Restrict findSingleInitializer @out arguments.

The client should handle @in/@inout arguments differently.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/Utilities/AddressUtils.swift

@@ -199,6 +199,9 @@ extension AccessBase {
     case let .stack(allocStack):
       baseAddr = allocStack
     case let .argument(arg):
+      guard arg.convention.isIndirectOut else {
+        return nil
+      }
       baseAddr = arg
     default:
       return nil
@@ -208,7 +211,10 @@ extension AccessBase {
          == .abortWalk {
       return nil
     }
-    return (initialAddress: baseAddr, initializingStore: walker.initializer!)
+    guard let initializingStore = walker.initializingStore else {
+      return nil
+    }
+    return (initialAddress: baseAddr, initializingStore: initializingStore)
   }
 }
 
@@ -241,15 +247,15 @@ struct AddressInitializationWalker: AddressDefUseWalker, AddressUseVisitor {
   var walkDownCache = WalkerCache<SmallProjectionPath>()
 
   var isProjected = false
-  var initializer: Instruction?
+  var initializingStore: Instruction?
 
   private mutating func setInitializer(instruction: Instruction) -> WalkResult {
     // An initializer must be unique and store the full value.
-    if initializer != nil || isProjected {
-      initializer = nil
+    if initializingStore != nil || isProjected {
+      initializingStore = nil
       return .abortWalk
     }
-    initializer = instruction
+    initializingStore = instruction
     return .continueWalk
   }
 }

SwiftCompilerSources/Sources/Optimizer/Utilities/LifetimeDependenceUtils.swift

@@ -66,11 +66,12 @@ import SIL
 /// Value.enclosingAccess iteratively to find to AccessBase. This
 /// walker is useful for finding the innermost access, which may also
 /// be relevant for diagnostics.
-func gatherVariableIntroducers(for value: Value, _ context: Context) -> [Value]
+func gatherVariableIntroducers(for value: Value, _ context: Context)
+  -> SingleInlineArray<Value>
 {
-  var introducers: [Value] = []
+  var introducers = SingleInlineArray<Value>()
   var useDefVisitor = VariableIntroducerUseDefWalker(context) {
-    introducers.append($0)
+    introducers.push($0)
     return .continueWalk
   }
   defer { useDefVisitor.deinitialize() }