bors c24c9067ee Auto merge of #88060 - TennyZhuang:optimize-vec-retain, r=dtolnay ... Optimize unnecessary check in Vec::retain The function `vec::Vec::retain` only have two stages: 1. Nothing was deleted. 2. Some elements were deleted. Here is an unnecessary check `if g.deleted_cnt > 0` in the loop, and it's difficult for compiler to optimize it. I split the loop into two stages manully and keep the code clean using const generics. I write a special but common bench case for this optimization. I call retain on vec but keep all elements. Before and after this optimization: ``` test vec::bench_retain_whole_100000 ... bench: 84,803 ns/iter (+/- 17,314) ``` ``` test vec::bench_retain_whole_100000 ... bench: 42,638 ns/iter (+/- 16,910) ``` The result is expected, there are two `if`s before the optimization and one `if` after.		2021-10-03 06:24:06 +00:00
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benches	Add benchmark for Vec::retain	2021-09-17 02:55:12 +08:00
src	Auto merge of #88060 - TennyZhuang:optimize-vec-retain, r=dtolnay	2021-10-03 06:24:06 +00:00
tests	Stabilize Iterator::map_while	2021-09-17 19:42:46 +03:00
Cargo.toml	rfc3052: Remove authors field from Cargo manifests	2021-07-29 14:56:05 -07:00