Refactor metrics out, and void their storage in release builds

Author: milseman

Sources/_StringProcessing/Engine/Metrics.swift

@@ -1,13 +1,71 @@
 extension Processor {
+#if PROCESSOR_MEASUREMENTS_ENABLED
   struct ProcessorMetrics {
     var instructionCounts: [Instruction.OpCode: Int] = [:]
     var backtracks: Int = 0
     var resets: Int = 0
+    var cycleCount: Int = 0
+
+    var isTracingEnabled: Bool = false
+    var shouldMeasureMetrics: Bool = false
+
+    init(isTracingEnabled: Bool, shouldMeasureMetrics: Bool) {
+      self.isTracingEnabled = isTracingEnabled
+      self.shouldMeasureMetrics = shouldMeasureMetrics
+    }
   }
-  
+#else
+  struct ProcessorMetrics {
+    var isTracingEnabled: Bool { false }
+    var shouldMeasureMetrics: Bool { false }
+    var cycleCount: Int { 0 }
+
+    init(isTracingEnabled: Bool, shouldMeasureMetrics: Bool) { }
+  }
+#endif
+}
+
+extension Processor {
+
+  mutating func startCycleMetrics() {
+#if PROCESSOR_MEASUREMENTS_ENABLED
+    if metrics.cycleCount == 0 {
+      trace()
+      measureMetrics()
+    }
+#endif
+  }
+
+  mutating func endCycleMetrics() {
+#if PROCESSOR_MEASUREMENTS_ENABLED
+    metrics.cycleCount += 1
+    trace()
+    measureMetrics()
+    _checkInvariants()
+#endif
+  }
+}
+
+extension Processor.ProcessorMetrics {
+
+  mutating func addReset() {
+#if PROCESSOR_MEASUREMENTS_ENABLED
+    self.resets += 1
+#endif
+  }
+
+  mutating func addBacktrack() {
+#if PROCESSOR_MEASUREMENTS_ENABLED
+    self.backtracks += 1
+#endif
+  }
+}
+
+extension Processor {
+#if PROCESSOR_MEASUREMENTS_ENABLED
   func printMetrics() {
     print("===")
-    print("Total cycle count: \(cycleCount)")
+    print("Total cycle count: \(metrics.cycleCount)")
     print("Backtracks: \(metrics.backtracks)")
     print("Resets: \(metrics.resets)")
     print("Instructions:")
@@ -30,8 +88,9 @@ extension Processor {
   }
 
   mutating func measureMetrics() {
-    if shouldMeasureMetrics {
+    if metrics.shouldMeasureMetrics {
       measure()
     }
   }
+#endif
 }

Sources/_StringProcessing/Engine/Processor.swift

@@ -86,11 +86,7 @@ struct Processor {
 
   var failureReason: Error? = nil
 
-  // MARK: Metrics, debugging, etc.
-  var cycleCount = 0
-  var isTracingEnabled: Bool
-  let shouldMeasureMetrics: Bool
-  var metrics: ProcessorMetrics = ProcessorMetrics()
+  var metrics: ProcessorMetrics
 }
 
 extension Processor {
@@ -116,8 +112,11 @@ extension Processor {
     self.subjectBounds = subjectBounds
     self.searchBounds = searchBounds
     self.matchMode = matchMode
-    self.isTracingEnabled = isTracingEnabled
-    self.shouldMeasureMetrics = shouldMeasureMetrics
+
+    self.metrics = ProcessorMetrics(
+      isTracingEnabled: isTracingEnabled,
+      shouldMeasureMetrics: shouldMeasureMetrics)
+
     self.currentPosition = searchBounds.lowerBound
 
     // Initialize registers with end of search bounds
@@ -144,8 +143,8 @@ extension Processor {
 
     self.state = .inProgress
     self.failureReason = nil
-    
-    if shouldMeasureMetrics { metrics.resets += 1 }
+
+    metrics.addReset()
     _checkInvariants()
   }
 
@@ -400,8 +399,8 @@ extension Processor {
     storedCaptures = capEnds
     registers.ints = intRegisters
     registers.positions = posRegisters
-    
-    if shouldMeasureMetrics { metrics.backtracks += 1 }
+
+    metrics.addBacktrack()
   }
 
   mutating func abort(_ e: Error? = nil) {
@@ -440,18 +439,8 @@ extension Processor {
     _checkInvariants()
     assert(state == .inProgress)
 
-#if PROCESSOR_MEASUREMENTS_ENABLED
-    if cycleCount == 0 {
-      trace()
-      measureMetrics()
-    }
-    defer {
-      cycleCount += 1
-      trace()
-      measureMetrics()
-      _checkInvariants()
-    }
-#endif
+    startCycleMetrics()
+    defer { endCycleMetrics() }
 
     let (opcode, payload) = fetch()
     switch opcode {

Sources/_StringProcessing/Engine/Tracing.swift

@@ -9,7 +9,12 @@
 //
 //===----------------------------------------------------------------------===//
 
+
+// TODO: Remove this protocol (and/or reuse it for something like a FastProcessor)
 extension Processor: TracedProcessor {
+  var cycleCount: Int { metrics.cycleCount }
+  var isTracingEnabled: Bool { metrics.isTracingEnabled }
+
   var isFailState: Bool { state == .fail }
   var isAcceptState: Bool { state == .accept }
 

Sources/_StringProcessing/Executor.swift

@@ -31,7 +31,7 @@ struct Executor {
       subjectBounds: subjectBounds,
       searchBounds: searchBounds)
 #if PROCESSOR_MEASUREMENTS_ENABLED
-    defer { if cpu.shouldMeasureMetrics { cpu.printMetrics() } }
+    defer { if cpu.metrics.shouldMeasureMetrics { cpu.printMetrics() } }
 #endif
     var low = searchBounds.lowerBound
     let high = searchBounds.upperBound
@@ -60,7 +60,7 @@ struct Executor {
     var cpu = engine.makeProcessor(
       input: input, bounds: subjectBounds, matchMode: mode)
 #if PROCESSOR_MEASUREMENTS_ENABLED
-    defer { if cpu.shouldMeasureMetrics { cpu.printMetrics() } }
+    defer { if cpu.metrics.shouldMeasureMetrics { cpu.printMetrics() } }
 #endif
     return try _match(input, from: subjectBounds.lowerBound, using: &cpu)
   }

Sources/_StringProcessing/Utility/Traced.swift

@@ -13,7 +13,7 @@
 // TODO: Place shared formatting and trace infrastructure here
 
 protocol Traced {
-  var isTracingEnabled: Bool { get set }
+  var isTracingEnabled: Bool { get }
 }
 
 protocol TracedProcessor: ProcessorProtocol, Traced {