[6.2 🍒] Fix ownership issues with sequences of partial_apply's in AutoDiff closure specialization pass

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ClosureSpecialization.swift

@@ -105,9 +105,9 @@ import SILBridging
 
 private let verbose = false
 
-private func log(_ message: @autoclosure () -> String) {
+private func log(prefix: Bool = true, _ message: @autoclosure () -> String) {
   if verbose {
-    print("### \(message())")
+    debugLog(prefix: prefix, message())
   }
 }
 
@@ -128,47 +128,48 @@ let autodiffClosureSpecialization = FunctionPass(name: "autodiff-closure-special
   }
 
   var remainingSpecializationRounds = 5
-  var callerModified = false
 
   repeat {
+    // TODO: Names here are pretty misleading. We are looking for a place where
+    // the pullback closure is created (so for `partial_apply` instruction).
     var callSites = gatherCallSites(in: function, context)
+    guard !callSites.isEmpty else {
+      return
+    }
 
-    if !callSites.isEmpty {
-      for callSite in callSites {
-        var (specializedFunction, alreadyExists) = getOrCreateSpecializedFunction(basedOn: callSite, context)
-
-        if !alreadyExists {
-          context.notifyNewFunction(function: specializedFunction, derivedFrom: callSite.applyCallee)
-        }
+    for callSite in callSites {
+      var (specializedFunction, alreadyExists) = getOrCreateSpecializedFunction(basedOn: callSite, context)
 
-        rewriteApplyInstruction(using: specializedFunction, callSite: callSite, context)
+      if !alreadyExists {
+        context.notifyNewFunction(function: specializedFunction, derivedFrom: callSite.applyCallee)
       }
 
-      var deadClosures: InstructionWorklist = callSites.reduce(into: InstructionWorklist(context)) { deadClosures, callSite in
-        callSite.closureArgDescriptors
-          .map { $0.closure }
-          .forEach { deadClosures.pushIfNotVisited($0) }
-      }
+      rewriteApplyInstruction(using: specializedFunction, callSite: callSite, context)
+    }
 
-      defer {
-        deadClosures.deinitialize()
-      }
+    var deadClosures: InstructionWorklist = callSites.reduce(into: InstructionWorklist(context)) { deadClosures, callSite in
+      callSite.closureArgDescriptors
+      .map { $0.closure }
+      .forEach { deadClosures.pushIfNotVisited($0) }
+    }
 
-      while let deadClosure = deadClosures.pop() {
-        let isDeleted = context.tryDeleteDeadClosure(closure: deadClosure as! SingleValueInstruction)
-        if isDeleted {
-          context.notifyInvalidatedStackNesting()
-        }
-      }
+    defer {
+      deadClosures.deinitialize()
+    }
 
-      if context.needFixStackNesting {
-        function.fixStackNesting(context)
+    while let deadClosure = deadClosures.pop() {
+      let isDeleted = context.tryDeleteDeadClosure(closure: deadClosure as! SingleValueInstruction)
+      if isDeleted {
+        context.notifyInvalidatedStackNesting()
       }
     }
 
-    callerModified = callSites.count > 0
+    if context.needFixStackNesting {
+      function.fixStackNesting(context)
+    }
+
     remainingSpecializationRounds -= 1
-  } while callerModified && remainingSpecializationRounds > 0
+  } while remainingSpecializationRounds > 0
 }
 
 // =========== Top-level functions ========== //
@@ -503,12 +504,6 @@ private func handleApplies(for rootClosure: SingleValueInstruction, callSiteMap:
       continue
     }
 
-    // Workaround for a problem with OSSA: https://github.com/swiftlang/swift/issues/78847
-    // TODO: remove this if-statement once the underlying problem is fixed.
-    if callee.hasOwnership {
-      continue
-    }
-
     if callee.isDefinedExternally {
       continue
     }
@@ -779,13 +774,13 @@ private extension SpecializationCloner {
 
     let clonedRootClosure = builder.cloneRootClosure(representedBy: closureArgDesc, capturedArguments: clonedClosureArgs)
 
-    let (finalClonedReabstractedClosure, releasableClonedReabstractedClosures) = 
+    let finalClonedReabstractedClosure =
       builder.cloneRootClosureReabstractions(rootClosure: closureArgDesc.closure, clonedRootClosure: clonedRootClosure,
                                              reabstractedClosure: callSite.appliedArgForClosure(at: closureArgDesc.closureArgIndex)!,
                                              origToClonedValueMap: origToClonedValueMap,
                                              self.context)
 
