bjoernager/rust
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Auto merge of #88242 - bonega:allocation_range, r=oli-obk

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Use custom wrap-around type instead of RangeInclusive

Two reasons:

1. More memory is allocated than necessary for `valid_range` in `Scalar`. The range is not used as an iterator and `exhausted` is never used.
2. `contains`, `count` etc. methods in `RangeInclusive` are doing very unhelpful(and dangerous!) things when used as a wrap-around range. - In general this PR wants to limit potentially confusing methods, that have a low probability of working.

Doing a local perf run, every metric shows improvement except for instructions.
Max-rss seem to have a very consistent improvement.

Sorry - newbie here, probably doing something wrong.
This commit is contained in:
bors 2021-08-25 02:17:41 +00:00
commit e5484cec0e
8 changed files with 115 additions and 81 deletions
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2
compiler/rustc_lint/src/types.rs
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@ -795,7 +795,7 @@ crate fn repr_nullable_ptr<'tcx>(
// Return the nullable type this Option-like enum can be safely represented with.
let field_ty_abi = &cx.layout_of(field_ty).unwrap().abi;
if let Abi::Scalar(field_ty_scalar) = field_ty_abi {
match (field_ty_scalar.valid_range.start(), field_ty_scalar.valid_range.end()) {
match (field_ty_scalar.valid_range.start, field_ty_scalar.valid_range.end) {
(0, _) => unreachable!("Non-null optimisation extended to a non-zero value."),
(1, _) => {
return Some(get_nullable_type(cx, field_ty).unwrap());