Rollup merge of #136330 - nnethercote:rm-unnecessary-hooks, r=oli-obk

Remove unnecessary hooks

Some hooks can be downgraded to vanilla functions.

r? `@oli-obk`

compiler/rustc_driver_impl/src/pretty.rs

@@ -7,6 +7,7 @@ use rustc_ast_pretty::pprust as pprust_ast;
 use rustc_middle::bug;
 use rustc_middle::mir::{write_mir_graphviz, write_mir_pretty};
 use rustc_middle::ty::{self, TyCtxt};
+use rustc_mir_build::thir::print::{thir_flat, thir_tree};
 use rustc_session::Session;
 use rustc_session::config::{OutFileName, PpHirMode, PpMode, PpSourceMode};
 use rustc_smir::rustc_internal::pretty::write_smir_pretty;
@@ -313,7 +314,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
             tcx.dcx().abort_if_errors();
             debug!("pretty printing THIR tree");
             for did in tcx.hir().body_owners() {
-                let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_tree(did));
+                let _ = writeln!(out, "{:?}:\n{}\n", did, thir_tree(tcx, did));
             }
             out
         }
@@ -324,7 +325,7 @@ pub fn print<'tcx>(sess: &Session, ppm: PpMode, ex: PrintExtra<'tcx>) {
             tcx.dcx().abort_if_errors();
             debug!("pretty printing THIR flat");
             for did in tcx.hir().body_owners() {
-                let _ = writeln!(out, "{:?}:\n{}\n", did, tcx.thir_flat(did));
+                let _ = writeln!(out, "{:?}:\n{}\n", did, thir_flat(tcx, did));
             }
             out
         }

compiler/rustc_middle/src/hooks/mod.rs

@@ -1,7 +1,7 @@
-//! "Hooks" provide a way for `tcx` functionality to be provided by some downstream crate without
-//! everything in rustc having to depend on that crate. This is somewhat similar to queries, but
-//! queries come with a lot of machinery for caching and incremental compilation, whereas hooks are
-//! just plain function pointers without any of the query magic.
+//! "Hooks" let you write `tcx` methods in downstream crates and call them in this crate, reducing
+//! the amount of code that needs to be in this crate (which is already very big). This is somewhat
+//! similar to queries, but queries come with a lot of machinery for caching and incremental
+//! compilation, whereas hooks are just plain function pointers without any of the query magic.
 
 use rustc_hir::def_id::{DefId, DefPathHash};
 use rustc_session::StableCrateId;
@@ -75,12 +75,6 @@ declare_hooks! {
     /// (Eligible functions might nevertheless be skipped for other reasons.)
     hook is_eligible_for_coverage(key: LocalDefId) -> bool;
 
-    /// Create the MIR for a given `DefId` - this includes
-    /// unreachable code.
-    /// You do not want to call this yourself, instead use the cached version
-    /// via `mir_built`
-    hook build_mir(key: LocalDefId) -> mir::Body<'tcx>;
-
     /// Imports all `SourceFile`s from the given crate into the current session.
     /// This normally happens automatically when we decode a `Span` from
     /// that crate's metadata - however, the incr comp cache needs
@@ -99,14 +93,11 @@ declare_hooks! {
     /// Will fetch a DefId from a DefPathHash for a foreign crate.
     hook def_path_hash_to_def_id_extern(hash: DefPathHash, stable_crate_id: StableCrateId) -> DefId;
 
-    /// Create a THIR tree for debugging.
-    hook thir_tree(key: LocalDefId) -> String;
-
-    /// Create a list-like THIR representation for debugging.
-    hook thir_flat(key: LocalDefId) -> String;
-
     /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
     /// can just link to the upstream crate and therefore don't need a mono item.
+    ///
+    /// Note: this hook isn't called within `rustc_middle` but #127779 suggests it's a hook instead
+    /// of a normal function because external tools might want to override it.
     hook should_codegen_locally(instance: crate::ty::Instance<'tcx>) -> bool;
 
     hook alloc_self_profile_query_strings() -> ();

compiler/rustc_mir_build/src/builder/custom/mod.rs

@@ -6,7 +6,7 @@
 //! present, and if so we branch off into this module, which implements the attribute by
 //! implementing a custom lowering from THIR to MIR.
 //!
-//! The result of this lowering is returned "normally" from the `build_mir` hook, with the only
+//! The result of this lowering is returned "normally" from `build_mir`, with the only
 //! notable difference being that the `injected` field in the body is set. Various components of the
 //! MIR pipeline, like borrowck and the pass manager will then consult this field (via
 //! `body.should_skip()`) to skip the parts of the MIR pipeline that precede the MIR phase the user

compiler/rustc_mir_build/src/builder/mod.rs

@@ -20,7 +20,6 @@ use rustc_infer::infer::{InferCtxt, TyCtxtInferExt};
 use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::middle::region;
 use rustc_middle::mir::*;
-use rustc_middle::query::TyCtxtAt;
 use rustc_middle::thir::{self, ExprId, LintLevel, LocalVarId, Param, ParamId, PatKind, Thir};
 use rustc_middle::ty::{self, ScalarInt, Ty, TyCtxt, TypeVisitableExt, TypingMode};
 use rustc_middle::{bug, span_bug};
@@ -45,9 +44,9 @@ pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
         .collect()
 }
 
