Auto merge of rust-lang#115920 - Zoxc:depkind-u16, r=cjgillot

Move `DepKind` to `rustc_query_system` and define it as `u16`

This moves the `DepKind` type to `rustc_query_system` where it's defined with an inner `u16` field. This decouples it from `rustc_middle` and is a step towards letting other crates define dep kinds. It also allows some type parameters to be removed. The `DepKind` trait is replaced with a `Deps` trait. That's used when some operations or information about dep kinds which is unavailable in `rustc_query_system` are still needed.

r? `@cjgillot`

Author: bors

Diff for: compiler/rustc_incremental/src/assert_dep_graph.rs

@@ -42,7 +42,7 @@ use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId, CRATE_DEF_ID};
 use rustc_hir::intravisit::{self, Visitor};
 use rustc_middle::dep_graph::{
-    DepGraphQuery, DepKind, DepNode, DepNodeExt, DepNodeFilter, EdgeFilter,
+    dep_kinds, DepGraphQuery, DepKind, DepNode, DepNodeExt, DepNodeFilter, EdgeFilter,
 };
 use rustc_middle::hir::nested_filter;
 use rustc_middle::ty::TyCtxt;
@@ -129,7 +129,7 @@ impl<'tcx> IfThisChanged<'tcx> {
                 let dep_node_interned = self.argument(attr);
                 let dep_node = match dep_node_interned {
                     None => {
-                        DepNode::from_def_path_hash(self.tcx, def_path_hash, DepKind::hir_owner)
+                        DepNode::from_def_path_hash(self.tcx, def_path_hash, dep_kinds::hir_owner)
                     }
                     Some(n) => {
                         match DepNode::from_label_string(self.tcx, n.as_str(), def_path_hash) {

Diff for: compiler/rustc_incremental/src/persist/load.rs

@@ -3,7 +3,7 @@
 use crate::errors;
 use rustc_data_structures::memmap::Mmap;
 use rustc_data_structures::unord::UnordMap;
-use rustc_middle::dep_graph::{SerializedDepGraph, WorkProductMap};
+use rustc_middle::dep_graph::{DepsType, SerializedDepGraph, WorkProductMap};
 use rustc_middle::query::on_disk_cache::OnDiskCache;
 use rustc_serialize::opaque::MemDecoder;
 use rustc_serialize::Decodable;
@@ -208,7 +208,7 @@ pub fn load_dep_graph(sess: &Session) -> DepGraphFuture {
                     return LoadResult::DataOutOfDate;
                 }
 
-                let dep_graph = SerializedDepGraph::decode(&mut decoder);
+                let dep_graph = SerializedDepGraph::decode::<DepsType>(&mut decoder);
 
                 LoadResult::Ok { data: (dep_graph, prev_work_products) }
             }

Diff for: compiler/rustc_interface/src/callbacks.rs

@@ -10,8 +10,10 @@
 //! origin crate when the `TyCtxt` is not present in TLS.
 
 use rustc_errors::{Diagnostic, TRACK_DIAGNOSTICS};
-use rustc_middle::dep_graph::TaskDepsRef;
+use rustc_middle::dep_graph::{DepNodeExt, TaskDepsRef};
 use rustc_middle::ty::tls;
+use rustc_query_system::dep_graph::dep_node::default_dep_kind_debug;
+use rustc_query_system::dep_graph::{DepContext, DepKind, DepNode};
 use std::fmt;
 
 fn track_span_parent(def_id: rustc_span::def_id::LocalDefId) {
@@ -59,10 +61,49 @@ fn def_id_debug(def_id: rustc_hir::def_id::DefId, f: &mut fmt::Formatter<'_>) ->
     write!(f, ")")
 }
 
+/// This is a callback from `rustc_query_system` as it cannot access the implicit state
+/// in `rustc_middle` otherwise.
+pub fn dep_kind_debug(kind: DepKind, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    tls::with_opt(|opt_tcx| {
+        if let Some(tcx) = opt_tcx {
+            write!(f, "{}", tcx.dep_kind_info(kind).name)
+        } else {
+            default_dep_kind_debug(kind, f)
+        }
+    })
+}
+
+/// This is a callback from `rustc_query_system` as it cannot access the implicit state
+/// in `rustc_middle` otherwise.
+pub fn dep_node_debug(node: DepNode, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    write!(f, "{:?}(", node.kind)?;
+
+    tls::with_opt(|opt_tcx| {
+        if let Some(tcx) = opt_tcx {
+            if let Some(def_id) = node.extract_def_id(tcx) {
+                write!(f, "{}", tcx.def_path_debug_str(def_id))?;
+            } else if let Some(ref s) = tcx.dep_graph.dep_node_debug_str(node) {
+                write!(f, "{s}")?;
+            } else {
+                write!(f, "{}", node.hash)?;
+            }
+        } else {
+            write!(f, "{}", node.hash)?;
+        }
+        Ok(())
+    })?;
+
+    write!(f, ")")
+}
+
 /// Sets up the callbacks in prior crates which we want to refer to the
 /// TyCtxt in.
 pub fn setup_callbacks() {
     rustc_span::SPAN_TRACK.swap(&(track_span_parent as fn(_)));
     rustc_hir::def_id::DEF_ID_DEBUG.swap(&(def_id_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+    rustc_query_system::dep_graph::dep_node::DEP_KIND_DEBUG
+        .swap(&(dep_kind_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
+    rustc_query_system::dep_graph::dep_node::DEP_NODE_DEBUG
+        .swap(&(dep_node_debug as fn(_, &mut fmt::Formatter<'_>) -> _));
     TRACK_DIAGNOSTICS.swap(&(track_diagnostic as _));
 }

