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Encode dep node edge count as u32 instead of usize #139636

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Merged
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Apr 14, 2025
Merged

Encode dep node edge count as u32 instead of usize #139636

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18 changes: 10 additions & 8 deletions compiler/rustc_query_system/src/dep_graph/serialized.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -226,12 +226,12 @@ impl SerializedDepGraph {

// If the length of this node's edge list is small, the length is stored in the header.
// If it is not, we fall back to another decoder call.
let num_edges = node_header.len().unwrap_or_else(|| d.read_usize());
let num_edges = node_header.len().unwrap_or_else(|| d.read_u32());

// The edges index list uses the same varint strategy as rmeta tables; we select the
// number of byte elements per-array not per-element. This lets us read the whole edge
// list for a node with one decoder call and also use the on-disk format in memory.
let edges_len_bytes = node_header.bytes_per_index() * num_edges;
let edges_len_bytes = node_header.bytes_per_index() * (num_edges as usize);
// The in-memory structure for the edges list stores the byte width of the edges on
// this node with the offset into the global edge data array.
let edges_header = node_header.edges_header(&edge_list_data);
Expand Down Expand Up @@ -296,7 +296,7 @@ struct SerializedNodeHeader<D> {
// The fields of a `SerializedNodeHeader`, this struct is an implementation detail and exists only
// to make the implementation of `SerializedNodeHeader` simpler.
struct Unpacked {
len: Option<usize>,
len: Option<u32>,
bytes_per_index: usize,
kind: DepKind,
hash: PackedFingerprint,
Expand Down Expand Up @@ -352,7 +352,7 @@ impl<D: Deps> SerializedNodeHeader<D> {
assert_eq!(fingerprint, res.fingerprint());
assert_eq!(node, res.node());
if let Some(len) = res.len() {
assert_eq!(edge_count, len);
assert_eq!(edge_count, len as usize);
}
}
Self { bytes, _marker: PhantomData }
Expand All @@ -366,7 +366,7 @@ impl<D: Deps> SerializedNodeHeader<D> {

let kind = head & mask(Self::KIND_BITS) as u16;
let bytes_per_index = (head >> Self::KIND_BITS) & mask(Self::WIDTH_BITS) as u16;
let len = (head as usize) >> (Self::WIDTH_BITS + Self::KIND_BITS);
let len = (head as u32) >> (Self::WIDTH_BITS + Self::KIND_BITS);

Unpacked {
len: len.checked_sub(1),
Expand All @@ -378,7 +378,7 @@ impl<D: Deps> SerializedNodeHeader<D> {
}

#[inline]
fn len(&self) -> Option<usize> {
fn len(&self) -> Option<u32> {
self.unpack().len
}

Expand Down Expand Up @@ -421,7 +421,8 @@ impl NodeInfo {
e.write_array(header.bytes);

if header.len().is_none() {
e.emit_usize(edges.len());
// The edges are all unique and the number of unique indices is less than u32::MAX.
e.emit_u32(edges.len().try_into().unwrap());
}

let bytes_per_index = header.bytes_per_index();
Expand Down Expand Up @@ -456,7 +457,8 @@ impl NodeInfo {
e.write_array(header.bytes);

if header.len().is_none() {
e.emit_usize(edge_count);
// The edges are all unique and the number of unique indices is less than u32::MAX.
e.emit_u32(edge_count.try_into().unwrap());
}

let bytes_per_index = header.bytes_per_index();
Expand Down
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