bjoernager/rust
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Introduce DotDotPos.

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This shrinks `hir::Pat` from 88 to 72 bytes.
This commit is contained in:
Nicholas Nethercote 2022-09-01 13:29:57 +10:00
parent 4314615ff8
commit e67f39f8bc
15 changed files with 85 additions and 47 deletions
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39
compiler/rustc_hir/src/hir.rs
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@ -1059,6 +1059,35 @@ impl fmt::Display for RangeEnd {
}
}
// Equivalent to `Option<usize>`. That type takes up 16 bytes on 64-bit, but
// this type only takes up 4 bytes, at the cost of being restricted to a
// maximum value of `u32::MAX - 1`. In practice, this is more than enough.
#[derive(Clone, Copy, PartialEq, Eq, Hash, HashStable_Generic)]
pub struct DotDotPos(u32);
impl DotDotPos {
// Panics if n >= u32::MAX.
pub fn new(n: Option<usize>) -> Self {
match n {
Some(n) => {
assert!(n < u32::MAX as usize);
Self(n as u32)
}
None => Self(u32::MAX),
}
}
pub fn as_opt_usize(&self) -> Option<usize> {
if self.0 == u32::MAX { None } else { Some(self.0 as usize) }
}
}
impl fmt::Debug for DotDotPos {
fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
self.as_opt_usize().fmt(f)
}
}
#[derive(Debug, HashStable_Generic)]
pub enum PatKind<'hir> {
/// Represents a wildcard pattern (i.e., `_`).
@ -1075,9 +1104,9 @@ pub enum PatKind<'hir> {
Struct(QPath<'hir>, &'hir [PatField<'hir>], bool),
/// A tuple struct/variant pattern `Variant(x, y, .., z)`.
/// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
/// If the `..` pattern fragment is present, then `DotDotPos` denotes its position.
/// `0 <= position <= subpats.len()`
TupleStruct(QPath<'hir>, &'hir [Pat<'hir>], Option<usize>),
TupleStruct(QPath<'hir>, &'hir [Pat<'hir>], DotDotPos),
/// An or-pattern `A | B | C`.
/// Invariant: `pats.len() >= 2`.
@ -1089,7 +1118,7 @@ pub enum PatKind<'hir> {
/// A tuple pattern (e.g., `(a, b)`).
/// If the `..` pattern fragment is present, then `Option<usize>` denotes its position.
/// `0 <= position <= subpats.len()`
Tuple(&'hir [Pat<'hir>], Option<usize>),
Tuple(&'hir [Pat<'hir>], DotDotPos),
/// A `box` pattern.
Box(&'hir Pat<'hir>),
@ -3486,8 +3515,8 @@ mod size_asserts {
static_assert_size!(ItemKind<'_>, 48);
static_assert_size!(Local<'_>, 64);
static_assert_size!(Param<'_>, 32);
static_assert_size!(Pat<'_>, 88);
static_assert_size!(PatKind<'_>, 64);
static_assert_size!(Pat<'_>, 72);
static_assert_size!(PatKind<'_>, 48);
static_assert_size!(Path<'_>, 48);
static_assert_size!(PathSegment<'_>, 56);
static_assert_size!(QPath<'_>, 24);