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::*;
  16 use rustc::mir::visit::MutVisitor;
  17 use rustc::mir::transform::{MirPass, MirSource};
  18
  19 pub struct NoLandingPads;
  20
  21 impl MirPass for NoLandingPads {
  22     fn run_pass<'a, 'tcx>(&self,
  23                           tcx: TyCtxt<'a, 'tcx, 'tcx>,
  24                           _: MirSource,
  25                           mir: &mut Mir<'tcx>) {
  26         no_landing_pads(tcx, mir)
  27     }
  28 }
  29
  30 pub fn no_landing_pads<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, mir: &mut Mir<'tcx>) {
  31     if tcx.sess.no_landing_pads() {
  32         NoLandingPads.visit_mir(mir);
  33     }
  34 }
  35
  36 impl<'tcx> MutVisitor<'tcx> for NoLandingPads {
  37     fn visit_terminator(&mut self,
  38                         bb: BasicBlock,
  39                         terminator: &mut Terminator<'tcx>,
  40                         location: Location) {
  41         match terminator.kind {
  42             TerminatorKind::Goto { .. } |
  43             TerminatorKind::Resume |
  44             TerminatorKind::Return |
  45             TerminatorKind::Unreachable |
  46             TerminatorKind::SwitchInt { .. } => {
  47                 /* nothing to do */
  48             },
  49             TerminatorKind::Call { cleanup: ref mut unwind, .. } |
  50             TerminatorKind::Assert { cleanup: ref mut unwind, .. } |
  51             TerminatorKind::DropAndReplace { ref mut unwind, .. } |
  52             TerminatorKind::Drop { ref mut unwind, .. } => {
  53                 unwind.take();
  54             },
  55         }
  56         self.super_terminator(bb, terminator, location);
  57     }
  58 }