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Small improvements in liveness pass #77229

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merged 7 commits into from
Sep 27, 2020
Merged

Small improvements in liveness pass #77229

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9b5835e
liveness: Remove redundant debug logging
tmiasko Sep 26, 2020
2fb1564
liveness: Remove redundant fields for a number of live nodes and vari…
tmiasko Sep 26, 2020
70f150b
liveness: Delay conversion from a symbol to a string until linting
tmiasko Sep 26, 2020
141b91d
liveness: Inline contents of specials struct
tmiasko Sep 26, 2020
49d1ce0
liveness: Remove unnecessary local variable exit_ln
tmiasko Sep 26, 2020
57d3897
liveness: Use newtype_index for Variable and LiveNode
tmiasko Sep 26, 2020
d68aa22
liveness: Access live nodes directly through self.lnks[ln]
tmiasko Sep 27, 2020
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96 changes: 45 additions & 51 deletions compiler/rustc_passes/src/liveness.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,7 +79,7 @@
//! ## Special nodes and variables
//!
//! We generate various special nodes for various, well, special purposes.
//! These are described in the `Specials` struct.
//! These are described in the `Liveness` struct.

use self::LiveNodeKind::*;
use self::VarKind::*;
Expand All @@ -96,7 +96,7 @@ use rustc_middle::hir::map::Map;
use rustc_middle::ty::query::Providers;
use rustc_middle::ty::{self, TyCtxt};
use rustc_session::lint;
use rustc_span::symbol::{sym, Symbol};
use rustc_span::symbol::{kw, sym, Symbol};
use rustc_span::Span;

use std::collections::VecDeque;
Expand Down Expand Up @@ -249,8 +249,6 @@ enum VarKind {
struct IrMaps<'tcx> {
tcx: TyCtxt<'tcx>,
body_owner: LocalDefId,
num_live_nodes: usize,
num_vars: usize,
live_node_map: HirIdMap<LiveNode>,
variable_map: HirIdMap<Variable>,
capture_info_map: HirIdMap<Rc<Vec<CaptureInfo>>>,
Expand All @@ -263,8 +261,6 @@ impl IrMaps<'tcx> {
IrMaps {
tcx,
body_owner,
num_live_nodes: 0,
num_vars: 0,
live_node_map: HirIdMap::default(),
variable_map: HirIdMap::default(),
capture_info_map: Default::default(),
Expand All @@ -274,9 +270,8 @@ impl IrMaps<'tcx> {
}

fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode {
let ln = LiveNode(self.num_live_nodes as u32);
let ln = LiveNode(self.lnks.len() as u32);
self.lnks.push(lnk);
self.num_live_nodes += 1;

debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx));

Expand All @@ -291,9 +286,8 @@ impl IrMaps<'tcx> {
}

fn add_variable(&mut self, vk: VarKind) -> Variable {
let v = Variable(self.num_vars as u32);
let v = Variable(self.var_kinds.len() as u32);
self.var_kinds.push(vk);
self.num_vars += 1;

match vk {
Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => {
Expand All @@ -315,9 +309,9 @@ impl IrMaps<'tcx> {
}
}

fn variable_name(&self, var: Variable) -> String {
fn variable_name(&self, var: Variable) -> Symbol {
match self.var_kinds[var.get()] {
Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name.to_string(),
Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name,
}
}

Expand Down Expand Up @@ -367,7 +361,6 @@ fn visit_fn<'tcx>(

if let Some(upvars) = ir.tcx.upvars_mentioned(def_id) {
for (&var_hir_id, _upvar) in upvars {
debug!("adding upvar {:?}", var_hir_id);
let var_name = ir.tcx.hir().name(var_hir_id);
fn_maps.add_variable(Upvar(var_hir_id, var_name));
}
Expand All @@ -379,7 +372,6 @@ fn visit_fn<'tcx>(
_ => false,
};
param.pat.each_binding(|_bm, hir_id, _x, ident| {
debug!("adding parameters {:?}", hir_id);
let var = if is_shorthand {
Local(LocalInfo { id: hir_id, name: ident.name, is_shorthand: true })
} else {
Expand Down Expand Up @@ -634,17 +626,6 @@ impl RWUTable {
}
}