Diff for: compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -126,8 +126,8 @@ macro_rules! provide_one {
             // External query providers call `crate_hash` in order to register a dependency
             // on the crate metadata. The exception is `crate_hash` itself, which obviously
             // doesn't need to do this (and can't, as it would cause a query cycle).
-            use rustc_middle::dep_graph::DepKind;
-            if DepKind::$name != DepKind::crate_hash && $tcx.dep_graph.is_fully_enabled() {
+            use rustc_middle::dep_graph::dep_kinds;
+            if dep_kinds::$name != dep_kinds::crate_hash && $tcx.dep_graph.is_fully_enabled() {
                 $tcx.ensure().crate_hash($def_id.krate);
             }
 

Diff for: compiler/rustc_middle/src/dep_graph/dep_node.rs

@@ -65,9 +65,9 @@ use rustc_hir::definitions::DefPathHash;
 use rustc_hir::{HirId, ItemLocalId, OwnerId};
 use rustc_query_system::dep_graph::FingerprintStyle;
 use rustc_span::symbol::Symbol;
-use std::hash::Hash;
 
-pub use rustc_query_system::dep_graph::{DepContext, DepNodeParams};
+pub use rustc_query_system::dep_graph::dep_node::DepKind;
+pub use rustc_query_system::dep_graph::{DepContext, DepNode, DepNodeParams};
 
 macro_rules! define_dep_nodes {
     (
@@ -84,55 +84,39 @@ macro_rules! define_dep_nodes {
         // encoding. The derived Encodable/Decodable uses leb128 encoding which is
         // dense when only considering this enum. But DepKind is encoded in a larger
         // struct, and there we can take advantage of the unused bits in the u16.
-        #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash)]
         #[allow(non_camel_case_types)]
-        #[repr(u16)]
-        pub enum DepKind {
+        #[repr(u16)] // Must be kept in sync with the inner type of `DepKind`.
+        enum DepKindDefs {
             $( $( #[$attr] )* $variant),*
         }
 
-        impl DepKind {
-            // This const implements two things: A bounds check so that we can decode
-            // a DepKind from a u16 with just one check, and a const check that the
-            // discriminants of the variants have been assigned consecutively from 0
-            // so that just the one comparison suffices to check that the u16 can be
-            // transmuted to a DepKind.
-            pub const VARIANTS: u16 = {
-                let deps: &[DepKind] = &[$(DepKind::$variant,)*];
-                let mut i = 0;
-                while i < deps.len() {
-                    if i as u16 != deps[i] as u16 {
-                        panic!();
-                    }
-                    i += 1;
-                }
-                deps.len() as u16
-            };
-        }
+        #[allow(non_upper_case_globals)]
+        pub mod dep_kinds {
+            use super::*;
 
-        impl<S: rustc_serialize::Encoder> rustc_serialize::Encodable<S> for DepKind {
-            #[inline]
-            fn encode(&self, s: &mut S) {
-                s.emit_u16(*self as u16);
-            }
+            $(
+                // The `as u16` cast must be kept in sync with the inner type of `DepKind`.
+                pub const $variant: DepKind = DepKind::new(DepKindDefs::$variant as u16);
+            )*
         }
 
