Add option to print number of instructions executed by swift-format

I’m planning to use this option to measure the performance of `swift-format` periodically on a fixed set of project to detect any performance regressions.

Author: ahoppen

Package.swift

@@ -47,6 +47,10 @@ let package = Package(
     // See the "Dependencies" section below.
   ],
   targets: [
+    .target(
+      name: "_InstructionCounter"
+    ),
+
     .target(
       name: "SwiftFormat",
       dependencies: [
@@ -108,6 +112,7 @@ let package = Package(
     .executableTarget(
       name: "swift-format",
       dependencies: [
+        "_InstructionCounter",
         "SwiftFormat",
         .product(name: "ArgumentParser", package: "swift-argument-parser"),
         .product(name: "SwiftSyntax", package: "swift-syntax"),

Sources/_InstructionCounter/include/InstructionsExecuted.h

@@ -0,0 +1,17 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdint.h>
+
+/// On macOS returns the number of instructions the process has executed since
+/// it was launched, on all other platforms returns 0.
+uint64_t getInstructionsExecuted();

Sources/_InstructionCounter/src/InstructionsExecuted.c

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#if __APPLE__
+#include <TargetConditionals.h>
+#if TARGET_OS_MAC && !TARGET_OS_IPHONE
+#define TARGET_IS_MACOS 1
+#endif
+#endif
+
+#include "InstructionsExecuted.h"
+
+#ifdef TARGET_IS_MACOS
+#include <libproc.h>
+#include <sys/resource.h>
+#include <unistd.h>
+
+uint64_t getInstructionsExecuted() {
+  struct rusage_info_v4 ru;
+  if (proc_pid_rusage(getpid(), RUSAGE_INFO_V4, (rusage_info_t *)&ru) == 0) {
+    return ru.ri_instructions;
+  }
+  return 0;
+}
+#else
+uint64_t getInstructionsExecuted() {
+  return 0;
+}
+#endif

Sources/swift-format/Subcommands/Format.swift

@@ -30,16 +30,21 @@ extension SwiftFormatCommand {
     @OptionGroup()
     var formatOptions: LintFormatOptions
 
+    @OptionGroup(visibility: .hidden)
+    var performanceMeasurementOptions: PerformanceMeasurementsOptions
+
     func validate() throws {
       if inPlace && formatOptions.paths.isEmpty {
         throw ValidationError("'--in-place' is only valid when formatting files")
       }
     }
 
     func run() throws {
-      let frontend = FormatFrontend(lintFormatOptions: formatOptions, inPlace: inPlace)
-      frontend.run()
-      if frontend.diagnosticsEngine.hasErrors { throw ExitCode.failure }
+      try performanceMeasurementOptions.countingInstructionsIfRequested {
+        let frontend = FormatFrontend(lintFormatOptions: formatOptions, inPlace: inPlace)
+        frontend.run()
+        if frontend.diagnosticsEngine.hasErrors { throw ExitCode.failure }
+      }
     }
   }
 }

Sources/swift-format/Subcommands/Lint.swift

@@ -28,12 +28,17 @@ extension SwiftFormatCommand {
     )
     var strict: Bool = false
 
-    func run() throws {
-      let frontend = LintFrontend(lintFormatOptions: lintOptions)
-      frontend.run()
+    @OptionGroup(visibility: .hidden)
+    var performanceMeasurementOptions: PerformanceMeasurementsOptions
 
-      if frontend.diagnosticsEngine.hasErrors || strict && frontend.diagnosticsEngine.hasWarnings {
-        throw ExitCode.failure
+    func run() throws {
+      try performanceMeasurementOptions.countingInstructionsIfRequested {
+        let frontend = LintFrontend(lintFormatOptions: lintOptions)
+        frontend.run()
+        
+        if frontend.diagnosticsEngine.hasErrors || strict && frontend.diagnosticsEngine.hasWarnings {
+          throw ExitCode.failure
+        }
       }
     }
   }

Sources/swift-format/Subcommands/PerformanceMeasurement.swift

@@ -0,0 +1,33 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2023 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+import ArgumentParser
+import _InstructionCounter
+
+struct PerformanceMeasurementsOptions: ParsableArguments {
+  @Flag(help: "Measure number of instructions executed by swift-format")
+  var measureInstructions = false
+
+  /// If `measureInstructions` is set, execute `body` and print the number of instructions
+  /// executed by it. Otherwise, just execute `body`
+  func printingInstructionCountIfRequested<T>(_ body: () throws -> T) rethrows -> T {
+    if !measureInstructions {
+      return try body()
+    } else {
+      let startInstructions = getInstructionsExecuted()
+      defer {
+        print("Instructions executed: \(getInstructionsExecuted() - startInstructions)")
+      }
+      return try body()
+    }
+  }
+}