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[5.0] [String] Last-minute ABI adjustment: 4-bit discriminator #21392

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Merged
merged 5 commits into from
Dec 20, 2018
Merged

[5.0] [String] Last-minute ABI adjustment: 4-bit discriminator #21392

merged 5 commits into from
Dec 20, 2018

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milseman
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@milseman milseman commented Dec 18, 2018 •
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5.0 cherry-pick of #21310

rdar://problem/46663653

@milseman milseman requested a review from a team as a code owner December 18, 2018 00:36
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@swift-ci please test

@milseman milseman requested a review from lorentey December 18, 2018 00:37
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Build failed
Swift Test Linux Platform
Git Sha - 4a4205b356bebf3b5e496db5e407d19dcfb4860a

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Swift Test OS X Platform
Git Sha - 4a4205b356bebf3b5e496db5e407d19dcfb4860a

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Failure is:

/Users/buildnode/jenkins/workspace/swift-PR-osx/branch-swift-5.0-branch/swiftpm/Sources/SourceControl/RepositoryManager.swift:42:37: error: 'Result' is ambiguous for type lookup in this context
19:41:24     public typealias LookupResult = Result<RepositoryHandle, AnyError>
19:41:24                                     ^~~~~~
19:41:24 Swift.Result:1:13: note: found this candidate
19:41:24 public enum Result<Success, Failure> where Failure : Error {
19:41:24             ^
19:41:24 Basic.Result:1:13: note: found this candidate
19:41:24 public enum Result<Value, ErrorType> where ErrorType : Error {
19:41:24             ^
19:41:24 --- bootstrap: error: build failed with exit status 1

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@swift-ci please test

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Build failed
Swift Test OS X Platform
Git Sha - 4a4205b356bebf3b5e496db5e407d19dcfb4860a

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@swift-ci please test

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Build failed
Swift Test OS X Platform
Git Sha - 4a4205b356bebf3b5e496db5e407d19dcfb4860a

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Build failed
Swift Test Linux Platform
Git Sha - 4a4205b356bebf3b5e496db5e407d19dcfb4860a

Andreas Jönsson and others added 4 commits December 19, 2018 14:17
@milseman
[stdlib] adds nullability type specifier to NSStringGetCStringTrampoline
21c59a7
@xwu @milseman
[gardening] Make edits for stdlib style [NFC]
09b5cf1
@milseman
[String] Refactor 32-bit StringObject.
9fdcb63 
Remove Discriminator, Flags, etc., abstractions from
StringObject. These cause code divergence between 32-bit and 64-bit
ABI, complicate ABI changes, and otherwise contribute to bloat.
@milseman
[String] Switch ABI to only use 4 discriminator bits.
7283f2c 
In anticipation of potential future HW features, e.g. armv8.5 memory
tagging, only use the high 4 bytes as discriminator bits in
_BridgeObject rather than the top 8 bits. Utilize two perf flags to
cover this instead. This requires shifting around a fair amount of
internal complexity.
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Please test with following pull request:
apple/swift-lldb#1169

@swift-ci please test

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Build failed
Swift Test Linux Platform
Git Sha - 0f6fbee9ce68919ae57b305cd8e786ad2f1093e6

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Build failed
Swift Test OS X Platform
Git Sha - 0f6fbee9ce68919ae57b305cd8e786ad2f1093e6

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Please test with following pull request:
apple/swift-lldb#1169

@swift-ci please test

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Please test with following pull request:
apple/swift-lldb#1169

@swift-ci please test os x platform

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@apple/swift5-branch-managers

Convergence

We will want this ASAP, preferably beta 1.

ABI impact

This change's String's ABI to only use the high 4 bits of _BridgeObject, effectively extending the address space to 60 bits. This is especially important for architectures implementing ARMv8.5 memory tagging.

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Build failed
Swift Test OS X Platform
Git Sha - 7283f2c

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Failure is due to an ABI checker bug that hasn't been cherry-picked to 5.0

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Please test with following pull request:
apple/swift-lldb#1169

@swift-ci please test

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Build failed
Swift Test OS X Platform
Git Sha - 7283f2c

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Build failed
Swift Test Linux Platform
Git Sha - 7283f2c

@AnnaZaks AnnaZaks merged commit 0070243 into swiftlang:swift-5.0-branch Dec 20, 2018
@rjmccall rjmccall mentioned this pull request Dec 20, 2018
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@milseman milseman deleted the 5_0_4_bit_string branch December 28, 2018 21:15
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@AnnaZaks AnnaZaks AnnaZaks approved these changes

@lorentey lorentey Awaiting requested review from lorentey

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@milseman @swift-ci @AnnaZaks @xwu