Replace mir_built query with a hook and use mir_const everywhere instead

Author: oli-obk

compiler/rustc_incremental/src/persist/dirty_clean.rs

@@ -65,7 +65,7 @@ const BASE_HIR: &[&str] = &[
 const BASE_IMPL: &[&str] =
     &[label_strs::associated_item_def_ids, label_strs::generics_of, label_strs::impl_trait_header];
 
-/// DepNodes for mir_built/Optimized, which is relevant in "executable"
+/// DepNodes for exported mir bodies, which is relevant in "executable"
 /// code, i.e., functions+methods
 const BASE_MIR: &[&str] = &[label_strs::optimized_mir, label_strs::promoted_mir];
 

compiler/rustc_middle/src/hooks/mod.rs

@@ -77,4 +77,10 @@ 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_const`
+    hook build_mir(key: LocalDefId) -> mir::Body<'tcx>;
 }

compiler/rustc_middle/src/query/mod.rs

@@ -485,19 +485,12 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    /// Fetch the MIR for a given `DefId` right after it's built - this includes
-    /// unreachable code.
-    query mir_built(key: LocalDefId) -> &'tcx Steal<mir::Body<'tcx>> {
-        desc { |tcx| "building MIR for `{}`", tcx.def_path_str(key) }
-    }
-
     /// Fetch the MIR for a given `DefId` up till the point where it is
     /// ready for const qualification.
     ///
     /// See the README for the `mir` module for details.
     query mir_const(key: LocalDefId) -> &'tcx Steal<mir::Body<'tcx>> {
         desc { |tcx| "preparing `{}` for borrow checking", tcx.def_path_str(key) }
-        no_hash
     }
 
     /// Try to build an abstract representation of the given constant.

compiler/rustc_mir_build/src/build/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 `mir_built` query, with the only
+//! The result of this lowering is returned "normally" from the `build_mir` hook, 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/build/mod.rs

@@ -18,6 +18,7 @@ use rustc_middle::hir::place::PlaceBase as HirPlaceBase;
 use rustc_middle::middle::region;
 use rustc_middle::mir::interpret::Scalar;
 use rustc_middle::mir::*;
+use rustc_middle::query::TyCtxtAt;
 use rustc_middle::thir::{
     self, BindingMode, ExprId, LintLevel, LocalVarId, Param, ParamId, PatKind, Thir,
 };
@@ -30,13 +31,6 @@ use rustc_target::spec::abi::Abi;
 
 use super::lints;
 
-pub(crate) fn mir_built(
-    tcx: TyCtxt<'_>,
-    def: LocalDefId,
-) -> &rustc_data_structures::steal::Steal<Body<'_>> {
-    tcx.alloc_steal_mir(mir_build(tcx, def))
-}
-
 pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
     tcx: TyCtxt<'tcx>,
     def_id: LocalDefId,
@@ -54,7 +48,8 @@ pub(crate) fn closure_saved_names_of_captured_variables<'tcx>(
 }
 
 /// Construct the MIR for a given `DefId`.
-fn mir_build<'tcx>(tcx: TyCtxt<'tcx>, def: LocalDefId) -> Body<'tcx> {
+pub(crate) fn mir_build<'tcx>(tcx: TyCtxtAt<'tcx>, def: LocalDefId) -> Body<'tcx> {
+    let tcx = tcx.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/check_unsafety.rs

@@ -139,7 +139,7 @@ impl<'tcx> UnsafetyVisitor<'_, 'tcx> {
     fn visit_inner_body(&mut self, def: LocalDefId) {
         if let Ok((inner_thir, expr)) = self.tcx.thir_body(def) {
             // Runs all other queries that depend on THIR.
-            self.tcx.ensure_with_value().mir_built(def);
+            self.tcx.ensure_with_value().mir_const(def);
             let inner_thir = &inner_thir.steal();
             let hir_context = self.tcx.local_def_id_to_hir_id(def);
             let safety_context = mem::replace(&mut self.safety_context, SafetyContext::Safe);
@@ -921,7 +921,7 @@ pub fn check_unsafety(tcx: TyCtxt<'_>, def: LocalDefId) {
 
     let Ok((thir, expr)) = tcx.thir_body(def) else { return };
     // Runs all other queries that depend on THIR.
-    tcx.ensure_with_value().mir_built(def);
+    tcx.ensure_with_value().mir_const(def);
     let thir = &thir.steal();
     // If `thir` is empty, a type error occurred, skip this body.
     if thir.exprs.is_empty() {

compiler/rustc_mir_build/src/lib.rs

@@ -23,14 +23,14 @@ mod errors;
 pub mod lints;
 mod thir;
 
