Merge pull request #82798 from eeckstein/fix-let-property-lowering

LetPropertyLowering: remove redundant phis after ssa-update

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LetPropertyLowering.swift

@@ -122,6 +122,8 @@ private func insertEndInitInstructions(
       use.set(to: ssaUpdater.getValue(atEndOf: use.instruction.parentBlock), context)
     }
   }
+  // This peephole optimization is required to avoid ownership errors.
+  replacePhisWithIncomingValues(phis: ssaUpdater.insertedPhis, context)
 }
 
 private func constructLetInitRegion(

SwiftCompilerSources/Sources/Optimizer/Utilities/SSAUpdater.swift

@@ -50,4 +50,14 @@ struct SSAUpdater<Context: MutatingContext> {
     context.notifyInstructionsChanged()
     return context._bridged.SSAUpdater_getValueInMiddleOfBlock(block.bridged).value
   }
+
+  var insertedPhis: [Phi] {
+    var phis = [Phi]()
+    let numPhis = context._bridged.SSAUpdater_getNumInsertedPhis()
+    phis.reserveCapacity(numPhis)
+    for idx in 0..<numPhis {
+      phis.append(Phi(context._bridged.SSAUpdater_getInsertedPhi(idx).value)!)
+    }
+    return phis
+  }
 }