Attempt to prevent throwing away unused values in Swift benchmarks

signalapp · Dec 16, 2024 · 5a92f51 · 5a92f51
1 parent 4951219
commit 5a92f51
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Showing 3 changed files with 21 additions and 10 deletions.
diff --git a/swift/Benchmarks/Sources/Benchmarks/EllipticCurveOperations.swift b/swift/Benchmarks/Sources/Benchmarks/EllipticCurveOperations.swift
@@ -11,20 +11,20 @@ private let BENCHMARK_PLAINTEXT_SIZES = [100, 1000, 10000]
 
 let privateKeyOperationsSuite = BenchmarkSuite(name: "PrivateKey") { suite in
     suite.benchmark("generate") {
-        _ = PrivateKey.generate()
+        blackHole(PrivateKey.generate())
     }
 
     let privateKey = PrivateKey.generate()
     for plaintextSize in BENCHMARK_PLAINTEXT_SIZES {
         let bytes = Data((0..<plaintextSize).map { _ in UInt8.random(in: UInt8.min...UInt8.max) })
         suite.benchmark("generateSignature/\(plaintextSize)bytes") {
-            _ = privateKey.generateSignature(message: bytes)
+            blackHole(privateKey.generateSignature(message: bytes))
         }
     }
 
     let otherPublicKey = PrivateKey.generate().publicKey
     suite.benchmark("keyAgreement") {
-        _ = privateKey.keyAgreement(with: otherPublicKey)
+        blackHole(privateKey.keyAgreement(with: otherPublicKey))
     }
 }
 
@@ -34,18 +34,18 @@ let publicKeyOperationsSuite = BenchmarkSuite(name: "PublicKey") { suite in
     let publicKeyBytes = publicKey.serialize()
 
     suite.benchmark("init") {
-        _ = try PublicKey(publicKeyBytes)
+        blackHole(try! PublicKey(publicKeyBytes))
     }
 
     suite.benchmark("serialize") {
-        _ = publicKey.serialize()
+        blackHole(publicKey.serialize())
     }
 
     for plaintextSize in BENCHMARK_PLAINTEXT_SIZES {
         let bytes = Data((0..<plaintextSize).map { _ in UInt8.random(in: UInt8.min...UInt8.max) })
         let signature = privateKey.generateSignature(message: bytes)
-        suite.benchmark("verifySignature/\(plaintextSize)") {
-            _ = try publicKey.verifySignature(message: bytes, signature: signature)
+        suite.benchmark("verifySignature/\(plaintextSize)bytes") {
+            blackHole(try! publicKey.verifySignature(message: bytes, signature: signature))
         }
     }
 }
diff --git a/swift/Benchmarks/Sources/Benchmarks/GroupSendEndorsements.swift b/swift/Benchmarks/Sources/Benchmarks/GroupSendEndorsements.swift
@@ -26,16 +26,16 @@ let groupSendEndorsementsSuite = BenchmarkSuite(name: "GroupSendEndorsements") {
         let response = GroupSendEndorsementsResponse.issue(groupMembers: encryptedMembers, keyPair: keyPair)
 
         suite.benchmark("receiveWithServiceIds/\(groupSize)") {
-            _ = try! response.receive(groupMembers: members, localUser: members[0], groupParams: groupParams, serverParams: serverPublicParams)
+            blackHole(try! response.receive(groupMembers: members, localUser: members[0], groupParams: groupParams, serverParams: serverPublicParams))
         }
         suite.benchmark("receiveWithCiphertexts/\(groupSize)") {
-            _ = try! response.receive(groupMembers: encryptedMembers, localUser: encryptedMembers[0], serverParams: serverPublicParams)
+            blackHole(try! response.receive(groupMembers: encryptedMembers, localUser: encryptedMembers[0], serverParams: serverPublicParams))
         }
 
         let endorsements = try! response.receive(groupMembers: members, localUser: members[0], groupParams: groupParams, serverParams: serverPublicParams)
 
         suite.benchmark("toToken/\(groupSize)") {
-            _ = endorsements.endorsements.map { $0.toToken(groupParams: groupParams) }
+            blackHole(endorsements.endorsements.map { $0.toToken(groupParams: groupParams) })
         }
     }
 }
diff --git a/swift/Benchmarks/Sources/Benchmarks/main.swift b/swift/Benchmarks/Sources/Benchmarks/main.swift
@@ -11,3 +11,14 @@ Benchmark.main([
     privateKeyOperationsSuite,
     publicKeyOperationsSuite,
 ])
+
+/// Attempts to prevent the value of `x` from being discarded by the optimizer.
+///
+/// See https://github.com/google/swift-benchmark/issues/69
+@inline(__always)
+internal func blackHole<T>(_ x: T) {
+    @_optimize(none)
+    func assumePointeeIsRead(_: UnsafeRawPointer) {}
+
+    withUnsafePointer(to: x) { assumePointeeIsRead($0) }
+}