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[naga] Use new NonMaxU32 type for Handle indices.

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Define a new type, `NonMaxU32`, that can represent any `u32` value
except `u32::MAX`, defined such that `Option<NonMaxU32>` is still a
32-bit value.

Change `Handle` to use `NonMaxU32`. Adjust all code that works
directly with handle indices to assume zero-based indices, not
one-based indices.
This commit is contained in:
Jim Blandy 2024-06-18 11:48:41 -07:00 committed by Teodor Tanasoaia
parent 7721e33693
commit 9f498fd571
7 changed files with 175 additions and 75 deletions
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41
naga/src/arena.rs
View File

@ -1,9 +1,11 @@
use std::{cmp::Ordering, fmt, hash, marker::PhantomData, num::NonZeroU32, ops};
use std::{cmp::Ordering, fmt, hash, marker::PhantomData, ops};
use crate::non_max_u32::NonMaxU32;
/// An unique index in the arena array that a handle points to.
/// The "non-zero" part ensures that an `Option<Handle<T>>` has
/// The "non-max" part ensures that an `Option<Handle<T>>` has
/// the same size and representation as `Handle<T>`.
type Index = NonZeroU32;
type Index = NonMaxU32;
use crate::{FastIndexSet, Span};
@ -89,13 +91,12 @@ impl<T> Handle<T> {
/// Returns the zero-based index of this handle.
pub const fn index(self) -> usize {
let index = self.index.get() - 1;
index as usize
self.index.get() as usize
}
/// Convert a `usize` index into a `Handle<T>`.
fn from_usize(index: usize) -> Self {
let handle_index = u32::try_from(index + 1)
let handle_index = u32::try_from(index)
.ok()
.and_then(Index::new)
.expect("Failed to insert into arena. Handle overflows");
@ -104,7 +105,7 @@ impl<T> Handle<T> {
/// Convert a `usize` index into a `Handle<T>`, without range checks.
const unsafe fn from_usize_unchecked(index: usize) -> Self {
Handle::new(Index::new_unchecked((index + 1) as u32))
Handle::new(Index::new_unchecked(index as u32))
}
/// Write this handle's index to `formatter`, preceded by `prefix`.
@ -174,7 +175,7 @@ impl<T> Clone for Range<T> {
impl<T> fmt::Debug for Range<T> {
fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
write!(formatter, "[{}..{}]", self.inner.start + 1, self.inner.end)
write!(formatter, "[{}..{}]", self.inner.start, self.inner.end - 1)
}
}
@ -182,9 +183,10 @@ impl<T> Iterator for Range<T> {
type Item = Handle<T>;
fn next(&mut self) -> Option<Self::Item> {
if self.inner.start < self.inner.end {
let next = self.inner.start;
self.inner.start += 1;
Some(Handle {
index: NonZeroU32::new(self.inner.start).unwrap(),
index: NonMaxU32::new(next).unwrap(),
marker: self.marker,
})
} else {
@ -209,11 +211,10 @@ impl<T> Range<T> {
pub fn first_and_last(&self) -> Option<(Handle<T>, Handle<T>)> {
if self.inner.start < self.inner.end {
Some((
// `Range::new_from_bounds` expects a 1-based, start- and
// end-inclusive range, but `self.inner` is a zero-based,
// end-exclusive range.
Handle::new(Index::new(self.inner.start + 1).unwrap()),
Handle::new(Index::new(self.inner.end).unwrap()),
// `Range::new_from_bounds` expects a start- and end-inclusive
// range, but `self.inner` is an end-exclusive range.
Handle::new(Index::new(self.inner.start).unwrap()),
Handle::new(Index::new(self.inner.end - 1).unwrap()),
))
} else {
None
@ -417,10 +418,7 @@ impl<T> Arena<T> {
return Ok(());
}
// `range.inner` is zero-based, but end-exclusive, so `range.inner.end`
// is actually the right one-based index for the last handle within the
// range.
let last_handle = Handle::new(range.inner.end.try_into().unwrap());
let last_handle = Handle::new(Index::new(range.inner.end - 1).unwrap());
if self.check_contains_handle(last_handle).is_err() {
return Err(BadRangeError::new(range.clone()));
}
@ -436,7 +434,7 @@ impl<T> Arena<T> {
let mut index = 0;
let mut retained = 0;
self.data.retain_mut(|elt| {
let handle = Handle::new(Index::new(index as u32 + 1).unwrap());
let handle = Handle::from_usize(index);
let keep = predicate(handle, elt);
// Since `predicate` needs mutable access to each element,
@ -602,7 +600,7 @@ impl<T> UniqueArena<T> {
UniqueArenaDrain {
inner_elts: self.set.drain(..),
inner_spans: self.span_info.drain(..),
index: Index::new(1).unwrap(),
index: Index::new(0).unwrap(),
}
}
}
@ -636,8 +634,7 @@ impl<T: Eq + hash::Hash> UniqueArena<T> {
/// the item's handle and a reference to it.
pub fn iter(&self) -> impl DoubleEndedIterator<Item = (Handle<T>, &T)> {
self.set.iter().enumerate().map(|(i, v)| {
let position = i + 1;
let index = unsafe { Index::new_unchecked(position as u32) };
let index = unsafe { Index::new_unchecked(i as u32) };
(Handle::new(index), v)
})
}

