Rollup merge of #105835 - tmiasko:cleanup-post-borrowck, r=JakobDegen

Refactor post borrowck cleanup passes

3 files changed, 28 insertions, 71 deletions

diff --git a/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs b/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
index 3378923c22c..d435d3ee69b 100644
--- a/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
+++ b/compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs
@@ -1,39 +1,44 @@
-//! This module provides a pass to replacing the following statements with
-//! [`Nop`]s
+//! This module provides a pass that removes parts of MIR that are no longer relevant after
+//! analysis phase and borrowck. In particular, it removes false edges, user type annotations and
+//! replaces following statements with [`Nop`]s:
 //!
 //!   - [`AscribeUserType`]
 //!   - [`FakeRead`]
 //!   - [`Assign`] statements with a [`Shallow`] borrow
 //!
-//! The `CleanFakeReadsAndBorrows` "pass" is actually implemented as two
-//! traversals (aka visits) of the input MIR. The first traversal,
-//! `DeleteAndRecordFakeReads`, deletes the fake reads and finds the
-//! temporaries read by [`ForMatchGuard`] reads, and `DeleteFakeBorrows`
-//! deletes the initialization of those temporaries.
-//!
 //! [`AscribeUserType`]: rustc_middle::mir::StatementKind::AscribeUserType
-//! [`Shallow`]: rustc_middle::mir::BorrowKind::Shallow
-//! [`FakeRead`]: rustc_middle::mir::StatementKind::FakeRead
 //! [`Assign`]: rustc_middle::mir::StatementKind::Assign
-//! [`ForMatchGuard`]: rustc_middle::mir::FakeReadCause::ForMatchGuard
+//! [`FakeRead`]: rustc_middle::mir::StatementKind::FakeRead
 //! [`Nop`]: rustc_middle::mir::StatementKind::Nop
+//! [`Shallow`]: rustc_middle::mir::BorrowKind::Shallow
 
 use crate::MirPass;
-use rustc_middle::mir::visit::MutVisitor;
-use rustc_middle::mir::{Body, BorrowKind, Location, Rvalue};
-use rustc_middle::mir::{Statement, StatementKind};
+use rustc_middle::mir::{Body, BorrowKind, Rvalue, StatementKind, TerminatorKind};
 use rustc_middle::ty::TyCtxt;
 
-pub struct CleanupNonCodegenStatements;
+pub struct CleanupPostBorrowck;
 
-pub struct DeleteNonCodegenStatements<'tcx> {
-    tcx: TyCtxt<'tcx>,
-}
+impl<'tcx> MirPass<'tcx> for CleanupPostBorrowck {
+    fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        for basic_block in body.basic_blocks.as_mut() {
+            for statement in basic_block.statements.iter_mut() {
+                match statement.kind {
+                    StatementKind::AscribeUserType(..)
+                    | StatementKind::Assign(box (_, Rvalue::Ref(_, BorrowKind::Shallow, _)))
+                    | StatementKind::FakeRead(..) => statement.make_nop(),
+                    _ => (),
+                }
+            }
+            let terminator = basic_block.terminator_mut();
+            match terminator.kind {
+                TerminatorKind::FalseEdge { real_target, .. }
+                | TerminatorKind::FalseUnwind { real_target, .. } => {
+                    terminator.kind = TerminatorKind::Goto { target: real_target };
+                }
+                _ => {}
+            }
+        }
 
-impl<'tcx> MirPass<'tcx> for CleanupNonCodegenStatements {
-    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let mut delete = DeleteNonCodegenStatements { tcx };
-        delete.visit_body_preserves_cfg(body);
         body.user_type_annotations.raw.clear();
 
         for decl in &mut body.local_decls {
@@ -41,19 +46,3 @@ impl<'tcx> MirPass<'tcx> for CleanupNonCodegenStatements {
         }
     }
 }
-
-impl<'tcx> MutVisitor<'tcx> for DeleteNonCodegenStatements<'tcx> {
-    fn tcx(&self) -> TyCtxt<'tcx> {
-        self.tcx
-    }
-
-    fn visit_statement(&mut self, statement: &mut Statement<'tcx>, location: Location) {
-        match statement.kind {
-            StatementKind::AscribeUserType(..)
-            | StatementKind::Assign(box (_, Rvalue::Ref(_, BorrowKind::Shallow, _)))
-            | StatementKind::FakeRead(..) => statement.make_nop(),
-            _ => (),
-        }
-        self.super_statement(statement, location);
-    }
-}
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 93200b28830..aba5a8580f1 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -77,8 +77,6 @@ mod match_branches;
 mod multiple_return_terminators;
 mod normalize_array_len;
 mod nrvo;
-// This pass is public to allow external drivers to perform MIR cleanup
-pub mod remove_false_edges;
 mod remove_noop_landing_pads;
 mod remove_storage_markers;
 mod remove_uninit_drops;
@@ -494,10 +492,9 @@ fn run_analysis_to_runtime_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>
 /// After this series of passes, no lifetime analysis based on borrowing can be done.
 fn run_analysis_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let passes: &[&dyn MirPass<'tcx>] = &[
-        &remove_false_edges::RemoveFalseEdges,
+        &cleanup_post_borrowck::CleanupPostBorrowck,
         &simplify_branches::SimplifyConstCondition::new("initial"),
         &remove_noop_landing_pads::RemoveNoopLandingPads,
-        &cleanup_post_borrowck::CleanupNonCodegenStatements,
         &simplify::SimplifyCfg::new("early-opt"),
         &deref_separator::Derefer,
     ];
diff --git a/compiler/rustc_mir_transform/src/remove_false_edges.rs b/compiler/rustc_mir_transform/src/remove_false_edges.rs
deleted file mode 100644
index 71f5ccf7e24..00000000000
--- a/compiler/rustc_mir_transform/src/remove_false_edges.rs
+++ /dev/null
@@ -1,29 +0,0 @@
-use rustc_middle::mir::{Body, TerminatorKind};
-use rustc_middle::ty::TyCtxt;
-
-use crate::MirPass;
-
-/// Removes `FalseEdge` and `FalseUnwind` terminators from the MIR.
-///
-/// These are only needed for borrow checking, and can be removed afterwards.
-///
-/// FIXME: This should probably have its own MIR phase.
-pub struct RemoveFalseEdges;
-
-impl<'tcx> MirPass<'tcx> for RemoveFalseEdges {
-    fn run_pass(&self, _: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        for block in body.basic_blocks_mut() {
-            let terminator = block.terminator_mut();
-            terminator.kind = match terminator.kind {
-                TerminatorKind::FalseEdge { real_target, .. } => {
-                    TerminatorKind::Goto { target: real_target }
-                }
-                TerminatorKind::FalseUnwind { real_target, .. } => {
-                    TerminatorKind::Goto { target: real_target }
-                }
-
-                _ => continue,
-            }
-        }
-    }
-}