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Handle let _ = x patterns in closure liveness analysis

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This commit is contained in:
Aman Arora 2020-11-01 16:39:47 -05:00
parent 825e9e45d1
commit fa381600dc
1 changed files with 49 additions and 20 deletions
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69
compiler/rustc_passes/src/liveness.rs
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@ -317,10 +317,11 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
// swap in a new set of IR maps for this body
let mut maps = IrMaps::new(self.tcx);
let hir_id = maps.tcx.hir().body_owner(body.id());
let def_id = maps.tcx.hir().local_def_id(hir_id);
let local_def_id = maps.tcx.hir().local_def_id(hir_id);
let def_id = local_def_id.to_def_id();
// Don't run unused pass for #[derive()]
if let Some(parent) = self.tcx.parent(def_id.to_def_id()) {
if let Some(parent) = self.tcx.parent(def_id) {
if let DefKind::Impl = self.tcx.def_kind(parent.expect_local()) {
if self.tcx.has_attr(parent, sym::automatically_derived) {
return;
@ -328,8 +329,8 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
}
}
if let Some(upvars) = maps.tcx.upvars_mentioned(def_id) {
for (&var_hir_id, _upvar) in upvars {
if let Some(captures) = maps.tcx.typeck(local_def_id).closure_captures.get(&def_id) {
for &var_hir_id in captures.keys() {
let var_name = maps.tcx.hir().name(var_hir_id);
maps.add_variable(Upvar(var_hir_id, var_name));
}
@ -340,7 +341,7 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
intravisit::walk_body(&mut maps, body);
// compute liveness
let mut lsets = Liveness::new(&mut maps, def_id);
let mut lsets = Liveness::new(&mut maps, local_def_id);
let entry_ln = lsets.compute(&body, hir_id);
lsets.log_liveness(entry_ln, body.id().hir_id);
@ -397,10 +398,18 @@ impl<'tcx> Visitor<'tcx> for IrMaps<'tcx> {
// construction site.
let mut call_caps = Vec::new();
let closure_def_id = self.tcx.hir().local_def_id(expr.hir_id);
if let Some(upvars) = self.tcx.upvars_mentioned(closure_def_id) {
call_caps.extend(upvars.iter().map(|(&var_id, upvar)| {
if let Some(captures) = self
.tcx
.typeck(closure_def_id)
.closure_captures
.get(&closure_def_id.to_def_id())
{
// If closure captures is Some, upvars_mentioned must also be Some
let upvars = self.tcx.upvars_mentioned(closure_def_id).unwrap();
call_caps.extend(captures.keys().map(|var_id| {
let upvar = upvars[var_id];
let upvar_ln = self.add_live_node(UpvarNode(upvar.span));
CaptureInfo { ln: upvar_ln, var_hid: var_id }
CaptureInfo { ln: upvar_ln, var_hid: *var_id }
}));
}
self.set_captures(expr.hir_id, call_caps);
@ -564,6 +573,7 @@ struct Liveness<'a, 'tcx> {
typeck_results: &'a ty::TypeckResults<'tcx>,
param_env: ty::ParamEnv<'tcx>,
upvars: Option<&'tcx FxIndexMap<hir::HirId, hir::Upvar>>,
closure_captures: Option<&'tcx FxIndexMap<hir::HirId, ty::UpvarId>>,
successors: IndexVec<LiveNode, Option<LiveNode>>,
rwu_table: RWUTable,
@ -587,6 +597,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
let typeck_results = ir.tcx.typeck(body_owner);
let param_env = ir.tcx.param_env(body_owner);
let upvars = ir.tcx.upvars_mentioned(body_owner);
let closure_captures = typeck_results.closure_captures.get(&body_owner.to_def_id());
let closure_ln = ir.add_live_node(ClosureNode);
let exit_ln = ir.add_live_node(ExitNode);
@ -600,6 +611,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
typeck_results,
param_env,
upvars,
closure_captures,
successors: IndexVec::from_elem_n(None, num_live_nodes),
rwu_table: RWUTable::new(num_live_nodes * num_vars),
closure_ln,
@ -850,14 +862,13 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
// if they are live on the entry to the closure, since only the closure
// itself can access them on subsequent calls.
if let Some(upvars) = self.upvars {
if let Some(closure_captures) = self.closure_captures {
// Mark upvars captured by reference as used after closure exits.
for (&var_hir_id, upvar) in upvars.iter().rev() {
let upvar_id = ty::UpvarId {
var_path: ty::UpvarPath { hir_id: var_hir_id },
closure_expr_id: self.body_owner,
};
match self.typeck_results.upvar_capture(upvar_id) {
// Since closure_captures is Some, upvars must exists too.
let upvars = self.upvars.unwrap();
for (&var_hir_id, upvar_id) in closure_captures {
let upvar = upvars[&var_hir_id];
match self.typeck_results.upvar_capture(*upvar_id) {
ty::UpvarCapture::ByRef(_) => {
let var = self.variable(var_hir_id, upvar.span);
self.acc(self.exit_ln, var, ACC_READ | ACC_USE);
@ -869,7 +880,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
let succ = self.propagate_through_expr(&body.value, self.exit_ln);
if self.upvars.is_none() {
if self.closure_captures.is_none() {
// Either not a closure, or closure without any captured variables.
// No need to determine liveness of captured variables, since there
// are none.
@ -1341,7 +1352,21 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
acc: u32,
) -> LiveNode {
match path.res {
Res::Local(hid) => self.access_var(hir_id, hid, succ, acc, path.span),
Res::Local(hid) => {
let in_upvars = self.upvars.map_or(false, |u| u.contains_key(&hid));
let in_captures = self.closure_captures.map_or(false, |c| c.contains_key(&hid));
match (in_upvars, in_captures) {
(false, _) | (true, true) => self.access_var(hir_id, hid, succ, acc, path.span),
(true, false) => {
// This case is possible when with RFC-2229, a wild pattern
// is used within a closure.
// eg: `let _ = x`. The closure doesn't capture x here,
// even though it's mentioned in the closure.
succ
}
}
}
_ => succ,
}
}
@ -1531,11 +1556,15 @@ impl<'tcx> Liveness<'_, 'tcx> {
}
fn warn_about_unused_upvars(&self, entry_ln: LiveNode) {
let upvars = match self.upvars {
let closure_captures = match self.closure_captures {
None => return,
Some(upvars) => upvars,
Some(closure_captures) => closure_captures,
};
for (&var_hir_id, upvar) in upvars.iter() {
// If closure_captures is Some(), upvars must be Some() too.
let upvars = self.upvars.unwrap();
for &var_hir_id in closure_captures.keys() {
let upvar = upvars[&var_hir_id];
let var = self.variable(var_hir_id, upvar.span);
let upvar_id = ty::UpvarId {
var_path: ty::UpvarPath { hir_id: var_hir_id },