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Auto merge of rust-lang#101710 - jyn514:move-dep-kind-node, r=cjgillot
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Move DepKindStruct from rustc_middle to rustc_query_system

Helps with rust-lang#96524. cc https://rust-lang.zulipchat.com/#narrow/stream/241847-t-compiler.2Fwg-incr-comp/topic/Moving.20.60DepKindStruct.60.20to.20rustc_query_system.20.2396524

r? `@cjgillot`
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bors committed Sep 25, 2022
2 parents f5193a9 + 00cde6d commit ff40f2e
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92 changes: 3 additions & 89 deletions compiler/rustc_middle/src/dep_graph/dep_node.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -69,79 +69,6 @@ use std::hash::Hash;

pub use rustc_query_system::dep_graph::{DepContext, DepNodeParams};

/// This struct stores metadata about each DepKind.
///
/// Information is retrieved by indexing the `DEP_KINDS` array using the integer value
/// of the `DepKind`. Overall, this allows to implement `DepContext` using this manual
/// jump table instead of large matches.
pub struct DepKindStruct<'tcx> {
/// Anonymous queries cannot be replayed from one compiler invocation to the next.
/// When their result is needed, it is recomputed. They are useful for fine-grained
/// dependency tracking, and caching within one compiler invocation.
pub is_anon: bool,

/// Eval-always queries do not track their dependencies, and are always recomputed, even if
/// their inputs have not changed since the last compiler invocation. The result is still
/// cached within one compiler invocation.
pub is_eval_always: bool,

/// Whether the query key can be recovered from the hashed fingerprint.
/// See [DepNodeParams] trait for the behaviour of each key type.
pub fingerprint_style: FingerprintStyle,

/// The red/green evaluation system will try to mark a specific DepNode in the
/// dependency graph as green by recursively trying to mark the dependencies of
/// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode`
/// where we don't know if it is red or green and we therefore actually have
/// to recompute its value in order to find out. Since the only piece of
/// information that we have at that point is the `DepNode` we are trying to
/// re-evaluate, we need some way to re-run a query from just that. This is what
/// `force_from_dep_node()` implements.
///
/// In the general case, a `DepNode` consists of a `DepKind` and an opaque
/// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint
/// is usually constructed by computing a stable hash of the query-key that the
/// `DepNode` corresponds to. Consequently, it is not in general possible to go
/// back from hash to query-key (since hash functions are not reversible). For
/// this reason `force_from_dep_node()` is expected to fail from time to time
/// because we just cannot find out, from the `DepNode` alone, what the
/// corresponding query-key is and therefore cannot re-run the query.
///
/// The system deals with this case letting `try_mark_green` fail which forces
/// the root query to be re-evaluated.
///
/// Now, if `force_from_dep_node()` would always fail, it would be pretty useless.
/// Fortunately, we can use some contextual information that will allow us to
/// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we
/// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a
/// valid `DefPathHash`. Since we also always build a huge table that maps every
/// `DefPathHash` in the current codebase to the corresponding `DefId`, we have
/// everything we need to re-run the query.
///
/// Take the `mir_promoted` query as an example. Like many other queries, it
/// just has a single parameter: the `DefId` of the item it will compute the
/// validated MIR for. Now, when we call `force_from_dep_node()` on a `DepNode`
/// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode`
/// is actually a `DefPathHash`, and can therefore just look up the corresponding
/// `DefId` in `tcx.def_path_hash_to_def_id`.
pub force_from_dep_node: Option<fn(tcx: TyCtxt<'tcx>, dep_node: DepNode) -> bool>,

