START_BLOCK cannot have incoming edges.

Author: cjgillot

compiler/rustc_mir_transform/src/add_call_guards.rs

@@ -30,7 +30,6 @@ pub(super) use self::AddCallGuards::*;
 impl<'tcx> crate::MirPass<'tcx> for AddCallGuards {
     fn run_pass(&self, _tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
         let mut pred_count = IndexVec::from_elem(0u8, &body.basic_blocks);
-        pred_count[START_BLOCK] = 1; // Add entry edge.
         for (_, data) in body.basic_blocks.iter_enumerated() {
             for succ in data.terminator().successors() {
                 pred_count[succ] = pred_count[succ].saturating_add(1);