Swift AccessUtils: remove AccessStoragePathWalker

Instead, place it's one and only API `visitAccessStorageRoots` into an extension of `ValueUseDefWalker`.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/TestPasses/AccessDumper.swift

@@ -48,11 +48,12 @@ let accessDumper = FunctionPass(name: "dump-access", {
   print("End accesses for \(function.name)")
 })
 
-private struct AccessStoragePathVisitor : AccessStoragePathWalker {
+private struct AccessStoragePathVisitor : ValueUseDefWalker {
   var walkUpCache = WalkerCache<Path>()
-  mutating func visit(accessStoragePath: ProjectedValue) {
-    print("    Storage: \(accessStoragePath.value)")
-    print("    Path: \"\(accessStoragePath.path)\"")
+  mutating func rootDef(value: Value, path: SmallProjectionPath) -> WalkResult {
+    print("    Storage: \(value)")
+    print("    Path: \"\(path)\"")
+    return .continueWalk
   }
 }
 

SwiftCompilerSources/Sources/Optimizer/Utilities/AccessUtils.swift

@@ -462,11 +462,7 @@ extension Value {
 ///   %addr = struct_element_addr %base : $X, #X.e
 ///   store %v to [trivial] %addr : $*Int
 /// ```
-protocol AccessStoragePathWalker : ValueUseDefWalker where Path == SmallProjectionPath {
-  mutating func visit(accessStoragePath: ProjectedValue)
-}
-
-extension AccessStoragePathWalker {
+extension ValueUseDefWalker where Path == SmallProjectionPath {
   /// The main entry point.
   /// Given an `accessPath` where the access base is a reference (class, tail, box), call
   /// the `visit` function for all storage roots with a the corresponding path.
@@ -486,9 +482,4 @@ extension AccessStoragePathWalker {
         return false
     }
   }
-
-  mutating func rootDef(value: Value, path: SmallProjectionPath) -> WalkResult {
-    visit(accessStoragePath: value.at(path))
-    return .continueWalk
-  }
 }