1 files changed, 43 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/multiple_return_terminators.rs b/compiler/rustc_mir_transform/src/multiple_return_terminators.rs
new file mode 100644
index 000000000..22b6dead9
--- /dev/null
+++ b/compiler/rustc_mir_transform/src/multiple_return_terminators.rs
@@ -0,0 +1,43 @@
+//! This pass removes jumps to basic blocks containing only a return, and replaces them with a
+//! return instead.
+
+use crate::{simplify, MirPass};
+use rustc_index::bit_set::BitSet;
+use rustc_middle::mir::*;
+use rustc_middle::ty::TyCtxt;
+
+pub struct MultipleReturnTerminators;
+
+impl<'tcx> MirPass<'tcx> for MultipleReturnTerminators {
+    fn is_enabled(&self, sess: &rustc_session::Session) -> bool {
+        sess.mir_opt_level() >= 4
+    }
+
+    fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
+        // find basic blocks with no statement and a return terminator
+        let mut bbs_simple_returns = BitSet::new_empty(body.basic_blocks().len());
+        let def_id = body.source.def_id();
+        let bbs = body.basic_blocks_mut();
+        for idx in bbs.indices() {
+            if bbs[idx].statements.is_empty()
+                && bbs[idx].terminator().kind == TerminatorKind::Return
+            {
+                bbs_simple_returns.insert(idx);
+            }
+        }
+
+        for bb in bbs {
+            if !tcx.consider_optimizing(|| format!("MultipleReturnTerminators {:?} ", def_id)) {
+                break;
+            }
+
+            if let TerminatorKind::Goto { target } = bb.terminator().kind {
+                if bbs_simple_returns.contains(target) {
+                    bb.terminator_mut().kind = TerminatorKind::Return;
+                }
+            }
+        }
+
+        simplify::remove_dead_blocks(tcx, body)
+    }
+}