From d1aa29cbeb7241520daec3b7fe5550bfaae6c03e Mon Sep 17 00:00:00 2001
From: "Jonathan J. Helmus" <jjhelmus@gmail.com>
Date: Tue, 20 Oct 2026 11:37:35 -0500
Subject: [PATCH] Cross-compile LoongArch with LLVM

Use Clang and lld with a Debian-provided sysroot and GCC runtime
objects. Install libcrypt into the sysroot as this was split from glibc.
---
 cpython-unix/build-libxcb.sh                   |  6 ------
 cpython-unix/build-xorgproto.sh                |  6 ------
 .../build.cross-loongarch64.Dockerfile         | 18 ++++++++++++------
 cpython-unix/targets.yml                       | 18 ++++++++++++++----
 4 files changed, 26 insertions(+), 22 deletions(-)

diff --git a/cpython-unix/build-libxcb.sh b/cpython-unix/build-libxcb.sh
index d99a235b4..b7935c151 100755
--- a/cpython-unix/build-libxcb.sh
+++ b/cpython-unix/build-libxcb.sh
@@ -13,12 +13,6 @@ export PKG_CONFIG_PATH=/tools/deps/share/pkgconfig:/tools/deps/lib/pkgconfig
 tar -xf "libxcb-${LIBXCB_VERSION}.tar.gz"
 pushd "libxcb-${LIBXCB_VERSION}"
 
-if [[ "${TARGET_TRIPLE}" = loongarch64* ]]; then
-    rm -f build-aux/config.guess build-aux/config.sub
-    curl -sSL -o build-aux/config.guess 'https://git.savannah.gnu.org/cgit/config.git/plain/config.guess'
-    curl -sSL -o build-aux/config.sub 'https://git.savannah.gnu.org/cgit/config.git/plain/config.sub'
-fi
-
 if [ "${CC}" = "musl-clang" ]; then
     EXTRA_FLAGS="--disable-shared"
 fi
diff --git a/cpython-unix/build-xorgproto.sh b/cpython-unix/build-xorgproto.sh
index 5eae50f3f..3f102be72 100755
--- a/cpython-unix/build-xorgproto.sh
+++ b/cpython-unix/build-xorgproto.sh
@@ -15,12 +15,6 @@ export PKG_CONFIG_PATH=/tools/deps/share/pkgconfig
 tar -xf "xorgproto-${XORGPROTO_VERSION}.tar.gz"
 pushd "xorgproto-${XORGPROTO_VERSION}"
 
-if [[ "${TARGET_TRIPLE}" = loongarch64* ]]; then
-    rm -f config.guess.sub config.sub
-    curl -sSL -o config.guess 'https://git.savannah.gnu.org/cgit/config.git/plain/config.guess'
-    curl -sSL -o config.sub 'https://git.savannah.gnu.org/cgit/config.git/plain/config.sub'
-fi
-
 CFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" CPPFLAGS="${EXTRA_TARGET_CFLAGS} -fPIC" LDFLAGS="${EXTRA_TARGET_LDFLAGS}" ./configure \
     --build="${BUILD_TRIPLE}" \
     --host="${TARGET_TRIPLE}" \
diff --git a/cpython-unix/build.cross-loongarch64.Dockerfile b/cpython-unix/build.cross-loongarch64.Dockerfile
index 2e78250ef..e95fbffa9 100644
--- a/cpython-unix/build.cross-loongarch64.Dockerfile
+++ b/cpython-unix/build.cross-loongarch64.Dockerfile
@@ -52,14 +52,20 @@ RUN apt-get install \
     zip \
     zlib1g-dev
 
+# Clang and lld use the Debian glibc sysroot and GCC startup/runtime objects.
 RUN apt-get install \
-    g++-loongarch64-linux-gnu \
-    gcc-loongarch64-linux-gnu \
-    libc6-dev-loong64-cross
+    libc6-dev-loong64-cross \
+    libgcc-14-dev-loong64-cross \
+    linux-libc-dev-loong64-cross
 
 RUN cd /tmp && \
     curl -LO https://snapshot.debian.org/archive/debian-ports/20240812T192057Z/pool-loong64/main/libx/libxcrypt/libcrypt-dev_4.4.36-4_loong64.deb && \
     curl -LO https://snapshot.debian.org/archive/debian-ports/20240812T192057Z/pool-loong64/main/libx/libxcrypt/libcrypt1_4.4.36-4_loong64.deb && \
-    dpkg -x libcrypt-dev_4.4.36-4_loong64.deb / && \
-    dpkg -x libcrypt1_4.4.36-4_loong64.deb / && \
-    rm -f /tmp/*.deb
+    dpkg -x libcrypt-dev_4.4.36-4_loong64.deb /tmp/crypt && \
+    dpkg -x libcrypt1_4.4.36-4_loong64.deb /tmp/crypt && \
+    cp -a /tmp/crypt/usr/lib/loongarch64-linux-gnu/. /usr/loongarch64-linux-gnu/lib/ && \
+    cp -a /tmp/crypt/usr/include/. /usr/loongarch64-linux-gnu/include/ && \
+    rm -rf /tmp/crypt /tmp/*.deb
+
+# Rewrite libc's lib and lib64 paths to be relative to the sysroot for LLD.
+RUN sed -i 's@/usr/loongarch64-linux-gnu/@/@g' /usr/loongarch64-linux-gnu/lib/libc.so
diff --git a/cpython-unix/targets.yml b/cpython-unix/targets.yml
index e8e814dc7..c3fb76b75 100644
--- a/cpython-unix/targets.yml
+++ b/cpython-unix/targets.yml
@@ -349,16 +349,26 @@ loongarch64-unknown-linux-gnu:
     - '3.15'
     - '3.16'
   docker_image_suffix: .cross-loongarch64
-  host_cc: /usr/bin/x86_64-linux-gnu-gcc
-  host_cxx: /usr/bin/x86_64-linux-gnu-g++
-  target_cc: /usr/bin/loongarch64-linux-gnu-gcc
-  target_cxx: /usr/bin/loongarch64-linux-gnu-g++
+  needs_toolchain: true
+  host_cc: clang
+  host_cxx: clang++
+  target_cc: clang
+  target_cxx: clang++
   target_cflags:
+    - '--target=loongarch64-unknown-linux-gnu'
+    - '--sysroot=/usr/loongarch64-linux-gnu'
+    - '--gcc-install-dir=/usr/lib/gcc-cross/loongarch64-linux-gnu/14'
+    - '-fuse-ld=lld'
+    - '-Wno-unused-command-line-argument'
     # Hardening
     - '-fstack-protector'
     - '-U_FORTIFY_SOURCE'
     - '-D_FORTIFY_SOURCE=2'
   target_ldflags:
+    - '--target=loongarch64-unknown-linux-gnu'
+    - '--sysroot=/usr/loongarch64-linux-gnu'
+    - '--gcc-install-dir=/usr/lib/gcc-cross/loongarch64-linux-gnu/14'
+    - '-fuse-ld=lld'
     # Hardening
     - '-Wl,-z,noexecstack'
     - '-Wl,-z,relro'