Auto merge of rust-lang#152096 - bjorn3:mir_encoding_cleanups, r=oli-obk

Couple of cleanups and optimizations around MIR encoding

Author: bors

compiler/rustc_metadata/src/rmeta/decoder.rs

@@ -1298,10 +1298,6 @@ impl<'a> CrateMetadataRef<'a> {
         }
     }
 
-    fn is_ctfe_mir_available(self, tcx: TyCtxt<'_>, id: DefIndex) -> bool {
-        self.root.tables.mir_for_ctfe.get((self, tcx), id).is_some()
-    }
-
     fn is_item_mir_available(self, tcx: TyCtxt<'_>, id: DefIndex) -> bool {
         self.root.tables.optimized_mir.get((self, tcx), id).is_some()
     }

compiler/rustc_metadata/src/rmeta/decoder/cstore_impl.rs

@@ -324,7 +324,6 @@ provide! { tcx, def_id, other, cdata,
     inherent_impls => { cdata.get_inherent_implementations_for_type(tcx, def_id.index) }
     attrs_for_def => { tcx.arena.alloc_from_iter(cdata.get_item_attrs(tcx, def_id.index)) }
     is_mir_available => { cdata.is_item_mir_available(tcx, def_id.index) }
-    is_ctfe_mir_available => { cdata.is_ctfe_mir_available(tcx, def_id.index) }
     cross_crate_inlinable => { table_direct }
 
     dylib_dependency_formats => { cdata.get_dylib_dependency_formats(tcx) }

compiler/rustc_metadata/src/rmeta/encoder.rs

@@ -1102,12 +1102,8 @@ fn should_encode_mir(
     def_id: LocalDefId,
 ) -> (bool, bool) {
     match tcx.def_kind(def_id) {
-        // Constructors
-        DefKind::Ctor(_, _) => {
-            let mir_opt_base = tcx.sess.opts.output_types.should_codegen()
-                || tcx.sess.opts.unstable_opts.always_encode_mir;
-            (true, mir_opt_base)
-        }
+        // instance_mir uses mir_for_ctfe rather than optimized_mir for constructors
+        DefKind::Ctor(_, _) => (true, false),
         // Constants
         DefKind::AnonConst | DefKind::InlineConst | DefKind::AssocConst | DefKind::Const => {
             (true, false)
@@ -1117,11 +1113,10 @@ fn should_encode_mir(
         DefKind::SyntheticCoroutineBody => (false, true),
         // Full-fledged functions + closures
         DefKind::AssocFn | DefKind::Fn | DefKind::Closure => {
-            let generics = tcx.generics_of(def_id);
             let opt = tcx.sess.opts.unstable_opts.always_encode_mir
                 || (tcx.sess.opts.output_types.should_codegen()
                     && reachable_set.contains(&def_id)
-                    && (generics.requires_monomorphization(tcx)
+                    && (tcx.generics_of(def_id).requires_monomorphization(tcx)
                         || tcx.cross_crate_inlinable(def_id)));
             // The function has a `const` modifier or is in a `const trait`.
             let is_const_fn = tcx.is_const_fn(def_id.to_def_id());

compiler/rustc_middle/src/queries.rs

@@ -1588,11 +1588,6 @@ rustc_queries! {
         separate_provide_extern
     }
 
-    query is_ctfe_mir_available(key: DefId) -> bool {
-        desc { |tcx| "checking if item has CTFE MIR available: `{}`", tcx.def_path_str(key) }
-        cache_on_disk_if { key.is_local() }
-        separate_provide_extern
-    }
     query is_mir_available(key: DefId) -> bool {
         desc { |tcx| "checking if item has MIR available: `{}`", tcx.def_path_str(key) }
         cache_on_disk_if { key.is_local() }

compiler/rustc_mir_transform/src/lib.rs

@@ -229,7 +229,6 @@ pub fn provide(providers: &mut Providers) {
         optimized_mir,
         check_liveness: liveness::check_liveness,
         is_mir_available,
-        is_ctfe_mir_available: is_mir_available,
         mir_callgraph_cyclic: inline::cycle::mir_callgraph_cyclic,
         mir_inliner_callees: inline::cycle::mir_inliner_callees,
         promoted_mir,

compiler/rustc_monomorphize/src/collector.rs

@@ -1085,7 +1085,9 @@ fn should_codegen_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) ->
         return false;
     }
 
-    if !tcx.is_mir_available(def_id) {
+    // See comment in should_encode_mir in rustc_metadata for why we don't report
+    // an error for constructors.
+    if !tcx.is_mir_available(def_id) && !matches!(tcx.def_kind(def_id), DefKind::Ctor(..)) {
         tcx.dcx().emit_fatal(NoOptimizedMir {
             span: tcx.def_span(def_id),
             crate_name: tcx.crate_name(def_id.krate),