Move MirPass to rustc_mir_transform.

Because that's now the only crate that uses it.

Moving stuff out of `rustc_middle` is always welcome.

I chose to use `impl crate::MirPass`/`impl crate::MirLint` (with
explicit `crate::`) everywhere because that's the only mention of
`MirPass`/`MirLint` used in all of these files. (Prior to this change,
`MirPass` was mostly imported via `use rustc_middle::mir::*` items.)

Author: nnethercote

compiler/rustc_middle/src/mir/mod.rs

@@ -3,8 +3,6 @@
 //! [rustc dev guide]: https://rustc-dev-guide.rust-lang.org/mir/index.html
 
 use std::borrow::Cow;
-use std::cell::RefCell;
-use std::collections::hash_map::Entry;
 use std::fmt::{self, Debug, Formatter};
 use std::ops::{Index, IndexMut};
 use std::{iter, mem};
@@ -26,7 +24,6 @@ use rustc_index::bit_set::BitSet;
 use rustc_index::{Idx, IndexSlice, IndexVec};
 use rustc_macros::{HashStable, TyDecodable, TyEncodable, TypeFoldable, TypeVisitable};
 use rustc_serialize::{Decodable, Encodable};
-use rustc_session::Session;
 use rustc_span::source_map::Spanned;
 use rustc_span::symbol::Symbol;
 use rustc_span::{Span, DUMMY_SP};
@@ -106,65 +103,6 @@ impl<'tcx> HasLocalDecls<'tcx> for Body<'tcx> {
     }
 }
 
-thread_local! {
-    static PASS_NAMES: RefCell<FxHashMap<&'static str, &'static str>> = {
-        RefCell::new(FxHashMap::default())
-    };
-}
-
-/// Converts a MIR pass name into a snake case form to match the profiling naming style.
-fn to_profiler_name(type_name: &'static str) -> &'static str {
-    PASS_NAMES.with(|names| match names.borrow_mut().entry(type_name) {
-        Entry::Occupied(e) => *e.get(),
-        Entry::Vacant(e) => {
-            let snake_case: String = type_name
-                .chars()
-                .flat_map(|c| {
-                    if c.is_ascii_uppercase() {
-                        vec!['_', c.to_ascii_lowercase()]
-                    } else if c == '-' {
-                        vec!['_']
-                    } else {
-                        vec![c]
-                    }
-                })
-                .collect();
-            let result = &*String::leak(format!("mir_pass{}", snake_case));
-            e.insert(result);
-            result
-        }
-    })
-}
-
-/// A streamlined trait that you can implement to create a pass; the
-/// pass will be named after the type, and it will consist of a main
-/// loop that goes over each available MIR and applies `run_pass`.
-pub trait MirPass<'tcx> {
-    fn name(&self) -> &'static str {
-        // FIXME Simplify the implementation once more `str` methods get const-stable.
-        // See copypaste in `MirLint`
-        const {
-            let name = std::any::type_name::<Self>();
-            crate::util::common::c_name(name)
-        }
-    }
-
-    fn profiler_name(&self) -> &'static str {
-        to_profiler_name(self.name())
-    }
-
-    /// Returns `true` if this pass is enabled with the current combination of compiler flags.
-    fn is_enabled(&self, _sess: &Session) -> bool {
-        true
-    }
-
-    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
-
-    fn is_mir_dump_enabled(&self) -> bool {
-        true
-    }
-}
-
 impl MirPhase {
     /// Gets the index of the current MirPhase within the set of all `MirPhase`s.
     ///

compiler/rustc_middle/src/util/common.rs

@@ -20,19 +20,3 @@ pub fn to_readable_str(mut val: usize) -> String {
 
     groups.join("_")
 }
-
-// const wrapper for `if let Some((_, tail)) = name.rsplit_once(':') { tail } else { name }`
-pub const fn c_name(name: &'static str) -> &'static str {
-    // FIXME Simplify the implementation once more `str` methods get const-stable.
-    // and inline into call site
-    let bytes = name.as_bytes();
-    let mut i = bytes.len();
-    while i > 0 && bytes[i - 1] != b':' {
-        i = i - 1;
-    }
-    let (_, bytes) = bytes.split_at(i);
-    match std::str::from_utf8(bytes) {
-        Ok(name) => name,
-        Err(_) => name,
-    }
-}

compiler/rustc_mir_transform/src/abort_unwinding_calls.rs

@@ -22,7 +22,7 @@ use rustc_target::spec::PanicStrategy;
 #[derive(PartialEq)]
 pub struct AbortUnwindingCalls;
 
