cotrol stacked borrows consistency check with its own feature flag

Cargo.toml

@@ -59,6 +59,7 @@ harness = false
 [features]
 default = ["stack-cache"]
 stack-cache = []
+stack-cache-consistency-check = ["stack-cache"]
 
 # Be aware that this file is inside a workspace when used via the
 # submodule in the rustc repo. That means there are many cargo features

ci/ci.sh

@@ -22,17 +22,24 @@ if [ "$HOST_TARGET" = i686-pc-windows-msvc ]; then
   BASH="C:/Program Files/Git/usr/bin/bash"
 fi
 
-# Determine configuration for installed build
-echo "Installing release version of Miri"
+# Global configuration
 export RUSTFLAGS="-D warnings"
 export CARGO_INCREMENTAL=0
 export CARGO_EXTRA_FLAGS="--locked"
+
+# Determine configuration for installed build
+echo "Installing release version of Miri"
 ./miri install
 
-# Prepare debug build for direct `./miri` invocations
-echo "Building debug version of Miri"
+echo "Checking various feature flag configurations"
 ./miri check --no-default-features # make sure this can be built
-./miri check --all-features # and this, too
+./miri check # and this, too
+# `--all-features` is used for the build below, so no extra check needed.
+
+# Prepare debug build for direct `./miri` invocations.
+# We enable all features to make sure the Stacked Borrows consistency check runs.
+echo "Building debug version of Miri"
+export CARGO_EXTRA_FLAGS="$CARGO_EXTRA_FLAGS --all-features"
 ./miri build --all-targets # the build that all the `./miri test` below will use
 
 endgroup

src/borrow_tracker/stacked_borrows/stack.rs

@@ -146,7 +146,7 @@ impl<'tcx> Stack {
     /// Panics if any of the caching mechanisms have broken,
     /// - The StackCache indices don't refer to the parallel items,
     /// - There are no Unique items outside of first_unique..last_unique
-    #[cfg(all(feature = "stack-cache", debug_assertions))]
+    #[cfg(feature = "stack-cache-consistency-check")]
     fn verify_cache_consistency(&self) {
         // Only a full cache needs to be valid. Also see the comments in find_granting_cache
         // and set_unknown_bottom.
@@ -190,7 +190,7 @@ impl<'tcx> Stack {
         tag: ProvenanceExtra,
         exposed_tags: &FxHashSet<BorTag>,
     ) -> Result<Option<usize>, ()> {
-        #[cfg(all(feature = "stack-cache", debug_assertions))]
+        #[cfg(feature = "stack-cache-consistency-check")]
         self.verify_cache_consistency();
 
         let ProvenanceExtra::Concrete(tag) = tag else {
@@ -327,7 +327,7 @@ impl<'tcx> Stack {
         // This primes the cache for the next access, which is almost always the just-added tag.
         self.cache.add(new_idx, new);
 
-        #[cfg(debug_assertions)]
+        #[cfg(feature = "stack-cache-consistency-check")]
         self.verify_cache_consistency();
     }
 
@@ -410,7 +410,7 @@ impl<'tcx> Stack {
             self.unique_range.end = self.unique_range.end.min(disable_start);
         }
 
-        #[cfg(all(feature = "stack-cache", debug_assertions))]
+        #[cfg(feature = "stack-cache-consistency-check")]
         self.verify_cache_consistency();
 
         Ok(())
@@ -465,7 +465,7 @@ impl<'tcx> Stack {
             self.unique_range = 0..0;
         }
 
-        #[cfg(all(feature = "stack-cache", debug_assertions))]
+        #[cfg(feature = "stack-cache-consistency-check")]
         self.verify_cache_consistency();
         Ok(())
     }