#[derive(Copy, Clone)]
struct Specials {
/// A live node representing a point of execution before closure entry &
/// after closure exit. Used to calculate liveness of captured variables
/// through calls to the same closure. Used for Fn & FnMut closures only.
closure_ln: LiveNode,
/// A live node representing every 'exit' from the function, whether it be
/// by explicit return, panic, or other means.
exit_ln: LiveNode,
}

const ACC_READ: u32 = 1;
const ACC_WRITE: u32 = 2;
const ACC_USE: u32 = 4;
Expand All @@ -653,10 +634,17 @@ struct Liveness<'a, 'tcx> {
ir: &'a mut IrMaps<'tcx>,
typeck_results: &'a ty::TypeckResults<'tcx>,
param_env: ty::ParamEnv<'tcx>,
s: Specials,
successors: Vec<LiveNode>,
rwu_table: RWUTable,

/// A live node representing a point of execution before closure entry &
/// after closure exit. Used to calculate liveness of captured variables
/// through calls to the same closure. Used for Fn & FnMut closures only.
closure_ln: LiveNode,
/// A live node representing every 'exit' from the function, whether it be
/// by explicit return, panic, or other means.
exit_ln: LiveNode,

// mappings from loop node ID to LiveNode
// ("break" label should map to loop node ID,
// it probably doesn't now)
Expand All @@ -666,24 +654,23 @@ struct Liveness<'a, 'tcx> {

impl<'a, 'tcx> Liveness<'a, 'tcx> {
fn new(ir: &'a mut IrMaps<'tcx>, def_id: LocalDefId) -> Liveness<'a, 'tcx> {
let specials = Specials {
closure_ln: ir.add_live_node(ClosureNode),
exit_ln: ir.add_live_node(ExitNode),
};

let typeck_results = ir.tcx.typeck(def_id);
let param_env = ir.tcx.param_env(def_id);

let num_live_nodes = ir.num_live_nodes;
let num_vars = ir.num_vars;
let closure_ln = ir.add_live_node(ClosureNode);
let exit_ln = ir.add_live_node(ExitNode);

let num_live_nodes = ir.lnks.len();
let num_vars = ir.var_kinds.len();

Liveness {
ir,
typeck_results,
param_env,
s: specials,
successors: vec![invalid_node(); num_live_nodes],
rwu_table: RWUTable::new(num_live_nodes * num_vars),
closure_ln,
exit_ln,
break_ln: Default::default(),
cont_ln: Default::default(),
}
Expand Down Expand Up @@ -721,7 +708,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
}

fn idx(&self, ln: LiveNode, var: Variable) -> usize {
ln.get() * self.ir.num_vars + var.get()
ln.get() * self.ir.var_kinds.len() + var.get()
}

fn live_on_entry(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> {
Expand Down Expand Up @@ -758,7 +745,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
{
let node_base_idx = self.idx(ln, Variable(0));
let succ_base_idx = self.idx(succ_ln, Variable(0));
for var_idx in 0..self.ir.num_vars {
for var_idx in 0..self.ir.var_kinds.len() {
op(self, node_base_idx + var_idx, succ_base_idx + var_idx);
}
}
Expand All @@ -768,7 +755,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
F: FnMut(usize) -> bool,
{
let node_base_idx = self.idx(ln, Variable(0));
for var_idx in 0..self.ir.num_vars {
for var_idx in 0..self.ir.var_kinds.len() {
let idx = node_base_idx + var_idx;
if test(idx) {
write!(wr, " {:?}", Variable(var_idx as u32))?;
Expand Down Expand Up @@ -799,7 +786,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
debug!(
"^^ liveness computation results for body {} (entry={:?})",
{
for ln_idx in 0..self.ir.num_live_nodes {
for ln_idx in 0..self.ir.lnks.len() {
debug!("{:?}", self.ln_str(LiveNode(ln_idx as u32)));
}
hir_id
Expand Down Expand Up @@ -943,14 +930,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
match self.typeck_results.upvar_capture(upvar_id) {
ty::UpvarCapture::ByRef(_) => {
let var = self.variable(var_hir_id, upvar.span);
self.acc(self.s.exit_ln, var, ACC_READ | ACC_USE);
self.acc(self.exit_ln, var, ACC_READ | ACC_USE);
}
ty::UpvarCapture::ByValue(_) => {}
}
}
}