-        impl<D: rustc_serialize::Decoder> rustc_serialize::Decodable<D> for DepKind {
-            #[inline]
-            fn decode(d: &mut D) -> DepKind {
-                let discrim = d.read_u16();
-                assert!(discrim < DepKind::VARIANTS);
-                // SAFETY: DepKind::VARIANTS checks that the discriminant values permit
-                // this one check to soundly guard the transmute.
-                unsafe {
-                    std::mem::transmute::<u16, DepKind>(discrim)
+        // This checks that the discriminants of the variants have been assigned consecutively
+        // from 0 so that they can be used as a dense index.
+        pub const DEP_KIND_VARIANTS: u16 = {
+            let deps = &[$(dep_kinds::$variant,)*];
+            let mut i = 0;
+            while i < deps.len() {
+                if i != deps[i].as_usize() {
+                    panic!();
                 }
+                i += 1;
             }
-        }
+            deps.len() as u16
+        };
 
         pub(super) fn dep_kind_from_label_string(label: &str) -> Result<DepKind, ()> {
             match label {
-                $(stringify!($variant) => Ok(DepKind::$variant),)*
+                $(stringify!($variant) => Ok(dep_kinds::$variant),)*
                 _ => Err(()),
             }
         }
@@ -158,12 +142,10 @@ rustc_query_append!(define_dep_nodes![
     [] fn CompileMonoItem() -> (),
 ]);
 
-static_assert_size!(DepKind, 2);
-
 // WARNING: `construct` is generic and does not know that `CompileCodegenUnit` takes `Symbol`s as keys.
 // Be very careful changing this type signature!
 pub(crate) fn make_compile_codegen_unit(tcx: TyCtxt<'_>, name: Symbol) -> DepNode {
-    DepNode::construct(tcx, DepKind::CompileCodegenUnit, &name)
+    DepNode::construct(tcx, dep_kinds::CompileCodegenUnit, &name)
 }
 
 // WARNING: `construct` is generic and does not know that `CompileMonoItem` takes `MonoItem`s as keys.
@@ -172,20 +154,9 @@ pub(crate) fn make_compile_mono_item<'tcx>(
     tcx: TyCtxt<'tcx>,
     mono_item: &MonoItem<'tcx>,
 ) -> DepNode {
-    DepNode::construct(tcx, DepKind::CompileMonoItem, mono_item)
+    DepNode::construct(tcx, dep_kinds::CompileMonoItem, mono_item)
 }
 
-pub type DepNode = rustc_query_system::dep_graph::DepNode<DepKind>;
-
-// We keep a lot of `DepNode`s in memory during compilation. It's not
-// required that their size stay the same, but we don't want to change
-// it inadvertently. This assert just ensures we're aware of any change.
-#[cfg(any(target_arch = "x86", target_arch = "x86_64"))]
-static_assert_size!(DepNode, 18);
-
-#[cfg(not(any(target_arch = "x86", target_arch = "x86_64")))]
-static_assert_size!(DepNode, 24);
-
 pub trait DepNodeExt: Sized {
     /// Extracts the DefId corresponding to this DepNode. This will work
     /// if two conditions are met:

Diff for: compiler/rustc_middle/src/dep_graph/mod.rs

@@ -6,49 +6,24 @@ use rustc_session::Session;
 #[macro_use]
 mod dep_node;
 
+pub use rustc_query_system::dep_graph::debug::EdgeFilter;
 pub use rustc_query_system::dep_graph::{
-    debug::DepNodeFilter, hash_result, DepContext, DepNodeColor, DepNodeIndex,
-    SerializedDepNodeIndex, WorkProduct, WorkProductId, WorkProductMap,
+    debug::DepNodeFilter, hash_result, DepContext, DepGraphQuery, DepNodeColor, DepNodeIndex, Deps,
+    SerializedDepGraph, SerializedDepNodeIndex, TaskDeps, TaskDepsRef, WorkProduct, WorkProductId,
+    WorkProductMap,
 };
 
-pub use dep_node::{label_strs, DepKind, DepNode, DepNodeExt};
+pub use dep_node::{dep_kinds, label_strs, DepKind, DepNode, DepNodeExt};
 pub(crate) use dep_node::{make_compile_codegen_unit, make_compile_mono_item};
 
-pub type DepGraph = rustc_query_system::dep_graph::DepGraph<DepKind>;
+pub type DepGraph = rustc_query_system::dep_graph::DepGraph<DepsType>;
 
-pub type TaskDeps = rustc_query_system::dep_graph::TaskDeps<DepKind>;
-pub type TaskDepsRef<'a> = rustc_query_system::dep_graph::TaskDepsRef<'a, DepKind>;
-pub type DepGraphQuery = rustc_query_system::dep_graph::DepGraphQuery<DepKind>;
-pub type SerializedDepGraph = rustc_query_system::dep_graph::SerializedDepGraph<DepKind>;
-pub type EdgeFilter = rustc_query_system::dep_graph::debug::EdgeFilter<DepKind>;
 pub type DepKindStruct<'tcx> = rustc_query_system::dep_graph::DepKindStruct<TyCtxt<'tcx>>;
 
