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Anticipate allocation sizes

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This commit is contained in:
Nadrieril 2023-12-01 01:14:35 +01:00
parent bd3a22115f
commit 7058df2f4e
1 changed files with 8 additions and 15 deletions
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23
compiler/rustc_mir_build/src/thir/pattern/usefulness.rs
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@ -599,9 +599,9 @@ impl<'p, 'tcx> PatStack<'p, 'tcx> {
// an or-pattern. Panics if `self` is empty.
fn expand_or_pat<'a>(&'a self) -> impl Iterator<Item = PatStack<'p, 'tcx>> + Captures<'a> {
self.head().flatten_or_pat().into_iter().map(move |pat| {
let mut new_pats = smallvec![pat];
new_pats.extend_from_slice(&self.pats[1..]);
PatStack { pats: new_pats }
let mut new = self.clone();
new.pats[0] = pat;
new
})
}
@ -732,18 +732,11 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
}
/// Build a new matrix from an iterator of `MatchArm`s.
fn new<'a>(
cx: &MatchCheckCtxt<'p, 'tcx>,
iter: impl Iterator<Item = &'a MatchArm<'p, 'tcx>>,
scrut_ty: Ty<'tcx>,
) -> Self
where
'p: 'a,
{
fn new(cx: &MatchCheckCtxt<'p, 'tcx>, arms: &[MatchArm<'p, 'tcx>], scrut_ty: Ty<'tcx>) -> Self {
let wild_pattern = cx.pattern_arena.alloc(DeconstructedPat::wildcard(scrut_ty, DUMMY_SP));
let wildcard_row = PatStack::from_pattern(wild_pattern);
let mut matrix = Matrix { rows: vec![], wildcard_row };
for (row_id, arm) in iter.enumerate() {
let mut matrix = Matrix { rows: Vec::with_capacity(arms.len()), wildcard_row };
for (row_id, arm) in arms.iter().enumerate() {
let v = MatrixRow {
pats: PatStack::from_pattern(arm.pat),
parent_row: row_id, // dummy, we won't read it
@ -806,7 +799,7 @@ impl<'p, 'tcx> Matrix<'p, 'tcx> {
ctor: &Constructor<'tcx>,
) -> Matrix<'p, 'tcx> {
let wildcard_row = self.wildcard_row.pop_head_constructor(pcx, ctor);
let mut matrix = Matrix { rows: vec![], wildcard_row };
let mut matrix = Matrix { rows: Vec::new(), wildcard_row };
for (i, row) in self.rows().enumerate() {
if ctor.is_covered_by(pcx, row.head().ctor()) {
let new_row = row.pop_head_constructor(pcx, ctor, i);
@ -1386,7 +1379,7 @@ pub(crate) fn compute_match_usefulness<'p, 'tcx>(
arms: &[MatchArm<'p, 'tcx>],
scrut_ty: Ty<'tcx>,
) -> UsefulnessReport<'p, 'tcx> {
let mut matrix = Matrix::new(cx, arms.iter(), scrut_ty);
let mut matrix = Matrix::new(cx, arms, scrut_ty);
let non_exhaustiveness_witnesses =
compute_exhaustiveness_and_reachability(cx, &mut matrix, true);