Xcode 4.1 Release was released on 29 Aug 2011 and requires macOS 10.6.8+.
It can be downloaded from https://download.developer.apple.com/Developer_Tools/xcode_4.1_for_snow_leopard_21110/xcode_4.1_for_snow_leopard.dmg.
Release notes are located at https://download.developer.apple.com/Developer_Tools/xcode_4.1_for_snow_leopard_21110/xcode_4.1_for_snow_leopard_readme.pdf.
The compilers it contains are:
- clang 2.1 (Build 163.7.1)
- LLVM-GCC (Build 2335.15.00)
- GCC 4.2 (Build 5666)