-impl rustc_query_system::dep_graph::DepKind for DepKind {
-    const NULL: Self = DepKind::Null;
-    const RED: Self = DepKind::Red;
-    const MAX: u16 = DepKind::VARIANTS - 1;
-
-    fn debug_node(node: &DepNode, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        write!(f, "{:?}(", node.kind)?;
-
-        ty::tls::with_opt(|opt_tcx| {
-            if let Some(tcx) = opt_tcx {
-                if let Some(def_id) = node.extract_def_id(tcx) {
-                    write!(f, "{}", tcx.def_path_debug_str(def_id))?;
-                } else if let Some(ref s) = tcx.dep_graph.dep_node_debug_str(*node) {
-                    write!(f, "{s}")?;
-                } else {
-                    write!(f, "{}", node.hash)?;
-                }
-            } else {
-                write!(f, "{}", node.hash)?;
-            }
-            Ok(())
-        })?;
-
-        write!(f, ")")
-    }
+#[derive(Clone)]
+pub struct DepsType;
 
+impl Deps for DepsType {
     fn with_deps<OP, R>(task_deps: TaskDepsRef<'_>, op: OP) -> R
     where
         OP: FnOnce() -> R,
@@ -70,24 +45,13 @@ impl rustc_query_system::dep_graph::DepKind for DepKind {
         })
     }
 
-    #[track_caller]
-    #[inline]
-    fn from_u16(u: u16) -> Self {
-        if u > Self::MAX {
-            panic!("Invalid DepKind {u}");
-        }
-        // SAFETY: See comment on DepKind::VARIANTS
-        unsafe { std::mem::transmute(u) }
-    }
-
-    #[inline]
-    fn to_u16(self) -> u16 {
-        self as u16
-    }
+    const DEP_KIND_NULL: DepKind = dep_kinds::Null;
+    const DEP_KIND_RED: DepKind = dep_kinds::Red;
+    const DEP_KIND_MAX: u16 = dep_node::DEP_KIND_VARIANTS - 1;
 }
 
 impl<'tcx> DepContext for TyCtxt<'tcx> {
-    type DepKind = DepKind;
+    type Deps = DepsType;
 
     #[inline]
     fn with_stable_hashing_context<R>(self, f: impl FnOnce(StableHashingContext<'_>) -> R) -> R {
@@ -111,6 +75,6 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
 
     #[inline]
     fn dep_kind_info(&self, dk: DepKind) -> &DepKindStruct<'tcx> {
-        &self.query_kinds[dk as usize]
+        &self.query_kinds[dk.as_usize()]
     }
 }

Diff for: compiler/rustc_middle/src/query/mod.rs

@@ -7,7 +7,6 @@
 #![allow(unused_parens)]
 
 use crate::dep_graph;
-use crate::dep_graph::DepKind;
 use crate::infer::canonical::{self, Canonical};
 use crate::lint::LintExpectation;
 use crate::metadata::ModChild;

Diff for: compiler/rustc_middle/src/query/plumbing.rs

@@ -37,7 +37,7 @@ pub struct DynamicQuery<'tcx, C: QueryCache> {
     pub eval_always: bool,
     pub dep_kind: DepKind,
     pub handle_cycle_error: HandleCycleError,
-    pub query_state: FieldOffset<QueryStates<'tcx>, QueryState<C::Key, DepKind>>,
+    pub query_state: FieldOffset<QueryStates<'tcx>, QueryState<C::Key>>,
     pub query_cache: FieldOffset<QueryCaches<'tcx>, C>,
     pub cache_on_disk: fn(tcx: TyCtxt<'tcx>, key: &C::Key) -> bool,
     pub execute_query: fn(tcx: TyCtxt<'tcx>, k: C::Key) -> C::Value,
@@ -53,7 +53,7 @@ pub struct DynamicQuery<'tcx, C: QueryCache> {
         fn(tcx: TyCtxt<'tcx>, key: &C::Key, index: SerializedDepNodeIndex) -> bool,
     pub hash_result: HashResult<C::Value>,
     pub value_from_cycle_error:
-        fn(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo<DepKind>], guar: ErrorGuaranteed) -> C::Value,
+        fn(tcx: TyCtxt<'tcx>, cycle: &[QueryInfo], guar: ErrorGuaranteed) -> C::Value,
     pub format_value: fn(&C::Value) -> String,
 }
 
@@ -402,7 +402,7 @@ macro_rules! define_callbacks {
         #[derive(Default)]
         pub struct QueryStates<'tcx> {
             $(
-                pub $name: QueryState<$($K)*, DepKind>,
+                pub $name: QueryState<$($K)*>,
             )*
         }
 
@@ -516,7 +516,7 @@ macro_rules! define_feedable {
                         }
                     }
                     None => {
-                        let dep_node = dep_graph::DepNode::construct(tcx, dep_graph::DepKind::$name, &key);
+                        let dep_node = dep_graph::DepNode::construct(tcx, dep_graph::dep_kinds::$name, &key);
                         let dep_node_index = tcx.dep_graph.with_feed_task(
                             dep_node,
                             tcx,