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Auto merge of #77229 - tmiasko:liveness, r=lcnr 

Small improvements in liveness pass

* Remove redundant debug logging (`add_variable` already contains logging).
* Remove redundant fields for a number of live nodes and variables.
* Delay conversion from a symbol to a string until linting.
* Inline contents of specials struct.
* Remove unnecessary local variable exit_ln.
* Use newtype_index for Variable and LiveNode.
* Access live nodes directly through self.lnks[ln].

No functional changes intended (except those related to the logging).
This commit is contained in:
bors 2020-09-27 19:38:01 +00:00
parent 4529af972e d68aa227c6
commit 7f7a1cbfd3
4 changed files with 91 additions and 121 deletions
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1
Cargo.lock
View File

@ -3891,6 +3891,7 @@ dependencies = [
"rustc_hir",
"rustc_index",
"rustc_middle",
"rustc_serialize",
"rustc_session",
"rustc_span",
"rustc_target",

1
compiler/rustc_passes/Cargo.toml
View File

@ -15,5 +15,6 @@ rustc_index = { path = "../rustc_index" }
rustc_session = { path = "../rustc_session" }
rustc_target = { path = "../rustc_target" }
rustc_ast = { path = "../rustc_ast" }
rustc_serialize = { path = "../rustc_serialize" }
rustc_span = { path = "../rustc_span" }
rustc_trait_selection = { path = "../rustc_trait_selection" }

2
compiler/rustc_passes/src/lib.rs
View File

@ -5,6 +5,8 @@
//! This API is completely unstable and subject to change.
#![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
#![feature(const_fn)]
#![feature(const_panic)]
#![feature(in_band_lifetimes)]
#![feature(nll)]
#![feature(or_patterns)]