-impl<'tcx> MirPass<'tcx> for AbortUnwindingCalls {
+impl<'tcx> crate::MirPass<'tcx> for AbortUnwindingCalls {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let def_id = body.source.def_id();
         let kind = tcx.def_kind(def_id);

compiler/rustc_mir_transform/src/add_call_guards.rs

@@ -30,7 +30,7 @@ pub use self::AddCallGuards::*;
  *
  */
 
-impl<'tcx> MirPass<'tcx> for AddCallGuards {
+impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         self.add_call_guards(body);
     }

compiler/rustc_mir_transform/src/add_moves_for_packed_drops.rs

@@ -37,7 +37,7 @@ use crate::util;
 /// blowup.
 pub struct AddMovesForPackedDrops;
 
-impl<'tcx> MirPass<'tcx> for AddMovesForPackedDrops {
+impl<'tcx> crate::MirPass<'tcx> for AddMovesForPackedDrops {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         debug!("add_moves_for_packed_drops({:?} @ {:?})", body.source, body.span);
         add_moves_for_packed_drops(tcx, body);

compiler/rustc_mir_transform/src/add_retag.rs

@@ -48,7 +48,7 @@ fn may_contain_reference<'tcx>(ty: Ty<'tcx>, depth: u32, tcx: TyCtxt<'tcx>) -> b
     }
 }
 
-impl<'tcx> MirPass<'tcx> for AddRetag {
+impl<'tcx> crate::MirPass<'tcx> for AddRetag {
     fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
         sess.opts.unstable_opts.mir_emit_retag
     }

compiler/rustc_mir_transform/src/add_subtyping_projections.rs

@@ -62,7 +62,7 @@ pub fn subtype_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     checker.patcher.apply(body);
 }
 
-impl<'tcx> MirPass<'tcx> for Subtyper {
+impl<'tcx> crate::MirPass<'tcx> for Subtyper {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         subtype_finder(tcx, body);
     }

compiler/rustc_mir_transform/src/check_alignment.rs

@@ -9,7 +9,7 @@ use tracing::{debug, trace};
 
 pub struct CheckAlignment;
 
-impl<'tcx> MirPass<'tcx> for CheckAlignment {
+impl<'tcx> crate::MirPass<'tcx> for CheckAlignment {
     fn is_enabled(&self, sess: &Session) -> bool {
         // FIXME(#112480) MSVC and rustc disagree on minimum stack alignment on x86 Windows
         if sess.target.llvm_target == "i686-pc-windows-msvc" {

compiler/rustc_mir_transform/src/check_const_item_mutation.rs

@@ -6,11 +6,11 @@ use rustc_session::lint::builtin::CONST_ITEM_MUTATION;
 use rustc_span::def_id::DefId;
 use rustc_span::Span;
 
-use crate::{errors, MirLint};
+use crate::errors;
 
 pub struct CheckConstItemMutation;
 
-impl<'tcx> MirLint<'tcx> for CheckConstItemMutation {
+impl<'tcx> crate::MirLint<'tcx> for CheckConstItemMutation {
     fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         let mut checker = ConstMutationChecker { body, tcx, target_local: None };
         checker.visit_body(body);

compiler/rustc_mir_transform/src/check_packed_ref.rs

@@ -3,11 +3,11 @@ use rustc_middle::mir::*;
 use rustc_middle::span_bug;
 use rustc_middle::ty::{self, TyCtxt};
 
-use crate::{errors, util, MirLint};
+use crate::{errors, util};
 
 pub struct CheckPackedRef;
 
-impl<'tcx> MirLint<'tcx> for CheckPackedRef {
+impl<'tcx> crate::MirLint<'tcx> for CheckPackedRef {
     fn run_lint(&self, tcx: TyCtxt<'tcx>, body: &Body<'tcx>) {
         let param_env = tcx.param_env(body.source.def_id());
         let source_info = SourceInfo::outermost(body.span);