-/// Construct the MIR for a given `DefId`.
-pub(crate) fn build_mir<'tcx>(tcx: TyCtxtAt<'tcx>, def: LocalDefId) -> Body<'tcx> {
-    let tcx = tcx.tcx;
+/// Create the MIR for a given `DefId`, including unreachable code. Do not call
+/// this directly; instead use the cached version via `mir_built`.
+pub fn build_mir<'tcx>(tcx: TyCtxt<'tcx>, def: LocalDefId) -> Body<'tcx> {
     tcx.ensure_with_value().thir_abstract_const(def);
     if let Err(e) = tcx.check_match(def) {
         return construct_error(tcx, def, e);

compiler/rustc_mir_build/src/lib.rs

@@ -14,11 +14,11 @@
 // The `builder` module used to be named `build`, but that was causing GitHub's
 // "Go to file" feature to silently ignore all files in the module, probably
 // because it assumes that "build" is a build-output directory. See #134365.
-mod builder;
+pub mod builder;
 mod check_tail_calls;
 mod check_unsafety;
 mod errors;
-mod thir;
+pub mod thir;
 
 use rustc_middle::util::Providers;
 
@@ -27,12 +27,9 @@ rustc_fluent_macro::fluent_messages! { "../messages.ftl" }
 pub fn provide(providers: &mut Providers) {
     providers.check_match = thir::pattern::check_match;
     providers.lit_to_const = thir::constant::lit_to_const;
-    providers.hooks.build_mir = builder::build_mir;
     providers.closure_saved_names_of_captured_variables =
         builder::closure_saved_names_of_captured_variables;
     providers.check_unsafety = check_unsafety::check_unsafety;
     providers.check_tail_calls = check_tail_calls::check_tail_calls;
     providers.thir_body = thir::cx::thir_body;
-    providers.hooks.thir_tree = thir::print::thir_tree;
-    providers.hooks.thir_flat = thir::print::thir_flat;
 }

compiler/rustc_mir_build/src/thir/mod.rs

@@ -7,5 +7,5 @@
 pub(crate) mod constant;
 pub(crate) mod cx;
 pub(crate) mod pattern;
-pub(crate) mod print;
+pub mod print;
 mod util;

compiler/rustc_mir_build/src/thir/print.rs

@@ -1,12 +1,13 @@
 use std::fmt::{self, Write};
 
-use rustc_middle::query::TyCtxtAt;
 use rustc_middle::thir::*;
 use rustc_middle::ty;
+use rustc_middle::ty::TyCtxt;
 use rustc_span::def_id::LocalDefId;
 
-pub(crate) fn thir_tree(tcx: TyCtxtAt<'_>, owner_def: LocalDefId) -> String {
-    match super::cx::thir_body(*tcx, owner_def) {
+/// Create a THIR tree for debugging.
+pub fn thir_tree(tcx: TyCtxt<'_>, owner_def: LocalDefId) -> String {
+    match super::cx::thir_body(tcx, owner_def) {
         Ok((thir, _)) => {
             let thir = thir.steal();
             let mut printer = ThirPrinter::new(&thir);
@@ -17,8 +18,9 @@ pub(crate) fn thir_tree(tcx: TyCtxtAt<'_>, owner_def: LocalDefId) -> String {
     }
 }
 
-pub(crate) fn thir_flat(tcx: TyCtxtAt<'_>, owner_def: LocalDefId) -> String {
-    match super::cx::thir_body(*tcx, owner_def) {
+/// Create a list-like THIR representation for debugging.
+pub fn thir_flat(tcx: TyCtxt<'_>, owner_def: LocalDefId) -> String {
+    match super::cx::thir_body(tcx, owner_def) {
         Ok((thir, _)) => format!("{:#?}", thir.steal()),
         Err(_) => "error".into(),
     }

compiler/rustc_mir_transform/src/lib.rs

@@ -33,6 +33,7 @@ use rustc_middle::mir::{
 use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
 use rustc_middle::util::Providers;
 use rustc_middle::{bug, query, span_bug};
+use rustc_mir_build::builder::build_mir;
 use rustc_span::source_map::Spanned;
 use rustc_span::{DUMMY_SP, sym};
 use tracing::debug;
@@ -368,7 +369,7 @@ fn mir_const_qualif(tcx: TyCtxt<'_>, def: LocalDefId) -> ConstQualifs {
 }
 
 fn mir_built(tcx: TyCtxt<'_>, def: LocalDefId) -> &Steal<Body<'_>> {
-    let mut body = tcx.build_mir(def);
+    let mut body = build_mir(tcx, def);
 
     pass_manager::dump_mir_for_phase_change(tcx, &body);