Henry Zongaro
Software Developer at IBM
Toronto, Ontario, Canada
Summary
🤩
Rockstar🎓
Top SchoolHenry Zongaro is a veteran software developer with over three decades of deep compiler and language-processor experience, currently contributing to the Testarossa JIT compiler and x86 code generation for the Eclipse OpenJ9 JVM. He has led front-end compiler efforts for IBM internal languages, worked on DataPower Gateway compilers, and played technical lead roles on IBM’s XSLT processors while representing IBM in W3C standards work. Henry’s practical expertise spans traditional optimizing back-ends, JVM bytecode generators, and platform-specific code generation and inlining optimizations for projects like Eclipse OMR and OpenJ9. He brings a rare combination of standards-level thinking and low-level code-generator problem solving, evidenced by contributions that reduce write-barrier overheads and enable inline atomic operations on POWER. Based in Toronto, he pairs long-standing IBM institutional knowledge with active open-source impact on high-profile JVM runtime components.
8 years of coding experience
University of TorontoB.Sc., Mathematics and Computer Science, B.Sc., Mathematics and Computer Science at University of Windsor
Github Skills (21)
c-language10
jvm10
runtimes10
computer-architecture10
architecture10
cpu-architecture10
java10
javas10
code-generation10
compiler-compiler10
compiler-design10
compiler10
cprogramming-language10
architectures10
jit10
Programming languages (6)
Github contributions (5)
eclipse-omr/omr
Sep 2018 - Jan 2023
Eclipse OMR™ Cross platform components for building reliable, high performance language runtimes
Role in this project:
Backend Developer
Backend DeveloperContributions:325 reviews, 58 commits, 130 PRs in 4 years 4 months
Contributions summary:Henry primarily contributed to the Eclipse OMR project, focusing on enhancing the compiler and code generation aspects of the runtime environment. Their work included adding support for inlining new atomic methods on the Power architecture, which involved modifying code related to code generation and tree evaluation. Furthermore, they addressed compiler-related bugs by avoiding inlining specific functions that exposed issues with the IBM xlC compiler, and updated comments to reflect the nature of the issue. They also made improvements related to internal inliner and optimization logic.
jitruntimesomrruntimeportability
eclipse-openj9/openj9
Jun 2018 - Jan 2023
Eclipse OpenJ9: A Java Virtual Machine for OpenJDK that's optimized for small footprint, fast start-up, and high throughput. Builds on Eclipse OMR (https://github.com/eclipse/omr) and combines with the Extensions for OpenJDK for OpenJ9 repo.
Role in this project:Back-end Developer
Back-end DeveloperContributions:664 reviews, 114 commits, 212 PRs in 4 years 7 months
Contributions summary:Henry primarily focused on compiler optimization, specifically improving code generation for the OpenJ9 JVM. They reworked x86 code generation for write barriers under gencon GC, introducing optimizations to reduce out-of-line write barrier calls. Further contributions included allowing inline atomic operations on the POWER architecture, addressing merging conflicts, and adjusting code to ensure a NULLCHK operation for BigDecimal and BigInteger operations are preserved when those operations are simplified.
runtimecompilerextensionseclipseomr
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