add bench workflow

.github/workflows/bench.yml

@@ -0,0 +1,38 @@
+name: Bench
+
+on:
+  pull_request:
+
+concurrency:
+  group: bench-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  bench:
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v3
+      - uses: dsherret/rust-toolchain-file@v1
+      - uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-check-${{ hashFiles('**/Cargo.lock') }}
+      - name: compare perf
+        run: |
+          git clone https://github.com/higherorderco/hvm-compare-perf
+          cd hvm-compare-perf
+          NO_COLOR=1 cargo run bench -r main -r ${{ github.sha }} -f programs/c2.hvmc > ../table
+      - name: write comment
+        run: |
+          echo 'Perf run for [`'`git rev-parse --short ${{ github.sha }}`'`](https://github.com/higherorderco/hvm-core/commit/${{ github.sha }}):'' >> comment
+          echo '```' >> comment
+          cat ../table >> comment
+          echo '```' >> comment
+      - name: post comment
+        run: gh pr comment ${{ github.event.number }} -F comment
+        env:
+          GH_TOKEN: ${{ github.token }}