Stop invalidating in CleanupPostBorrowck.

Author: cjgillot

compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs

@@ -17,15 +17,17 @@
 //! [`SpanMarker`]: rustc_middle::mir::coverage::CoverageKind::SpanMarker
 
 use rustc_middle::mir::coverage::CoverageKind;
-use rustc_middle::mir::{Body, BorrowKind, CastKind, Rvalue, StatementKind, TerminatorKind};
+use rustc_middle::mir::*;
 use rustc_middle::ty::TyCtxt;
 use rustc_middle::ty::adjustment::PointerCoercion;
 
 pub(super) struct CleanupPostBorrowck;
 
 impl<'tcx> crate::MirPass<'tcx> for CleanupPostBorrowck {
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        for basic_block in body.basic_blocks.as_mut() {
+        // Manually invalidate CFG caches if we actually change a terminator's edges.
+        let mut invalidate_cfg = false;
+        for basic_block in body.basic_blocks.as_mut_preserves_cfg().iter_mut() {
             for statement in basic_block.statements.iter_mut() {
                 match statement.kind {
                     StatementKind::AscribeUserType(..)
@@ -59,16 +61,23 @@ impl<'tcx> crate::MirPass<'tcx> for CleanupPostBorrowck {
                     _ => (),
                 }
             }
+
+            // If we change any terminator, we need to ensure that we invalidated the CFG cache.
             let terminator = basic_block.terminator_mut();
             match terminator.kind {
                 TerminatorKind::FalseEdge { real_target, .. }
                 | TerminatorKind::FalseUnwind { real_target, .. } => {
+                    invalidate_cfg = true;
                     terminator.kind = TerminatorKind::Goto { target: real_target };
                 }
                 _ => {}
             }
         }
 
+        if invalidate_cfg {
+            body.basic_blocks.invalidate_cfg_cache();
+        }
+
         body.user_type_annotations.raw.clear();
 
         for decl in &mut body.local_decls {