src/librustc_mir/transform/no_landing_pads.rs

   1 // Copyright 2015 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! This pass removes the unwind branch of all the terminators when the no-landing-pads option is
  12 //! specified.
  13
  14 use rustc::ty::TyCtxt;
  15 use rustc::mir::repr::*;
  16 use rustc::mir::visit::MutVisitor;
  17 use rustc::mir::transform::{Pass, MirPass, MirSource};
  18
  19 pub struct NoLandingPads;
  20
  21 impl<'tcx> MutVisitor<'tcx> for NoLandingPads {
  22     fn visit_terminator(&mut self,
  23                         bb: BasicBlock,
  24                         terminator: &mut Terminator<'tcx>,
  25                         location: Location) {
  26         match terminator.kind {
  27             TerminatorKind::Goto { .. } |
  28             TerminatorKind::Resume |
  29             TerminatorKind::Return |
  30             TerminatorKind::Unreachable |
  31             TerminatorKind::If { .. } |
  32             TerminatorKind::Switch { .. } |
  33             TerminatorKind::SwitchInt { .. } => {
  34                 /* nothing to do */
  35             },
  36             TerminatorKind::Call { cleanup: ref mut unwind, .. } |
  37             TerminatorKind::Assert { cleanup: ref mut unwind, .. } |
  38             TerminatorKind::DropAndReplace { ref mut unwind, .. } |
  39             TerminatorKind::Drop { ref mut unwind, .. } => {
  40                 unwind.take();
  41             },
  42         }
  43         self.super_terminator(bb, terminator, location);
  44     }
  45 }
  46
  47 impl<'tcx> MirPass<'tcx> for NoLandingPads {
  48     fn run_pass<'a>(&mut self, tcx: TyCtxt<'a, 'tcx, 'tcx>,
  49                     _: MirSource, mir: &mut Mir<'tcx>) {
  50         if tcx.sess.no_landing_pads() {
  51             self.visit_mir(mir);
  52         }
  53     }
  54 }
  55
  56 impl Pass for NoLandingPads {}