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// 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.
use rustc::hir::def_id::DefId;
use rustc::mir::Mir;
use rustc::infer::InferCtxt;
use rustc::ty::{self, RegionKind, RegionVid};
use rustc::util::nodemap::FxHashMap;
use std::collections::BTreeSet;
use transform::MirSource;
use transform::type_check;
use util::liveness::{self, LivenessMode, LivenessResult, LocalSet};
use util as mir_util;
use self::mir_util::PassWhere;
mod constraint_generation;
mod subtype_constraint_generation;
mod free_regions;
pub(crate) mod region_infer;
use self::region_infer::RegionInferenceContext;
mod renumber;
/// Computes the (non-lexical) regions from the input MIR.
///
/// This may result in errors being reported.
pub fn compute_regions<'a, 'gcx, 'tcx>(
infcx: &InferCtxt<'a, 'gcx, 'tcx>,
def_id: DefId,
param_env: ty::ParamEnv<'gcx>,
mir: &mut Mir<'tcx>,
) -> RegionInferenceContext<'tcx> {
// Compute named region information.
let free_regions = &free_regions::free_regions(infcx, def_id);
// Replace all regions with fresh inference variables.
renumber::renumber_mir(infcx, free_regions, mir);
// Run the MIR type-checker.
let mir_node_id = infcx.tcx.hir.as_local_node_id(def_id).unwrap();
let constraint_sets = &type_check::type_check(infcx, mir_node_id, param_env, mir);
// Create the region inference context, taking ownership of the region inference
// data that was contained in `infcx`.
let var_origins = infcx.take_region_var_origins();
let mut regioncx = RegionInferenceContext::new(var_origins, free_regions, mir);
subtype_constraint_generation::generate(&mut regioncx, free_regions, mir, constraint_sets);
// Compute what is live where.
let liveness = &LivenessResults {
regular: liveness::liveness_of_locals(
&mir,
LivenessMode {
include_regular_use: true,
include_drops: false,
},
),
drop: liveness::liveness_of_locals(
&mir,
LivenessMode {
include_regular_use: false,
include_drops: true,
},
),
};
// Generate non-subtyping constraints.
constraint_generation::generate_constraints(infcx, &mut regioncx, &mir, param_env, liveness);
// Solve the region constraints.
regioncx.solve(infcx, &mir);
// Dump MIR results into a file, if that is enabled. This let us
// write unit-tests.
dump_mir_results(infcx, liveness, MirSource::item(def_id), &mir, ®ioncx);
regioncx
}
struct LivenessResults {
regular: LivenessResult,
drop: LivenessResult,
}
fn dump_mir_results<'a, 'gcx, 'tcx>(
infcx: &InferCtxt<'a, 'gcx, 'tcx>,
liveness: &LivenessResults,
source: MirSource,
mir: &Mir<'tcx>,
regioncx: &RegionInferenceContext,
) {
if !mir_util::dump_enabled(infcx.tcx, "nll", source) {
return;
}
let regular_liveness_per_location: FxHashMap<_, _> = mir.basic_blocks()
.indices()
.flat_map(|bb| {
let mut results = vec![];
liveness
.regular
.simulate_block(&mir, bb, |location, local_set| {
results.push((location, local_set.clone()));
});
results
})
.collect();
let drop_liveness_per_location: FxHashMap<_, _> = mir.basic_blocks()
.indices()
.flat_map(|bb| {
let mut results = vec![];
liveness
.drop
.simulate_block(&mir, bb, |location, local_set| {
results.push((location, local_set.clone()));
});
results
})
.collect();
mir_util::dump_mir(infcx.tcx, None, "nll", &0, source, mir, |pass_where, out| {
match pass_where {
// Before the CFG, dump out the values for each region variable.
PassWhere::BeforeCFG => for region in regioncx.regions() {
writeln!(out, "| {:?}: {:?}", region, regioncx.region_value(region))?;
},
// Before each basic block, dump out the values
// that are live on entry to the basic block.
PassWhere::BeforeBlock(bb) => {
let s = live_variable_set(&liveness.regular.ins[bb], &liveness.drop.ins[bb]);
writeln!(out, " | Live variables on entry to {:?}: {}", bb, s)?;
}
PassWhere::InCFG(location) => {
let s = live_variable_set(
®ular_liveness_per_location[&location],
&drop_liveness_per_location[&location],
);
writeln!(out, " | Live variables at {:?}: {}", location, s)?;
}
PassWhere::AfterCFG => {}
}
Ok(())
});
}
/// Right now, we piggy back on the `ReVar` to store our NLL inference
/// regions. These are indexed with `RegionVid`. This method will
/// assert that the region is a `ReVar` and extract its interal index.
/// This is reasonable because in our MIR we replace all free regions
/// with inference variables.
pub trait ToRegionVid {
fn to_region_vid(&self) -> RegionVid;
}
impl ToRegionVid for RegionKind {
fn to_region_vid(&self) -> RegionVid {
if let &ty::ReVar(vid) = self {
vid
} else {
bug!("region is not an ReVar: {:?}", self)
}
}
}
fn live_variable_set(regular: &LocalSet, drops: &LocalSet) -> String {
// sort and deduplicate:
let all_locals: BTreeSet<_> = regular.iter().chain(drops.iter()).collect();
// construct a string with each local, including `(drop)` if it is
// only dropped, versus a regular use.
let mut string = String::new();
for local in all_locals {
string.push_str(&format!("{:?}", local));
if !regular.contains(&local) {
assert!(drops.contains(&local));
string.push_str(" (drop)");
}
string.push_str(", ");
}
let len = if string.is_empty() {
0
} else {
string.len() - 2
};
format!("[{}]", &string[..len])
}
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