42
naga/src/compact/handle_set_map.rs
View File

@ -1,14 +1,13 @@
use crate::arena::{Arena, Handle, Range, UniqueArena};
type Index = std::num::NonZeroU32;
type Index = crate::non_max_u32::NonMaxU32;
/// A set of `Handle<T>` values.
pub struct HandleSet<T> {
/// Bound on zero-based indexes of handles stored in this set.
/// Bound on indexes of handles stored in this set.
len: usize,
/// `members[i]` is true if the handle with zero-based index `i`
/// is a member.
/// `members[i]` is true if the handle with index `i` is a member.
members: bit_set::BitSet,
/// This type is indexed by values of type `T`.
@ -27,8 +26,6 @@ impl<T> HandleSet<T> {
/// Add `handle` to the set.
pub fn insert(&mut self, handle: Handle<T>) {
// Note that, oddly, `Handle::index` does not return a 1-based
// `Index`, but rather a zero-based `usize`.
self.members.insert(handle.index());
}
@ -40,8 +37,6 @@ impl<T> HandleSet<T> {
}
pub fn contains(&self, handle: Handle<T>) -> bool {
// Note that, oddly, `Handle::index` does not return a 1-based
// `Index`, but rather a zero-based `usize`.
self.members.contains(handle.index())
}
}
@ -66,10 +61,9 @@ impl<T: std::hash::Hash + Eq> ArenaType<T> for UniqueArena<T> {
pub struct HandleMap<T> {
/// The indices assigned to handles in the compacted module.
///
/// If `new_index[i]` is `Some(n)`, then `n` is the 1-based
/// `Index` of the compacted `Handle` corresponding to the
/// pre-compacted `Handle` whose zero-based index is `i`. ("Clear
/// as mud.")
/// If `new_index[i]` is `Some(n)`, then `n` is the `Index` of the
/// compacted `Handle` corresponding to the pre-compacted `Handle`
/// whose index is `i`.
new_index: Vec<Option<Index>>,
/// This type is indexed by values of type `T`.
@ -78,11 +72,11 @@ pub struct HandleMap<T> {
impl<T: 'static> HandleMap<T> {
pub fn from_set(set: HandleSet<T>) -> Self {
let mut next_index = Index::new(1).unwrap();
let mut next_index = Index::new(0).unwrap();
Self {
new_index: (0..set.len)
.map(|zero_based_index| {
if set.members.contains(zero_based_index) {
.map(|index| {
if set.members.contains(index) {
// This handle will be retained in the compacted version,
// so assign it a new index.
let this = next_index;
@ -111,11 +105,9 @@ impl<T: 'static> HandleMap<T> {
log::trace!(
"adjusting {} handle [{}] -> [{:?}]",
std::any::type_name::<T>(),
old.index() + 1,
old.index(),
self.new_index[old.index()]
);
// Note that `Handle::index` returns a zero-based index,
// but `Handle::new` accepts a 1-based `Index`.
self.new_index[old.index()].map(Handle::new)
}
@ -147,20 +139,18 @@ impl<T: 'static> HandleMap<T> {
pub fn adjust_range(&self, range: &mut Range<T>, compacted_arena: &Arena<T>) {
let mut index_range = range.zero_based_index_range();
let compacted;
// Remember that the indices we retrieve from `new_index` are 1-based
// compacted indices, but the index range we're computing is zero-based
// compacted indices.
if let Some(first1) = index_range.find_map(|i| self.new_index[i as usize]) {
if let Some(first) = index_range.find_map(|i| self.new_index[i as usize]) {
// The first call to `find_map` mutated `index_range` to hold the
// remainder of original range, which is exactly the range we need
// to search for the new last handle.
if let Some(last1) = index_range.rev().find_map(|i| self.new_index[i as usize]) {
// Build a zero-based end-exclusive range, given one-based handle indices.
compacted = first1.get() - 1..last1.get();
if let Some(last) = index_range.rev().find_map(|i| self.new_index[i as usize]) {
// Build an end-exclusive range, given the two included indices
// `first` and `last`.
compacted = first.get()..last.get() + 1;
} else {
// The range contains only a single live handle, which
// we identified with the first `find_map` call.
compacted = first1.get() - 1..first1.get();
compacted = first.get()..first.get() + 1;
}
} else {
compacted = 0..0;

