Enable quantification optimizations for scalar semantics (#671)

*  Quantified scalar semantic matching

Author: milseman

Sources/_StringProcessing/ByteCodeGen.swift

@@ -23,7 +23,9 @@ extension Compiler {
     var hasEmittedFirstMatchableAtom = false
 
     private let compileOptions: _CompileOptions
-    fileprivate var optimizationsEnabled: Bool { !compileOptions.contains(.disableOptimizations) }
+    fileprivate var optimizationsEnabled: Bool {
+      !compileOptions.contains(.disableOptimizations)
+    }
 
     init(
       options: MatchingOptions,
@@ -665,10 +667,10 @@ fileprivate extension Compiler.ByteCodeGen {
     _ minTrips: Int,
     _ extraTrips: Int?
   ) -> Bool {
+    let isScalarSemantics = options.semanticLevel == .unicodeScalar
     guard optimizationsEnabled
             && minTrips <= QuantifyPayload.maxStorableTrips
             && extraTrips ?? 0 <= QuantifyPayload.maxStorableTrips
-            && options.semanticLevel == .graphemeCluster
             && kind != .reluctant else {
       return false
     }
@@ -678,7 +680,7 @@ fileprivate extension Compiler.ByteCodeGen {
       guard let bitset = ccc.asAsciiBitset(options) else {
         return false
       }
-      builder.buildQuantify(bitset: bitset, kind, minTrips, extraTrips)
+      builder.buildQuantify(bitset: bitset, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics)
 
     case .atom(let atom):
       switch atom {
@@ -687,17 +689,17 @@ fileprivate extension Compiler.ByteCodeGen {
         guard let val = c._singleScalarAsciiValue else {
           return false
         }
-        builder.buildQuantify(asciiChar: val, kind, minTrips, extraTrips)
+        builder.buildQuantify(asciiChar: val, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics)
 
       case .any:
         builder.buildQuantifyAny(
-          matchesNewlines: true, kind, minTrips, extraTrips)
+          matchesNewlines: true, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics)
       case .anyNonNewline:
         builder.buildQuantifyAny(
-          matchesNewlines: false, kind, minTrips, extraTrips)
+          matchesNewlines: false, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics)
       case .dot:
         builder.buildQuantifyAny(
-          matchesNewlines: options.dotMatchesNewline, kind, minTrips, extraTrips)
+          matchesNewlines: options.dotMatchesNewline, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics)
 
       case .characterClass(let cc):
         // Custom character class that consumes a single grapheme
@@ -706,7 +708,8 @@ fileprivate extension Compiler.ByteCodeGen {
           model: model,
           kind,
           minTrips,
-          extraTrips)
+          extraTrips,
+          isScalarSemantics: isScalarSemantics)
       default:
         return false
       }

Sources/_StringProcessing/Engine/Backtracking.swift

@@ -16,6 +16,11 @@ extension Processor {
     // Quantifiers may store a range of positions to restore to
     var rangeStart: Position?
     var rangeEnd: Position?
+
+    // FIXME: refactor, for now this field is only used for quantifier save
+    //        points. We should try to separate out the concerns better.
+    var isScalarSemantics: Bool
+
     // The end of the call stack, so we can slice it off
     // when failing inside a call.
     //
@@ -68,7 +73,11 @@ extension Processor {
         rangeStart = nil
         rangeEnd = nil
       } else {
-        input.formIndex(before: &rangeEnd!)
+        if isScalarSemantics {
+          input.unicodeScalars.formIndex(before: &rangeEnd!)
+        } else {
+          input.formIndex(before: &rangeEnd!)
+        }
       }
     }
   }
@@ -82,19 +91,23 @@ extension Processor {
       pos: addressOnly ? nil : currentPosition,
       rangeStart: nil,
       rangeEnd: nil,
+      isScalarSemantics: false, // FIXME: refactor away
       stackEnd: .init(callStack.count),
       captureEnds: storedCaptures,
       intRegisters: registers.ints,
       posRegisters: registers.positions)
   }
 
-  func startQuantifierSavePoint() -> SavePoint {
+  func startQuantifierSavePoint(
+    isScalarSemantics: Bool
+  ) -> SavePoint {
     // Restores to the instruction AFTER the current quantifier instruction
     SavePoint(
       pc: controller.pc + 1,
       pos: nil,
       rangeStart: nil,
       rangeEnd: nil,
+      isScalarSemantics: isScalarSemantics,
       stackEnd: .init(callStack.count),
       captureEnds: storedCaptures,
       intRegisters: registers.ints,

