GitHub not caching the LLVM build on Windows

[skill-issue0]

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on: [push, pull_request]

jobs:
  x86_64-windows-llvm:
    runs-on: windows-2022
    steps:
      - name: Enable Developer Command Prompt
        uses: ilammy/msvc-dev-cmd@cec98b9d092141f74527d0afa6feb2af698cfe89 # v1.12.1

      - name: Cache LLVM
        id: cache-llvm
        uses: actions/cache@v3
        with:
          path: llvm
          key: llvm-libs-16.0.3-msvc

      - name: Download LLVM
        if: steps.cache-llvm.outputs.cache-hit != 'true'
        run: |
          iwr https://github.com/llvm/llvm-project/releases/download/llvmorg-16.0.3/llvm-16.0.3.src.tar.xz -OutFile llvm.tar.xz
          (Get-FileHash -Algorithm SHA256 .\llvm.tar.xz).hash -eq "D820E63BC3A6F4F833EC69A1EF49A2E81992E90BC23989F98946914B061AB6C7"
          7z x llvm.tar.xz
          7z x llvm.tar
          mv llvm-* llvm-src
      - name: Download LLVM's CMake files
        if: steps.cache-llvm.outputs.cache-hit != 'true'
        run: |
          iwr https://github.com/llvm/llvm-project/releases/download/llvmorg-16.0.3/cmake-16.0.3.src.tar.xz -OutFile cmake.tar.xz
          (Get-FileHash -Algorithm SHA256 .\cmake.tar.xz).hash -eq "B6D83C91F12757030D8361DEDC5DD84357B3EDB8DA406B5D0850DF8B6F7798B1"
          7z x cmake.tar.xz
          7z x cmake.tar
          mv cmake-* cmake
      - name: Build LLVM
        if: steps.cache-llvm.outputs.cache-hit != 'true'
        working-directory: ./llvm-src
        run: |
          cmake . -Thost=x64 -DLLVM_TARGETS_TO_BUILD="X86;AArch64" -DLLVM_USE_CRT_RELEASE=MT -DBUILD_SHARED_LIBS=OFF -DCMAKE_FIND_USE_SYSTEM_ENVIRONMENT_PATH=OFF -DLLVM_INCLUDE_BENCHMARKS=OFF -DLLVM_INCLUDE_TESTS=OFF -DLLVM_ENABLE_ZSTD=OFF
          cmake --build . --config Release
          cmake -DCMAKE_INSTALL_PREFIX=$(pwd)\llvm -P cmake_install.cmake
          
  x86_64-windows-test:
    runs-on: windows-2022
    needs: [x86_64-windows-llvm]
    steps:
      - name: Disable CRLF line ending substitution
        run: |
          git config --global core.autocrlf false
      - name: Enable Developer Command Prompt
        uses: ilammy/msvc-dev-cmd@cec98b9d092141f74527d0afa6feb2af698cfe89 # v1.12.1

      - name: Restore LLVM
        uses: actions/cache/restore@v3
        with:
          path: llvm
          key: llvm-libs-16.0.3-msvc
          fail-on-cache-miss: true```

This is my workflow. In the LLVM step, cable manages to build llvm after a long time and my workflow didn't even cache it. 

[nirav-gajera]

To fix this, you can update the cache-llvm step to include the fail-on-cache-miss option. This will ensure that the workflow will only build LLVM from scratch if the cache is missing.

- name: Cache LLVM
  id: cache-llvm
  uses: actions/cache@v3
  with:
    path: llvm
    key: llvm-libs-16.0.3-msvc
    restore-keys: llvm-libs-16.0.3-msvc
    fail-on-cache-miss: true

[skill-issue0]

Lemme try and turn real quick

[skill-issue0]

Error: Failed to restore cache entry. Exiting as fail-on-cache-miss is set. Input key: llvm-libs-16.0.3-msvc
I get this error now

[nirav-gajera]

actions/cache#1114
actions/runner#2448

[skill-issue0]

Can you make changes to my workflow (repo: skill-issue0/test), would really appreciate as I have not found the correct fix, u can submit a PR or edit my current workflow code and send the updated one here 🙏

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[Ravenwater]

I am running into this issue as well. Caching works on Linux and MacOS but fails on Windows.

Run actions/cache@v3
  with:
    path: llvm-install
    key: Windows-llvm-release/19.x-
    enableCrossOsArchive: false
    fail-on-cache-miss: false
    lookup-only: false
  env:
    pythonLocation: C:\hostedtoolcache\windows\Python\3.1[2](https://github.com/branes-ai/dfa-dynamics/actions/runs/13610185201/job/38046314295#step:4:2).9\x64
    PKG_CONFIG_PATH: C:\hostedtoolcache\windows\Python\[3](https://github.com/branes-ai/dfa-dynamics/actions/runs/13610185201/job/38046314295#step:4:3).12.9\x64/lib/pkgconfig
    Python_ROOT_DIR: C:\hostedtoolcache\windows\Python\3.12.9\x6[4](https://github.com/branes-ai/dfa-dynamics/actions/runs/13610185201/job/38046314295#step:4:4)
    Python2_ROOT_DIR: C:\hostedtoolcache\windows\Python\3.12.9\x[6](https://github.com/branes-ai/dfa-dynamics/actions/runs/13610185201/job/38046314295#step:4:6)4
    Python3_ROOT_DIR: C:\hostedtoolcache\windows\Python\3.12.[9](https://github.com/branes-ai/dfa-dynamics/actions/runs/13610185201/job/38046314295#step:4:9)\x64
Cache not found for input keys: Windows-llvm-release/19.x-

Is this a known issue, or has it been resolved?

[Ravenwater]

In my case, it appears that the GitHub action is failing to build the cache:

At 3.5 hrs per CI action to build the LLVM tree on the Windows target, this is sucking the wind out of our productivity to support Windows. Any insights would be greatly appreciated.

[Ravenwater]

Interesting: it appears that the cache entry is only created when the whole action succeeds, not just the LLVM build: I removed all the Windows build failures so it could succeed throughout the complete CI flow and it deposited the LLVM build artifact.