208
compiler/rustc_passes/src/liveness.rs
View File

@ -62,13 +62,13 @@
//! - `reader`: the `LiveNode` ID of some node which will read the value
//! that `V` holds on entry to `N`. Formally: a node `M` such
//! that there exists a path `P` from `N` to `M` where `P` does not
//! write `V`. If the `reader` is `invalid_node()`, then the current
//! write `V`. If the `reader` is `INVALID_NODE`, then the current
//! value will never be read (the variable is dead, essentially).
//!
//! - `writer`: the `LiveNode` ID of some node which will write the
//! variable `V` and which is reachable from `N`. Formally: a node `M`
//! such that there exists a path `P` from `N` to `M` and `M` writes
//! `V`. If the `writer` is `invalid_node()`, then there is no writer
//! `V`. If the `writer` is `INVALID_NODE`, then there is no writer
//! of `V` that follows `N`.
//!
//! - `used`: a boolean value indicating whether `V` is *used*. We
@ -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::*;
@ -92,34 +92,29 @@ use rustc_hir::def::*;
use rustc_hir::def_id::LocalDefId;
use rustc_hir::intravisit::{self, FnKind, NestedVisitorMap, Visitor};
use rustc_hir::{Expr, HirId, HirIdMap, HirIdSet, Node};
use rustc_index::vec::IndexVec;
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;
use std::fmt;
use std::io;
use std::io::prelude::*;
use std::rc::Rc;
#[derive(Copy, Clone, PartialEq)]
struct Variable(u32);
#[derive(Copy, Clone, PartialEq)]
struct LiveNode(u32);
impl Variable {
fn get(&self) -> usize {
self.0 as usize
rustc_index::newtype_index! {
pub struct Variable {
DEBUG_FORMAT = "v({})",
}
}
impl LiveNode {
fn get(&self) -> usize {
self.0 as usize
rustc_index::newtype_index! {
pub struct LiveNode {
DEBUG_FORMAT = "ln({})",
const INVALID_NODE = LiveNode::MAX_AS_U32,
}
}
@ -183,18 +178,6 @@ pub fn provide(providers: &mut Providers) {
*providers = Providers { check_mod_liveness, ..*providers };
}
impl fmt::Debug for LiveNode {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "ln({})", self.get())
}
}
impl fmt::Debug for Variable {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
write!(f, "v({})", self.get())
}
}
// ______________________________________________________________________
// Creating ir_maps
//
@ -218,15 +201,11 @@ impl fmt::Debug for Variable {
// assignment. And so forth.
impl LiveNode {
fn is_valid(&self) -> bool {
self.0 != u32::MAX
fn is_valid(self) -> bool {
self != INVALID_NODE
}
}
fn invalid_node() -> LiveNode {
LiveNode(u32::MAX)
}
struct CaptureInfo {
ln: LiveNode,
var_hid: HirId,
@ -249,13 +228,11 @@ 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>>>,
var_kinds: Vec<VarKind>,
lnks: Vec<LiveNodeKind>,
var_kinds: IndexVec<Variable, VarKind>,
lnks: IndexVec<LiveNode, LiveNodeKind>,
}
impl IrMaps<'tcx> {
@ -263,20 +240,16 @@ 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(),
var_kinds: Vec::new(),
lnks: Vec::new(),
var_kinds: IndexVec::new(),
lnks: IndexVec::new(),
}
}
fn add_live_node(&mut self, lnk: LiveNodeKind) -> LiveNode {
let ln = LiveNode(self.num_live_nodes as u32);
self.lnks.push(lnk);
self.num_live_nodes += 1;
let ln = self.lnks.push(lnk);
debug!("{:?} is of kind {}", ln, live_node_kind_to_string(lnk, self.tcx));
@ -291,9 +264,7 @@ impl IrMaps<'tcx> {
}
fn add_variable(&mut self, vk: VarKind) -> Variable {
let v = Variable(self.num_vars as u32);
self.var_kinds.push(vk);
self.num_vars += 1;
let v = self.var_kinds.push(vk);
match vk {
Local(LocalInfo { id: node_id, .. }) | Param(node_id, _) | Upvar(node_id, _) => {
@ -315,14 +286,14 @@ impl IrMaps<'tcx> {
}
}
fn variable_name(&self, var: Variable) -> String {
match self.var_kinds[var.get()] {
Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name.to_string(),
fn variable_name(&self, var: Variable) -> Symbol {
match self.var_kinds[var] {
Local(LocalInfo { name, .. }) | Param(_, name) | Upvar(_, name) => name,
}
}
fn variable_is_shorthand(&self, var: Variable) -> bool {
match self.var_kinds[var.get()] {
match self.var_kinds[var] {
Local(LocalInfo { is_shorthand, .. }) => is_shorthand,