/// Invoke a query to put the on-disk cached value in memory.
pub try_load_from_on_disk_cache: Option<fn(TyCtxt<'tcx>, DepNode)>,
}

impl DepKind {
#[inline(always)]
pub fn fingerprint_style(self, tcx: TyCtxt<'_>) -> FingerprintStyle {
// Only fetch the DepKindStruct once.
let data = tcx.query_kind(self);
if data.is_anon {
return FingerprintStyle::Opaque;
}
data.fingerprint_style
}
}

macro_rules! define_dep_nodes {
(
$($(#[$attr:meta])*
Expand All @@ -159,7 +86,7 @@ macro_rules! define_dep_nodes {
$( $( #[$attr] )* $variant),*
}

fn dep_kind_from_label_string(label: &str) -> Result<DepKind, ()> {
pub(super) fn dep_kind_from_label_string(label: &str) -> Result<DepKind, ()> {
match label {
$(stringify!($variant) => Ok(DepKind::$variant),)*
_ => Err(()),
Expand Down Expand Up @@ -214,11 +141,6 @@ static_assert_size!(DepNode, 18);
static_assert_size!(DepNode, 24);

pub trait DepNodeExt: Sized {
/// Construct a DepNode from the given DepKind and DefPathHash. This
/// method will assert that the given DepKind actually requires a
/// single DefId/DefPathHash parameter.
fn from_def_path_hash(tcx: TyCtxt<'_>, def_path_hash: DefPathHash, kind: DepKind) -> Self;

/// Extracts the DefId corresponding to this DepNode. This will work
/// if two conditions are met:
///
Expand All @@ -243,14 +165,6 @@ pub trait DepNodeExt: Sized {
}

impl DepNodeExt for DepNode {
/// Construct a DepNode from the given DepKind and DefPathHash. This
/// method will assert that the given DepKind actually requires a
/// single DefId/DefPathHash parameter.
fn from_def_path_hash(tcx: TyCtxt<'_>, def_path_hash: DefPathHash, kind: DepKind) -> DepNode {
debug_assert!(kind.fingerprint_style(tcx) == FingerprintStyle::DefPathHash);
DepNode { kind, hash: def_path_hash.0.into() }
}

/// Extracts the DefId corresponding to this DepNode. This will work
/// if two conditions are met:
///
Expand All @@ -262,7 +176,7 @@ impl DepNodeExt for DepNode {
/// refers to something from the previous compilation session that
/// has been removed.
fn extract_def_id<'tcx>(&self, tcx: TyCtxt<'tcx>) -> Option<DefId> {
if self.kind.fingerprint_style(tcx) == FingerprintStyle::DefPathHash {
if tcx.fingerprint_style(self.kind) == FingerprintStyle::DefPathHash {
Some(tcx.def_path_hash_to_def_id(DefPathHash(self.hash.into()), &mut || {
panic!("Failed to extract DefId: {:?} {}", self.kind, self.hash)
}))
Expand All @@ -279,7 +193,7 @@ impl DepNodeExt for DepNode {
) -> Result<DepNode, ()> {
let kind = dep_kind_from_label_string(label)?;

match kind.fingerprint_style(tcx) {
match tcx.fingerprint_style(kind) {
FingerprintStyle::Opaque => Err(()),
FingerprintStyle::Unit => Ok(DepNode::new_no_params(tcx, kind)),
FingerprintStyle::DefPathHash => {
Expand Down
52 changes: 6 additions & 46 deletions compiler/rustc_middle/src/dep_graph/mod.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -11,15 +11,17 @@ pub use rustc_query_system::dep_graph::{
SerializedDepNodeIndex, WorkProduct, WorkProductId,
};

pub use dep_node::{label_strs, DepKind, DepKindStruct, DepNode, DepNodeExt};
pub use dep_node::{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 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;
Expand Down Expand Up @@ -91,50 +93,8 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
self.sess
}

#[inline(always)]
fn fingerprint_style(&self, kind: DepKind) -> rustc_query_system::dep_graph::FingerprintStyle {
kind.fingerprint_style(*self)
}

#[inline(always)]
fn is_eval_always(&self, kind: DepKind) -> bool {
self.query_kind(kind).is_eval_always
}

fn try_force_from_dep_node(&self, dep_node: DepNode) -> bool {
debug!("try_force_from_dep_node({:?}) --- trying to force", dep_node);

