Xcode 7.1 Release was released on 21 Oct 2015 and requires macOS 10.10.5+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/Xcode_7.1/Xcode_7.1.dmg.
Release notes are located at https://developer.apple.com/library/content/releasenotes/DeveloperTools/RN-Xcode/Chapters/Introduction.html#//apple_ref/doc/uid/TP40001051-CH1-SW300.
The SDKs it contains are:
- iOS 13B137
- macOS 15A278
- tvOS 13T393
- watchOS 13S343
The compilers it contains are:
- clang 7.0.0 (Build 700.1.76)
- swift 2.1 (Build 700.1.101.6)
- LLVM-GCC 3.7.0 (Build )