5b24e12785
Simplify the implementation of iterators over slices of ZSTs Currently, slice iterators over ZSTs store `end = start.wrapping_byte_add(len)`. That's slightly convenient for `is_empty`, but kinda annoying for pretty much everything else -- see bugs like #42789, for example. This PR instead changes it to just `end = ptr::invalid(len)` instead. That's easier to think about (IMHO, at least) as well as easier to represent. `next` is still to big to get inlined into the mir-opt/pre-codegen/ tests, but if I bump the inline threshold to force it to show the whole thing, this implementation is also less MIR: ``` > git diff --numstat 241 370 tests/mir-opt/pre-codegen/slice_iter.forward_loop.PreCodegen.after.mir 255 329 tests/mir-opt/pre-codegen/slice_iter.reverse_loop.PreCodegen.after.mir 184 216 tests/mir-opt/pre-codegen/slice_iter.slice_iter_mut_next_back.PreCodegen.after.mir 182 254 tests/mir-opt/pre-codegen/slice_iter.slice_iter_next.PreCodegen.after.mir ``` (That's ≈70 lines less for `Iter::next`, for example.) r? `@ghost` ~~Built atop #111282, so draft until that lands.~~ |
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| Cargo.toml | ||