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Unroll switch ranges if possible.

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This commit is contained in:
Stephen Chung
2022-07-18 08:54:10 +08:00
parent 107193e35f
commit 4b760d1d0f
5 changed files with 132 additions and 60 deletions
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21
src/parser.rs
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@@ -39,6 +39,9 @@ const SCOPE_SEARCH_BARRIER_MARKER: &str = "$ BARRIER $";
/// The message: `TokenStream` never ends
const NEVER_ENDS: &str = "`Token`";
/// Unroll `switch` ranges no larger than this.
const SMALL_SWITCH_RANGE: usize = 16;
/// _(internals)_ A type that encapsulates the current state of the parser.
/// Exported under the `internals` feature only.
pub struct ParseState<'e> {
@@ -1138,6 +1141,7 @@ impl Engine {
let stmt = self.parse_stmt(input, state, lib, settings.level_up())?;
let need_comma = !stmt.is_self_terminated();
let has_condition = !matches!(condition, Expr::BoolConstant(true, ..));
blocks.push((condition, stmt).into());
let index = blocks.len() - 1;
@@ -1159,14 +1163,15 @@ impl Engine {
if let Some(mut r) = range_value {
if !r.is_empty() {
if let Some(n) = r.single_int() {
// Unroll single range
let value = Dynamic::from_int(n);
let hasher = &mut get_hasher();
value.hash(hasher);
let hash = hasher.finish();
cases.entry(hash).or_insert(index);
// Do not unroll ranges if there are previous non-unrolled ranges
if !has_condition && ranges.is_empty() && r.len() <= SMALL_SWITCH_RANGE
{
// Unroll small range
for n in r {
let hasher = &mut get_hasher();
Dynamic::from_int(n).hash(hasher);
cases.entry(hasher.finish()).or_insert(index);
}
} else {
// Other range
r.set_index(index);