Auto merge of #108638 - Zoxc:erase-query-values-map, r=cjgillot

Use dynamic dispatch for queries

This replaces most concrete query values `V` with `MaybeUninit<[u8; { size_of::<V>() }]>` reducing the code instantiated by queries. The compile time of `rustc_query_impl` is reduced by 27%. It is an alternative to https://github.com/rust-lang/rust/pull/107937 which uses unstable const generics while this uses a `EraseType` trait which maps query values to their erased variant.

This is achieved by introducing an `Erased` type which does sanity check with `cfg(debug_assertions)`. The query caches gets instantiated with these erased types leaving the code in `rustc_query_system` unaware of them. `rustc_query_system` is changed to use instances of `QueryConfig` so that `rustc_query_impl` can pass in `DynamicConfig` which holds a pointer to a virtual table.

<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check</td><td align="right">1.7055s</td><td align="right">1.6949s</td><td align="right"> -0.62%</td></tr><tr><td>🟣 <b>hyper</b>:check</td><td align="right">0.2547s</td><td align="right">0.2528s</td><td align="right"> -0.73%</td></tr><tr><td>🟣 <b>regex</b>:check</td><td align="right">0.9590s</td><td align="right">0.9553s</td><td align="right"> -0.39%</td></tr><tr><td>🟣 <b>syn</b>:check</td><td align="right">1.5457s</td><td align="right">1.5440s</td><td align="right"> -0.11%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check</td><td align="right">5.9092s</td><td align="right">5.9009s</td><td align="right"> -0.14%</td></tr><tr><td>Total</td><td align="right">10.3741s</td><td align="right">10.3479s</td><td align="right"> -0.25%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9960s</td><td align="right"> -0.40%</td></tr></table>

<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check:initial</td><td align="right">2.0605s</td><td align="right">2.0575s</td><td align="right"> -0.15%</td></tr><tr><td>🟣 <b>hyper</b>:check:initial</td><td align="right">0.3218s</td><td align="right">0.3216s</td><td align="right"> -0.07%</td></tr><tr><td>🟣 <b>regex</b>:check:initial</td><td align="right">1.1848s</td><td align="right">1.1839s</td><td align="right"> -0.07%</td></tr><tr><td>🟣 <b>syn</b>:check:initial</td><td align="right">1.9409s</td><td align="right">1.9376s</td><td align="right"> -0.17%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check:initial</td><td align="right">7.3105s</td><td align="right">7.2928s</td><td align="right"> -0.24%</td></tr><tr><td>Total</td><td align="right">12.8185s</td><td align="right">12.7935s</td><td align="right"> -0.20%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">0.9986s</td><td align="right"> -0.14%</td></tr></table>

<table><tr><td rowspan="2">Benchmark</td><td colspan="1"><b>Before</b></th><td colspan="2"><b>After</b></th></tr><tr><td align="right">Time</td><td align="right">Time</td><td align="right">%</th></tr><tr><td>🟣 <b>clap</b>:check:unchanged</td><td align="right">0.4606s</td><td align="right">0.4617s</td><td align="right"> 0.24%</td></tr><tr><td>🟣 <b>hyper</b>:check:unchanged</td><td align="right">0.1335s</td><td align="right">0.1336s</td><td align="right"> 0.08%</td></tr><tr><td>🟣 <b>regex</b>:check:unchanged</td><td align="right">0.3324s</td><td align="right">0.3346s</td><td align="right"> 0.65%</td></tr><tr><td>🟣 <b>syn</b>:check:unchanged</td><td align="right">0.6268s</td><td align="right">0.6307s</td><td align="right"> 0.64%</td></tr><tr><td>🟣 <b>syntex_syntax</b>:check:unchanged</td><td align="right">1.8248s</td><td align="right">1.8508s</td><td align="right">💔  1.43%</td></tr><tr><td>Total</td><td align="right">3.3779s</td><td align="right">3.4113s</td><td align="right"> 0.99%</td></tr><tr><td>Summary</td><td align="right">1.0000s</td><td align="right">1.0061s</td><td align="right"> 0.61%</td></tr></table>

It's based on https://github.com/rust-lang/rust/pull/108167.

r? `@cjgillot`

3 files changed, 42 insertions, 52 deletions

diff --git a/compiler/rustc_query_system/src/query/config.rs b/compiler/rustc_query_system/src/query/config.rs
index bb9ea50a1ea..7e47d701205 100644
--- a/compiler/rustc_query_system/src/query/config.rs
+++ b/compiler/rustc_query_system/src/query/config.rs
@@ -4,6 +4,7 @@ use crate::dep_graph::{DepNode, DepNodeParams, SerializedDepNodeIndex};
 use crate::error::HandleCycleError;
 use crate::ich::StableHashingContext;
 use crate::query::caches::QueryCache;
+use crate::query::DepNodeIndex;
 use crate::query::{QueryContext, QueryInfo, QueryState};
 
 use rustc_data_structures::fingerprint::Fingerprint;
@@ -12,8 +13,6 @@ use std::hash::Hash;
 
 pub type HashResult<V> = Option<fn(&mut StableHashingContext<'_>, &V) -> Fingerprint>;
 
-pub type TryLoadFromDisk<Qcx, V> = Option<fn(Qcx, SerializedDepNodeIndex) -> Option<V>>;
-
 pub trait QueryConfig<Qcx: QueryContext>: Copy {
     fn name(self) -> &'static str;
 
@@ -43,7 +42,13 @@ pub trait QueryConfig<Qcx: QueryContext>: Copy {
 
     fn compute(self, tcx: Qcx, key: Self::Key) -> Self::Value;
 
