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use rustc::mir::{Location, Lvalue, Mir, Operand, ProjectionElem, Rvalue, Local};
use rustc::mir::transform::{MirPass, MirSource, Pass};
use rustc::mir::visit::{MutVisitor, Visitor};
use rustc::ty::TyCtxt;
use rustc::util::nodemap::FxHashSet;
use rustc_data_structures::indexed_vec::Idx;
use std::mem;
pub struct InstCombine {
optimizations: OptimizationList,
}
impl InstCombine {
pub fn new() -> InstCombine {
InstCombine {
optimizations: OptimizationList::default(),
}
}
}
impl Pass for InstCombine {}
impl<'tcx> MirPass<'tcx> for InstCombine {
fn run_pass<'a>(&mut self,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
_: MirSource,
mir: &mut Mir<'tcx>) {
if tcx.sess.opts.debugging_opts.mir_opt_level == 0 {
return
}
{
let mut optimization_finder = OptimizationFinder::new(mir, tcx);
optimization_finder.visit_mir(mir);
self.optimizations = optimization_finder.optimizations
}
MutVisitor::visit_mir(&mut *self, mir);
}
}
impl<'tcx> MutVisitor<'tcx> for InstCombine {
fn visit_rvalue(&mut self, rvalue: &mut Rvalue<'tcx>, location: Location) {
if self.optimizations.and_stars.remove(&location) {
debug!("Replacing `&*`: {:?}", rvalue);
let new_lvalue = match *rvalue {
Rvalue::Ref(_, _, Lvalue::Projection(ref mut projection)) => {
mem::replace(&mut projection.base, Lvalue::Local(Local::new(0)))
}
_ => bug!("Detected `&*` but didn't find `&*`!"),
};
*rvalue = Rvalue::Use(Operand::Consume(new_lvalue))
}
self.super_rvalue(rvalue, location)
}
}
struct OptimizationFinder<'b, 'a, 'tcx:'a+'b> {
mir: &'b Mir<'tcx>,
tcx: TyCtxt<'a, 'tcx, 'tcx>,
optimizations: OptimizationList,
}
impl<'b, 'a, 'tcx:'b> OptimizationFinder<'b, 'a, 'tcx> {
fn new(mir: &'b Mir<'tcx>, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> OptimizationFinder<'b, 'a, 'tcx> {
OptimizationFinder {
mir: mir,
tcx: tcx,
optimizations: OptimizationList::default(),
}
}
}
impl<'b, 'a, 'tcx> Visitor<'tcx> for OptimizationFinder<'b, 'a, 'tcx> {
fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
if let Rvalue::Ref(_, _, Lvalue::Projection(ref projection)) = *rvalue {
if let ProjectionElem::Deref = projection.elem {
if projection.base.ty(self.mir, self.tcx).to_ty(self.tcx).is_region_ptr() {
self.optimizations.and_stars.insert(location);
}
}
}
self.super_rvalue(rvalue, location)
}
}
#[derive(Default)]
struct OptimizationList {
and_stars: FxHashSet<Location>,
}