Make force_from_dep_node a function pointer.
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bee1fbb67e
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@ -66,6 +66,7 @@ use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, CRATE_DEF_INDEX};
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use rustc_hir::definitions::DefPathHash;
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use rustc_hir::HirId;
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use rustc_span::symbol::Symbol;
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use rustc_span::DUMMY_SP;
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use std::hash::Hash;
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pub use rustc_query_system::dep_graph::{DepContext, DepNodeParams};
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@ -95,6 +96,50 @@ pub struct DepKindStruct {
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// can be made a specialized associated const.
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can_reconstruct_query_key: fn() -> bool,
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/// The red/green evaluation system will try to mark a specific DepNode in the
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/// dependency graph as green by recursively trying to mark the dependencies of
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/// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode`
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/// where we don't know if it is red or green and we therefore actually have
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/// to recompute its value in order to find out. Since the only piece of
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/// information that we have at that point is the `DepNode` we are trying to
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/// re-evaluate, we need some way to re-run a query from just that. This is what
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/// `force_from_dep_node()` implements.
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///
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/// In the general case, a `DepNode` consists of a `DepKind` and an opaque
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/// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint
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/// is usually constructed by computing a stable hash of the query-key that the
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/// `DepNode` corresponds to. Consequently, it is not in general possible to go
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/// back from hash to query-key (since hash functions are not reversible). For
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/// this reason `force_from_dep_node()` is expected to fail from time to time
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/// because we just cannot find out, from the `DepNode` alone, what the
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/// corresponding query-key is and therefore cannot re-run the query.
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///
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/// The system deals with this case letting `try_mark_green` fail which forces
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/// the root query to be re-evaluated.
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///
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/// Now, if `force_from_dep_node()` would always fail, it would be pretty useless.
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/// Fortunately, we can use some contextual information that will allow us to
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/// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we
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/// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a
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/// valid `DefPathHash`. Since we also always build a huge table that maps every
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/// `DefPathHash` in the current codebase to the corresponding `DefId`, we have
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/// everything we need to re-run the query.
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///
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/// Take the `mir_promoted` query as an example. Like many other queries, it
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/// just has a single parameter: the `DefId` of the item it will compute the
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/// validated MIR for. Now, when we call `force_from_dep_node()` on a `DepNode`
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/// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode`
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/// is actually a `DefPathHash`, and can therefore just look up the corresponding
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/// `DefId` in `tcx.def_path_hash_to_def_id`.
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///
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/// When you implement a new query, it will likely have a corresponding new
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/// `DepKind`, and you'll have to support it here in `force_from_dep_node()`. As
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/// a rule of thumb, if your query takes a `DefId` or `LocalDefId` as sole parameter,
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/// then `force_from_dep_node()` should not fail for it. Otherwise, you can just
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/// add it to the "We don't have enough information to reconstruct..." group in
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/// the match below.
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pub(super) force_from_dep_node: fn(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool,
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/// Invoke a query to put the on-disk cached value in memory.
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pub(super) try_load_from_on_disk_cache: fn(TyCtxt<'_>, &DepNode),
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}
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@ -156,7 +201,7 @@ macro_rules! contains_eval_always_attr {
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pub mod dep_kind {
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use super::*;
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use crate::ty::query::{queries, query_keys};
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use rustc_query_system::query::QueryDescription;
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use rustc_query_system::query::{force_query, QueryDescription};
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// We use this for most things when incr. comp. is turned off.