let succ = self.propagate_through_expr(&body.value, self.s.exit_ln);
let succ = self.propagate_through_expr(&body.value, self.exit_ln);

match fk {
FnKind::Method(..) | FnKind::ItemFn(..) => return succ,
Expand All @@ -973,19 +960,19 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
// Propagate through calls to the closure.
let mut first_merge = true;
loop {
self.init_from_succ(self.s.closure_ln, succ);
self.init_from_succ(self.closure_ln, succ);
for param in body.params {
param.pat.each_binding(|_bm, hir_id, _x, ident| {
let var = self.variable(hir_id, ident.span);
self.define(self.s.closure_ln, var);
self.define(self.closure_ln, var);
})
}

if !self.merge_from_succ(self.s.exit_ln, self.s.closure_ln, first_merge) {
if !self.merge_from_succ(self.exit_ln, self.closure_ln, first_merge) {
break;
}
first_merge = false;
assert_eq!(succ, self.propagate_through_expr(&body.value, self.s.exit_ln));
assert_eq!(succ, self.propagate_through_expr(&body.value, self.exit_ln));
}

succ
Expand Down Expand Up @@ -1107,7 +1094,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {

hir::ExprKind::Ret(ref o_e) => {
// ignore succ and subst exit_ln:
let exit_ln = self.s.exit_ln;
let exit_ln = self.exit_ln;
self.propagate_through_opt_expr(o_e.as_ref().map(|e| &**e), exit_ln)
}

Expand Down Expand Up @@ -1182,7 +1169,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
self.typeck_results.expr_ty(expr),
self.param_env,
) {
self.s.exit_ln
self.exit_ln
} else {
succ
};
Expand All @@ -1197,7 +1184,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
self.typeck_results.expr_ty(expr),
self.param_env,
) {
self.s.exit_ln
self.exit_ln
} else {
succ
};
Expand Down Expand Up @@ -1234,7 +1221,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
hir::ExprKind::InlineAsm(ref asm) => {
// Handle non-returning asm
let mut succ = if asm.options.contains(InlineAsmOptions::NORETURN) {
self.s.exit_ln
self.exit_ln
} else {
succ
};
Expand Down Expand Up @@ -1595,7 +1582,14 @@ impl<'tcx> Liveness<'_, 'tcx> {

fn should_warn(&self, var: Variable) -> Option<String> {
let name = self.ir.variable_name(var);
if name.is_empty() || name.as_bytes()[0] == b'_' { None } else { Some(name) }
if name == kw::Invalid {
return None;
}
let name: &str = &name.as_str();
if name.as_bytes()[0] == b'_' {
return None;
}
Some(name.to_owned())
}

fn warn_about_unused_upvars(&self, entry_ln: LiveNode) {
Expand Down Expand Up @@ -1667,7 +1661,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
// bindings, and we also consider the first pattern to be the "authoritative" set of ids.
// However, we should take the ids and spans of variables with the same name from the later
// patterns so the suggestions to prefix with underscores will apply to those too.
let mut vars: FxIndexMap<String, (LiveNode, Variable, Vec<(HirId, Span)>)> = <_>::default();
let mut vars: FxIndexMap<Symbol, (LiveNode, Variable, Vec<(HirId, Span)>)> = <_>::default();

pat.each_binding(|_, hir_id, pat_sp, ident| {
let ln = entry_ln.unwrap_or_else(|| self.live_node(hir_id, pat_sp));
Expand Down Expand Up @@ -1697,7 +1691,7 @@ impl<'tcx> Liveness<'_, 'tcx> {
// {ret}`, there is only one node, so asking about
// assigned_on_exit() is not meaningful.
let is_assigned =
if ln == self.s.exit_ln { false } else { self.assigned_on_exit(ln, var).is_some() };
if ln == self.exit_ln { false } else { self.assigned_on_exit(ln, var).is_some() };

if is_assigned {
self.ir.tcx.struct_span_lint_hir(
Expand Down