Auto merge of #136201 - davidv1992:eliminate-field-offset-alt, r=<try>

Removed dependency on the field-offset crate, alternate approach

This is an alternate approach to reach the same goals as #136003. As it touches the core of the query system, this too probably should be evaluated for performance.

r? `@Mark-Simulacrum`

Author: bors

Cargo.lock

@@ -1195,16 +1195,6 @@ version = "2.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "37909eebbb50d72f9059c3b6d82c0463f2ff062c9e95845c43a6c9c0355411be"
 
-[[package]]
-name = "field-offset"
-version = "0.3.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "38e2275cc4e4fc009b0669731a1e5ab7ebf11f469eaede2bab9309a5b4d6057f"
-dependencies = [
- "memoffset",
- "rustc_version",
-]
-
 [[package]]
 name = "filetime"
 version = "0.2.25"
@@ -2269,15 +2259,6 @@ dependencies = [
  "libc",
 ]
 
-[[package]]
-name = "memoffset"
-version = "0.9.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "488016bfae457b036d996092f6cb448677611ce4449e970ceaf42695203f218a"
-dependencies = [
- "autocfg",
-]
-
 [[package]]
 name = "mime"
 version = "0.3.17"
@@ -4119,7 +4100,6 @@ version = "0.0.0"
 dependencies = [
  "bitflags",
  "either",
- "field-offset",
  "gsgdt",
  "polonius-engine",
  "rustc-rayon-core",
@@ -4365,7 +4345,6 @@ dependencies = [
 name = "rustc_query_impl"
 version = "0.0.0"
 dependencies = [
- "field-offset",
  "measureme",
  "rustc_data_structures",
  "rustc_errors",

compiler/rustc_middle/Cargo.toml

@@ -7,7 +7,6 @@ edition = "2021"
 # tidy-alphabetical-start
 bitflags = "2.4.1"
 either = "1.5.0"
-field-offset = "0.3.5"
 gsgdt = "0.1.2"
 polonius-engine = "0.13.0"
 rustc-rayon-core = { version = "0.5.0" }

compiler/rustc_middle/src/query/plumbing.rs

@@ -1,6 +1,5 @@
 use std::ops::Deref;
 
-use field_offset::FieldOffset;
 use rustc_data_structures::sync::{AtomicU64, WorkerLocal};
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_hir::hir_id::OwnerId;
@@ -24,8 +23,8 @@ 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>>,
-    pub query_cache: FieldOffset<QueryCaches<'tcx>, C>,
+    pub query_state: usize,
+    pub query_cache: usize,
     pub cache_on_disk: fn(tcx: TyCtxt<'tcx>, key: &C::Key) -> bool,
     pub execute_query: fn(tcx: TyCtxt<'tcx>, k: C::Key) -> C::Value,
     pub compute: fn(tcx: TyCtxt<'tcx>, key: C::Key) -> C::Value,

compiler/rustc_query_impl/Cargo.toml

@@ -5,7 +5,6 @@ edition = "2021"
 
 [dependencies]
 # tidy-alphabetical-start
-field-offset = "0.3.5"
 measureme = "11"
 rustc_data_structures = { path = "../rustc_data_structures" }
 rustc_errors = { path = "../rustc_errors" }

compiler/rustc_query_impl/src/lib.rs

@@ -11,7 +11,6 @@
 #![warn(unreachable_pub)]
 // tidy-alphabetical-end
 
-use field_offset::offset_of;
 use rustc_data_structures::stable_hasher::HashStable;
 use rustc_data_structures::sync::AtomicU64;
 use rustc_middle::arena::Arena;
@@ -89,15 +88,27 @@ where
     where
         QueryCtxt<'tcx>: 'a,
     {
-        self.dynamic.query_state.apply(&qcx.tcx.query_system.states)
+        // Safety:
+        // This is just manually doing the subfield referencing through pointer math.
+        unsafe {
+            &*(&qcx.tcx.query_system.states as *const QueryStates<'tcx>)
+                .byte_add(self.dynamic.query_state)
+                .cast::<QueryState<Self::Key>>()
+        }
     }
 
     #[inline(always)]
     fn query_cache<'a>(self, qcx: QueryCtxt<'tcx>) -> &'a Self::Cache
     where
         'tcx: 'a,
     {
-        self.dynamic.query_cache.apply(&qcx.tcx.query_system.caches)
+        // Safety:
+        // This is just manually doing the subfield referencing through pointer math.
+        unsafe {
+            &*(&qcx.tcx.query_system.caches as *const QueryCaches<'tcx>)
+                .byte_add(self.dynamic.query_cache)
+                .cast::<Self::Cache>()
+        }
     }
 
     #[inline(always)]

compiler/rustc_query_impl/src/plumbing.rs

@@ -605,8 +605,8 @@ macro_rules! define_queries {
                     eval_always: is_eval_always!([$($modifiers)*]),
                     dep_kind: dep_graph::dep_kinds::$name,
                     handle_cycle_error: handle_cycle_error!([$($modifiers)*]),
-                    query_state: offset_of!(QueryStates<'tcx> => $name),
-                    query_cache: offset_of!(QueryCaches<'tcx> => $name),
+                    query_state: std::mem::offset_of!(QueryStates<'tcx>, $name),
+                    query_cache: std::mem::offset_of!(QueryCaches<'tcx>, $name),
                     cache_on_disk: |tcx, key| ::rustc_middle::query::cached::$name(tcx, key),
                     execute_query: |tcx, key| erase(tcx.$name(key)),
                     compute: |tcx, key| {

src/tools/tidy/src/deps.rs

@@ -285,7 +285,6 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "expect-test",
     "fallible-iterator", // dependency of `thorin`
     "fastrand",
-    "field-offset",
     "flate2",
     "fluent-bundle",
     "fluent-langneg",
@@ -327,7 +326,6 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "measureme",
     "memchr",
     "memmap2",
-    "memoffset",
     "miniz_oxide",
     "nix",
     "nu-ansi-term",
@@ -367,14 +365,12 @@ const PERMITTED_RUSTC_DEPENDENCIES: &[&str] = &[
     "rustc-rayon-core",
     "rustc-stable-hash",
     "rustc_apfloat",
-    "rustc_version",
     "rustix",
     "ruzstd", // via object in thorin-dwp
     "ryu",
     "scoped-tls",
     "scopeguard",
     "self_cell",
-    "semver",
     "serde",
     "serde_derive",
     "serde_json",