// We must avoid ever having to call `force_from_dep_node()` for a
// `DepNode::codegen_unit`:
// Since we cannot reconstruct the query key of a `DepNode::codegen_unit`, we
// would always end up having to evaluate the first caller of the
// `codegen_unit` query that *is* reconstructible. This might very well be
// the `compile_codegen_unit` query, thus re-codegenning the whole CGU just
// to re-trigger calling the `codegen_unit` query with the right key. At
// that point we would already have re-done all the work we are trying to
// avoid doing in the first place.
// The solution is simple: Just explicitly call the `codegen_unit` query for
// each CGU, right after partitioning. This way `try_mark_green` will always
// hit the cache instead of having to go through `force_from_dep_node`.
// This assertion makes sure, we actually keep applying the solution above.
debug_assert!(
dep_node.kind != DepKind::codegen_unit,
"calling force_from_dep_node() on DepKind::codegen_unit"
);

let cb = self.query_kind(dep_node.kind);
if let Some(f) = cb.force_from_dep_node {
f(*self, dep_node);
true
} else {
false
}
}

fn try_load_from_on_disk_cache(&self, dep_node: DepNode) {
let cb = self.query_kind(dep_node.kind);
if let Some(f) = cb.try_load_from_on_disk_cache {
f(*self, dep_node)
}
#[inline]
fn dep_kind_info(&self, dep_kind: DepKind) -> &DepKindStruct<'tcx> {
&self.query_kinds[dep_kind as usize]
}
}
8 changes: 2 additions & 6 deletions compiler/rustc_middle/src/ty/context.rs
View file
Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
//! Type context book-keeping.
use crate::arena::Arena;
use crate::dep_graph::{DepGraph, DepKind, DepKindStruct};
use crate::dep_graph::{DepGraph, DepKindStruct};
use crate::hir::place::Place as HirPlace;
use crate::infer::canonical::{Canonical, CanonicalVarInfo, CanonicalVarInfos};
use crate::lint::{struct_lint_level, LintLevelSource};
Expand Down Expand Up @@ -1085,7 +1085,7 @@ pub struct GlobalCtxt<'tcx> {

pub queries: &'tcx dyn query::QueryEngine<'tcx>,
pub query_caches: query::QueryCaches<'tcx>,
query_kinds: &'tcx [DepKindStruct<'tcx>],
pub(crate) query_kinds: &'tcx [DepKindStruct<'tcx>],

// Internal caches for metadata decoding. No need to track deps on this.
pub ty_rcache: Lock<FxHashMap<ty::CReaderCacheKey, Ty<'tcx>>>,
Expand Down Expand Up @@ -1292,10 +1292,6 @@ impl<'tcx> TyCtxt<'tcx> {
}
}

pub(crate) fn query_kind(self, k: DepKind) -> &'tcx DepKindStruct<'tcx> {
&self.query_kinds[k as usize]
}

/// Constructs a `TyKind::Error` type and registers a `delay_span_bug` to ensure it gets used.
#[track_caller]
pub fn ty_error(self) -> Ty<'tcx> {
Expand Down
18 changes: 18 additions & 0 deletions compiler/rustc_query_impl/src/plumbing.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -380,6 +380,24 @@ where
Q::Key: DepNodeParams<TyCtxt<'tcx>>,
Q::Value: Value<TyCtxt<'tcx>>,
{
// We must avoid ever having to call `force_from_dep_node()` for a
// `DepNode::codegen_unit`:
// Since we cannot reconstruct the query key of a `DepNode::codegen_unit`, we
// would always end up having to evaluate the first caller of the
// `codegen_unit` query that *is* reconstructible. This might very well be
// the `compile_codegen_unit` query, thus re-codegenning the whole CGU just
// to re-trigger calling the `codegen_unit` query with the right key. At
// that point we would already have re-done all the work we are trying to
// avoid doing in the first place.
// The solution is simple: Just explicitly call the `codegen_unit` query for
// each CGU, right after partitioning. This way `try_mark_green` will always
// hit the cache instead of having to go through `force_from_dep_node`.
// This assertion makes sure, we actually keep applying the solution above.
debug_assert!(
dep_node.kind != DepKind::codegen_unit,
"calling force_from_dep_node() on DepKind::codegen_unit"
);

if let Some(key) = Q::Key::recover(tcx, &dep_node) {
#[cfg(debug_assertions)]
let _guard = tracing::span!(tracing::Level::TRACE, stringify!($name), ?key).entered();
Expand Down
73 changes: 73 additions & 0 deletions compiler/rustc_query_system/src/dep_graph/dep_node.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,7 @@ use crate::ich::StableHashingContext;

use rustc_data_structures::fingerprint::{Fingerprint, PackedFingerprint};
use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
use rustc_hir::definitions::DefPathHash;
use std::fmt;
use std::hash::Hash;

