1 //! This pass removes jumps to basic blocks containing only a return, and replaces them with a
4 use crate::transform::{simplify, MirPass};
5 use rustc_index::bit_set::BitSet;
6 use rustc_middle::mir::*;
7 use rustc_middle::ty::TyCtxt;
9 pub struct MultipleReturnTerminators;
11 impl<'tcx> MirPass<'tcx> for MultipleReturnTerminators {
12 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
13 if tcx.sess.opts.debugging_opts.mir_opt_level < 3 {
17 // find basic blocks with no statement and a return terminator
18 let mut bbs_simple_returns = BitSet::new_empty(body.basic_blocks().len());
19 let bbs = body.basic_blocks_mut();
20 for idx in bbs.indices() {
21 if bbs[idx].statements.is_empty()
22 && bbs[idx].terminator().kind == TerminatorKind::Return
24 bbs_simple_returns.insert(idx);
29 if let TerminatorKind::Goto { target } = bb.terminator().kind {
30 if bbs_simple_returns.contains(target) {
31 bb.terminator_mut().kind = TerminatorKind::Return;
36 simplify::remove_dead_blocks(body)