3 files changed, 5 insertions, 26 deletions
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 90d7cbee976..bfd0de85438 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -76,7 +76,7 @@ mod unreachable_prop;
 use rustc_const_eval::transform::check_consts;
 use rustc_const_eval::transform::promote_consts;
 use rustc_const_eval::transform::validate;
-use rustc_const_eval::transform::MirPass;
+pub use rustc_const_eval::transform::MirPass;
 use rustc_mir_dataflow::rustc_peek;
 
 pub fn provide(providers: &mut Providers) {
diff --git a/compiler/rustc_mir_transform/src/remove_zsts.rs b/compiler/rustc_mir_transform/src/remove_zsts.rs
index 25e3c52132c..d93ffa38c69 100644
--- a/compiler/rustc_mir_transform/src/remove_zsts.rs
+++ b/compiler/rustc_mir_transform/src/remove_zsts.rs
@@ -9,6 +9,10 @@ pub struct RemoveZsts;
 
 impl<'tcx> MirPass<'tcx> for RemoveZsts {
     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        // Avoid query cycles (generators require optimized MIR for layout).
+        if tcx.type_of(body.source.def_id()).is_generator() {
+            return;
+        }
         let param_env = tcx.param_env(body.source.def_id());
         let (basic_blocks, local_decls) = body.basic_blocks_and_local_decls_mut();
         for block in basic_blocks.iter_mut() {
diff --git a/compiler/rustc_mir_transform/src/simplify.rs b/compiler/rustc_mir_transform/src/simplify.rs
index e3cfd1d0afc..d6cd505cbb5 100644
--- a/compiler/rustc_mir_transform/src/simplify.rs
+++ b/compiler/rustc_mir_transform/src/simplify.rs
@@ -95,8 +95,6 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
     pub fn simplify(mut self) {
         self.strip_nops();
 
-        let mut start = START_BLOCK;
-
         // Vec of the blocks that should be merged. We store the indices here, instead of the
         // statements itself to avoid moving the (relatively) large statements twice.
         // We do not push the statements directly into the target block (`bb`) as that is slower
@@ -105,8 +103,6 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
         loop {
             let mut changed = false;
 
-            self.collapse_goto_chain(&mut start, &mut changed);
-
             for bb in self.basic_blocks.indices() {
                 if self.pred_count[bb] == 0 {
                     continue;
@@ -149,27 +145,6 @@ impl<'a, 'tcx> CfgSimplifier<'a, 'tcx> {
                 break;
             }
         }
-
-        if start != START_BLOCK {
-            debug_assert!(self.pred_count[START_BLOCK] == 0);
-            self.basic_blocks.swap(START_BLOCK, start);
-            self.pred_count.swap(START_BLOCK, start);
-
-            // pred_count == 1 if the start block has no predecessor _blocks_.
-            if self.pred_count[START_BLOCK] > 1 {
-                for (bb, data) in self.basic_blocks.iter_enumerated_mut() {
-                    if self.pred_count[bb] == 0 {
-                        continue;
-                    }
-
-                    for target in data.terminator_mut().successors_mut() {
-                        if *target == start {
-                            *target = START_BLOCK;
-                        }
-                    }
-                }
-            }
-        }
     }
 
     /// This function will return `None` if