Sources/_StringProcessing/Engine/InstPayload.swift

@@ -370,6 +370,10 @@ extension Instruction.Payload {
   }
 }
 
+// TODO: Consider switching all quantification to a quantification
+//       instruction, where the general path has an instruction list (i.e. a
+//       slice of a list)
+
 // MARK: Struct definitions
 struct QuantifyPayload: RawRepresentable {
   let rawValue: UInt64
@@ -380,9 +384,12 @@ struct QuantifyPayload: RawRepresentable {
     case builtin = 4
   }
 
+  // TODO: figure out how to better organize this...
+
   // Future work: optimize this layout -> payload type should be a fast switch
   // The top 8 bits are reserved for the opcode so we have 56 bits to work with
-  // b55-b38 - Unused
+  // b55-b39 - Unused
+  // b39-b38 - isScalarSemantics
   // b38-b35 - Payload type (one of 4 types, stored on 3 bits)
   // b35-b27 - minTrips (8 bit int)
   // b27-b18 - extraTrips (8 bit value, one bit for nil)
@@ -393,6 +400,7 @@ struct QuantifyPayload: RawRepresentable {
   static var minTripsShift: UInt64    { 27 }
   static var typeShift: UInt64        { 35 }
   static var maxStorableTrips: UInt64 { (1 << 8) - 1 }
+  static var isScalarSemanticsBit: UInt64 { 1 &<< 38 }
 
   var quantKindMask: UInt64  { 3 }
   var extraTripsMask: UInt64 { 0x1FF }
@@ -404,7 +412,8 @@ struct QuantifyPayload: RawRepresentable {
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
     _ extraTrips: Int?,
-    _ type: PayloadType
+    _ type: PayloadType,
+    isScalarSemantics: Bool
   ) -> UInt64 {
     let kindVal: UInt64
     switch kind {
@@ -415,11 +424,14 @@ struct QuantifyPayload: RawRepresentable {
     case .possessive:
       kindVal = 2
     }
+    // TODO: refactor / reimplement
     let extraTripsVal: UInt64 = extraTrips == nil ? 1 : UInt64(extraTrips!) << 1
-    return (kindVal << QuantifyPayload.quantKindShift) +
-    (extraTripsVal << QuantifyPayload.extraTripsShift) +
-    (UInt64(minTrips) << QuantifyPayload.minTripsShift) +
-    (type.rawValue << QuantifyPayload.typeShift)
+    let scalarSemanticsBit = isScalarSemantics ? Self.isScalarSemanticsBit : 0
+    return (kindVal << QuantifyPayload.quantKindShift) |
+    (extraTripsVal << QuantifyPayload.extraTripsShift) |
+    (UInt64(minTrips) << QuantifyPayload.minTripsShift) |
+    (type.rawValue << QuantifyPayload.typeShift) |
+    scalarSemanticsBit
   }
 
   init(rawValue: UInt64) {
@@ -431,46 +443,49 @@ struct QuantifyPayload: RawRepresentable {
     bitset: AsciiBitsetRegister,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     assert(bitset.bits <= _payloadMask)
     self.rawValue = bitset.bits
-      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .bitset)
+      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .bitset, isScalarSemantics: isScalarSemantics)
   }
 
   init(
     asciiChar: UInt8,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     self.rawValue = UInt64(asciiChar)
-      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .asciiChar)
+      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .asciiChar, isScalarSemantics: isScalarSemantics)
   }
 
   init(
     matchesNewlines: Bool,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     self.rawValue = (matchesNewlines ? 1 : 0)
-      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .any)
+      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .any, isScalarSemantics: isScalarSemantics)
   }
 
   init(
     model: _CharacterClassModel,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     assert(model.cc.rawValue < 0xFF)
-    assert(model.matchLevel != .unicodeScalar)
     let packedModel = model.cc.rawValue
       + (model.isInverted ? 1 << 9 : 0)
       + (model.isStrictASCII ? 1 << 10 : 0)
     self.rawValue = packedModel
-      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .builtin)
+      + QuantifyPayload.packInfoValues(kind, minTrips, extraTrips, .builtin, isScalarSemantics: isScalarSemantics)
   }
 
   var type: PayloadType {
@@ -500,6 +515,10 @@ struct QuantifyPayload: RawRepresentable {
     }
   }
 
+  var isScalarSemantics: Bool {
+    rawValue & Self.isScalarSemanticsBit != 0
+  }
+
   var bitset: AsciiBitsetRegister {
     TypedInt(self.rawValue & payloadMask)
   }

