Compute default query providers at compile-time

All of the `provide` functions are made `const`, allowing
us to compute the default local and extern query providers
entirely at compile-time.

In addition to moving runtime work to compile-time, this will
allow our internal documentation to show all query implementations,
once #87038 is implemented.

Author: Aaron1011

compiler/rustc_codegen_ssa/src/back/symbol_export.rs

@@ -357,7 +357,7 @@ fn is_unreachable_local_definition_provider(tcx: TyCtxt<'_>, def_id: LocalDefId)
     !tcx.reachable_set(()).contains(&def_id)
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.reachable_non_generics = reachable_non_generics_provider;
     providers.is_reachable_non_generic = is_reachable_non_generic_provider_local;
     providers.exported_symbols = exported_symbols_provider_local;
@@ -367,7 +367,7 @@ pub fn provide(providers: &mut Providers) {
     providers.wasm_import_module_map = wasm_import_module_map;
 }
 
-pub fn provide_extern(providers: &mut Providers) {
+pub const fn provide_extern(providers: &mut Providers) {
     providers.is_reachable_non_generic = is_reachable_non_generic_provider_extern;
     providers.upstream_monomorphizations_for = upstream_monomorphizations_for_provider;
 }

compiler/rustc_codegen_ssa/src/base.rs

@@ -849,7 +849,7 @@ impl CrateInfo {
     }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.backend_optimization_level = |tcx, cratenum| {
         let for_speed = match tcx.sess.opts.optimize {
             // If globally no optimisation is done, #[optimize] has no effect.

compiler/rustc_codegen_ssa/src/lib.rs

@@ -5,6 +5,8 @@
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(associated_type_bounds)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 //! This crate contains codegen code that is used by all codegen backends (LLVM and others).
@@ -161,13 +163,13 @@ pub struct CodegenResults {
     pub crate_info: CrateInfo,
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     crate::back::symbol_export::provide(providers);
     crate::base::provide(providers);
     crate::target_features::provide(providers);
 }
 
-pub fn provide_extern(providers: &mut Providers) {
+pub const fn provide_extern(providers: &mut Providers) {
     crate::back::symbol_export::provide_extern(providers);
 }
 

compiler/rustc_codegen_ssa/src/target_features.rs

@@ -245,7 +245,7 @@ pub fn supported_target_features(sess: &Session) -> &'static [(&'static str, Opt
     }
 }
 
-pub(crate) fn provide(providers: &mut Providers) {
+pub(crate) const fn provide(providers: &mut Providers) {
     providers.supported_target_features = |tcx, cnum| {
         assert_eq!(cnum, LOCAL_CRATE);
         if tcx.sess.opts.actually_rustdoc {

compiler/rustc_interface/src/lib.rs

@@ -1,5 +1,7 @@
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![feature(internal_output_capture)]
 #![feature(nll)]
 #![feature(once_cell)]

compiler/rustc_interface/src/passes.rs

@@ -45,7 +45,6 @@ use std::any::Any;
 use std::cell::RefCell;
 use std::ffi::OsString;
 use std::io::{self, BufWriter, Write};
-use std::lazy::SyncLazy;
 use std::marker::PhantomPinned;
 use std::path::PathBuf;
 use std::pin::Pin;
@@ -737,35 +736,35 @@ pub fn prepare_outputs(
     Ok(outputs)
 }
 
