Add option to mir::MutVisitor to not invalidate CFG.

This also applies that option to some uses of the visitor

compiler/rustc_mir_transform/src/cleanup_post_borrowck.rs

@@ -33,7 +33,7 @@ pub struct DeleteNonCodegenStatements<'tcx> {
 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(body);
+        delete.visit_body_preserves_cfg(body);
         body.user_type_annotations.raw.clear();
 
         for decl in &mut body.local_decls {

compiler/rustc_mir_transform/src/const_prop.rs

@@ -951,7 +951,7 @@ impl<'tcx> MutVisitor<'tcx> for ConstPropagator<'_, 'tcx> {
     }
 
     fn visit_body(&mut self, body: &mut Body<'tcx>) {
-        for (bb, data) in body.basic_blocks_mut().iter_enumerated_mut() {
+        for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
             self.visit_basic_block_data(bb, data);
         }
     }

compiler/rustc_mir_transform/src/deref_separator.rs

@@ -90,7 +90,7 @@ pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
     let patch = MirPatch::new(body);
     let mut checker = DerefChecker { tcx, patcher: patch, local_decls: body.local_decls.clone() };
 
-    for (bb, data) in body.basic_blocks_mut().iter_enumerated_mut() {
+    for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
         checker.visit_basic_block_data(bb, data);
     }
 

compiler/rustc_mir_transform/src/elaborate_box_derefs.rs

@@ -116,7 +116,7 @@ impl<'tcx> MirPass<'tcx> for ElaborateBoxDerefs {
                 ElaborateBoxDerefVisitor { tcx, unique_did, nonnull_did, local_decls, patch };
 
             for (block, BasicBlockData { statements, terminator, .. }) in
-                body.basic_blocks.as_mut().iter_enumerated_mut()
+                body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut()
             {
                 let mut index = 0;
                 for statement in statements {

compiler/rustc_mir_transform/src/nrvo.rs

@@ -53,10 +53,10 @@ impl<'tcx> MirPass<'tcx> for RenameReturnPlace {
             def_id, returned_local
         );
 
-        RenameToReturnPlace { tcx, to_rename: returned_local }.visit_body(body);
+        RenameToReturnPlace { tcx, to_rename: returned_local }.visit_body_preserves_cfg(body);
 
         // Clean up the `NOP`s we inserted for statements made useless by our renaming.
-        for block_data in body.basic_blocks_mut() {
+        for block_data in body.basic_blocks.as_mut_preserves_cfg() {
             block_data.statements.retain(|stmt| stmt.kind != mir::StatementKind::Nop);
         }
 

compiler/rustc_mir_transform/src/reveal_all.rs

@@ -19,7 +19,7 @@ impl<'tcx> MirPass<'tcx> for RevealAll {
         }
 
         let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id());
-        RevealAllVisitor { tcx, param_env }.visit_body(body);
+        RevealAllVisitor { tcx, param_env }.visit_body_preserves_cfg(body);
     }
 }
 

compiler/rustc_mir_transform/src/simplify.rs

@@ -412,7 +412,7 @@ pub fn simplify_locals<'tcx>(body: &mut Body<'tcx>, tcx: TyCtxt<'tcx>) {
     if map.iter().any(Option::is_none) {
         // Update references to all vars and tmps now
         let mut updater = LocalUpdater { map, tcx };
-        updater.visit_body(body);
+        updater.visit_body_preserves_cfg(body);
 
         body.local_decls.shrink_to_fit();
     }
@@ -548,7 +548,7 @@ fn remove_unused_definitions(used_locals: &mut UsedLocals, body: &mut Body<'_>)
     while modified {
         modified = false;
 
-        for data in body.basic_blocks_mut() {
+        for data in body.basic_blocks.as_mut_preserves_cfg() {
             // Remove unnecessary StorageLive and StorageDead annotations.
             data.statements.retain(|statement| {
                 let keep = match &statement.kind {