1
naga/src/lib.rs
View File

@ -277,6 +277,7 @@ pub mod compact;
pub mod error;
pub mod front;
pub mod keywords;
mod non_max_u32;
pub mod proc;
mod span;
pub mod valid;

111
naga/src/non_max_u32.rs Normal file
View File

@ -0,0 +1,111 @@
//! [`NonMaxU32`], a 32-bit type that can represent any value except [`u32::MAX`].
//!
//! Naga would like `Option<Handle<T>>` to be a 32-bit value, which means we
//! need to exclude some index value for use in representing [`None`]. We could
//! have [`Handle`] store a [`NonZeroU32`], but zero is a very useful value for
//! indexing. We could have a [`Handle`] store a value one greater than its index,
//! but it turns out that it's not uncommon to want to work with [`Handle`]s'
//! indices, so that bias of 1 becomes more visible than one would like.
//!
//! This module defines the type [`NonMaxU32`], for which `Option<NonMaxU32>` is
//! still a 32-bit value, but which is directly usable as a [`Handle`] index
//! type. It still uses a bias of 1 under the hood, but that fact is isolated
//! within the implementation.
//!
//! [`Handle`]: crate::arena::Handle
//! [`NonZeroU32`]: std::num::NonZeroU32
#![allow(dead_code)]
use std::num::NonZeroU32;
/// An unsigned 32-bit value known not to be [`u32::MAX`].
///
/// A `NonMaxU32` value can represent any value in the range `0 .. u32::MAX -
/// 1`, and an `Option<NonMaxU32>` is still a 32-bit value. In other words,
/// `NonMaxU32` is just like [`NonZeroU32`], except that a different value is
/// missing from the full `u32` range.
///
/// Since zero is a very useful value in indexing, `NonMaxU32` is more useful
/// for representing indices than [`NonZeroU32`].
///
/// # Implementation
///
/// A `NonMaxU32` whose value is `n` is a newtype around a [`NonZeroU32`] whose
/// value is `n + 1`. This way, the range of values `NonMaxU32` can represent,
/// `0..=u32::MAX - 1`, is mapped to the range `1..=u32::MAX`, which is the
/// range that [`NonZeroU32`] can represent. (And conversely, since [`u32`]
/// addition wraps around, the unrepresentable value [`u32::MAX`] becomes the
/// unrepresentable value `0`.)
///
/// [`NonZeroU32`]: std::num::NonZeroU32
#[derive(Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)]
#[cfg_attr(feature = "serialize", derive(serde::Serialize))]
#[cfg_attr(feature = "deserialize", derive(serde::Deserialize))]
#[cfg_attr(
any(feature = "serialize", feature = "deserialize"),
serde(transparent)
)]
#[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
pub struct NonMaxU32(NonZeroU32);
impl NonMaxU32 {
/// Construct a [`NonMaxU32`] whose value is `n`, if possible.
pub const fn new(n: u32) -> Option<Self> {
// If `n` is `u32::MAX`, then `n.wrapping_add(1)` is `0`,
// so `NonZeroU32::new` returns `None` in exactly the case
// where we must return `None`.
match NonZeroU32::new(n.wrapping_add(1)) {
Some(non_zero) => Some(NonMaxU32(non_zero)),
None => None,
}
}
/// Return the value of `self` as a [`u32`].
pub const fn get(self) -> u32 {
self.0.get() - 1
}
/// Construct a [`NonMaxU32`] whose value is `n`.
///
/// # Safety
///
/// The value of `n` must not be [`u32::MAX`].
pub const unsafe fn new_unchecked(n: u32) -> NonMaxU32 {
NonMaxU32(unsafe { NonZeroU32::new_unchecked(n + 1) })
}
/// Construct a [`NonMaxU32`] whose value is `index`.
///
/// # Safety
///
/// - The value of `index` must be strictly less than [`u32::MAX`].
pub const unsafe fn from_usize_unchecked(index: usize) -> Self {
NonMaxU32(unsafe { NonZeroU32::new_unchecked(index as u32 + 1) })
}
pub fn checked_add(self, n: u32) -> Option<Self> {
// Adding `n` to `self` produces `u32::MAX` if and only if
// adding `n` to `self.0` produces `0`. So we can simply
// call `NonZeroU32::checked_add` and let its check for zero
// determine whether our add would have produced `u32::MAX`.
Some(NonMaxU32(self.0.checked_add(n)?))
}
}
impl std::fmt::Debug for NonMaxU32 {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.get().fmt(f)
}
}
impl std::fmt::Display for NonMaxU32 {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
self.get().fmt(f)
}
}
#[test]
fn size() {
use core::mem::size_of;
assert_eq!(size_of::<Option<NonMaxU32>>(), size_of::<u32>());
}