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pub const Null: DepKindStruct = DepKindStruct {
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@ -165,6 +210,7 @@ pub mod dep_kind {
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is_eval_always: false,
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can_reconstruct_query_key: || true,
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force_from_dep_node: |_, dep_node| bug!("force_from_dep_node: encountered {:?}", dep_node),
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try_load_from_on_disk_cache: |_, _| {},
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};
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@ -175,6 +221,7 @@ pub mod dep_kind {
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is_eval_always: true,
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can_reconstruct_query_key: || true,
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force_from_dep_node: |_, dep_node| bug!("force_from_dep_node: encountered {:?}", dep_node),
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try_load_from_on_disk_cache: |_, _| {},
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};
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@ -184,6 +231,7 @@ pub mod dep_kind {
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is_eval_always: false,
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can_reconstruct_query_key: || false,
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force_from_dep_node: |_, _| false,
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try_load_from_on_disk_cache: |_, _| {},
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};
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@ -193,6 +241,7 @@ pub mod dep_kind {
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is_eval_always: false,
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can_reconstruct_query_key: || false,
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force_from_dep_node: |_, _| false,
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try_load_from_on_disk_cache: |_, _| {},
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};
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@ -217,6 +266,24 @@ pub mod dep_kind {
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<query_keys::$variant<'_> as DepNodeParams<TyCtxt<'_>>>::recover(tcx, dep_node)
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}
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fn force_from_dep_node(tcx: TyCtxt<'_>, dep_node: &DepNode) -> bool {
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if !can_reconstruct_query_key() {
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return false;
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}
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if let Some(key) = recover(tcx, dep_node) {
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force_query::<queries::$variant<'_>, _>(
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tcx,
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key,
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DUMMY_SP,
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*dep_node
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);
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return true;
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}
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false
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}
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fn try_load_from_on_disk_cache(tcx: TyCtxt<'_>, dep_node: &DepNode) {
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if !can_reconstruct_query_key() {
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return
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@ -238,6 +305,7 @@ pub mod dep_kind {
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is_anon,
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is_eval_always,
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can_reconstruct_query_key,
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force_from_dep_node,
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try_load_from_on_disk_cache,
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}
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};)*
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@ -8,7 +8,6 @@ use rustc_hir::def_id::LocalDefId;
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mod dep_node;
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pub(crate) use rustc_query_system::dep_graph::DepNodeParams;
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pub use rustc_query_system::dep_graph::{
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debug, hash_result, DepContext, DepNodeColor, DepNodeIndex, SerializedDepNodeIndex,
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WorkProduct, WorkProductId,
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@ -155,7 +154,26 @@ impl<'tcx> DepContext for TyCtxt<'tcx> {
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}
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debug!("try_force_from_dep_node({:?}) --- trying to force", dep_node);
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ty::query::force_from_dep_node(*self, dep_node)
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// We must avoid ever having to call `force_from_dep_node()` for a
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// `DepNode::codegen_unit`:
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// Since we cannot reconstruct the query key of a `DepNode::codegen_unit`, we
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// would always end up having to evaluate the first caller of the
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// `codegen_unit` query that *is* reconstructible. This might very well be
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// the `compile_codegen_unit` query, thus re-codegenning the whole CGU just
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// to re-trigger calling the `codegen_unit` query with the right key. At
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// that point we would already have re-done all the work we are trying to
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// avoid doing in the first place.
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// The solution is simple: Just explicitly call the `codegen_unit` query for
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// each CGU, right after partitioning. This way `try_mark_green` will always
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// hit the cache instead of having to go through `force_from_dep_node`.
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// This assertion makes sure, we actually keep applying the solution above.
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debug_assert!(
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dep_node.kind != DepKind::codegen_unit,
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"calling force_from_dep_node() on DepKind::codegen_unit"
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);
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(dep_node.kind.force_from_dep_node)(*self, dep_node)
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}
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fn has_errors_or_delayed_span_bugs(&self) -> bool {
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@ -1,4 +1,4 @@
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use crate::dep_graph::{self, DepKind, DepNode, DepNodeParams};
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use crate::dep_graph;
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use crate::hir::exports::Export;
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use crate::hir::map;
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use crate::infer::canonical::{self, Canonical};
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@ -103,112 +103,6 @@ pub use self::profiling_support::{IntoSelfProfilingString, QueryKeyStringBuilder
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rustc_query_append! { [define_queries!][<'tcx>] }
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/// The red/green evaluation system will try to mark a specific DepNode in the
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/// dependency graph as green by recursively trying to mark the dependencies of
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/// that `DepNode` as green. While doing so, it will sometimes encounter a `DepNode`
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/// where we don't know if it is red or green and we therefore actually have
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/// to recompute its value in order to find out. Since the only piece of
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/// information that we have at that point is the `DepNode` we are trying to
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/// re-evaluate, we need some way to re-run a query from just that. This is what
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/// `force_from_dep_node()` implements.
