Jon Roelofs
Compiler Engineer at Apple
Cupertino, California, United States
Summary
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Rockstar🎓
Top SchoolJon Roelofs is a seasoned compiler engineer with 26 years of experience, currently working on compiler technology at Apple in Cupertino. He has a deep track record across industry leaders and startups—contributing to LLVM/Clang, libc++, and target-specific backends while shipping ARM64 and Apple M-series support and upstream baremetal tooling. His work spans low-level code generation, instruction selection, and toolchain infrastructure, plus practical testing and CI instrumentation from prototypes at Intel to production compiler features. An active open-source contributor, Jon has made influential fixes and architectural tweaks in the widely used llvm-project repositories, reflecting both attention to standards and pragmatic engineering. Beyond compilers he brings firmware and high-performance computing experience, a combination that helps him bridge hardware constraints and compiler optimizations.
26 years of coding experience
11 years of employment as a software developer
Bachelor of Science, Computer Science, Mathematics, Bachelor of Science, Computer Science, Mathematics at Colorado State UniversityRed Rocks Community College
Stackoverflow
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Github Skills (24)
cpp-library10
assembly10
c-language10
llvm10
testing10
c1110
standard-library10
c1710
code-generation10
compiler-compiler10
assemble10
assembler10
c-libraries10
compiler-optimization10
compiler10
Programming languages (13)
Github contributions (5)
llvm/llvm-project
Jan 2020 - Mar 2025
The LLVM Project is a collection of modular and reusable compiler and toolchain technologies.
Role in this project:
Back-end Developer
Back-end DeveloperContributions:451 reviews, 109 PRs, 388 pushes in 5 years 2 months
Contributions summary:Jon primarily contributed to the LLVM project, focusing on compiler and toolchain technologies. They made improvements to the ADT (Abstract Data Types) and SelectionDAG components, implementing enhancements for ARM64 architecture, and adding support for the apple-m4 target. They also worked on the ScheduleDAG, setting fixed sizes and re-arranging members to reduce the size of the SUnit struct. Moreover, they addressed issues with the statepoint and LLVM-C interfaces.
compilerstechnologiesclangsubmittoolchain
llvm-mirror/libcxx
Aug 2014 - Dec 2017
Project moved to: https://github.com/llvm/llvm-project
Role in this project:Back-end Developer
Back-end DeveloperContributions:56 commits in 3 years 5 months
Contributions summary:Jon primarily contributed to the libcxx project, which is the C++ Standard Library implementation for the LLVM project. Their work focused on addressing issues related to the C++ Standard Library, including fixing mask checking in `ctype_byname`, improving the temporary filename generation for tests, and reverting changes that didn't conform to the C++ standard. Additionally, they added support for newlib as the C library for the locale part and made adjustments for systems without POSIX threads, along with making a variety of improvements to the testing infrastructure.
llvm
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