2
naga/src/valid/function.rs
View File

@ -1474,7 +1474,7 @@ impl super::Validator {
if self.flags.contains(super::ValidationFlags::EXPRESSIONS) {
if let Some(unvisited) = self.needs_visit.iter().next() {
let index = std::num::NonZeroU32::new(unvisited as u32 + 1).unwrap();
let index = crate::non_max_u32::NonMaxU32::new(unvisited as u32).unwrap();
let handle = Handle::new(index);
return Err(FunctionError::UnvisitedExpression(handle)
.with_span_handle(handle, &fun.expressions));

5
naga/src/valid/handles.rs
View File

@ -5,11 +5,12 @@ use crate::{
Handle,
};
use crate::non_max_u32::NonMaxU32;
use crate::{Arena, UniqueArena};
use super::ValidationError;
use std::{convert::TryInto, hash::Hash, num::NonZeroU32};
use std::{convert::TryInto, hash::Hash};
impl super::Validator {
/// Validates that all handles within `module` are:
@ -688,7 +689,7 @@ impl<T> Handle<T> {
Ok(self)
} else {
let erase_handle_type = |handle: Handle<_>| {
Handle::new(NonZeroU32::new((handle.index() + 1).try_into().unwrap()).unwrap())
Handle::new(NonMaxU32::new((handle.index()).try_into().unwrap()).unwrap())
};
Err(FwdDepError {
subject: erase_handle_type(self),

