SIL: add lookup(method:) in VTable and WitnessTable

Author: eeckstein

SwiftCompilerSources/Sources/SIL/VTable.swift

@@ -91,6 +91,15 @@ public struct VTable : CustomStringConvertible, NoReflectionChildren {
 
   public var isSpecialized: Bool { specializedClassType != nil }
 
+  /// A lookup for a specific method with O(1) complexity.
+  public func lookup(method: DeclRef) -> Entry? {
+    let bridgedEntryOrNil = bridged.lookupMethod(method.bridged)
+    if bridgedEntryOrNil.hasEntry {
+      return Entry(bridged: bridgedEntryOrNil.entry)
+    }
+    return nil
+  }
+
   public var description: String {
     return String(taking: bridged.getDebugDescription())
   }

SwiftCompilerSources/Sources/SIL/WitnessTable.swift

@@ -99,6 +99,16 @@ public struct WitnessTable : CustomStringConvertible, NoReflectionChildren {
     }
   }
 
+  /// A lookup for a specific method with O(n) complexity.
+  public func lookup(method: DeclRef) -> Function? {
+    for entry in entries {
+      if case .method(let req, let impl) = entry, req == method {
+        return impl
+      }
+    }
+    return nil
+  }
+
   public var entries: EntryArray { EntryArray(witnessTable: self) }
 
   public var isDefinition: Bool { !bridged.isDeclaration() }

include/swift/SIL/SILBridging.h

@@ -948,6 +948,7 @@ struct BridgedVTableEntry {
     Override
   };
 
+  BridgedVTableEntry() : storage{0, 0, 0, 0, 0} {};
   BRIDGED_INLINE BridgedVTableEntry(const swift::SILVTableEntry &entry);
   BRIDGED_INLINE const swift::SILVTableEntry &unbridged() const;
 
@@ -961,6 +962,14 @@ struct BridgedVTableEntry {
                                    BridgedDeclRef methodDecl, BridgedFunction implementation);
 };
 
+struct OptionalBridgedVTableEntry {
+  BridgedVTableEntry entry;
+  bool hasEntry = false;
+
+  OptionalBridgedVTableEntry() {}
+  OptionalBridgedVTableEntry(BridgedVTableEntry e) : entry(e), hasEntry(true) {}
+};
+
 struct BridgedVTableEntryArray {
   BridgedVTableEntry base;
   SwiftInt count;
@@ -973,6 +982,7 @@ struct BridgedVTable {
   BRIDGED_INLINE SwiftInt getNumEntries() const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedVTableEntry getEntry(SwiftInt index) const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedDeclObj getClass() const;
+  SWIFT_IMPORT_UNSAFE BRIDGED_INLINE OptionalBridgedVTableEntry lookupMethod(BridgedDeclRef member) const;
   SWIFT_IMPORT_UNSAFE BRIDGED_INLINE BridgedType getSpecializedClassType() const;
   BRIDGED_INLINE void replaceEntries(BridgedArrayRef bridgedEntries) const;
 };

include/swift/SIL/SILBridgingImpl.h

@@ -1808,6 +1808,18 @@ BridgedDeclObj BridgedVTable::getClass() const {
   return vTable->getClass();
 }
 
+OptionalBridgedVTableEntry BridgedVTable::lookupMethod(BridgedDeclRef member) const {
+  if (vTable->getEntries().empty()) {
+    return OptionalBridgedVTableEntry();
+  }
+  swift::SILModule &mod = vTable->getEntries()[0].getImplementation()->getModule();
+  if (auto entry = vTable->getEntry(mod, member.unbridged()))
+    return BridgedVTableEntry(entry.value());
+
+  return OptionalBridgedVTableEntry();
+}
+
+
 BridgedType BridgedVTable::getSpecializedClassType() const {
   return {vTable->getClassType()};
 }