Expand Down Expand Up @@ -88,6 +89,17 @@ impl<K: DepKind> DepNode<K> {

dep_node
}

/// Construct a DepNode from the given DepKind and DefPathHash. This
/// method will assert that the given DepKind actually requires a
/// single DefId/DefPathHash parameter.
pub fn from_def_path_hash<Ctxt>(tcx: Ctxt, def_path_hash: DefPathHash, kind: K) -> Self
where
Ctxt: super::DepContext<DepKind = K>,
{
debug_assert!(tcx.fingerprint_style(kind) == FingerprintStyle::DefPathHash);
DepNode { kind, hash: def_path_hash.0.into() }
}
}

impl<K: DepKind> fmt::Debug for DepNode<K> {
Expand Down Expand Up @@ -149,6 +161,67 @@ where
}
}

/// This struct stores metadata about each DepKind.
///
/// Information is retrieved by indexing the `DEP_KINDS` array using the integer value
/// of the `DepKind`. Overall, this allows to implement `DepContext` using this manual
/// jump table instead of large matches.
pub struct DepKindStruct<CTX: DepContext> {
/// Anonymous queries cannot be replayed from one compiler invocation to the next.
/// When their result is needed, it is recomputed. They are useful for fine-grained
/// dependency tracking, and caching within one compiler invocation.
pub is_anon: bool,

/// Eval-always queries do not track their dependencies, and are always recomputed, even if
/// their inputs have not changed since the last compiler invocation. The result is still
/// cached within one compiler invocation.
pub is_eval_always: bool,

/// Whether the query key can be recovered from the hashed fingerprint.
/// See [DepNodeParams] trait for the behaviour of each key type.
pub fingerprint_style: FingerprintStyle,

/// The red/green evaluation system will try to mark a specific DepNode in the
/// dependency graph as green by recursively trying to mark the dependencies of
/// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode`
/// where we don't know if it is red or green and we therefore actually have
/// to recompute its value in order to find out. Since the only piece of
/// information that we have at that point is the `DepNode` we are trying to
/// re-evaluate, we need some way to re-run a query from just that. This is what
/// `force_from_dep_node()` implements.
///
/// In the general case, a `DepNode` consists of a `DepKind` and an opaque
/// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint
/// is usually constructed by computing a stable hash of the query-key that the
/// `DepNode` corresponds to. Consequently, it is not in general possible to go
/// back from hash to query-key (since hash functions are not reversible). For
/// this reason `force_from_dep_node()` is expected to fail from time to time
/// because we just cannot find out, from the `DepNode` alone, what the
/// corresponding query-key is and therefore cannot re-run the query.
///
/// The system deals with this case letting `try_mark_green` fail which forces
/// the root query to be re-evaluated.
///
/// Now, if `force_from_dep_node()` would always fail, it would be pretty useless.
/// Fortunately, we can use some contextual information that will allow us to
/// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we
/// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a
/// valid `DefPathHash`. Since we also always build a huge table that maps every
/// `DefPathHash` in the current codebase to the corresponding `DefId`, we have
/// everything we need to re-run the query.
///
/// Take the `mir_promoted` query as an example. Like many other queries, it
/// just has a single parameter: the `DefId` of the item it will compute the
/// validated MIR for. Now, when we call `force_from_dep_node()` on a `DepNode`
/// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode`
/// is actually a `DefPathHash`, and can therefore just look up the corresponding
/// `DefId` in `tcx.def_path_hash_to_def_id`.
pub force_from_dep_node: Option<fn(tcx: CTX, dep_node: DepNode<CTX::DepKind>) -> bool>,

/// Invoke a query to put the on-disk cached value in memory.
pub try_load_from_on_disk_cache: Option<fn(CTX, DepNode<CTX::DepKind>)>,
}

/// A "work product" corresponds to a `.o` (or other) file that we
/// save in between runs. These IDs do not have a `DefId` but rather
/// some independent path or string that persists between runs without
Expand Down
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