-use rustc_middle::query::Providers;
+use rustc_middle::util::Providers;
 
 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.mir_built = build::mir_built;
+    providers.hooks.build_mir = build::mir_build;
     providers.closure_saved_names_of_captured_variables =
         build::closure_saved_names_of_captured_variables;
     providers.check_unsafety = check_unsafety::check_unsafety;

compiler/rustc_mir_transform/src/check_unsafety.rs

@@ -497,8 +497,8 @@ fn mir_unsafety_check_result(tcx: TyCtxt<'_>, def: LocalDefId) -> &UnsafetyCheck
     debug!("unsafety_violations({:?})", def);
 
     // N.B., this borrow is valid because all the consumers of
-    // `mir_built` force this.
-    let body = &tcx.mir_built(def).borrow();
+    // `mir_const` force this.
+    let body = &tcx.mir_const(def).borrow();
 
     if body.is_custom_mir() || body.tainted_by_errors.is_some() {
         return tcx.arena.alloc(UnsafetyCheckResult {

compiler/rustc_mir_transform/src/ffi_unwind_calls.rs

@@ -53,7 +53,7 @@ fn has_ffi_unwind_calls(tcx: TyCtxt<'_>, local_def_id: LocalDefId) -> bool {
         return false;
     }
 
-    let body = &*tcx.mir_built(local_def_id).borrow();
+    let body = &*tcx.mir_const(local_def_id).borrow();
 
     let body_ty = tcx.type_of(def_id).skip_binder();
     let body_abi = match body_ty.kind() {

compiler/rustc_mir_transform/src/lib.rs

@@ -288,10 +288,7 @@ fn mir_const(tcx: TyCtxt<'_>, def: LocalDefId) -> &Steal<Body<'_>> {
         tcx.ensure_with_value().mir_unsafety_check_result(def);
     }
 
-    // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
-    tcx.ensure_with_value().has_ffi_unwind_calls(def);
-
-    let mut body = tcx.mir_built(def).steal();
+    let mut body = tcx.build_mir(def);
 
     pass_manager::dump_mir_for_phase_change(tcx, &body);
 
@@ -339,6 +336,8 @@ fn mir_promoted(
         | DefKind::AnonConst => tcx.mir_const_qualif(def),
         _ => ConstQualifs::default(),
     };
+    // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
+    tcx.ensure_with_value().has_ffi_unwind_calls(def);
     let mut body = tcx.mir_const(def).steal();
     if let Some(error_reported) = const_qualifs.tainted_by_errors {
         body.tainted_by_errors = Some(error_reported);

tests/ui/binding/issue-53114-safety-checks.stderr

@@ -1,3 +1,23 @@
+error[E0793]: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:23:13
+   |
+LL |     let _ = &p.b;
+   |             ^^^^
+   |
+   = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
+   = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
+error[E0793]: reference to packed field is unaligned
+  --> $DIR/issue-53114-safety-checks.rs:28:17
+   |
+LL |     let (_,) = (&p.b,);
+   |                 ^^^^
+   |
+   = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
+   = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
+   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
+
 error[E0133]: access to union field is unsafe and requires unsafe function or block
   --> $DIR/issue-53114-safety-checks.rs:24:13
    |
@@ -31,20 +51,20 @@ LL |     let (_,) = (&u2.a,);
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:23:13
+  --> $DIR/issue-53114-safety-checks.rs:37:16
    |
-LL |     let _ = &p.b;
-   |             ^^^^
+LL |     let _: _ = &p.b;
+   |                ^^^^
    |
    = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:28:17
+  --> $DIR/issue-53114-safety-checks.rs:42:20
    |
-LL |     let (_,) = (&p.b,);
-   |                 ^^^^
+LL |     let (_,): _ = (&p.b,);
+   |                    ^^^^
    |
    = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
@@ -83,20 +103,20 @@ LL |     let (_,): _ = (&u2.a,);
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
 error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:37:16
+  --> $DIR/issue-53114-safety-checks.rs:51:11
    |
-LL |     let _: _ = &p.b;
-   |                ^^^^
+LL |     match &p.b  { _ => { } }
+   |           ^^^^
    |
    = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
    = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
 
 error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:42:20
+  --> $DIR/issue-53114-safety-checks.rs:56:12
    |
-LL |     let (_,): _ = (&p.b,);
-   |                    ^^^^
+LL |     match (&p.b,)  { (_,) => { } }
+   |            ^^^^
    |
    = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
    = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
@@ -134,26 +154,6 @@ LL |     match (&u2.a,) { (_,) => { } }
    |
    = note: the field may not be properly initialized: using uninitialized data will cause undefined behavior
 
