Eugene Rozenfeld
Principal Software Engineer at Microsoft
Redmond, Washington, United States
Summary
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Rockstar🎓
Top SchoolEugene Rozenfeld is a Principal Software Engineer based in Redmond with over 11 years of focused experience optimizing .NET runtimes and compilers. At Microsoft he has driven low-level, performance-critical work across projects like LLILC, the .NET runtime JIT, the .NET linker, and Mono.Cecil—contributions that include implementing MSIL instructions, improving JIT morphing and liveness analysis, and reducing runtime memory and codegen overhead. His expertise spans compiler back-ends, runtime internals, and interop/linking robustness, with a clear track record of bug fixes that materially improve performance and correctness. Trained in computer science and applied mathematics at Cornell and Kyiv Polytechnic, he blends rigorous academic foundations with pragmatic engineering judgment. An understated strength is his knack for small, targeted changes—removing redundant initialization, caching small method bodies, and cleaning unused code—that yield outsized improvements in large systems.
11 years of coding experience
1 year of employment as a software developer
B.A. M.Eng. Computer Science Mathematics, B.A. M.Eng. Computer Science Mathematics at Cornell UniversityIgor Sikorsky Kyiv Polytechnic Institute
English, Russian, Ukrainian
Stackoverflow
21reputation
760reached
1answer
0questions
Github Skills (29)
c-language10
back-end-development10
compiler-development10
net10
dotnet10
c1110
gcc10
c1710
asp-net10
mono-cecil10
performance-optimization10
bytecode10
dotnet-core10
compiler-optimization10
performance-tuning10
Programming languages (5)
Github contributions (5)
dotnet/llilc
Feb 2015 - Sep 2015
This repo contains LLILC, an LLVM based compiler for .NET Core. It includes a set of cross-platform .NET code generation tools that enables compilation of MSIL byte code to LLVM supported platforms.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:94 commits, 57 PRs, 29 pushes in 7 months
Contributions summary:Eugene primarily contributed to the back-end of the .NET Core compiler project, focusing on the implementation and improvement of the LLILC compiler. Their work involved fixing bugs related to specific instructions, improving the formatting of code, deleting unused methods, and implementing loading and storing of array elements and other MSIL instructions, such as ldelem, stelem, and jmp. The user added support for synchronized methods by integrating calls to MONITOR_ENTER and MONITOR_EXIT, as well as implementing features for ReadyToRun.
bytecodecode-generationcompilerdotnetllvm
dotnet/linker
Nov 2016 - May 2018
Role in this project:Back-end Developer
Back-end DeveloperContributions:46 commits, 51 PRs, 3 pushes in 1 year 6 months
Contributions summary:Eugene primarily worked on enhancing the linker's functionality, including adding features for type forwarders and interop parameters. They implemented fixes for marking exported nested types and improved the assembly output process. Furthermore, they introduced options to keep assemblies with only type forwarders and ignore unresolved elements, demonstrating a focus on robustness and supporting .NET Core scenarios.
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