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Summary:
Attached is a sample project that uses regular expressions to scan the contents of a document. Regular expressions are used to parse the structure

Document = Paragraph
Paragraph = Line LineBreak
Line = .+ LineBreak

The project includes the Objective-C and Swift versions of this code, and is a line-by-line conversion. It also has performance tests for each. The Objective-C takes ~ 0.081 s on my machine to parse the entire document. I have been unable to get the The Swift test to finish because it takes many, many times longer. If I only parse the 1st paragraph of the document with Swift, though, it takes ~ 0.2 s to run (instructions to do this in the code).

The performance difference is shocking. Changing the Swift compiler optimization to -O (fastest) does not improve the situation.

Steps to Reproduce:
1. Open the attached project.
2. Cmd-U to run the tests

Expected Results:
The ObjC tests and the Swift tests should finish in roughly the same amount of time.

Actual Results:
The Swift code runs dramatically slower. It's not even close.

Version:
Xcode Version 6.3 (6D543q)

Notes:
This is happening on my MacBookPro11,1 (2.4 Ghz i5, 8 GB RAM), in case it's machine specific issue.

* The sample project referred to here is available at https://github.com/nyousefi/SwiftRegexSlowness