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Remove extraneous branch from push #241

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merged 1 commit into from Nov 30, 2020
Merged

Remove extraneous branch from push #241

merged 1 commit into from Nov 30, 2020

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mpdn
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@mpdn mpdn commented Nov 30, 2020

push does two branches on the "smallness" of the smallvec: one before the reserve check and one after. LLVM doesn't seem to optimize the second branch away for the (very common) non-growing case. In addition, in the growing branch we know the memory will be on the heap, so no need to branch here.

On my machine, this improves bench_push from approx 300ns to 263ns (+/- 5 on both).

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mbrubeck commented Nov 30, 2020

@bors-servo r+

Thanks!

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bors-servo commented Nov 30, 2020

📌 Commit 79f4132 has been approved by mbrubeck

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bors-servo commented Nov 30, 2020

Testing commit 79f4132 with merge c3e8aa3...

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bors-servo commented Nov 30, 2020

☀️ Test successful - checks-travis
Approved by: mbrubeck
Pushing c3e8aa3 to master...

@bors-servo bors-servo merged commit c3e8aa3 into servo:master Nov 30, 2020
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mbrubeck added a commit to mbrubeck/rust-smallvec that referenced this issue Dec 4, 2020
Release notes:

* Improve performance of `push` (servo#241).
@mbrubeck mbrubeck mentioned this pull request Dec 4, 2020
bors-servo added a commit that referenced this issue Dec 4, 2020
Version 1.5.1

Release notes:

* Improve performance of `push` (#241).
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3 participants