compute effects: Don't modify the effects if they didn't change

This avoids sending a change notification which can trigger unnecessary other invalidations.

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ComputeEscapeEffects.swift

@@ -28,16 +28,15 @@ import SIL
 let computeEscapeEffects = FunctionPass(name: "compute-escape-effects", {
   (function: Function, context: PassContext) in
 
-  var newEffects = Stack<EscapeEffects.ArgumentEffect>(context)
-  defer { newEffects.deinitialize() }
+  var newEffects = function.effects.escapeEffects.arguments.filter {!$0.isDerived }
 
   let returnInst = function.returnInstruction
   let argsWithDefinedEffects = getArgIndicesWithDefinedEscapingEffects(of: function)
 
   for arg in function.arguments {
     // We are not interested in arguments with trivial types.
     if !arg.type.isNonTrivialOrContainsRawPointer(in: function) { continue }
-    
+
     // Also, we don't want to override defined effects.
     if argsWithDefinedEffects.contains(arg.index) { continue }
 
@@ -52,7 +51,7 @@ let computeEscapeEffects = FunctionPass(name: "compute-escape-effects", {
                                                     context) {
       let effect = EscapeEffects.ArgumentEffect(.notEscaping, argumentIndex: arg.index,
                                                 pathPattern: SmallProjectionPath(.anything))
-      newEffects.push(effect)
+      newEffects.append(effect)
       continue
     }
 
@@ -65,17 +64,22 @@ let computeEscapeEffects = FunctionPass(name: "compute-escape-effects", {
     }
   }
 
+  // Don't modify the effects if they didn't change. This avoids sending a change notification
+  // which can trigger unnecessary other invalidations.
+  if newEffects == function.effects.escapeEffects.arguments {
+    return
+  }
+
   context.modifyEffects(in: function) { (effects: inout FunctionEffects) in
-    effects.escapeEffects.arguments = effects.escapeEffects.arguments.filter { !$0.isDerived }
-    effects.escapeEffects.arguments.append(contentsOf: newEffects)
+    effects.escapeEffects.arguments = newEffects
   }
 })
 
 
 /// Returns true if an argument effect was added.
 private
 func addArgEffects(_ arg: FunctionArgument, argPath ap: SmallProjectionPath,
-                   to newEffects: inout Stack<EscapeEffects.ArgumentEffect>,
+                   to newEffects: inout [EscapeEffects.ArgumentEffect],
                    _ returnInst: ReturnInst?, _ context: PassContext) -> Bool {
   // Correct the path if the argument is not a class reference itself, but a value type
   // containing one or more references.
@@ -159,7 +163,7 @@ func addArgEffects(_ arg: FunctionArgument, argPath ap: SmallProjectionPath,
     effect = EscapeEffects.ArgumentEffect(.escapingToArgument(toArgIdx, toPath, exclusive),
                                           argumentIndex: arg.index, pathPattern: argPath)
   }
-  newEffects.push(effect)
+  newEffects.append(effect)
   return true
 }
 

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ComputeSideEffects.swift

@@ -66,6 +66,14 @@ let computeSideEffects = FunctionPass(name: "compute-side-effects", {
     collectedEffects.addEffectsForEcapingArgument(argument: argument)
   }
 
+  // Don't modify the effects if they didn't change. This avoids sending a change notification
+  // which can trigger unnecessary other invalidations.
+  if let existingEffects = function.effects.sideEffects,
+     existingEffects.arguments == collectedEffects.argumentEffects,
+     existingEffects.global == collectedEffects.globalEffects {
+    return
+  }
+
   // Finally replace the function's side effects.
   context.modifyEffects(in: function) { (effects: inout FunctionEffects) in
     effects.sideEffects = SideEffects(arguments: collectedEffects.argumentEffects, global: collectedEffects.globalEffects)

SwiftCompilerSources/Sources/SIL/Effects.swift

@@ -134,9 +134,9 @@ public struct EscapeEffects : CustomStringConvertible, NoReflectionChildren {
   }
 
   /// An escape effect on a function argument.
-  public struct ArgumentEffect : CustomStringConvertible, NoReflectionChildren {
+  public struct ArgumentEffect : Equatable, CustomStringConvertible, NoReflectionChildren {
 
-    public enum Kind {
+    public enum Kind : Equatable {
       /// The argument value does not escape.
       ///
       /// Syntax examples: