[ci] cache verilator

.github/workflows/python-package.yml

@@ -23,18 +23,20 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
+    - name: Cache verilator
+      uses: actions/cache@v4
+      env:
+        cache-name: cache-verilator-new
+      with:
+        path: /home/runner/work/verilator
+        key: verilator-v5${{ env.cache-name }}
+
     - name: Install verilator
       run: |
         sudo apt-get install -y --no-install-recommends help2man make g++ perl python3 autoconf flex bison libfl2 libfl-dev zlib1g zlib1g-dev
-        git clone https://github.com/verilator/verilator.git
-        cd verilator
-        git reset --hard v5.028
-        autoconf
-        ./configure
-        make -j $(nproc)
-        sudo make install
-        cd ..
-        rm -rf verilator
+        export VERILATOR_ROOT="/home/runner/work/verilator" \
+        export PATH="$VERILATOR_ROOT/bin:$PATH" \
+        sudo bash ./script/install_verilator.sh
 
     - name: Install verilator-uvm
       run: |

script/install_verilator.sh

@@ -0,0 +1,25 @@
+#! /bin/bash
+
+# VERILATOR_ROOT="$PWD/verilator"
+
+# Clone repo only if it doesn't exist
+if [ ! -d $VERILATOR_ROOT ]; then
+    cd $VERILATOR_ROOT/../
+    git clone https://github.com/verilator/verilator.git
+fi
+
+cd $VERILATOR_ROOT
+
+# Returns non-zero if no .o files exist
+find -name '*.o' | grep -q .
+
+# If .o files don't exist, do autoconf and do make
+if [ $? -ne 0 ]; then
+    git checkout v5.028
+    autoconf
+    ./configure --prefix="$VERILATOR_ROOT"
+    make -j `nproc`
+    make install
+else
+    echo "Verilator already built, skipping compile/install steps"
+fi