Param(..) | Upvar(..) => false,
}
@ -331,10 +302,6 @@ impl IrMaps<'tcx> {
fn set_captures(&mut self, hir_id: HirId, cs: Vec<CaptureInfo>) {
self.capture_info_map.insert(hir_id, Rc::new(cs));
}
fn lnk(&self, ln: LiveNode) -> LiveNodeKind {
self.lnks[ln.get()]
}
}
fn visit_fn<'tcx>(
@ -367,7 +334,6 @@ 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));
}
@ -379,7 +345,6 @@ 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 {
@ -564,10 +529,10 @@ struct RWUTable {
unpacked_rwus: Vec<RWU>,
}
// A constant representing `RWU { reader: invalid_node(); writer: invalid_node(); used: false }`.
// A constant representing `RWU { reader: INVALID_NODE; writer: INVALID_NODE; used: false }`.
const INV_INV_FALSE: u32 = u32::MAX;
// A constant representing `RWU { reader: invalid_node(); writer: invalid_node(); used: true }`.
// A constant representing `RWU { reader: INVALID_NODE; writer: INVALID_NODE; used: true }`.
const INV_INV_TRUE: u32 = u32::MAX - 1;
impl RWUTable {
@ -578,8 +543,8 @@ impl RWUTable {
fn get(&self, idx: usize) -> RWU {
let packed_rwu = self.packed_rwus[idx];
match packed_rwu {
INV_INV_FALSE => RWU { reader: invalid_node(), writer: invalid_node(), used: false },
INV_INV_TRUE => RWU { reader: invalid_node(), writer: invalid_node(), used: true },
INV_INV_FALSE => RWU { reader: INVALID_NODE, writer: INVALID_NODE, used: false },
INV_INV_TRUE => RWU { reader: INVALID_NODE, writer: INVALID_NODE, used: true },
_ => self.unpacked_rwus[packed_rwu as usize],
}
}
@ -587,7 +552,7 @@ impl RWUTable {
fn get_reader(&self, idx: usize) -> LiveNode {
let packed_rwu = self.packed_rwus[idx];
match packed_rwu {
INV_INV_FALSE | INV_INV_TRUE => invalid_node(),
INV_INV_FALSE | INV_INV_TRUE => INVALID_NODE,
_ => self.unpacked_rwus[packed_rwu as usize].reader,
}
}
@ -595,7 +560,7 @@ impl RWUTable {
fn get_writer(&self, idx: usize) -> LiveNode {
let packed_rwu = self.packed_rwus[idx];
match packed_rwu {
INV_INV_FALSE | INV_INV_TRUE => invalid_node(),
INV_INV_FALSE | INV_INV_TRUE => INVALID_NODE,
_ => self.unpacked_rwus[packed_rwu as usize].writer,
}
}
@ -615,7 +580,7 @@ impl RWUTable {
}
fn assign_unpacked(&mut self, idx: usize, rwu: RWU) {
if rwu.reader == invalid_node() && rwu.writer == invalid_node() {
if rwu.reader == INVALID_NODE && rwu.writer == INVALID_NODE {
// When we overwrite an indexing entry in `self.packed_rwus` with
// `INV_INV_{TRUE,FALSE}` we don't remove the corresponding entry
// from `self.unpacked_rwus`; it's not worth the effort, and we
@ -634,17 +599,6 @@ 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;
@ -653,10 +607,17 @@ 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>,
successors: IndexVec<LiveNode, 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)
@ -666,24 +627,23 @@ 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],
successors: IndexVec::from_elem_n(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(),
}
@ -721,18 +681,18 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
}
fn idx(&self, ln: LiveNode, var: Variable) -> usize {
ln.get() * self.ir.num_vars + var.get()
ln.index() * self.ir.var_kinds.len() + var.index()
}
fn live_on_entry(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> {
assert!(ln.is_valid());
let reader = self.rwu_table.get_reader(self.idx(ln, var));
if reader.is_valid() { Some(self.ir.lnk(reader)) } else { None }
if reader.is_valid() { Some(self.ir.lnks[reader]) } else { None }
}
// Is this variable live on entry to any of its successor nodes?
fn live_on_exit(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> {
let successor = self.successors[ln.get()];
let successor = self.successors[ln];
self.live_on_entry(successor, var)
}
@ -744,11 +704,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
fn assigned_on_entry(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> {
assert!(ln.is_valid());
let writer = self.rwu_table.get_writer(self.idx(ln, var));
if writer.is_valid() { Some(self.ir.lnk(writer)) } else { None }
