AddressUtils: refactor the findSingleInitializer API.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/Utilities/AddressUtils.swift

@@ -192,8 +192,7 @@ extension AccessBase {
   /// with the initialized address. This does not guarantee that all
   /// uses of that address are dominated by the store or even that the
   /// store is a direct use of `address`.
-  func findSingleInitializer(_ context: some Context)
-    -> (initialAddress: Value, initializingStore: Instruction)? {
+  func findSingleInitializer(_ context: some Context) -> (initialAddress: Value, initializingStore: Instruction)? {
     let baseAddr: Value
     switch self {
     case let .stack(allocStack):
@@ -206,15 +205,7 @@ extension AccessBase {
     default:
       return nil
     }
-    var walker = AddressInitializationWalker(context: context)
-    if walker.walkDownUses(ofAddress: baseAddr, path: SmallProjectionPath())
-         == .abortWalk {
-      return nil
-    }
-    guard let initializingStore = walker.initializingStore else {
-      return nil
-    }
-    return (initialAddress: baseAddr, initializingStore: initializingStore)
+    return AddressInitializationWalker.findSingleInitializer(ofAddress: baseAddr, context: context)
   }
 }
 
@@ -223,6 +214,9 @@ extension AccessBase {
 // Implements AddressUseVisitor to guarantee that we can't miss any
 // stores. This separates escapingAddressUse from leafAddressUse.
 //
+// Main entry point:
+//  static func findSingleInitializer(ofAddress: Value, context: some Context)
+//
 // TODO: Make AddressDefUseWalker always conform to AddressUseVisitor once we're
 // ready to debug changes to escape analysis etc...
 //
@@ -249,6 +243,19 @@ struct AddressInitializationWalker: AddressDefUseWalker, AddressUseVisitor {
   var isProjected = false
   var initializingStore: Instruction?
 
+  static func findSingleInitializer(ofAddress baseAddr: Value, context: some Context)
+    -> (initialAddress: Value, initializingStore: Instruction)? {
+
+    var walker = AddressInitializationWalker(context: context)
+    if walker.walkDownUses(ofAddress: baseAddr, path: SmallProjectionPath()) == .abortWalk {
+      return nil
+    }
+    guard let initializingStore = walker.initializingStore else {
+      return nil
+    }
+    return (initialAddress: baseAddr, initializingStore: initializingStore)
+  }
+
   private mutating func setInitializer(instruction: Instruction) -> WalkResult {
     // An initializer must be unique and store the full value.
     if initializingStore != nil || isProjected {