoutOf, TyAndLayout};
 use rustc_middle::ty::{self, Instance, Ty, TyCtxt};
@@ -619,7 +619,9 @@ 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(()).codegen_units;
+    let MonoItemPartitions { codegen_units, autodiff_items, .. } =
+        tcx.collect_and_partition_mono_items(());
+    let autodiff_fncs = autodiff_items.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
@@ -690,6 +692,10 @@ 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

compiler/rustc_codegen_ssa/src/codegen_attrs.rs

@@ -1,5 +1,10 @@
+use std::str::FromStr;
+
 use rustc_ast::attr::list_contains_name;
-use rustc_ast::{MetaItemInner, attr};
+use rustc_ast::expand::autodiff_attrs::{
+    AutoDiffAttrs, DiffActivity, DiffMode, valid_input_activity, valid_ret_activity,
+};
+use rustc_ast::{MetaItem, MetaItemInner, attr};
 use rustc_attr_parsing::{InlineAttr, InstructionSetAttr, OptimizeAttr};
 use rustc_data_structures::fx::FxHashMap;
 use rustc_errors::codes::*;
@@ -13,6 +18,7 @@ use rustc_middle::middle::codegen_fn_attrs::{
 };
 use rustc_middle::mir::mono::Linkage;
 use rustc_middle::query::Providers;
+use rustc_middle::span_bug;
 use rustc_middle::ty::{self as ty, TyCtxt};
 use rustc_session::parse::feature_err;
 use rustc_session::{Session, lint};
@@ -65,6 +71,13 @@ fn codegen_fn_attrs(tcx: TyCtxt<'_>, did: LocalDefId) -> CodegenFnAttrs {
         codegen_fn_attrs.flags |= CodegenFnAttrFlags::TRACK_CALLER;
     }
 
+    // If our rustc version supports autodiff/enzyme, then we call our handler
+    // to check for any `#[rustc_autodiff(...)]` attributes.
+    if cfg!(llvm_enzyme) {
+        let ad = autodiff_attrs(tcx, did.into());
+        codegen_fn_attrs.autodiff_item = ad;
+    }
+
     // When `no_builtins` is applied at the crate level, we should add the
     // `no-builtins` attribute to each function to ensure it takes effect in LTO.
     let crate_attrs = tcx.hir().attrs(rustc_hir::CRATE_HIR_ID);
@@ -856,6 +869,109 @@ impl<'a> MixedExportNameAndNoMangleState<'a> {
     }
 }
 
+/// 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) -> Option<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.
+    // FIXME(ZuseZ4): re-enable this check. Currently we add multiple, which doesn't cause harm but
+    // looks strange e.g. under cargo-expand.
+    let attr = match &attrs[..] {
+        [] => return None,
+        [attr] => attr,
+        // These two attributes are the same and unfortunately duplicated due to a previous bug.
+        [attr, _attr2] => attr,
+        _ => {
+            //FIXME(ZuseZ4): Once we fixed our parser, we should also prohibit the two-attribute
+            //branch above.
+            span_bug!(attrs[1].span, "cg_ssa: rustc_autodiff should only exist once per source");
+        }
+    };
+
+    let list = attr.meta_item_list().unwrap_or_default();
+
+    // empty autodiff attribute macros (i.e. `#[autodiff]`) are used to mark source functions
+    if list.is_empty() {
+        return Some(AutoDiffAttrs::source());
+    }
+
+    let [mode, input_activities @ .., ret_activity] = &list[..] else {
+        span_bug!(attr.span, "rustc_autodiff attribute must contain mode and activities");
+    };
+    let mode = if let MetaItemInner::MetaItem(MetaItem { path: ref p1, .. }) = mode {
+        p1.segments.first().unwrap().ident
+    } else {
+        span_bug!(attr.span, "rustc_autodiff attribute must contain mode");
+    };
+
+    // parse mode
+    let mode = match mode.as_str() {
+        "Forward" => DiffMode::Forward,
+        "Reverse" => DiffMode::Reverse,
+        "ForwardFirst" => DiffMode::ForwardFirst,
+        "ReverseFirst" => DiffMode::ReverseFirst,
+        _ => {
+            span_bug!(mode.span, "rustc_autodiff attribute contains invalid mode");
+        }
+    };
+
+    // 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 {
+        span_bug!(attr.span, "rustc_autodiff attribute must contain the return activity");
+    };
+
+    // Then parse it into an actual DiffActivity
+    let Ok(ret_activity) = DiffActivity::from_str(ret_symbol.as_str()) else {
+        span_bug!(ret_symbol.span, "invalid return activity");
+    };
+
+    // Now parse all the intermediate (input) activities
+    let mut arg_activities: Vec<DiffActivity> = vec![];
+    for arg in input_activities {
+        let arg_symbol = if let MetaItemInner::MetaItem(MetaItem { path: ref p2, .. }) = arg {
+            match p2.segments.first() {
+                Some(x) => x.ident,
+                None => {
+                    span_bug!(
+                        arg.span(),
+                        "rustc_autodiff attribute must contain the input activity"
+                    );
+                }
+            }
+        } else {
+            span_bug!(arg.span(), "rustc_autodiff attribute must contain the input activity");
+        };
+
+        match DiffActivity::from_str(arg_symbol.as_str()) {
+            Ok(arg_activity) => arg_activities.push(arg_activity),
+            Err(_) => {
+                span_bug!(arg_symbol.span, "invalid input activity");
+            }
+        }
+    }
+
+    for &input in &arg_activities {
+        if !valid_input_activity(mode, input) {
+            span_bug!(attr.span, "Invalid input activity {} for {} mode", input, mode);
+        }
+    }
+    if !valid_ret_activity(mode, ret_activity) {
+        span_bug!(attr.span, "Invalid return activity {} for {} mode", ret_activity, mode);
+    }
+
+    Some(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 };
 }