diff --git a/src/librustc_middle/mir/mod.rs b/src/librustc_middle/mir/mod.rs
index 566817ea0d02793574aa2dea8e01a2611aec8ff5..858ab0dbe009962c9434b8363e25a97cc66efd7d 100644
--- a/src/librustc_middle/mir/mod.rs
+++ b/src/librustc_middle/mir/mod.rs
@@ -164,7 +164,7 @@ pub struct Body<'tcx> {
     /// FIXME(oli-obk): rewrite the promoted during promotion to eliminate the cell components.
     pub ignore_interior_mut_in_const_validation: bool,
 
-    pub predecessor_cache: PredecessorCache,
+    predecessor_cache: PredecessorCache,
 }
 
 impl<'tcx> Body<'tcx> {
diff --git a/src/librustc_middle/mir/predecessors.rs b/src/librustc_middle/mir/predecessors.rs
index 8f1f927852119c2fcaf978008be73fb77a260d17..9508365886aa790f3f83d029d9cf7106afac8fca 100644
--- a/src/librustc_middle/mir/predecessors.rs
+++ b/src/librustc_middle/mir/predecessors.rs
@@ -1,3 +1,5 @@
+//! Lazily compute the reverse control-flow graph for the MIR.
+
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::sync::{Lock, Lrc};
 use rustc_index::vec::IndexVec;
@@ -10,13 +12,13 @@
 pub type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>;
 
 #[derive(Clone, Debug)]
-pub struct PredecessorCache {
+pub(super) struct PredecessorCache {
     cache: Lock<Option<Lrc<Predecessors>>>,
 }
 
 impl PredecessorCache {
     #[inline]
-    pub fn new() -> Self {
+    pub(super) fn new() -> Self {
         PredecessorCache { cache: Lock::new(None) }
     }
 
@@ -27,7 +29,7 @@ pub fn new() -> Self {
     /// callers of `invalidate` have a unique reference to the MIR and thus to the predecessor
     /// cache. This means we don't actually need to take a lock when `invalidate` is called.
     #[inline]
-    pub fn invalidate(&mut self) {
+    pub(super) fn invalidate(&mut self) {
         *self.cache.get_mut() = None;
     }
 
@@ -37,7 +39,7 @@ pub fn invalidate(&mut self) {
     /// `cache` is only held inside this function. As long as no other locks are taken while
     /// computing the predecessor graph, deadlock is impossible.
     #[inline]
-    pub fn compute(
+    pub(super) fn compute(
         &self,
         basic_blocks: &IndexVec<BasicBlock, BasicBlockData<'_>>,
     ) -> Lrc<Predecessors> {