Fix just a few stacked borrow issues, and improve extend performance - #111
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This simplification -- borrowing self.len instead of self, leads to an improvement in the extend_from_slice benchmark. It's also guided by the discussion of stacked borrows; the old code would be invalid, because the whole self is borrowed while ptr is derived from self.
The benchmark was optimized out totally. We think of that as a good sign, the new extend became transparent to the compiler and we had to get smarter in how to fool it.
… from self Again, stacked borrows model makes the `self.set_len()` call illegal because we are holding (and are going to use) another raw pointer derived from self, `tail`.
bluss
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Nov 25, 2018
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There is bound to be more issues to fix than this. cc #97 |
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Extend: This simplification -- borrowing self.len instead of self, leads to
an improvement in the extend_from_slice benchmark.
It's also guided by the discussion of stacked borrows; the old code
would be invalid, because the whole self is borrowed while ptr is derived from
self.
In truncate, don't access self while holding raw pointer derived from self
Again, stacked borrows model makes the
self.set_len()call illegalbecause we are holding (and are going to use) another raw pointer
derived from self,
tail.bench comparison for extend. Caveat might be that optimization can also be influenced by how the code can be optimized in the benchmark.