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[SR-9272] Potential invalid benchmarks (used to skip allocations) #51748

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milseman mannequin opened this issue Nov 15, 2018 · 1 comment
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[SR-9272] Potential invalid benchmarks (used to skip allocations) #51748

milseman mannequin opened this issue Nov 15, 2018 · 1 comment
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standard library Area: Standard library umbrella

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@milseman
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milseman mannequin commented Nov 15, 2018

Previous ID SR-9272
Radar None
Original Reporter @milseman
Type Sub-task
Status Resolved
Resolution Done
Additional Detail from JIRA
Votes 0
Component/s Standard Library
Labels Sub-task
Assignee None
Priority Medium

md5: b9900e5c108e58bcfd1b07d1c575141e

Parent-Task:

Issue Description:

For StringFromLongWholeSubstringGeneric and StringFromLongWholeSubstring, we spend more time now in `malloc` than the entire benchmark used to run in. It's possible that the old implementation was somehow getting constant folded away and the intended effects were not actually being measured.

We need to investigate further to make sure.
@milseman
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milseman mannequin commented Dec 6, 2018

Turns out 4.2 had a fast-path for when a Substring covers all of its backing storage. In that case, we just retain. Fixed in #21072

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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