-pub static DEFAULT_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
-    let providers = &mut Providers::default();
+pub const DEFAULT_QUERY_PROVIDERS: Providers = {
+    let mut providers = Providers::default();
     providers.analysis = analysis;
-    proc_macro_decls::provide(providers);
-    plugin::build::provide(providers);
-    rustc_middle::hir::provide(providers);
-    mir::provide(providers);
-    mir_build::provide(providers);
-    rustc_privacy::provide(providers);
-    typeck::provide(providers);
-    ty::provide(providers);
-    traits::provide(providers);
-    rustc_passes::provide(providers);
-    rustc_resolve::provide(providers);
-    rustc_traits::provide(providers);
-    rustc_ty_utils::provide(providers);
-    rustc_metadata::provide(providers);
-    rustc_lint::provide(providers);
-    rustc_symbol_mangling::provide(providers);
-    rustc_codegen_ssa::provide(providers);
-    *providers
-});
-
-pub static DEFAULT_EXTERN_QUERY_PROVIDERS: SyncLazy<Providers> = SyncLazy::new(|| {
-    let mut extern_providers = *DEFAULT_QUERY_PROVIDERS;
+    proc_macro_decls::provide(&mut providers);
+    plugin::build::provide(&mut providers);
+    rustc_middle::hir::provide(&mut providers);
+    mir::provide(&mut providers);
+    mir_build::provide(&mut providers);
+    rustc_privacy::provide(&mut providers);
+    typeck::provide(&mut providers);
+    ty::provide(&mut providers);
+    traits::provide(&mut providers);
+    rustc_passes::provide(&mut providers);
+    rustc_resolve::provide(&mut providers);
+    rustc_traits::provide(&mut providers);
+    rustc_ty_utils::provide(&mut providers);
+    rustc_metadata::provide(&mut providers);
+    rustc_lint::provide(&mut providers);
+    rustc_symbol_mangling::provide(&mut providers);
+    rustc_codegen_ssa::provide(&mut providers);
+    providers
+};
+
+pub const DEFAULT_EXTERN_QUERY_PROVIDERS: Providers = {
+    let mut extern_providers = DEFAULT_QUERY_PROVIDERS;
     rustc_metadata::provide_extern(&mut extern_providers);
     rustc_codegen_ssa::provide_extern(&mut extern_providers);
     extern_providers
-});
+};
 
 pub struct QueryContext<'tcx> {
     gcx: &'tcx GlobalCtxt<'tcx>,
@@ -808,10 +807,10 @@ pub fn create_global_ctxt<'tcx>(
     let query_result_on_disk_cache = rustc_incremental::load_query_result_cache(sess);
 
     let codegen_backend = compiler.codegen_backend();
-    let mut local_providers = *DEFAULT_QUERY_PROVIDERS;
+    let mut local_providers = DEFAULT_QUERY_PROVIDERS;
     codegen_backend.provide(&mut local_providers);
 
-    let mut extern_providers = *DEFAULT_EXTERN_QUERY_PROVIDERS;
+    let mut extern_providers = DEFAULT_EXTERN_QUERY_PROVIDERS;
     codegen_backend.provide(&mut extern_providers);
     codegen_backend.provide_extern(&mut extern_providers);
 

compiler/rustc_interface/src/proc_macro_decls.rs

@@ -32,6 +32,6 @@ impl<'v> ItemLikeVisitor<'v> for Finder<'_> {
     fn visit_foreign_item(&mut self, _foreign_item: &hir::ForeignItem<'_>) {}
 }
 
-pub(crate) fn provide(providers: &mut Providers) {
+pub(crate) const fn provide(providers: &mut Providers) {
     *providers = Providers { proc_macro_decls_static, ..*providers };
 }

compiler/rustc_lint/src/levels.rs

@@ -698,6 +698,6 @@ impl<'tcx> intravisit::Visitor<'tcx> for LintLevelMapBuilder<'_, 'tcx> {
     }
 }
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     providers.lint_levels = lint_levels;
 }

compiler/rustc_lint/src/lib.rs

@@ -37,6 +37,8 @@
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(control_flow_enum)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 #[macro_use]
@@ -96,7 +98,7 @@ pub use rustc_session::lint::Level::{self, *};
 pub use rustc_session::lint::{BufferedEarlyLint, FutureIncompatibleInfo, Lint, LintId};
 pub use rustc_session::lint::{LintArray, LintPass};
 
-pub fn provide(providers: &mut Providers) {
+pub const fn provide(providers: &mut Providers) {
     levels::provide(providers);
     *providers = Providers { lint_mod, ..*providers };
 }

compiler/rustc_metadata/src/lib.rs

@@ -8,6 +8,8 @@
 #![feature(min_specialization)]
 #![feature(try_blocks)]
 #![feature(never_type)]
+#![feature(const_fn_fn_ptr_basics)]
+#![feature(const_mut_refs)]
 #![recursion_limit = "256"]
 
 extern crate proc_macro;