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//! Def-use analysis.
use rustc_index::vec::IndexVec;
use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor};
use rustc_middle::mir::{Body, Local, Location, VarDebugInfo};
use rustc_middle::ty::TyCtxt;
use std::mem;
pub struct DefUseAnalysis {
info: IndexVec<Local, Info>,
}
#[derive(Clone)]
pub struct Info {
// FIXME(eddyb) use smallvec where possible.
pub defs_and_uses: Vec<Use>,
var_debug_info_indices: Vec<usize>,
}
#[derive(Clone)]
pub struct Use {
pub context: PlaceContext,
pub location: Location,
}
impl DefUseAnalysis {
pub fn new(body: &Body<'_>) -> DefUseAnalysis {
DefUseAnalysis { info: IndexVec::from_elem_n(Info::new(), body.local_decls.len()) }
}
pub fn analyze(&mut self, body: &Body<'_>) {
self.clear();
let mut finder = DefUseFinder {
info: mem::take(&mut self.info),
var_debug_info_index: 0,
in_var_debug_info: false,
};
finder.visit_body(&body);
self.info = finder.info
}
fn clear(&mut self) {
for info in &mut self.info {
info.clear();
}
}
pub fn local_info(&self, local: Local) -> &Info {
&self.info[local]
}
fn mutate_defs_and_uses(
&self,
local: Local,
body: &mut Body<'tcx>,
new_local: Local,
tcx: TyCtxt<'tcx>,
) {
let mut visitor = MutateUseVisitor::new(local, new_local, tcx);
let info = &self.info[local];
for place_use in &info.defs_and_uses {
visitor.visit_location(body, place_use.location)
}
// Update debuginfo as well, alongside defs/uses.
for &i in &info.var_debug_info_indices {
visitor.visit_var_debug_info(&mut body.var_debug_info[i]);
}
}
// FIXME(pcwalton): this should update the def-use chains.
pub fn replace_all_defs_and_uses_with(
&self,
local: Local,
body: &mut Body<'tcx>,
new_local: Local,
tcx: TyCtxt<'tcx>,
) {
self.mutate_defs_and_uses(local, body, new_local, tcx)
}
}
struct DefUseFinder {
info: IndexVec<Local, Info>,
var_debug_info_index: usize,
in_var_debug_info: bool,
}
impl Visitor<'_> for DefUseFinder {
fn visit_local(&mut self, &local: &Local, context: PlaceContext, location: Location) {
let info = &mut self.info[local];
if self.in_var_debug_info {
info.var_debug_info_indices.push(self.var_debug_info_index);
} else {
info.defs_and_uses.push(Use { context, location });
}
}
fn visit_var_debug_info(&mut self, var_debug_info: &VarDebugInfo<'tcx>) {
assert!(!self.in_var_debug_info);
self.in_var_debug_info = true;
self.super_var_debug_info(var_debug_info);
self.in_var_debug_info = false;
self.var_debug_info_index += 1;
}
}
impl Info {
fn new() -> Info {
Info { defs_and_uses: vec![], var_debug_info_indices: vec![] }
}
fn clear(&mut self) {
self.defs_and_uses.clear();
self.var_debug_info_indices.clear();
}
pub fn def_count(&self) -> usize {
self.defs_and_uses.iter().filter(|place_use| place_use.context.is_mutating_use()).count()
}
pub fn def_count_not_including_drop(&self) -> usize {
self.defs_not_including_drop().count()
}
pub fn defs_not_including_drop(&self) -> impl Iterator<Item = &Use> {
self.defs_and_uses
.iter()
.filter(|place_use| place_use.context.is_mutating_use() && !place_use.context.is_drop())
}
pub fn use_count(&self) -> usize {
self.defs_and_uses.iter().filter(|place_use| place_use.context.is_nonmutating_use()).count()
}
}
struct MutateUseVisitor<'tcx> {
query: Local,
new_local: Local,
tcx: TyCtxt<'tcx>,
}
impl MutateUseVisitor<'tcx> {
fn new(query: Local, new_local: Local, tcx: TyCtxt<'tcx>) -> MutateUseVisitor<'tcx> {
MutateUseVisitor { query, new_local, tcx }
}
}
impl MutVisitor<'tcx> for MutateUseVisitor<'tcx> {
fn tcx(&self) -> TyCtxt<'tcx> {
self.tcx
}
fn visit_local(&mut self, local: &mut Local, _context: PlaceContext, _location: Location) {
if *local == self.query {
*local = self.new_local;
}
}
}
|
