Support benchmarking PRs

Per https://bencher.dev/docs/how-to/github-actions/#benchmark-fork-pr-and-upload-from-default-branch

.github/workflows/pr-benchmark-upload-from-main.yml

@@ -0,0 +1,72 @@
+name: Track Benchmarks
+
+on:
+  workflow_run:
+    workflows: [Run and Cache Benchmarks]
+    types:
+      - completed
+
+jobs:
+  track_with_bencher:
+    if: github.event.workflow_run.conclusion == 'success'
+    runs-on: ubuntu-22.04
+    env:
+      BENCHER_PROJECT: h264-reader
+      BENCHER_ADAPTER: rust_iai_callgrind
+      BENCHER_TESTBED: ubuntu-22.04
+      BENCHMARK_RESULTS: benchmark_results.txt
+      PR_EVENT: event.json
+    steps:
+      - name: Download Benchmark Results
+        uses: actions/github-script@v6
+        with:
+          script: |
+            async function downloadArtifact(artifactName) {
+              let allArtifacts = await github.rest.actions.listWorkflowRunArtifacts({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                run_id: context.payload.workflow_run.id,
+              });
+              let matchArtifact = allArtifacts.data.artifacts.filter((artifact) => {
+                return artifact.name == artifactName
+              })[0];
+              if (!matchArtifact) {
+                core.setFailed(`Failed to find artifact: ${artifactName}`);
+              }
+              let download = await github.rest.actions.downloadArtifact({
+                owner: context.repo.owner,
+                repo: context.repo.repo,
+                artifact_id: matchArtifact.id,
+                archive_format: 'zip',
+              });
+              let fs = require('fs');
+              fs.writeFileSync(`${process.env.GITHUB_WORKSPACE}/${artifactName}.zip`, Buffer.from(download.data));
+            }
+            await downloadArtifact(process.env.BENCHMARK_RESULTS);
+            await downloadArtifact(process.env.PR_EVENT);
+      - name: Unzip Benchmark Results
+        run: |
+          unzip $BENCHMARK_RESULTS.zip
+          unzip $PR_EVENT.zip
+      - name: Export PR Event Data
+        uses: actions/github-script@v6
+        with:
+          script: |
+            let fs = require('fs');
+            let prEvent = JSON.parse(fs.readFileSync(process.env.PR_EVENT, {encoding: 'utf8'}));
+            core.exportVariable("PR_HEAD", `${prEvent.number}/merge`);
+            core.exportVariable("PR_BASE", prEvent.pull_request.base.ref);
+            core.exportVariable("PR_DEFAULT", prEvent.pull_request.base.repo.default_branch);
+            core.exportVariable("PR_NUMBER", prEvent.number);
+      - uses: bencherdev/bencher@main
+      - name: Track Benchmarks with Bencher
+        run: |
+          bencher run \
+          --if-branch '${{ env.PR_HEAD }}' \
+          --else-if-branch '${{ env.PR_BASE }}' \
+          --else-if-branch '${{ env.PR_DEFAULT }}' \
+          --ci-number '${{ env.PR_NUMBER }}' \
+          --github-actions "${{ secrets.GITHUB_TOKEN }}" \
+          --token "${{ secrets.BENCHER_API_TOKEN }}" \
+          --err \
+          --file "$BENCHMARK_RESULTS"

.github/workflows/pr-benchmark.yml

@@ -0,0 +1,28 @@
+name: Run and Cache Benchmarks
+
+on:
+  pull_request:
+    types: [opened, reopened, synchronize]
+
+jobs:
+  benchmark:
+    name: Run Benchmarks
+    runs-on: ubuntu-22.04
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cargo-bins/cargo-binstall@main
+
+      - run: sudo apt-get install valgrind
+      - run: cargo binstall --no-confirm [email protected]
+      - run: |
+          IAI_CALLGRIND_COLOR=never cargo bench --bench ci_bench > benchmark_results.txt
+      - name: Upload Benchmark Results
+        uses: actions/upload-artifact@v4
+        with:
+          name: benchmark_results.txt
+          path: ./benchmark_results.txt
+      - name: Upload GitHub Pull Request Event
+        uses: actions/upload-artifact@v4
+        with:
+          name: event.json
+          path: ${{ github.event_path }}

benches/README.md

@@ -16,4 +16,6 @@ There are two benchmarks here,
    - run using `cargo bench --bench ci_bench`
 
 The latter benchmark is run from a github actions workflow on commits to the main branch and the benchmark results are
-uploaded to [bencher.dev](https://bencher.dev/perf/h264-reader).
+uploaded to [bencher.dev](https://bencher.dev/perf/h264-reader).
+
+[![h264-reader - Bencher](https://api.bencher.dev/v0/projects/h264-reader/perf/img?branches=a53abf65-ea6e-482e-8c55-cf6726e77864&testbeds=19d2a260-47fc-44ec-b7f8-314d88408ce7&benchmarks=cc26ec97-55ef-43a5-860f-861ae847d8b3&measures=1dc590ca-477f-4477-8295-672b05d33086&start_time=1706605032000&end_time=1709197032000 "h264-reader")](https://bencher.dev/perf/h264-reader?key=true&reports_per_page=4&branches_per_page=8&testbeds_per_page=8&benchmarks_per_page=8&reports_page=1&branches_page=1&testbeds_page=1&benchmarks_page=1)