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///
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/// In the general case, a `DepNode` consists of a `DepKind` and an opaque
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/// GUID/fingerprint that will uniquely identify the node. This GUID/fingerprint
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/// is usually constructed by computing a stable hash of the query-key that the
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/// `DepNode` corresponds to. Consequently, it is not in general possible to go
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/// back from hash to query-key (since hash functions are not reversible). For
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/// this reason `force_from_dep_node()` is expected to fail from time to time
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/// because we just cannot find out, from the `DepNode` alone, what the
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/// corresponding query-key is and therefore cannot re-run the query.
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///
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/// The system deals with this case letting `try_mark_green` fail which forces
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/// the root query to be re-evaluated.
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///
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/// Now, if `force_from_dep_node()` would always fail, it would be pretty useless.
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/// Fortunately, we can use some contextual information that will allow us to
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/// reconstruct query-keys for certain kinds of `DepNode`s. In particular, we
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/// enforce by construction that the GUID/fingerprint of certain `DepNode`s is a
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/// valid `DefPathHash`. Since we also always build a huge table that maps every
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/// `DefPathHash` in the current codebase to the corresponding `DefId`, we have
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/// everything we need to re-run the query.
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///
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/// Take the `mir_promoted` query as an example. Like many other queries, it
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/// just has a single parameter: the `DefId` of the item it will compute the
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/// validated MIR for. Now, when we call `force_from_dep_node()` on a `DepNode`
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/// with kind `MirValidated`, we know that the GUID/fingerprint of the `DepNode`
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/// is actually a `DefPathHash`, and can therefore just look up the corresponding
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/// `DefId` in `tcx.def_path_hash_to_def_id`.
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///
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/// When you implement a new query, it will likely have a corresponding new
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/// `DepKind`, and you'll have to support it here in `force_from_dep_node()`. As
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/// a rule of thumb, if your query takes a `DefId` or `LocalDefId` as sole parameter,
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/// then `force_from_dep_node()` should not fail for it. Otherwise, you can just
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/// add it to the "We don't have enough information to reconstruct..." group in
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/// the match below.
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pub fn force_from_dep_node<'tcx>(tcx: TyCtxt<'tcx>, dep_node: &DepNode) -> bool {
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// We must avoid ever having to call `force_from_dep_node()` for a
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// `DepNode::codegen_unit`:
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// Since we cannot reconstruct the query key of a `DepNode::codegen_unit`, we
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// would always end up having to evaluate the first caller of the
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// `codegen_unit` query that *is* reconstructible. This might very well be
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// the `compile_codegen_unit` query, thus re-codegenning the whole CGU just
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// to re-trigger calling the `codegen_unit` query with the right key. At
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// that point we would already have re-done all the work we are trying to
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// avoid doing in the first place.
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// The solution is simple: Just explicitly call the `codegen_unit` query for
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// each CGU, right after partitioning. This way `try_mark_green` will always
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// hit the cache instead of having to go through `force_from_dep_node`.
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// This assertion makes sure, we actually keep applying the solution above.
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debug_assert!(
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dep_node.kind != DepKind::codegen_unit,
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"calling force_from_dep_node() on DepKind::codegen_unit"
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);
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if !dep_node.kind.can_reconstruct_query_key() {
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return false;
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}
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macro_rules! force_from_dep_node {
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($($(#[$attr:meta])* [$($modifiers:tt)*] $name:ident($K:ty),)*) => {
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match dep_node.kind {
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// These are inputs that are expected to be pre-allocated and that
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// should therefore always be red or green already.
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DepKind::CrateMetadata |
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// These are anonymous nodes.
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DepKind::TraitSelect |
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// We don't have enough information to reconstruct the query key of
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// these.
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DepKind::CompileCodegenUnit |
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// Forcing this makes no sense.
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DepKind::Null => {
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bug!("force_from_dep_node: encountered {:?}", dep_node)
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}
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$(DepKind::$name => {
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debug_assert!(<$K as DepNodeParams<TyCtxt<'_>>>::can_reconstruct_query_key());
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if let Some(key) = <$K as DepNodeParams<TyCtxt<'_>>>::recover(tcx, dep_node) {
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force_query::<queries::$name<'_>, _>(
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tcx,
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key,
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DUMMY_SP,
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*dep_node
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);
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return true;
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}
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})*
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}
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}
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}
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rustc_dep_node_append! { [force_from_dep_node!][] }
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false
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}
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mod sealed {
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use super::{DefId, LocalDefId};
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