AddressUtils: handle address initialization inside _modify.

We can assume that memory is already initialized at the point of a 'yield'; a
yield use does not need to invalidate the single-initialization property for
temporary stack allocations.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/Utilities/AddressUtils.swift

@@ -341,8 +341,9 @@ extension AddressInitializationWalker {
   }
 
   mutating func yieldedAddressUse(of operand: Operand) -> WalkResult {
-    // An inout yield is a partial write.
-    return .abortWalk
+    // An inout yield is a partial write. Initialization via coroutine is not supported, so we assume a prior
+    // initialization must dominate the yield.
+    return .continueWalk
   }
 
   mutating func dependentAddressUse(of operand: Operand, into value: Value)