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Cache the ROCm and plain-clang Windows builds through sccache - #557
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bernardladenthin merged 1 commit intoOct 22, 2026
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The two ROCm jobs are the pipeline's critical path (Windows 2:40-4:15 h,
Linux ~2:50 h for the build step) and neither cached a single HIP TU:
- Windows: CMake's Platform/Windows-Clang.cmake implements
CMAKE_MSVC_RUNTIME_LIBRARY=MultiThreaded for clang with the GNU front
end as `-Xclang -flto-visibility-public-std -D_MT -Xclang
--dependent-lib=libcmt`, and sccache (0.18.0 and main) refuses the
first flag ("Can't handle UnknownFlag arguments with -Xclang"). Every
TU of the ROCm module (TheRock's clang compiles HIP as C++ there) and
of the plain-clang CPU job was a miss; the CPU job had its sccache
install step removed for that reason.
- Linux: ggml compiles the HIP TUs as the CMake language HIP, which the
C/CXX launchers build.sh sets never reach (2 requests in the stats).
llama/cmake/msvc-runtime-gnu-clang.cmake, loaded through
CMAKE_USER_MAKE_RULES_OVERRIDE before project(), maps MultiThreaded and
MultiThreadedDebug to -fms-runtime-lib=static[_dbg] for that toolchain
only -- the driver flag llama/CMakeLists.txt already passed next to
CMake's sequence, which hands cc1 the same flags without -Xclang.
CMAKE_MSVC_RUNTIME_LIBRARY keeps its value: an empty one reached
try_compile and broke the C compiler check (mainCRTStartup undefined).
build.sh adds CMAKE_HIP_COMPILER_LAUNCHER for GGML_HIP builds, and
build-windows-x86_64 installs sccache again.
build.sh and build.bat default SCCACHE_IDLE_TIMEOUT to 0: with 600 s the
server stopped during long builds and the summary table counted only
what came after (67 of ~160 requests on Windows ROCm, 2 on Linux).
Measured before the change, one GPU target (gfx1100), sccache 0.18.0
over a local WebDAV server standing in for Depot:
- Windows, MSVC 14.44 (as windows-2022), TheRock 10.0.0 clang 23:
today 157 requests all refused, 325 s; with the override 0 refused,
377 s cold, 25 s warm.
- Linux, Docker, the CI wheels: 310 s uncached, 304 s cold, 157/157
hits and 10 s warm.
- Objects, nine TUs (C, C++, seven HIP) with a pinned -cuid: every
section identical between the old and the new flags except .drectve,
where CMake's sequence repeated /DEFAULTLIB:libcmt.lib; through
sccache and without it identical up to the COFF timestamp. Without a
pinned CUID HIP objects differ in the __hip_cuid_<hash> name, which
clang derives from the command line sccache slightly changes -- the
build.sh comment that called a hit bit-identical says so now.
- This tree (b11827) configured on Windows: no -Xclang on any Release
TU, ggml-base 9/9 requests cacheable.
A local build with sccache's disk backend hits mozilla/sccache#2788
(HIP --offload-compress vs. the preprocessor cache mode, "Failed to
parse included file path"); that mode does not exist for WebDAV, and
SCCACHE_DIRECT=false avoids it locally. Documented in CLAUDE.md.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VszvDmRRPP1UcwozsUMY1L
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Summary
-Xclang -flto-visibility-public-std, which sccache refuses, so every TU was a cache miss (the ROCm job is the pipeline's critical path, 2:40-4:15 h). Newllama/cmake/msvc-runtime-gnu-clang.cmake, loaded viaCMAKE_USER_MAKE_RULES_OVERRIDE, selects the same runtime with the driver flag-fms-runtime-lib=static;build-windows-x86_64installs sccache again.build.shaddsCMAKE_HIP_COMPILER_LAUNCHERforGGML_HIPbuilds.build.sh/build.batdefaultSCCACHE_IDLE_TIMEOUT=0, so the job summary's statistics count every request (they showed 67 resp. 2 of ~160).Test plan
Measured locally before the change (one GPU target, sccache 0.18.0 over a local WebDAV server as a stand-in for Depot):
-Xclang)-cuid): every section identical between old and new flags except.drectve(CMake repeated/DEFAULTLIB:libcmt.lib); through sccache vs. without identical up to the COFF timestamp. Unpinned, HIP objects differ only in the__hip_cuid_<hash>name (clang hashes the command line) -- documented inbuild.shand CLAUDE.md.-Xclangon any Release TU.check-natives.py,check-run-scripts.py,check-release-gate.py,check-shared-files.pyclean; workflow parses as YAML.build-windows-x86_64in the### sccache statisticssummary (the first run fills the cache) -- that run gives the real number for 23/27 targets.Related issues / PRs
--offload-compress. mozilla/sccache#2788 matters only for a local build with the disk backend (SCCACHE_DIRECT=false), not for CI over WebDAV.Checklist
CONTRIBUTING.mdandCODE_OF_CONDUCT.md🤖 Generated with Claude Code
https://claude.ai/code/session_01VszvDmRRPP1UcwozsUMY1L