[libc][Github] Perform baremetal libc builds

[Prabhuk]

Currently there are no 32 bit presubmit builds for libc. This PR
performs 32 bit build only (no test) to check any changes that land in
libc break 32 bit builds.

Co-authored-by: Aiden Grossman aidengrossman@google.com

[llvmbot]

@llvm/pr-subscribers-github-workflow

Author: Prabhu Rajasekaran (Prabhuk)

Changes

Currently there are no 32 bit presubmit builds for libc. This PR
performs 32 bit build only (no test) to check any changes that land in
libc break 32 bit builds.

---

Full diff: https://github.com/llvm/llvm-project/pull/167583.diff

1 Files Affected:

• (modified) .github/workflows/libc-fullbuild-tests.yml (+24)

diff --git a/.github/workflows/libc-fullbuild-tests.yml b/.github/workflows/libc-fullbuild-tests.yml
index 3a048aeb9405b..dfa4c8e4c4764 100644
--- a/.github/workflows/libc-fullbuild-tests.yml
+++ b/.github/workflows/libc-fullbuild-tests.yml
@@ -24,30 +24,42 @@ jobs:
             cpp_compiler: clang++-22
             target: x86_64-unknown-linux-llvm
             include_scudo: ON
+            enable_baremetal_build: OFF
           - os: ubuntu-24.04
             build_type: Release
             c_compiler: clang-22
             cpp_compiler: clang++-22
             target: x86_64-unknown-linux-llvm
             include_scudo: ON
+            enable_baremetal_build: OFF
           - os: ubuntu-24.04
             build_type: MinSizeRel
             c_compiler: clang-22
             cpp_compiler: clang++-22
             target: x86_64-unknown-linux-llvm
             include_scudo: ON
+            enable_baremetal_build: OFF
           - os: ubuntu-24.04-arm
             build_type: Debug
             c_compiler: clang-22
             cpp_compiler: clang++-22
             target: aarch64-unknown-linux-llvm
             include_scudo: ON
+            enable_baremetal_build: OFF
           - os: ubuntu-24.04
             build_type: Debug
             c_compiler: clang-22
             cpp_compiler: clang++-22
             target: x86_64-unknown-uefi-llvm
             include_scudo: OFF
+            enable_baremetal_build: OFF
+          - os: ubuntu-24.04
+            build__type: Release
+            c_compiler: clang-22
+            cpp_compiler: clang++-22
+            target: armv6m-none-eabi
+            include_scudo: OFF
+            enable_baremetal_build: ON
           # TODO: add back gcc build when it is fixed
           # - c_compiler: gcc
           #   cpp_compiler: g++
@@ -102,6 +114,18 @@ jobs:
             -DCOMPILER_RT_SCUDO_STANDALONE_BUILD_SHARED=OFF"
         fi
 
+        if [[ ${{ matrix.enable_baremetal_build}} == "ON" ]]; then
+            export RUNTIMES="$RUNTIMES;libc"
+            export CMAKE_FLAGS="
+              -DCMAKE_BUILD_TYPE=Release
+              -DLLVM_LIBC_FULL_BUILD=ON
+              -DCMAKE_C_COMPILER_TARGET=armv6m-none-abi
+              -DCMAKE_CXX_COMPILER_TARGET=armv6m-none-abi
+              -DCMAKE_ASM_COMPILER_TARGET=armv6m-none-abi
+              -DCMAKE_C_FLAGS=-mfloat-abi=soft
+              -DCMAKE_CXX_FLAGS=-mfloat-abi=soft"
+        fi
+
         cmake -B ${{ steps.strings.outputs.build-output-dir }} \
         -DCMAKE_CXX_COMPILER=${{ matrix.cpp_compiler }} \
         -DCMAKE_C_COMPILER=${{ matrix.c_compiler }} \

[Prabhuk]

@boomanaiden154 -- Not able to kick off armv6m config with my changes. Can you PTAL why?

[boomanaiden154]

Invalid workflow definition https://github.com/Prabhuk/llvm-project/actions/runs/19280147652.

You can see those kinds of failures in your forks actions page: https://github.com/Prabhuk/llvm-project/actions.

[Prabhuk]

Thank you @boomanaiden154
The config attempt is made after my changes though they break:
https://github.com/llvm/llvm-project/actions/runs/19280310278/job/55129774341?pr=167583

I'll try to address them next.

[zwuis]

Co-Authored by: @boomanaiden154

Should be Co-authored-by: name <name@example.com>.

https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors

[Prabhuk]

Co-Authored by: @boomanaiden154

Should be Co-authored-by: name <name@example.com>.

https://docs.github.com/en/pull-requests/committing-changes-to-your-project/creating-and-editing-commits/creating-a-commit-with-multiple-authors

@boomanaiden154 -- which email address of yours should I use here?

[boomanaiden154]

which email address of yours should I use here?

aidengrossman@google.com is what I'm using these days for my LLVM contributions.

[boomanaiden154]

Github Actions changes LGTM.

It would be good for Petr to sign off on the CMake cache changes though. The flags you have to set for some of the ARM targets are a bit weird.

[s-barannikov]

Is double underscore intended here?

[Prabhuk]

Definitely not. Thanks for catching this. I'll send a patch.