48
naga/tests/out/dot/quad.dot
View File

@ -1,23 +1,23 @@
digraph Module {
subgraph cluster_globals {
label="Globals"
g0 [ shape=hexagon label="[1] Handle/'u_texture'" ]
g1 [ shape=hexagon label="[2] Handle/'u_sampler'" ]
g0 [ shape=hexagon label="[0] Handle/'u_texture'" ]
g1 [ shape=hexagon label="[1] Handle/'u_sampler'" ]
}
subgraph cluster_ep0 {
label="Vertex/'vert_main'"
node [ style=filled ]
ep0_e0 [ color="#8dd3c7" label="[1] Argument[0]" ]
ep0_e1 [ color="#8dd3c7" label="[2] Argument[1]" ]
ep0_e2 [ fillcolor="#ffffb3" label="[3] Constant" ]
ep0_e3 [ color="#fdb462" label="[4] Multiply" ]
ep0_e0 [ color="#8dd3c7" label="[0] Argument[0]" ]
ep0_e1 [ color="#8dd3c7" label="[1] Argument[1]" ]
ep0_e2 [ fillcolor="#ffffb3" label="[2] Constant" ]
ep0_e3 [ color="#fdb462" label="[3] Multiply" ]
ep0_e0 -> ep0_e3 [ label="right" ]
ep0_e2 -> ep0_e3 [ label="left" ]
ep0_e4 [ fillcolor="#ffffb3" label="[5] Literal" ]
ep0_e5 [ fillcolor="#ffffb3" label="[6] Literal" ]
ep0_e6 [ color="#bebada" label="[7] Compose" ]
ep0_e4 [ fillcolor="#ffffb3" label="[4] Literal" ]
ep0_e5 [ fillcolor="#ffffb3" label="[5] Literal" ]
ep0_e6 [ color="#bebada" label="[6] Compose" ]
{ ep0_e3 ep0_e4 ep0_e5 } -> ep0_e6
ep0_e7 [ color="#bebada" label="[8] Compose" ]
ep0_e7 [ color="#bebada" label="[7] Compose" ]
{ ep0_e1 ep0_e6 } -> ep0_e7
ep0_s0 [ shape=square label="Root" ]
ep0_s1 [ shape=square label="Emit" ]
@ -34,24 +34,24 @@ digraph Module {
subgraph cluster_ep1 {
label="Fragment/'frag_main'"
node [ style=filled ]
ep1_e0 [ color="#8dd3c7" label="[1] Argument[0]" ]
ep1_e1 [ color="#ffffb3" label="[2] Global" ]
ep1_e0 [ color="#8dd3c7" label="[0] Argument[0]" ]
ep1_e1 [ color="#ffffb3" label="[1] Global" ]
g0 -> ep1_e1 [fillcolor=gray]
ep1_e2 [ color="#ffffb3" label="[3] Global" ]
ep1_e2 [ color="#ffffb3" label="[2] Global" ]
g1 -> ep1_e2 [fillcolor=gray]
ep1_e3 [ color="#80b1d3" label="[4] ImageSample" ]
ep1_e3 [ color="#80b1d3" label="[3] ImageSample" ]
ep1_e2 -> ep1_e3 [ label="sampler" ]
ep1_e1 -> ep1_e3 [ label="image" ]
ep1_e0 -> ep1_e3 [ label="coordinate" ]
ep1_e4 [ color="#8dd3c7" label="[5] AccessIndex[3]" ]
ep1_e4 [ color="#8dd3c7" label="[4] AccessIndex[3]" ]
ep1_e3 -> ep1_e4 [ label="base" ]
ep1_e5 [ fillcolor="#ffffb3" label="[6] Literal" ]
ep1_e6 [ color="#fdb462" label="[7] Equal" ]
ep1_e5 [ fillcolor="#ffffb3" label="[5] Literal" ]
ep1_e6 [ color="#fdb462" label="[6] Equal" ]
ep1_e5 -> ep1_e6 [ label="right" ]
ep1_e4 -> ep1_e6 [ label="left" ]
ep1_e7 [ color="#8dd3c7" label="[8] AccessIndex[3]" ]
ep1_e7 [ color="#8dd3c7" label="[7] AccessIndex[3]" ]
ep1_e3 -> ep1_e7 [ label="base" ]
ep1_e8 [ color="#fdb462" label="[9] Multiply" ]
ep1_e8 [ color="#fdb462" label="[8] Multiply" ]
ep1_e3 -> ep1_e8 [ label="right" ]
ep1_e7 -> ep1_e8 [ label="left" ]
ep1_s0 [ shape=square label="Root" ]
@ -87,11 +87,11 @@ digraph Module {
subgraph cluster_ep2 {
label="Fragment/'fs_extra'"
node [ style=filled ]
ep2_e0 [ fillcolor="#ffffb3" label="[1] Literal" ]
ep2_e1 [ fillcolor="#ffffb3" label="[2] Literal" ]
ep2_e2 [ fillcolor="#ffffb3" label="[3] Literal" ]
ep2_e3 [ fillcolor="#ffffb3" label="[4] Literal" ]
ep2_e4 [ fillcolor="#bebada" label="[5] Compose" ]
ep2_e0 [ fillcolor="#ffffb3" label="[0] Literal" ]
ep2_e1 [ fillcolor="#ffffb3" label="[1] Literal" ]
ep2_e2 [ fillcolor="#ffffb3" label="[2] Literal" ]
ep2_e3 [ fillcolor="#ffffb3" label="[3] Literal" ]
ep2_e4 [ fillcolor="#bebada" label="[4] Compose" ]
{ ep2_e0 ep2_e1 ep2_e2 ep2_e3 } -> ep2_e4
ep2_s0 [ shape=square label="Root" ]
ep2_s1 [ shape=square label="Emit" ]