69 lines
2 KiB
Rust
69 lines
2 KiB
Rust
// Copyright 2016 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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use std::cell::{Ref, RefCell};
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use rustc_data_structures::indexed_vec::IndexVec;
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use mir::{Mir, BasicBlock};
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use rustc_serialize as serialize;
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#[derive(Clone, Debug)]
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pub struct Cache {
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predecessors: RefCell<Option<IndexVec<BasicBlock, Vec<BasicBlock>>>>
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}
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impl serialize::Encodable for Cache {
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fn encode<S: serialize::Encoder>(&self, s: &mut S) -> Result<(), S::Error> {
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serialize::Encodable::encode(&(), s)
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}
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}
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impl serialize::Decodable for Cache {
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fn decode<D: serialize::Decoder>(d: &mut D) -> Result<Self, D::Error> {
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serialize::Decodable::decode(d).map(|_v: ()| Self::new())
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}
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}
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impl Cache {
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pub fn new() -> Self {
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Cache {
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predecessors: RefCell::new(None)
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}
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}
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pub fn invalidate(&self) {
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// FIXME: consider being more fine-grained
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*self.predecessors.borrow_mut() = None;
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}
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pub fn predecessors(&self, mir: &Mir) -> Ref<IndexVec<BasicBlock, Vec<BasicBlock>>> {
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if self.predecessors.borrow().is_none() {
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*self.predecessors.borrow_mut() = Some(calculate_predecessors(mir));
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}
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Ref::map(self.predecessors.borrow(), |p| p.as_ref().unwrap())
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}
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}
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fn calculate_predecessors(mir: &Mir) -> IndexVec<BasicBlock, Vec<BasicBlock>> {
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let mut result = IndexVec::from_elem(vec![], mir.basic_blocks());
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for (bb, data) in mir.basic_blocks().iter_enumerated() {
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if let Some(ref term) = data.terminator {
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for &tgt in term.successors().iter() {
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result[tgt].push(bb);
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}
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}
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}
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result
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}
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