Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
Add post-pass to remove EndRegions of unborrowed extents.
- Loading branch information
Showing
3 changed files
with
88 additions
and
0 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,84 @@ | ||
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT | ||
// file at the top-level directory of this distribution and at | ||
// http://rust-lang.org/COPYRIGHT. | ||
// | ||
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or | ||
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license | ||
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your | ||
// option. This file may not be copied, modified, or distributed | ||
// except according to those terms. | ||
|
||
//! This module provides one pass, `CleanEndRegions`, that reduces the | ||
//! set of `EndRegion` statements in the MIR. | ||
//! | ||
//! The "pass" is actually implemented as two traversals (aka visits) | ||
//! of the input MIR. The first traversal, `GatherBorrowedRegions`, | ||
//! finds all of the regions in the MIR that are involved in a borrow. | ||
//! | ||
//! The second traversal, `DeleteTrivialEndRegions`, walks over the | ||
//! MIR and removes any `EndRegion` that is applied to a region that | ||
//! was not seen in the previous pass. | ||
|
||
use rustc_data_structures::fx::FxHashSet; | ||
|
||
use rustc::middle::region::CodeExtent; | ||
use rustc::mir::transform::{MirPass, MirSource}; | ||
use rustc::mir::{BasicBlock, Location, Mir, Rvalue, Statement, StatementKind}; | ||
use rustc::mir::visit::{MutVisitor, Visitor}; | ||
use rustc::ty::{RegionKind, TyCtxt}; | ||
|
||
pub struct CleanEndRegions; | ||
|
||
struct GatherBorrowedRegions { | ||
seen_regions: FxHashSet<CodeExtent>, | ||
} | ||
|
||
struct DeleteTrivialEndRegions<'a> { | ||
seen_regions: &'a FxHashSet<CodeExtent>, | ||
} | ||
|
||
impl MirPass for CleanEndRegions { | ||
fn run_pass<'a, 'tcx>(&self, | ||
_tcx: TyCtxt<'a, 'tcx, 'tcx>, | ||
_source: MirSource, | ||
mir: &mut Mir<'tcx>) { | ||
let mut gather = GatherBorrowedRegions { seen_regions: FxHashSet() }; | ||
gather.visit_mir(mir); | ||
|
||
let mut delete = DeleteTrivialEndRegions { seen_regions: &mut gather.seen_regions }; | ||
delete.visit_mir(mir); | ||
} | ||
} | ||
|
||
impl<'tcx> Visitor<'tcx> for GatherBorrowedRegions { | ||
fn visit_rvalue(&mut self, | ||
rvalue: &Rvalue<'tcx>, | ||
location: Location) { | ||
if let Rvalue::Ref(r, _, _) = *rvalue { | ||
if let RegionKind::ReScope(ce) = *r { | ||
self.seen_regions.insert(ce); | ||
} | ||
} | ||
self.super_rvalue(rvalue, location); | ||
} | ||
} | ||
|
||
impl<'a, 'tcx> MutVisitor<'tcx> for DeleteTrivialEndRegions<'a> { | ||
fn visit_statement(&mut self, | ||
block: BasicBlock, | ||
statement: &mut Statement<'tcx>, | ||
location: Location) { | ||
let mut delete_it = false; | ||
|
||
if let StatementKind::EndRegion(ref extent) = statement.kind { | ||
if !self.seen_regions.contains(extent) { | ||
delete_it = true; | ||
} | ||
} | ||
|
||
if delete_it { | ||
statement.kind = StatementKind::Nop; | ||
} | ||
self.super_statement(block, statement, location); | ||
} | ||
} |
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters