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fix bug in simplify_cfg with inf. loops

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This commit is contained in:
Niko Matsakis 2016-03-22 16:19:44 -04:00
parent a61c1759c7
commit f976e222e9
1 changed files with 18 additions and 8 deletions
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26
src/librustc_mir/transform/simplify_cfg.rs
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@ -12,6 +12,7 @@ use rustc::middle::const_eval::ConstVal;
use rustc::middle::ty::TyCtxt;
use rustc::mir::repr::*;
use rustc::mir::transform::{MirPass, Pass};
use pretty;
use syntax::ast::NodeId;
use super::remove_dead_blocks::RemoveDeadBlocks;
@ -30,16 +31,22 @@ impl SimplifyCfg {
let mut seen: Vec<BasicBlock> = Vec::with_capacity(8);
while mir.basic_block_data(target).statements.is_empty() {
debug!("final_target: target={:?}", target);
match mir.basic_block_data(target).terminator().kind {
TerminatorKind::Goto { target: next } => {
if seen.contains(&next) {
return None;
// NB -- terminator may have been swapped with `None`
// below, in which case we have a cycle and just want
// to stop
if let Some(ref terminator) = mir.basic_block_data(target).terminator {
match terminator.kind {
TerminatorKind::Goto { target: next } => {
if seen.contains(&next) {
return None;
}
seen.push(next);
target = next;
}
seen.push(next);
target = next;
_ => break
}
_ => break
} else {
break
}
}
@ -106,8 +113,11 @@ impl SimplifyCfg {
impl<'tcx> MirPass<'tcx> for SimplifyCfg {
fn run_pass(&mut self, tcx: &TyCtxt<'tcx>, id: NodeId, mir: &mut Mir<'tcx>) {
let mut counter = 0;
let mut changed = true;
while changed {
pretty::dump_mir(tcx, "simplify_cfg", &counter, id, mir, None);
counter += 1;
changed = self.simplify_branches(mir);
changed |= self.remove_goto_chains(mir);
RemoveDeadBlocks.run_pass(tcx, id, mir);