Status & roadmap#

Pigweed Toolchain is actively developed and used in production across upstream Pigweed and partner projects. This page summarizes what is ready for production use today and what is on the roadmap across Pigweed and upstream LLVM.

Status#

  • Compiler, linker, and binary utilities: Clang, LLD, and the LLVM binary utilities (llvm-objdump, llvm-nm, llvm-size, llvm-readelf, llvm-strip, llvm-objcopy, llvm-cov) are production-ready and continuously built and tested against tip-of-tree LLVM on Linux, macOS, and Windows hosts.

  • Baremetal C and C++ runtimes: Prebuilt compiler-rt, LLVM libc, and libc++ multilibs ship with the toolchain for standard Arm Cortex-M, Arm Cortex-A, and 32-bit RISC-V targets (see Supported targets and hosts).

  • Build system support:

    • Bazel: First-class hermetic toolchains using rules_cc and the packaged LLVM runtimes (LLVM libc, libc++, compiler-rt) with no external GCC dependency.

    • GN: Supported for host and Arm Cortex-M targets via CIPD; Arm Cortex-M GN toolchains currently borrow C standard library headers and archives from arm-none-eabi-gcc.

    • CMake: Helper functions are provided in pw_toolchain/arm_clang/clang_flags.cmake, but full CMake toolchain files are not yet available.

  • Static and dynamic analysis: clang-tidy, clang-format, clangd, compile-time thread/lifetime safety annotations, trapping UBSan, and source-based code coverage are supported out of the box.

Roadmap and ongoing work#

Pigweed and upstream LLVM engineers are actively working on the following areas to make baremetal LLVM adoption and GNU-to-LLVM migrations smoother:

  • Multilib support: Selecting the correct runtime library variant based on target architecture flags (like hardware floating-point units or specific instruction extensions) relies on multilib configurations. Standardizing multilib selection mechanisms in Clang and ensuring complete coverage across microcontroller variants is an active area of development.

  • Runtime libraries for specialized targets: While Pigweed ships runtime libraries for standard Arm Cortex-M and RISC-V cores, projects with specialized architectures or vendor-specific instruction extensions may require building custom versions of runtime libraries like compiler-rt, LLVM libc, and libc++.

  • Stack frame sizing: Inlining heuristics can change stack frame usage. Because embedded tasks typically operate with fixed stack allocations, stack usage should be monitored when changing optimization levels. Call Graph Information that is under development in Clang/LLVM can be used to analyze stack usage.

  • Linker script semantics: Embedded applications rely on linker scripts to place code and data into distinct SRAM and flash memory regions. Differences between GNU LD and LLD, particularly regarding memory region allocation and non-contiguous section packing, require careful script evaluation.

  • LTO with heterogeneous memory layouts: Placing symbols into designated memory sections using section attributes can interact unexpectedly with whole-program optimization passes. Developing higher-level memory placement representations for LTO remains an area of ongoing discussion.

If your project is blocked on a missing target, runtime feature, or linker script construct, reach out to the Pigweed team (Support).