if writer.is_valid() { Some(self.ir.lnks[writer]) } else { None }
}
fn assigned_on_exit(&self, ln: LiveNode, var: Variable) -> Option<LiveNodeKind> {
let successor = self.successors[ln.get()];
let successor = self.successors[ln];
self.assigned_on_entry(successor, var)
}
@ -756,9 +716,9 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
where
F: FnMut(&mut Liveness<'a, 'tcx>, usize, usize),
{
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 {
let node_base_idx = self.idx(ln, Variable::from(0u32));
let succ_base_idx = self.idx(succ_ln, Variable::from(0u32));
for var_idx in 0..self.ir.var_kinds.len() {
op(self, node_base_idx + var_idx, succ_base_idx + var_idx);
}
}
@ -767,11 +727,11 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
where
F: FnMut(usize) -> bool,
{
let node_base_idx = self.idx(ln, Variable(0));
for var_idx in 0..self.ir.num_vars {
let node_base_idx = self.idx(ln, Variable::from(0u32));
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))?;
write!(wr, " {:?}", Variable::from(var_idx))?;
}
}
Ok(())
@ -782,14 +742,14 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
let mut wr = Vec::new();
{
let wr = &mut wr as &mut dyn Write;
write!(wr, "[ln({:?}) of kind {:?} reads", ln.get(), self.ir.lnk(ln));
write!(wr, "[{:?} of kind {:?} reads", ln, self.ir.lnks[ln]);
self.write_vars(wr, ln, |idx| self.rwu_table.get_reader(idx).is_valid());
write!(wr, " writes");
self.write_vars(wr, ln, |idx| self.rwu_table.get_writer(idx).is_valid());
write!(wr, " uses");
self.write_vars(wr, ln, |idx| self.rwu_table.get_used(idx));
write!(wr, " precedes {:?}]", self.successors[ln.get()]);
write!(wr, " precedes {:?}]", self.successors[ln]);
}
String::from_utf8(wr).unwrap()
}
@ -799,8 +759,8 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
debug!(
"^^ liveness computation results for body {} (entry={:?})",
{
for ln_idx in 0..self.ir.num_live_nodes {
debug!("{:?}", self.ln_str(LiveNode(ln_idx as u32)));
for ln_idx in 0..self.ir.lnks.len() {
debug!("{:?}", self.ln_str(LiveNode::from(ln_idx)));
}
hir_id
},
@ -809,7 +769,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
}
fn init_empty(&mut self, ln: LiveNode, succ_ln: LiveNode) {
self.successors[ln.get()] = succ_ln;
self.successors[ln] = succ_ln;
// It is not necessary to initialize the RWUs here because they are all
// set to INV_INV_FALSE when they are created, and the sets only grow
@ -818,7 +778,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
fn init_from_succ(&mut self, ln: LiveNode, succ_ln: LiveNode) {
// more efficient version of init_empty() / merge_from_succ()
self.successors[ln.get()] = succ_ln;
self.successors[ln] = succ_ln;
self.indices2(ln, succ_ln, |this, idx, succ_idx| {
this.rwu_table.copy_packed(idx, succ_idx);
@ -891,7 +851,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
let mut rwu = self.rwu_table.get(idx);
if (acc & ACC_WRITE) != 0 {
rwu.reader = invalid_node();
rwu.reader = INVALID_NODE;
rwu.writer = ln;
}
@ -943,14 +903,14 @@ 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,
@ -973,19 +933,19 @@ 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
@ -1106,9 +1066,8 @@ 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;
self.propagate_through_opt_expr(o_e.as_ref().map(|e| &**e), exit_ln)
// Ignore succ and subst exit_ln.
self.propagate_through_opt_expr(o_e.as_ref().map(|e| &**e), self.exit_ln)
}
hir::ExprKind::Break(label, ref opt_expr) => {
@ -1182,7 +1141,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
self.typeck_results.expr_ty(expr),
self.param_env,
) {
self.s.exit_ln
self.exit_ln
} else {
succ
};
@ -1197,7 +1156,7 @@ impl<'a, 'tcx> Liveness<'a, 'tcx> {
self.typeck_results.expr_ty(expr),
self.param_env,
) {
self.s.exit_ln
self.exit_ln
} else {
succ
};
@ -1234,7 +1193,7 @@ 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
};
@ -1595,7 +1554,14 @@ 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) {
@ -1667,7 +1633,7 @@ 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));
@ -1697,7 +1663,7 @@ 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(