[llvm] [Github][libc] Add qemu-system-hexagon to the libc container (PR #219433)

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<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-github-workflow

Author: quic-k

<details>
<summary>Changes</summary>

Running the LLVM libc bare-metal hermetic tests for Hexagon requires a Hexagon system emulator, which is not available as a distribution package, so build just the hexagon-softmmu target from source. The machine model the tests use ("-M sim") currently only exists in the Qualcomm fork of QEMU, so pin to a tag from there.

libfdt-dev avoids a configure-time download of the dtc subproject and python3-venv lets QEMU bootstrap its vendored meson, since Ubuntu 24.04 ships an older one than QEMU requires. -Werror is disabled so the image does not fail to rebuild on a new warning from the base image compiler, and the installed binary is smoke-tested before the source is removed.

This only makes the emulator available in the image. Enabling the Hexagon libc tests in CI is a follow-up change.

---
Full diff: https://github.com/llvm/llvm-project/pull/219433.diff


1 Files Affected:

- (modified) .github/workflows/containers/libc/Dockerfile (+27-1) 


``````````diff
diff --git a/.github/workflows/containers/libc/Dockerfile b/.github/workflows/containers/libc/Dockerfile
index d2cb71435059a..b79da99176c14 100644
--- a/.github/workflows/containers/libc/Dockerfile
+++ b/.github/workflows/containers/libc/Dockerfile
@@ -1,6 +1,7 @@
 FROM docker.io/library/ubuntu:24.04
 
 # MPFR is required by some of the mathlib tests.
+# The last few packages are needed to build qemu-system-hexagon below.
 RUN apt-get update && \
     apt-get install -y \
     git \
@@ -36,7 +37,13 @@ RUN apt-get update && \
     gnupg \
     cmake \
     m4 \
-    linux-libc-dev && \
+    linux-libc-dev \
+    libglib2.0-dev \
+    libfdt-dev \
+    pkg-config \
+    python3-venv \
+    flex \
+    bison && \
     apt-get clean && \
     rm -rf /var/lib/apt/lists/*
 
@@ -56,6 +63,25 @@ RUN apt-get install -y llvm-23-tools && \
     ln -s -t /usr/bin $(dpkg -L llvm-23-tools | grep '^/usr/lib/llvm-23/bin/') && \
     ln -s /usr/lib/llvm-23/bin/llvm-link /usr/bin/llvm-link
 
+# Build qemu-system-hexagon, which is needed to run the LLVM libc bare-metal
+# hermetic tests for Hexagon. Hexagon system emulation is not available as a
+# distribution package, and the machine model used by the tests ("-M sim")
+# currently only exists in the Qualcomm fork, so build it from source and pin
+# to a tag from there. The dependencies it needs are installed above.
+RUN git clone --depth 1 --branch hexagon-sysemu-23-apr-2026 \
+    https://github.com/qualcomm/qemu.git qemu-hexagon && \
+    cd qemu-hexagon && \
+    ./configure \
+    --target-list=hexagon-softmmu \
+    --prefix=/opt/qemu-hexagon \
+    --disable-werror && \
+    ninja -C build install && \
+    /opt/qemu-hexagon/bin/qemu-system-hexagon -M help | grep -q '^sim ' && \
+    cd .. && \
+    rm -rf qemu-hexagon
+
+ENV PATH="/opt/qemu-hexagon/bin:${PATH}"
+
 # Install gmp and mpfr for cross compilation
 RUN wget https://ftp.gnu.org/gnu/gmp/gmp-6.3.0.tar.xz && \
     tar -xf gmp-6.3.0.tar.xz && \

``````````

</details>


https://github.com/llvm/llvm-project/pull/219433