-error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:51:11
-   |
-LL |     match &p.b  { _ => { } }
-   |           ^^^^
-   |
-   = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
-   = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
-   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
-
-error[E0793]: reference to packed field is unaligned
-  --> $DIR/issue-53114-safety-checks.rs:56:12
-   |
-LL |     match (&p.b,)  { (_,) => { } }
-   |            ^^^^
-   |
-   = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
-   = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
-   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
-
 error: aborting due to 18 previous errors
 
 Some errors have detailed explanations: E0133, E0793.

tests/ui/coroutine/clone-rpit.next.stderr

@@ -14,17 +14,12 @@ note: ...which requires promoting constants in MIR for `foo::{closure#0}`...
    |
 LL |     move |_: ()| {
    |     ^^^^^^^^^^^^
-note: ...which requires preparing `foo::{closure#0}` for borrow checking...
-  --> $DIR/clone-rpit.rs:14:5
-   |
-LL |     move |_: ()| {
-   |     ^^^^^^^^^^^^
 note: ...which requires checking if `foo::{closure#0}` contains FFI-unwind calls...
   --> $DIR/clone-rpit.rs:14:5
    |
 LL |     move |_: ()| {
    |     ^^^^^^^^^^^^
-note: ...which requires building MIR for `foo::{closure#0}`...
+note: ...which requires preparing `foo::{closure#0}` for borrow checking...
   --> $DIR/clone-rpit.rs:14:5
    |
 LL |     move |_: ()| {

tests/ui/resolve/multiple_definitions_attribute_merging.stderr

@@ -19,7 +19,7 @@ LL | struct Dealigned<T>(u8, T);
    = Box<dyn Any>
 query stack during panic:
 #0 [mir_const] preparing `<impl at $DIR/multiple_definitions_attribute_merging.rs:15:10: 15:19>::eq` for borrow checking
-#1 [mir_promoted] promoting constants in MIR for `<impl at $DIR/multiple_definitions_attribute_merging.rs:15:10: 15:19>::eq`
+#1 [check_unsafety] unsafety-checking `<impl at $DIR/multiple_definitions_attribute_merging.rs:15:10: 15:19>::eq`
 end of query stack
 error: aborting due to 2 previous errors
 

tests/ui/resolve/proc_macro_generated_packed.stderr

@@ -10,7 +10,7 @@ LL | struct Dealigned<T>(u8, T);
    = Box<dyn Any>
 query stack during panic:
 #0 [mir_const] preparing `<impl at $DIR/proc_macro_generated_packed.rs:15:10: 15:19>::eq` for borrow checking
-#1 [mir_promoted] promoting constants in MIR for `<impl at $DIR/proc_macro_generated_packed.rs:15:10: 15:19>::eq`
+#1 [check_unsafety] unsafety-checking `<impl at $DIR/proc_macro_generated_packed.rs:15:10: 15:19>::eq`
 end of query stack
 error: aborting due to 1 previous error
 

tests/ui/type-alias-enum-variants/self-in-enum-definition.stderr

@@ -37,11 +37,6 @@ LL |     V3 = Self::V1 {} as u8 + 2,
 note: ...which requires preparing `Alpha::V3::{constant#0}` for borrow checking...
   --> $DIR/self-in-enum-definition.rs:5:10
    |
-LL |     V3 = Self::V1 {} as u8 + 2,
-   |          ^^^^^^^^^^^^^^^^^^^^^
-note: ...which requires building MIR for `Alpha::V3::{constant#0}`...
-  --> $DIR/self-in-enum-definition.rs:5:10
-   |
 LL |     V3 = Self::V1 {} as u8 + 2,
    |          ^^^^^^^^^^^^^^^^^^^^^
    = note: ...which requires computing layout of `Alpha`...