LLVM Weekly - #656, July 27th 2026

Welcome to the six hundred and fifty-sixth issue of LLVM Weekly, a weekly newsletter (published every Monday) covering developments in LLVM, Clang, and related projects. LLVM Weekly is brought to you by Alex Bradbury. Subscribe to future issues at https://llvmweekly.org and pass it on to anyone else you think may be interested. Please send any tips or feedback via email: asb@asbradbury.org, or Mastodon: @llvmweekly@fosstodon.org / @asb@fosstodon.org, or Bluesky: @llvmweekly.org / @asbradbury.org.

News and articles from around the web and events

I didn’t spot any particular blog posts or news this time round. As always, feel free to drop me an email if there’s something you think I should include.

According to the LLVM Calendar in the coming week there will be the following:

• Office hours with the following hosts: None this week.
• Online sync-ups on the following topics: formal specification, LLVM pointer authentication, OpenMP in LLVM, Flang, RISC-V, LLVM libc, HLSL, LLVM libc math.
• For more details see the LLVM calendar, getting involved documentation on online sync ups and office hours.

On the forums

• Mafê Guimarães posted an RFC related to their GSoC work on improving HLSL support in clangd.

• Bojun Seo proposed adding a DoubleFreeSanitizer.

• Tatiana Larina started an RFC thread on adding lightweight instrumentation, “ a new Clang/LLVM instrumentation mode that reuses the frontend site selection from -fprofile-instr-generate but lowers instrumentation sites to a user-defined callback instead of inline counters.”

• LLVM 23.1.0-rc1 was released.

• Donát Nagy suggests unifying PthreadLockChecker and BlockInCriticalSection checkers in Clang’s static analyser.

• Yaxun (Sam) Liu posted an RFC on adding __builtin_pointee_address_space to clang. Respondents are suggesting that a general __addressspaceof() operator may be better.

• Victor Perez would like to add LLVM IR-style floating point literals to MLIR.

• Bea Healy and Moritz Scherer shared an RFC on adding an AXI4 dialect to CIRCT.

LLVM commits

• A MachineRegisterClassInfo analysis pass was added which can cache the result of RegisterClassInfo to save compile time. a9a25df.

• A scalar replacement of aggregates pass implementation for logical pointers (i.e. those created by llvm.structured.gep and llvm.structured.alloca) was implemented. 03b5c52.

• The RISC-V backend now always enables memcmp/bcmp expansion for pointers known to be aligned. ca276b4.

• A more efficient algorithm for identifying cycles was used. e49aac8.

• Triple::getDefaultFloatABI was added. 8bbaac6.

• lit was migrated to ProcessPoolExecutor. 14bfc424.

• The deprecated BranchInst was removed now the migration to UncondBr and CondBr was completed. 14304ef.

Clang commits

• A flag -fdefined-pointer-subtraction was added for making pointer subtraction defined. 6d8d3f8.

• ClangIR’s lowering learned to generate a cleanup region for loops when needed. e00944c.

• A performance-expensive-value-or clang-tidy check was added which identifies calls to value_or on optional types where the return type is expensive to copy. 2e32c6c.

Other project commits

• LLDB now has a document on platform/target support requirements. b227ed7.

• An MLIR commit was landed introducing full support for raising WASM MLIR to other dialects. f61499b.

• Initial documentation was added on adding a new BOLT backend. a822836.

• float128 emulation was introduced to LLVM’s libc. 7c445ab.

• std::function_ref was implemented in libcxx. a434fe8.