Sources/_StringProcessing/Engine/MEBuilder.swift

@@ -222,44 +222,48 @@ extension MEProgram.Builder {
     bitset: DSLTree.CustomCharacterClass.AsciiBitset,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     instructions.append(.init(
       .quantify,
-      .init(quantify: .init(bitset: makeAsciiBitset(bitset), kind, minTrips, extraTrips))))
+      .init(quantify: .init(bitset: makeAsciiBitset(bitset), kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics))))
   }
 
   mutating func buildQuantify(
     asciiChar: UInt8,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     instructions.append(.init(
       .quantify,
-      .init(quantify: .init(asciiChar: asciiChar, kind, minTrips, extraTrips))))
+      .init(quantify: .init(asciiChar: asciiChar, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics))))
   }
 
   mutating func buildQuantifyAny(
     matchesNewlines: Bool,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     instructions.append(.init(
       .quantify,
-      .init(quantify: .init(matchesNewlines: matchesNewlines, kind, minTrips, extraTrips))))
+      .init(quantify: .init(matchesNewlines: matchesNewlines, kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics))))
   }
 
   mutating func buildQuantify(
     model: _CharacterClassModel,
     _ kind: AST.Quantification.Kind,
     _ minTrips: Int,
-    _ extraTrips: Int?
+    _ extraTrips: Int?,
+    isScalarSemantics: Bool
   ) {
     instructions.append(.init(
       .quantify,
-      .init(quantify: .init(model: model,kind, minTrips, extraTrips))))
+      .init(quantify: .init(model: model,kind, minTrips, extraTrips, isScalarSemantics: isScalarSemantics))))
   }
 
   mutating func buildAccept() {

Sources/_StringProcessing/Engine/MEQuantify.swift

@@ -1,21 +1,20 @@
 extension Processor {
   func _doQuantifyMatch(_ payload: QuantifyPayload) -> Input.Index? {
-    // TODO: This optimization is only enabled for grapheme cluster semantics,
-    //       we want these for scalar semantics as well.
+    let isScalarSemantics = payload.isScalarSemantics
 
     switch payload.type {
     case .bitset:
       return input.matchBitset(
         registers[payload.bitset],
         at: currentPosition,
         limitedBy: end,
-        isScalarSemantics: false)
+        isScalarSemantics: isScalarSemantics)
     case .asciiChar:
       return input.matchScalar(
         UnicodeScalar.init(_value: UInt32(payload.asciiChar)),
         at: currentPosition,
         limitedBy: end,
-        boundaryCheck: true,
+        boundaryCheck: !isScalarSemantics,
         isCaseInsensitive: false)
     case .builtin:
       // FIXME: bounds check? endIndex or end?
@@ -26,17 +25,20 @@ extension Processor {
         at: currentPosition,
         isInverted: payload.builtinIsInverted,
         isStrictASCII: payload.builtinIsStrict,
-        isScalarSemantics: false)
+        isScalarSemantics: isScalarSemantics)
     case .any:
       // FIXME: endIndex or end?
       guard currentPosition < input.endIndex else { return nil }
 
       if payload.anyMatchesNewline {
+        if isScalarSemantics {
+          return input.unicodeScalars.index(after: currentPosition)
+        }
         return input.index(after: currentPosition)
       }
 
       return input.matchAnyNonNewline(
-        at: currentPosition, isScalarSemantics: false)
+        at: currentPosition, isScalarSemantics: isScalarSemantics)
     }
   }
 
@@ -46,7 +48,9 @@ extension Processor {
   mutating func runQuantify(_ payload: QuantifyPayload) -> Bool {
     var trips = 0
     var extraTrips = payload.extraTrips
-    var savePoint = startQuantifierSavePoint()
+    var savePoint = startQuantifierSavePoint(
+      isScalarSemantics: payload.isScalarSemantics
+    )
 
     while true {
       if trips >= payload.minTrips {
@@ -85,7 +89,9 @@ extension Processor {
     assert(payload.quantKind == .eager
            && payload.minTrips == 0
            && payload.extraTrips == nil)
-    var savePoint = startQuantifierSavePoint()
+    var savePoint = startQuantifierSavePoint(
+      isScalarSemantics: payload.isScalarSemantics
+    )
 
     while true {
       savePoint.updateRange(newEnd: currentPosition)
@@ -107,7 +113,9 @@ extension Processor {
     assert(payload.quantKind == .eager
            && payload.minTrips == 1
            && payload.extraTrips == nil)
-    var savePoint = startQuantifierSavePoint()
+    var savePoint = startQuantifierSavePoint(
+      isScalarSemantics: payload.isScalarSemantics
+    )
     while true {
       let next = _doQuantifyMatch(payload)
       guard let idx = next else { break }