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Speed up IntRange::from_pat

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Previously, this method called the more general `pat_constructor`
function, which can return other pattern variants besides `IntRange`.
Then it throws away any non-`IntRange` variants. Specialize it so work
is only done when it could result in an `IntRange`.
This commit is contained in:
Dylan MacKenzie 2020-09-22 12:41:30 -07:00
parent 1ec980d225
commit bb6c249f99
1 changed files with 27 additions and 3 deletions
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30
compiler/rustc_mir_build/src/thir/pattern/_match.rs
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@ -1787,9 +1787,32 @@ impl<'tcx> IntRange<'tcx> {
param_env: ty::ParamEnv<'tcx>,
pat: &Pat<'tcx>,
) -> Option<IntRange<'tcx>> {
match pat_constructor(tcx, param_env, pat)? {
IntRange(range) => Some(range),
_ => None,
// This MUST be kept in sync with `pat_constructor`.
match *pat.kind {
PatKind::AscribeUserType { .. } => bug!(), // Handled by `expand_pattern`
PatKind::Or { .. } => bug!("Or-pattern should have been expanded earlier on."),
PatKind::Binding { .. }
| PatKind::Wild
| PatKind::Leaf { .. }
| PatKind::Deref { .. }
| PatKind::Variant { .. }
| PatKind::Array { .. }
| PatKind::Slice { .. } => None,
PatKind::Constant { value } => Self::from_const(tcx, param_env, value, pat.span),
PatKind::Range(PatRange { lo, hi, end }) => {
let ty = lo.ty;
Self::from_range(
tcx,
lo.eval_bits(tcx, param_env, lo.ty),
hi.eval_bits(tcx, param_env, hi.ty),
ty,
&end,
pat.span,
)
}
}
}
@ -2196,6 +2219,7 @@ fn pat_constructor<'tcx>(
param_env: ty::ParamEnv<'tcx>,
pat: &Pat<'tcx>,
) -> Option<Constructor<'tcx>> {
// This MUST be kept in sync with `IntRange::from_pat`.
match *pat.kind {
PatKind::AscribeUserType { .. } => bug!(), // Handled by `expand_pattern`
PatKind::Binding { .. } | PatKind::Wild => None,