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[SR-12393] Slow type-checking for array literal containing bitshifts of int literals #54830

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swift-ci opened this issue Mar 21, 2020 · 3 comments
Open

[SR-12393] Slow type-checking for array literal containing bitshifts of int literals #54830

swift-ci opened this issue Mar 21, 2020 · 3 comments
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance type checker Area → compiler: Semantic analysis

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@swift-ci
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Previous ID SR-12393
Radar rdar://problem/60832861
Original Reporter Tiza (JIRA User)
Type Bug
Environment

Catalina 10.15.4b6, Xcode 11.4 beta 3 (11N132i)

Additional Detail from JIRA
Votes 0
Component/s Compiler
Labels Bug, Performance, TypeChecker
Assignee None
Priority Medium

md5: aabb2b8bb59f18232a1855b1b0fcb431

Issue Description:

I've tried to translate a piece of C-Code to Swift and learned that bit shifts to fill arrays increases compile time exponentially.

let bitmask = [
 1<<0, 1<<0,
 1<<1, 1<<1,
 1<<2, 1<<2,
 1<<3, 1<<3
 ]

This compiles on a MacBook Pro i7 in 10s+ and one more line with two items doesn't compile anymore due to time out. Debug code size of this piece is more than 1KB.
@beccadax
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@swift-ci create

@beccadax
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This is an issue with type checker performance.

@beccadax
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Using -debug-constraints produces 165 MB of output, including:

---Solver statistics---
Total number of scopes explored: 127940
Maximum depth reached while exploring solutions: 28
Time: 5.291655e+04ms
Comparing 6561 viable solutions

Exponential behavior, anyone?

@swift-ci swift-ci transferred this issue from apple/swift-issues Apr 25, 2022
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bug A deviation from expected or documented behavior. Also: expected but undesirable behavior. compiler The Swift compiler in itself performance type checker Area → compiler: Semantic analysis
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@beccadax @swift-ci