-    let allClonedReleasableClosures = [clonedRootClosure] + releasableClonedReabstractedClosures
+    let allClonedReleasableClosures = [ finalClonedReabstractedClosure ];
     return (finalClonedReabstractedClosure, allClonedReleasableClosures)
   }
 
@@ -935,10 +930,9 @@ private extension Builder {
 
   func cloneRootClosureReabstractions(rootClosure: Value, clonedRootClosure: Value, reabstractedClosure: Value,
                                       origToClonedValueMap: [HashableValue: Value], _ context: FunctionPassContext) 
-    -> (finalClonedReabstractedClosure: SingleValueInstruction, releasableClonedReabstractedClosures: [PartialApplyInst]) 
+    -> SingleValueInstruction
   {
     func inner(_ rootClosure: Value, _ clonedRootClosure: Value, _ reabstractedClosure: Value, 
-               _ releasableClonedReabstractedClosures: inout [PartialApplyInst], 
                _ origToClonedValueMap: inout [HashableValue: Value]) -> Value {
       switch reabstractedClosure {
         case let reabstractedClosure where reabstractedClosure == rootClosure:
@@ -947,23 +941,23 @@ private extension Builder {
 
         case let cvt as ConvertFunctionInst:
           let toBeReabstracted = inner(rootClosure, clonedRootClosure, cvt.fromFunction, 
-                                       &releasableClonedReabstractedClosures, &origToClonedValueMap)
+                                       &origToClonedValueMap)
           let reabstracted = self.createConvertFunction(originalFunction: toBeReabstracted, resultType: cvt.type, 
                                                         withoutActuallyEscaping: cvt.withoutActuallyEscaping)
           origToClonedValueMap[cvt] = reabstracted
           return reabstracted
 
         case let cvt as ConvertEscapeToNoEscapeInst:
           let toBeReabstracted = inner(rootClosure, clonedRootClosure, cvt.fromFunction, 
-                                       &releasableClonedReabstractedClosures, &origToClonedValueMap)
+                                       &origToClonedValueMap)
           let reabstracted = self.createConvertEscapeToNoEscape(originalFunction: toBeReabstracted, resultType: cvt.type,
                                                                 isLifetimeGuaranteed: true)
           origToClonedValueMap[cvt] = reabstracted
           return reabstracted
 
         case let pai as PartialApplyInst:
           let toBeReabstracted = inner(rootClosure, clonedRootClosure, pai.arguments[0], 
-                                       &releasableClonedReabstractedClosures, &origToClonedValueMap)
+                                       &origToClonedValueMap)
 
           guard let function = pai.referencedFunction else {
             log("Parent function of callSite: \(rootClosure.parentFunction)")
@@ -978,13 +972,11 @@ private extension Builder {
                                                      calleeConvention: pai.calleeConvention, 
                                                      hasUnknownResultIsolation: pai.hasUnknownResultIsolation, 
                                                      isOnStack: pai.isOnStack)
-          releasableClonedReabstractedClosures.append(reabstracted)
           origToClonedValueMap[pai] = reabstracted
           return reabstracted
 
         case let mdi as MarkDependenceInst:
-          let toBeReabstracted = inner(rootClosure, clonedRootClosure, mdi.value, &releasableClonedReabstractedClosures, 
-                                       &origToClonedValueMap)
+          let toBeReabstracted = inner(rootClosure, clonedRootClosure, mdi.value, &origToClonedValueMap)
           let base = origToClonedValueMap[mdi.base]!
           let reabstracted = self.createMarkDependence(value: toBeReabstracted, base: base, kind: .Escaping)
           origToClonedValueMap[mdi] = reabstracted
@@ -998,11 +990,10 @@ private extension Builder {
       }
     }
 
-    var releasableClonedReabstractedClosures: [PartialApplyInst] = []
     var origToClonedValueMap = origToClonedValueMap
     let finalClonedReabstractedClosure = inner(rootClosure, clonedRootClosure, reabstractedClosure, 
-                                               &releasableClonedReabstractedClosures, &origToClonedValueMap)
-    return (finalClonedReabstractedClosure as! SingleValueInstruction, releasableClonedReabstractedClosures)
+                                               &origToClonedValueMap)
+    return (finalClonedReabstractedClosure as! SingleValueInstruction)
   }
 
   func destroyPartialApply(pai: PartialApplyInst, _ context: FunctionPassContext){