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Simplify hash table drops - #40739
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This replaces the `std::collections::hash::table::RevMoveBuckets` iterator with a simpler `while` loop. This iterator was only used for dropping the remaining elements of a `RawTable`, so instead we can just loop through directly and drop them in place. This should be functionally equivalent to the former code, but a little easier to read. I was hoping it might have some performance benefit too, but it seems the optimizer was already good enough to see through the iterator -- the generated code is nearly the same. Maybe it will still help if an element type has more complicated drop code.
rust-highfive
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Mar 22, 2017
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r? @sfackler (rust_highfive has picked a reviewer for you, use r? to override) |
Even if you don't see performance improvements, replacing iterators with while/for loops often reduces compilation time. You can see this very well in iterator-heavy code, that compiles much slower than equivalent code made of for/while loops (and probably the amount of RAM used to compile the code is different, the iterators-based code uses lot of types). |
arthurprs
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Mar 23, 2017
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There's no tangible benefit but I'd settle for a net loss of LOC 👍
alexcrichton
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Mar 23, 2017
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@bors: r=arthurprs delegate=arthurprs |
bors
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Mar 23, 2017
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✌️ @arthurprs can now approve this pull request |
bors
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Mar 23, 2017
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📌 Commit a033f1a has been approved by |
frewsxcv added a commit
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Mar 24, 2017
Simplify hash table drops This replaces the `std::collections::hash::table::RevMoveBuckets` iterator with a simpler `while` loop. This iterator was only used for dropping the remaining elements of a `RawTable`, so instead we can just loop through directly and drop them in place. This should be functionally equivalent to the former code, but a little easier to read. I was hoping it might have some performance benefit too, but it seems the optimizer was already good enough to see through the iterator -- the generated code is nearly the same. Maybe it will still help if an element type has more complicated drop code.
frewsxcv added a commit
to frewsxcv/rust
that referenced
this pull request
Mar 24, 2017
Simplify hash table drops This replaces the `std::collections::hash::table::RevMoveBuckets` iterator with a simpler `while` loop. This iterator was only used for dropping the remaining elements of a `RawTable`, so instead we can just loop through directly and drop them in place. This should be functionally equivalent to the former code, but a little easier to read. I was hoping it might have some performance benefit too, but it seems the optimizer was already good enough to see through the iterator -- the generated code is nearly the same. Maybe it will still help if an element type has more complicated drop code.
bors added a commit
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Mar 24, 2017
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This replaces the
std::collections::hash::table::RevMoveBucketsiterator with a simpler
whileloop. This iterator was only used fordropping the remaining elements of a
RawTable, so instead we can justloop through directly and drop them in place.
This should be functionally equivalent to the former code, but a little
easier to read. I was hoping it might have some performance benefit
too, but it seems the optimizer was already good enough to see through
the iterator -- the generated code is nearly the same. Maybe it will
still help if an element type has more complicated drop code.