44 lines
1.4 KiB
Rust
44 lines
1.4 KiB
Rust
//! This pass removes jumps to basic blocks containing only a return, and replaces them with a
|
|
//! return instead.
|
|
|
|
use crate::transform::{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 run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
|
|
if tcx.sess.opts.debugging_opts.mir_opt_level < 3 {
|
|
return;
|
|
}
|
|
|
|
// 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(body)
|
|
}
|
|
}
|