Extensive experience in compilers and programming language runtimes such as LLVM, the Swift toolchain, the Android ART runtime, the Hotspot JVM, the Maxine VM. A Swift and LLVM committer (@hjyamachi) and an OpenJDK Hotspot group member (https://openjdk.org/census#hiroshi).

Experience

The Browser CompanyCompiler Engineer

2023 — Now

Compiler engineer at the Swift Toolchain team. The Swift toolchain team. Worked on the Swift Toolchain, including debugging low-level bugs in the Swift compiler and the LLDB debugger, taking the Windows/ARM64 compiler from a kind-of-working state to a production quality state, getting the Clang/LLVM Content-Addressable Storage (CAS) working on Windows, and helping ship the Arc browser on Windows

Commit history:

Swift https://github.com/swiftlang/swift/pulls?q=is%3Apr+is%3Aclosed+author%3Ahjyamauchi

LLVM https://github.com/swiftlang/llvm-project/pulls?q=is%3Apr+is%3Aclosed+author%3Ahjyamauchi

LLVM https://github.com/llvm/llvm-project/pulls?q=is%3Apr+is%3Aclosed+author%3Ahjyamauchi

GoogleSoftware Engineer

2007 — 2023

Staff Software Engineer. April 2021-March 2023. The emerging toolchains team. Worked on a CPU/userspace emulator and binary translator to facilitate CPU architecture migration.

Staff Software Engineer. June 2017-April 2021. The C++ compiler optimization team. Worked on LLVM compiler / profile guided optimizations. Improved the CPython performance compiled by Clang/LLVM to be on par with GCC and implemented the profile guided control height reduction optimization in LLVM that improved the search benchmark.

Commit history: https://github.com/llvm/llvm-project/commits/main?author=hjyamauchi

Staff Software Engineer. March 2013-June 2017. The Android ART runtime team. Created the ROSAlloc memory allocator (Android L/M/N) that improved the memory allocation performance by up to 4x. Created the low-pause Concurrent Copying garbage collector (Android O and later) that reduced the pause time down to the microseconds level and enabled heap compaction without stopping the app.

Commit history: https://android-review.googlesource.com/q/owner:yamauchi%2540google.com+status:merged

Senior Software Engineer. August 2008-March 2013. The Java Platform team. Worked on the Hotspot Java Virtual Machine, its dynamic memory management (garbage collection), CPU profiling and JIT compilers. Enhanced the Hotspot JVM's CMS garbage collector to reduce the pause times (by a factor of 3-4) and memory usage (hundreds of GBs saved across the fleet) for Google servers.

Blog about my OpenJDK work and contributions: https://hiroshiyamauchi.blogspot.com/

My OpenJDK patches: http://cr.openjdk.java.net/~hiroshi/webrevs/

September 2007-August 2008. The Java Infrastructure team. Worked on the Java SSTable library.

Jan 2007-September 2007. The Mobile Search team. Worked on a mobile web search frontend and the first mobile calendar web app for iPhone.