feat: add example benchmark workflow

.github/workflows/benchmark.yml

@@ -0,0 +1,48 @@
+name: Benchmarks
+
+on:
+  push:
+   branches:
+    - master
+  pull_request:
+
+jobs:
+  test:
+    name: Benchmark library
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout sources
+        uses: actions/checkout@v4
+
+      - name: Install Nargo
+        uses: noir-lang/[email protected]
+        with:
+          toolchain: 0.34.0
+
+      - name: Install bb
+        run: |
+          npm install -g bbup
+          bbup -nv 0.34.0
+
+      - name: Build Noir benchmark programs
+        run: nargo export
+
+      - name: Generate gates report
+        run: ./scripts/build-gates-report.sh
+        env:
+          BACKEND: /home/runner/.bb/bb
+
+      - name: Compare gates reports
+        id: gates_diff
+        uses: noir-lang/noir-gates-diff@1931aaaa848a1a009363d6115293f7b7fc72bb87
+        with:
+          report: gates_report.json
+          summaryQuantile: 0.9 # only display the 10% most significant circuit size diffs in the summary (defaults to 20%)
+
+      - name: Add gates diff to sticky comment
+        if: github.event_name == 'pull_request' || github.event_name == 'pull_request_target'
+        uses: marocchino/sticky-pull-request-comment@v2
+        with:
+          # delete the comment in case changes no longer impact circuit sizes
+          delete: ${{ !steps.gates_diff.outputs.markdown }}
+          message: ${{ steps.gates_diff.outputs.markdown }}

.gitignore

@@ -1 +1,3 @@
-target
+target
+export
+gates_report.json

scripts/build-gates-report.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+set -e
+
+BACKEND=${BACKEND:-bb}
+
+cd $(dirname "$0")/../
+
+artifacts_path="./export"
+artifacts=$(ls $artifacts_path)
+
+echo "{\"programs\": [" > gates_report.json
+
+# Bound for checking where to place last parentheses 
+NUM_ARTIFACTS=$(ls -1q "$artifacts_path" | wc -l)
+
+ITER="1"
+for artifact in $artifacts; do    
+    ARTIFACT_NAME=$(basename "$artifact")
+
+    GATES_INFO=$($BACKEND gates -b "$artifacts_path/$artifact")
+    MAIN_FUNCTION_INFO=$(echo $GATES_INFO | jq -r '.functions[0] | .name = "main"')
+    echo "{\"package_name\": \"$ARTIFACT_NAME\", \"functions\": [$MAIN_FUNCTION_INFO]" >> gates_report.json
+
+    if (($ITER == $NUM_ARTIFACTS)); then
+        echo "}" >> gates_report.json
+    else 
+        echo "}, " >> gates_report.json
+    fi
+
+    ITER=$(( $ITER + 1 ))
+done
+
+echo "]}" >> gates_report.json 
+
+

src/lib.nr

@@ -3,3 +3,13 @@
 fn smoke_test() {
     assert(true);
 }
+
+// This is an example benchmark.
+// Changes to the number of constraints generated by this function will show in PRs.
+#[export]
+fn bench_test(mut x: Field) -> Field {
+    for _ in 0..100 {
+        x *= x;
+    }
+    x
+}