Only download llvm when necessary (#9)

llvm-config is now found by the following order:

1. the value of env var LLVM_CONFIG_CMD
2. the installed llvm-config-14 in the Ubuntu 22.04 images
3. download clang+llvm 13 and use the downloaded binary

install.sh

@@ -11,24 +11,34 @@ echo $PYBUDA_ROOT
 cd $PYBUDA_ROOT
 export TVM_HOME=$PYBUDA_ROOT/third_party/tvm
 
-# Download / untar LLVM
-cd $PYBUDA_ROOT/third_party
-if [ ! -d "$PYBUDA_ROOT/third_party/llvm" ]; then
-  wget -q https://github.com/llvm/llvm-project/releases/download/llvmorg-13.0.0/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz
-  LLVM_TAR=$PYBUDA_ROOT/third_party/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz
-  LLVM_DIR=$PYBUDA_ROOT/third_party/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04
-  tar -xf $LLVM_TAR && mv $LLVM_DIR $PYBUDA_ROOT/third_party/llvm && rm -f $LLVM_TAR
-fi
-
 cd $TVM_HOME
 git submodule init; git submodule update
 
 mkdir -p build
 cp $TVM_HOME/cmake/config.cmake $TVM_HOME/build
 cd $TVM_HOME/build
 
-# Link the LLVM thats just been downloaded
-LLVM_LINK=$PYBUDA_ROOT/third_party/llvm/bin/llvm-config
+
+if [[ -n $LLVM_CONFIG_CMD && -e $LLVM_CONFIG_CMD ]]; then
+    # pass in through environment variable
+    echo Using "$LLVM_CONFIG_CMD" as LLVM_LINK
+    LLVM_LINK="$LLVM_CONFIG_CMD"
+elif [[ -e /usr/bin/llvm-config-14 ]]; then
+    # should be present; llvm-14 is included in our ubuntu 22.04 images
+    echo Using /usr/bin/llvm-config-14 as LLVM_LINK
+    LLVM_LINK=/usr/bin/llvm-config-14
+else
+    # Download / untar LLVM
+    echo Downloading llvm
+    if [ ! -d "$PYBUDA_ROOT/third_party/llvm" ]; then
+        wget -q https://github.com/llvm/llvm-project/releases/download/llvmorg-13.0.0/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz
+        LLVM_TAR=$PYBUDA_ROOT/third_party/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04.tar.xz
+        LLVM_DIR=$PYBUDA_ROOT/third_party/clang+llvm-13.0.0-x86_64-linux-gnu-ubuntu-20.04
+        tar -xf $LLVM_TAR && mv $LLVM_DIR $PYBUDA_ROOT/third_party/llvm && rm -f $LLVM_TAR
+    fi
+    # Link the LLVM thats just been downloaded
+    LLVM_LINK=$PYBUDA_ROOT/third_party/llvm/bin/llvm-config
+fi
 sed -i "s#/usr/bin/llvm-config#$LLVM_LINK#g" $TVM_HOME/build/config.cmake
 
 if [[ "$TVM_BUILD_CONFIG" == "debug" ]]; then