Doug Gregor
Senior Compiler Engineer - Swift C Objective-C at Apple
Sunnyvale, California, United States
Summary
🤩
Rockstar🎓
Top SchoolDoug Gregor is a senior compiler engineer with 25 years of experience, currently shaping Swift and related tooling at Apple from Sunnyvale, California. He brings deep expertise in compiler internals—parser, type checker, SILGen—and has driven language evolution work across Swift repositories including swift, swift-driver, swift-syntax, and the Swift Package Manager. His contributions span bridging Swift and Objective‑C, module/AST serialization in Clang, and runtime/debugger integration in LLDB, demonstrating rare cross-cutting knowledge of language, tooling, and runtime. Before Apple he worked on GCC and Boost, blending rigorous academic training (RPI Ph.D.) with practical library and documentation work that improved portability and build processes. Colleagues rely on him for thoughtful refactors that modernize APIs (e.g., ErrorProtocol→Error, concurrency syntax support) while keeping large codebases buildable and performant.
24 years of coding experience
9 years of employment as a software developer
B.S., Ph.D, Computer Science, B.S., Ph.D, Computer Science at Rensselaer Polytechnic Institute
Stackoverflow
411reputation
8kreached
4answers
0questions
Github Skills (72)
go-modules10
python10
package-management10
abstract-syntax-tree10
testing10
foundation-sites10
refactor10
code-generation10
compiler-construction10
code-cleanup10
refactoring10
clang10
concurrency10
data-serialization10
lldb10
Programming languages (14)
Github contributions (5)
llvm-mirror/clang
Apr 2008 - Oct 2017
Mirror kept for legacy. Moved to https://github.com/llvm/llvm-project
Role in this project:
Back-end Developer
Back-end DeveloperContributions:5172 commits in 9 years 7 months
Contributions summary:Doug primarily contributed to the Clang compiler codebase, focusing on improving the module system, specifically the areas of code completion, diagnostics, and the global module index. The contributions involved modifying the AST reader, the preprocessor, and related serialization/deserialization components, with the goal of addressing bugs and enhancing module-related tooling. The work included incorporating user feedback and addressing specific performance issues observed when building or using modules, and was related to the compiler and associated build processes.
keptwindowsllvmcc-plus-plus
swiftlang/swift
Feb 2022 - Jan 2023
The Swift Programming Language
Role in this project:Back-end Developer
Back-end DeveloperContributions:1924 reviews, 558 commits, 5151 PRs in 11 months
Contributions summary:Doug's commits focus on the development of the Swift language, specifically related to macro expansion, typed throws, and protocol conformances. Their work involves implementing, testing, and refining core language features, including improvements to the handling of concurrency within the standard library. The user's contributions involve modifications to the parser, type checker, and SILGen, demonstrating a strong understanding of the compiler internals.
swift-programmingswift-programming-languageprogramming-languageswift
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