-    fn try_load_from_disk(self, qcx: Qcx, idx: &Self::Key) -> TryLoadFromDisk<Qcx, Self::Value>;
+    fn try_load_from_disk(
+        self,
+        tcx: Qcx,
+        key: &Self::Key,
+        prev_index: SerializedDepNodeIndex,
+        index: DepNodeIndex,
+    ) -> Option<Self::Value>;
 
     fn loadable_from_disk(self, qcx: Qcx, key: &Self::Key, idx: SerializedDepNodeIndex) -> bool;
 
diff --git a/compiler/rustc_query_system/src/query/mod.rs b/compiler/rustc_query_system/src/query/mod.rs
index fa1f51b04da..f7619d75be7 100644
--- a/compiler/rustc_query_system/src/query/mod.rs
+++ b/compiler/rustc_query_system/src/query/mod.rs
@@ -12,7 +12,7 @@ pub use self::caches::{
 };
 
 mod config;
-pub use self::config::{HashResult, QueryConfig, TryLoadFromDisk};
+pub use self::config::{HashResult, QueryConfig};
 
 use crate::dep_graph::DepKind;
 use crate::dep_graph::{DepNodeIndex, HasDepContext, SerializedDepNodeIndex};
diff --git a/compiler/rustc_query_system/src/query/plumbing.rs b/compiler/rustc_query_system/src/query/plumbing.rs
index 3b17c665fb7..4aaedc7a6c1 100644
--- a/compiler/rustc_query_system/src/query/plumbing.rs
+++ b/compiler/rustc_query_system/src/query/plumbing.rs
@@ -564,59 +564,44 @@ where
 
     // First we try to load the result from the on-disk cache.
     // Some things are never cached on disk.
-    if let Some(try_load_from_disk) = query.try_load_from_disk(qcx, &key) {
-        let prof_timer = qcx.dep_context().profiler().incr_cache_loading();
-
-        // The call to `with_query_deserialization` enforces that no new `DepNodes`
-        // are created during deserialization. See the docs of that method for more
-        // details.
-        let result = qcx
-            .dep_context()
-            .dep_graph()
-            .with_query_deserialization(|| try_load_from_disk(qcx, prev_dep_node_index));
-
-        prof_timer.finish_with_query_invocation_id(dep_node_index.into());
-
-        if let Some(result) = result {
-            if std::intrinsics::unlikely(
-                qcx.dep_context().sess().opts.unstable_opts.query_dep_graph,
-            ) {
-                dep_graph_data.mark_debug_loaded_from_disk(*dep_node)
-            }
-
-            let prev_fingerprint = dep_graph_data.prev_fingerprint_of(prev_dep_node_index);
-            // If `-Zincremental-verify-ich` is specified, re-hash results from
-            // the cache and make sure that they have the expected fingerprint.
-            //
-            // If not, we still seek to verify a subset of fingerprints loaded
-            // from disk. Re-hashing results is fairly expensive, so we can't
-            // currently afford to verify every hash. This subset should still
-            // give us some coverage of potential bugs though.
-            let try_verify = prev_fingerprint.split().1.as_u64() % 32 == 0;
-            if std::intrinsics::unlikely(
-                try_verify || qcx.dep_context().sess().opts.unstable_opts.incremental_verify_ich,
-            ) {
-                incremental_verify_ich(
-                    *qcx.dep_context(),
-                    dep_graph_data,
-                    &result,
-                    prev_dep_node_index,
-                    query.hash_result(),
-                    query.format_value(),
-                );
-            }
+    if let Some(result) = query.try_load_from_disk(qcx, key, prev_dep_node_index, dep_node_index) {
+        if std::intrinsics::unlikely(qcx.dep_context().sess().opts.unstable_opts.query_dep_graph) {
+            dep_graph_data.mark_debug_loaded_from_disk(*dep_node)
+        }
 
-            return Some((result, dep_node_index));
+        let prev_fingerprint = dep_graph_data.prev_fingerprint_of(prev_dep_node_index);
+        // If `-Zincremental-verify-ich` is specified, re-hash results from
+        // the cache and make sure that they have the expected fingerprint.
+        //
+        // If not, we still seek to verify a subset of fingerprints loaded
+        // from disk. Re-hashing results is fairly expensive, so we can't
+        // currently afford to verify every hash. This subset should still
+        // give us some coverage of potential bugs though.
+        let try_verify = prev_fingerprint.split().1.as_u64() % 32 == 0;
+        if std::intrinsics::unlikely(
+            try_verify || qcx.dep_context().sess().opts.unstable_opts.incremental_verify_ich,
+        ) {
+            incremental_verify_ich(
+                *qcx.dep_context(),
+                dep_graph_data,
+                &result,
+                prev_dep_node_index,
+                query.hash_result(),
+                query.format_value(),
+            );
         }
 
-        // We always expect to find a cached result for things that
-        // can be forced from `DepNode`.
-        debug_assert!(
-            !qcx.dep_context().fingerprint_style(dep_node.kind).reconstructible(),
-            "missing on-disk cache entry for reconstructible {dep_node:?}"
-        );
+        return Some((result, dep_node_index));
     }
 
+    // We always expect to find a cached result for things that
+    // can be forced from `DepNode`.
+    debug_assert!(
+        !query.cache_on_disk(*qcx.dep_context(), key)
+            || !qcx.dep_context().fingerprint_style(dep_node.kind).reconstructible(),
+        "missing on-disk cache entry for {dep_node:?}"
+    );
+
     // Sanity check for the logic in `ensure`: if the node is green and the result loadable,
     // we should actually be able to load it.
     debug_assert!(