Auto merge of #98872 - JakobDegen:no-invalidate, r=davidtwco

Add method to mutate MIR body without invalidating CFG caches.

In addition to adding this method, a handful of passes are updated to use it. There's still quite a few passes that could in principle make use of this as well, but do not at the moment because they use `VisitorMut` or `MirPatch`, which needs additional support for this.

The method name is slightly unwieldy, but I don't expect anyone to be writing it a lot, and at least it says what it does. If anyone has a suggestion for a better name though, would be happy to rename.

r? rust-lang/mir-opt

compiler/rustc_mir_transform/src/dead_store_elimination.rs

@@ -66,7 +66,7 @@ pub fn eliminate<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>, borrowed: &BitS
         return;
     }
 
-    let bbs = body.basic_blocks_mut();
+    let bbs = body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate().0;
     for Location { block, statement_index } in patch {
         bbs[block].statements[statement_index].make_nop();
     }

compiler/rustc_mir_transform/src/deaggregator.rs

@@ -11,7 +11,8 @@ impl<'tcx> MirPass<'tcx> for Deaggregator {
     }
 
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-        let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+        let (basic_blocks, local_decls, _) =
+            body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate();
         let local_decls = &*local_decls;
         for bb in basic_blocks {
             bb.expand_statements(|stmt| {

compiler/rustc_mir_transform/src/lower_slice_len.rs

@@ -26,7 +26,9 @@ pub fn lower_slice_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         return;
     };
 
-    let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+    // The one successor remains unchanged, so no need to invalidate
+    let (basic_blocks, local_decls, _) =
+        body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate();
 
     for block in basic_blocks {
         // lower `<[_]>::len` calls

compiler/rustc_mir_transform/src/normalize_array_len.rs

@@ -32,7 +32,9 @@ impl<'tcx> MirPass<'tcx> for NormalizeArrayLen {
 }
 
 pub fn normalize_array_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
-    let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+    // We don't ever touch terminators, so no need to invalidate the CFG cache
+    let (basic_blocks, local_decls, _) =
+        body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate();
 
     // do a preliminary analysis to see if we ever have locals of type `[T;N]` or `&[T;N]`
     let mut interesting_locals = BitSet::new_empty(local_decls.len());

compiler/rustc_mir_transform/src/remove_storage_markers.rs

@@ -17,7 +17,7 @@ impl<'tcx> MirPass<'tcx> for RemoveStorageMarkers {
         }
 
         trace!("Running RemoveStorageMarkers on {:?}", body.source);
-        for data in body.basic_blocks_mut() {
+        for data in body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate().0 {
             data.statements.retain(|statement| match statement.kind {
                 StatementKind::StorageLive(..)
                 | StatementKind::StorageDead(..)

compiler/rustc_mir_transform/src/remove_zsts.rs

@@ -18,7 +18,8 @@ impl<'tcx> MirPass<'tcx> for RemoveZsts {
             return;
         }
         let param_env = tcx.param_env(body.source.def_id());
-        let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
+        let (basic_blocks, local_decls, _) =
+            body.basic_blocks_local_decls_mut_and_var_debug_info_no_invalidate();
         for block in basic_blocks.iter_mut() {
             for statement in block.statements.iter_mut() {
                 if let StatementKind::Assign(box (place, _)) | StatementKind::Deinit(box place) =