Maintainer of LLVM MC, Clang driver, lld/ELF, and libunwind
California, USA
Joined November 2012
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lld 24.x optimization preview: parallel symbol interning. Linking clang-release at --threads=8: 181 -> 151 ms
lld linking Chromium (CREL, --icf=all): 3.46 -> 2.08 s. In chromium-debug, Moore's partition refinement algorithm performs poorly.
In 2020, reviewing lld's --optimize-bb-jumps (reviews.llvm.org/D68065), I asked that the pass run inside finalizeAddressDependentContent "to accommodate thunks and linker script symbol changes." The author replied: "Could we do this in a later patch?" There was no later patch.
and another lld maintainer independently flagged the misplacement and found my 2020 comment.
When I left Google in 2024, --optimize-bb-jumps still had no users. The answer was always "we will use it." Today nothing in llvm-project passes the flag; only three lld tests do.
That placement was a wrong-code bug from day one: the pass shrinks .text after .relr.dyn is computed, so RELR entries point at the wrong words.
Since a change this year, .eh_frame_hdr search keys go stale too.
An AI-assisted patch surfaced it recently,
maskray.me/blog/who-pays-for… Who pays for Clang
Another AI slop post. Commits by employer, What each funder works on, Review, Shared and vendor-specific work
I spent many hours driving the agent through Discourse threads, slides, source trees, and LinkedIn profiles to generate this AI slop: maskray.me/blog/clangir-and-… ClangIR and the cost of MLIR
Comment on "RFC: Enable ClangIR Build By Default-" discourse.llvm.org/t/rfc-ena… Current feeling: it might be a huge opportunity cost
The new funders build GPU and accelerator compilers, and their other compilers (Flang, Triton, IREE, their own stacks) are built on MLIR. For them, a Clang that emits an MLIR dialect is the point, not an implementation detail.
github.com/MaskRay/ccls/rele…
Indexed forwarding functions such as std::make_unique<A>(...) and std::vector<A>::emplace_back(...).
Hover on an auto variable in a function template shows the deduced type when the template has exactly one instantiation.
Adapt to LLVM 22, 23 and 24.
edgls is a C/C++ language server built on the EDG C/C++ front end. It is a fork of ccls with the clang-based parts replaced: the indexer, diagnostics, compile command handling, code completion, signature help, and formatting. github.com/MaskRay/edgls
Verdict: Slower than clang
Settling an old score: --fortran-common (added in 2020) was removed from lld/ELF in September 2026, removing one blocker of fully parallel input file parsing and symbol resolution.
I made a typo earlier and wrote 'useful' instead of 'useless' regarding the 'testsuite must pass' requirement. The author agreed without question. Their other replies are almost direct copy pastes.
Extractive patches from a new contributor to llvm binary tuilities.
"But it's Codex output the author doesn't really own, so reviewers end up supplying the understanding."
llvm-project really should really adopt a ghostty-style vouch system.
There is finally a migration path for LLVM's llvm::cl::opt, off dynamic initialization and onto a data-only TableGen representation: one struct per library, constant-initialized, read with a single load. No option spellings change. discourse.llvm.org/t/rfc-dec…