2 files changed, 64 insertions, 0 deletions

diff --git a/README.md b/README.md
index 599237c..3a7e427 100644
--- a/README.md
+++ b/README.md
@@ -235,6 +235,29 @@ URI: ghttps://github.com/openembedded/bitbake.git
 branch: master
 revision: HEAD
 ```
+# Using Devtool and Upstream Development
+
+All LLVM based recipes use single llvm source directory, As a LLVM
+developer, you might want to work on your own repository to build
+related recipes, devtool can we useful in establishing such a workflow
+there is a script provided `scripts/devtool-clang.sh` which can assist
+in setting up all the recipes to use custom LLVM repository, in order
+to setup repository make sure that it has all the needed patches applied
+or else it will fail to build. Such a tree is already prepared and kept
+in sync at
+
+https://github.com/kraj/llvm-project
+
+There are branches under `oe` namespace which carry the needed OE patches
+
+```
+cd $TOPDIR/workspace/sources
+git clone https://github.com/kraj/llvm-project -b oe/main llvm-project
+```
+
+Once project is setup and meta-clang is added, run `devtool-clang.sh`
+script which will do the needed for setting up external sources for the
+yocto recipes, now yocto will use custom LLVM tree for its needs.
 
 # Contributing
 
diff --git a/scripts/devtool-clang.sh b/scripts/devtool-clang.sh
new file mode 100755
index 0000000..08f9214
--- /dev/null
+++ b/scripts/devtool-clang.sh
@@ -0,0 +1,41 @@
+#!/usr/bin/env sh
+# Clone the repository first if not already done locally
+# git clone https://github.com/kraj/llvm-project -b oe/main /mnt/b/yoe/master/workspace/sources/llvm-project
+#
+# if local repository exists then make a clone/copy
+# git clone /home/kraj/work/llvm-project /mnt/b/yoe/master/workspace/sources/llvm-project
+#
+layerloc="$(dirname "$0")/../conf/layer.conf"
+workspace="$(dirname "$0")/../../../workspace"
+
+origver=$(grep "LLVMVERSION =" < "$layerloc" | awk '{print $3}' | tr -d '"')
+
+major=$(grep -e "set(LLVM_VERSION_MAJOR [0-9]" < "$workspace"/sources/llvm-project/cmake/Modules/LLVMVersion.cmake| cut -d ' ' -f 4 | sed "s/)//")
+minor=$(grep -e "set(LLVM_VERSION_MINOR [0-9]" < "$workspace"/sources/llvm-project/cmake/Modules/LLVMVersion.cmake| cut -d ' ' -f 4 | sed "s/)//")
+patch=$(grep -e "set(LLVM_VERSION_PATCH [0-9]" < "$workspace"/sources/llvm-project/cmake/Modules/LLVMVersion.cmake| cut -d ' ' -f 4 | sed "s/)//")
+
+recipes="\
+llvm-project-source-$origver \
+clang \
+clang-cross-riscv64 \
+clang-crosssdk-x86_64 \
+clang-cross-canadian-riscv64 \
+nativesdk-clang-glue \
+compiler-rt \
+compiler-rt-sanitizers \
+libclc \
+libcxx \
+openmp \
+"
+
+for recipe in $recipes; do
+  devtool modify -n "$recipe" "$workspace/sources/llvm-project"
+  sed -i "/pn-$recipe /p;s/pn-$recipe /pn-nativesdk-$recipe /g" "$workspace"/appends/"$recipe"*.bbappend
+  sed -i "/pn-$recipe /p;s/pn-$recipe /pn-$recipe-native /g" "$workspace"/appends/"$recipe"*.bbappend
+done
+
+for f in "$workspace"/appends/*.bbappend; do
+  { echo "MAJOR_VER = \"$major\"" ; echo "MINOR_VER = \"$minor\"" ; echo "PATCH_VER = \"$patch\"" ; } >> "$f"
+done
+
+sed -i -e "s/$origver/$major.$minor.$patch/g" "$workspace"/appends/llvm-project-source.bbappend