Fix the easy stuff.

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -763,7 +763,7 @@ extension ModuleDependencyGraph {
 
         func stringIndex(field i: Int) throws -> Int {
           let u = record.fields[i]
-          guard u < UInt64(internedStringTable.endIndex) else {
+          guard u < UInt64(internedStringTable.count) else {
             throw malformedError
           }
           return Int(u)
@@ -775,18 +775,18 @@ extension ModuleDependencyGraph {
           let s = try internedString(field: i)
           return s.isEmpty ? nil : s
         }
-        func dependencyKey(fields: (kindCode: Int,
-                                    declAspect: Int,
-                                    context: Int,
-                                    identifier: Int)
+        func dependencyKey(kindCodeField: Int,
+                           declAspectField: Int,
+                           contextField: Int,
+                           identifierField: Int
         ) throws -> DependencyKey {
-          let kindCode = record.fields[fields.kindCode]
-          guard let declAspect = DependencyKey.DeclAspect(record.fields[fields.declAspect])
+          let kindCode = record.fields[kindCodeField]
+          guard let declAspect = DependencyKey.DeclAspect(record.fields[declAspectField])
           else {
             throw malformedError
           }
-          let context = try internedString(field: fields.context)
-          let identifier = try internedString(field: fields.identifier)
+          let context = try internedString(field: contextField)
+          let identifier = try internedString(field: identifierField)
           let designator = try DependencyKey.Designator(
             kindCode: kindCode, context: context, name: identifier,
             internedStringTable: internedStringTable, fileSystem: fileSystem)
@@ -805,13 +805,18 @@ extension ModuleDependencyGraph {
 
           self.majorVersion = record.fields[0]
           self.minorVersion = record.fields[1]
+          let stringCount = record.fields[2]
+          internedStringTable.reserveCapacity(Int(stringCount))
           self.compilerVersionString = String(decoding: compilerVersionBlob, as: UTF8.self)
         case .moduleDepGraphNode:
            guard record.fields.count == 6
           else {
             throw malformedError
           }
-          let key = try dependencyKey(fields: (0, 1, 2, 3))
+          let key = try dependencyKey(kindCodeField: 0,
+                                      declAspectField: 1,
+                                      contextField: 2,
+                                      identifierField: 3)
           let depSourceFileOrNone = try nonemptyInternedString(field: 4)
           let depSource = try depSourceFileOrNone.map {
             internedFile -> DependencySource in
@@ -833,7 +838,11 @@ extension ModuleDependencyGraph {
           else {
             throw malformedError
           }
-          self.currentDefKey = try dependencyKey(fields: (0, 1, 2, 3))
+          self.currentDefKey = try dependencyKey(
+            kindCodeField: 0,
+            declAspectField: 1,
+            contextField: 2,
+            identifierField: 3)
         case .useIDNode:
           guard let key = self.currentDefKey,
                   record.fields.count == 1 else {
@@ -1025,6 +1034,7 @@ extension ModuleDependencyGraph {
         $0.append(RecordID.metadata)
         $0.append(serializedGraphVersion.majorForWriting)
         $0.append(serializedGraphVersion.minorForWriting)
+        $0.append(min(UInt(internedStringTable.count), UInt(UInt32.max)))
       },
       blob: self.compilerVersion)
     }
@@ -1068,6 +1078,8 @@ extension ModuleDependencyGraph {
         .fixed(bitWidth: 16),
         // Minor version
         .fixed(bitWidth: 16),
+        // Number of strings to be interned
+        .fixed(bitWidth: 32),
         // Frontend version
         .blob,
       ])

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraphParts/InternedStrings.swift

@@ -10,8 +10,6 @@
 //
 //===----------------------------------------------------------------------===//
 
-import Foundation
-
 public protocol InternedStringTableHolder {
   var internedStringTable: InternedStringTable {get}
 }
@@ -21,7 +19,7 @@ public struct InternedString: CustomStringConvertible, Equatable, Hashable {
   let index: Int
 
   fileprivate init(_ s: String, _ table: InternedStringTable) {
-    self.init(index: s.isEmpty ? 0 : table.index(s))
+    self.init(index: s.isEmpty ? 0 : table.intern(s))
   }
 
   public var isEmpty: Bool { index == 0 }
@@ -37,7 +35,7 @@ public struct InternedString: CustomStringConvertible, Equatable, Hashable {
     return r
   }
 
-  public func lookup(`in` holder: InternedStringTableHolder) -> String {
+  public func lookup(in holder: InternedStringTableHolder) -> String {
     holder.internedStringTable.strings[index]
   }
 
@@ -56,28 +54,28 @@ public func isInIncreasingOrder(
   lhs.lookup(in: holder) < rhs.lookup(in: holder)
 }
 
-extension InternedString {
-  public static func < (lhs: InternedString, rhs: InternedString) -> Bool {
-    lhs.index < rhs.index
-  }
-}
-
 /// Hardcode empty as 0
 public class InternedStringTable {
   var strings = [""]
   fileprivate var indices = ["": 0]
 
   public init() {}
 
-  fileprivate func index(_ s: String) -> Int {
+  fileprivate func intern(_ s: String) -> Int {
     if let i = indices[s] { return i }
     let i = strings.count
     strings.append(s)
     indices[s] = i
     return i
   }
 
-  var endIndex: Int { strings.count }
+  var count: Int { strings.count }
+  
+  func reserveCapacity(_ minimumCapacity: Int) {
+    strings.reserveCapacity(minimumCapacity)
+    indices.reserveCapacity(minimumCapacity)
+  }
+
 }
 
 extension InternedStringTable: InternedStringTableHolder {