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Simplify implementation of Namer::namespace. (#1438)

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Eliminate `Namer::namespace_index` and remove namespace indices from
`Namer::unique` keys. Instead, implement `Namer::namespace` by just swapping in
a fresh table for the duration of the call.

Create the fresh hash table with the right initial capacity. The prior
implementation did manage to avoid allocations by sharing a hash table, and we'd
like to not lose that advantage entirely.

This has no effect on generated code.
This commit is contained in:
Jim Blandy
2021-09-29 12:55:37 -07:00
committed by GitHub
parent a4bf25a0d5
commit 92a97fb7d5
1 changed files with 21 additions and 18 deletions
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39
src/proc/namer.rs
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@@ -21,10 +21,9 @@ pub enum NameKey {
/// that may need identifiers in a textual backend.
#[derive(Default)]
pub struct Namer {
unique: FastHashMap<(String, u32), u32>,
/// The last numeric suffix used for each base name.
unique: FastHashMap<String, u32>,
keywords: FastHashSet<String>,
/// Currently active namespace.
namespace_index: u32,
reserved_prefixes: Vec<String>,
}
@@ -55,14 +54,14 @@ impl Namer {
/// This function should be used **after** [`Namer`](crate::proc::Namer) initialization by [`reset`](Self::reset()) function.
pub fn call_unique(&mut self, string: &str) -> String {
let base = self.sanitize(string);
match self.unique.entry((base, self.namespace_index)) {
match self.unique.entry(base) {
Entry::Occupied(mut e) => {
*e.get_mut() += 1;
format!("{}{}", e.key().0, e.get())
format!("{}{}", e.key(), e.get())
}
Entry::Vacant(e) => {
let name = &e.key().0;
if self.keywords.contains(&e.key().0) {
let name = e.key();
if self.keywords.contains(e.key()) {
let name = format!("{}1", name);
e.insert(1);
name
@@ -75,14 +74,14 @@ impl Namer {
pub fn call(&mut self, label_raw: &str) -> String {
let base = self.sanitize(label_raw);
match self.unique.entry((base, self.namespace_index)) {
match self.unique.entry(base) {
Entry::Occupied(mut e) => {
*e.get_mut() += 1;
format!("{}{}", e.key().0, e.get())
format!("{}{}", e.key(), e.get())
}
Entry::Vacant(e) => {
let name = &e.key().0;
if self.keywords.contains(&e.key().0) {
let name = e.key();
if self.keywords.contains(e.key()) {
let name = format!("{}1", name);
e.insert(1);
name
@@ -102,12 +101,16 @@ impl Namer {
})
}
fn namespace(&mut self, f: impl FnOnce(&mut Self)) {
self.namespace_index += 1;
f(self);
let current_ns = self.namespace_index;
self.unique.retain(|&(_, ns), _| ns != current_ns);
self.namespace_index -= 1;
/// Enter a local namespace for things like structs.
///
/// Struct member names only need to be unique amongst themselves, not
/// globally. This function temporarily establishes a fresh, empty naming
/// context for the duration of the call to `body`.
fn namespace(&mut self, capacity: usize, body: impl FnOnce(&mut Self)) {
let fresh = FastHashMap::with_capacity_and_hasher(capacity, Default::default());
let outer = std::mem::replace(&mut self.unique, fresh);
body(self);
self.unique = outer;
}
pub fn reset(
@@ -133,7 +136,7 @@ impl Namer {
if let crate::TypeInner::Struct { ref members, .. } = ty.inner {
// struct members have their own namespace, because access is always prefixed
self.namespace(|namer| {
self.namespace(members.len(), |namer| {
for (index, member) in members.iter().enumerate() {
let name = namer.call_or(&member.name, "member");
output.insert(NameKey::StructMember(ty_handle, index as u32), name);