Merge pull request #68327 from eeckstein/fix-compiletime-bug

[5.9] AliasAnalysis: add complexity limits to some basic utility functions

Author: eeckstein

SwiftCompilerSources/Sources/Optimizer/Analysis/AliasAnalysis.swift

@@ -63,7 +63,7 @@ struct AliasAnalysis {
   static func register() {
     BridgedAliasAnalysis.registerAnalysis(
       // getMemEffectsFn
-      { (bridgedCtxt: BridgedPassContext, bridgedVal: BridgedValue, bridgedInst: BridgedInstruction) -> swift.MemoryBehavior in
+      { (bridgedCtxt: BridgedPassContext, bridgedVal: BridgedValue, bridgedInst: BridgedInstruction, complexityBudget: Int) -> swift.MemoryBehavior in
         let context = FunctionPassContext(_bridged: bridgedCtxt)
         let inst = bridgedInst.instruction
         let val = bridgedVal.value
@@ -77,23 +77,28 @@ struct AliasAnalysis {
             case (true, true):   return .MayReadWrite
           }
         }
-        if val.at(path).isEscaping(using: EscapesToInstructionVisitor(target: inst, isAddress: true), context) {
+        if val.at(path).isEscaping(using: EscapesToInstructionVisitor(target: inst, isAddress: true),
+                                   complexityBudget: complexityBudget, context) {
           return .MayReadWrite
         }
         return .None
       },
 
       // isObjReleasedFn
-      { (bridgedCtxt: BridgedPassContext, bridgedObj: BridgedValue, bridgedInst: BridgedInstruction) -> Bool in
+      { (bridgedCtxt: BridgedPassContext, bridgedObj: BridgedValue, bridgedInst: BridgedInstruction, complexityBudget: Int) -> Bool in
         let context = FunctionPassContext(_bridged: bridgedCtxt)
         let inst = bridgedInst.instruction
         let obj = bridgedObj.value
         let path = SmallProjectionPath(.anyValueFields)
         if let apply = inst as? ApplySite {
-          let effect = getOwnershipEffect(of: apply, for: obj, path: path, context)
+          // Workaround for quadratic complexity in ARCSequenceOpts.
+          // We need to use an ever lower budget to not get into noticable compile time troubles.
+          let budget = complexityBudget / 10
+          let effect = getOwnershipEffect(of: apply, for: obj, path: path, complexityBudget: budget, context)
           return effect.destroy
         }
-        return obj.at(path).isEscaping(using: EscapesToInstructionVisitor(target: inst, isAddress: false), context)
+        return obj.at(path).isEscaping(using: EscapesToInstructionVisitor(target: inst, isAddress: false),
+                                       complexityBudget: complexityBudget, context)
       },
 
       // isAddrVisibleFromObj
@@ -144,9 +149,10 @@ private func getMemoryEffect(of apply: ApplySite, for address: Value, path: Smal
   return memoryEffects
 }
 
-private func getOwnershipEffect(of apply: ApplySite, for value: Value, path: SmallProjectionPath, _ context: FunctionPassContext) -> SideEffects.Ownership {
+private func getOwnershipEffect(of apply: ApplySite, for value: Value, path: SmallProjectionPath,
+                                complexityBudget: Int, _ context: FunctionPassContext) -> SideEffects.Ownership {
   let visitor = SideEffectsVisitor(apply: apply, calleeAnalysis: context.calleeAnalysis, isAddress: false)
-  if let result = value.at(path).visit(using: visitor, context) {
+  if let result = value.at(path).visit(using: visitor, complexityBudget: complexityBudget, context) {
     // The resulting effects are the argument effects to which `value` escapes to.
     return result.ownership
   } else {

SwiftCompilerSources/Sources/Optimizer/Utilities/EscapeUtils.swift

@@ -99,8 +99,10 @@ extension ProjectedValue {
   /// it returns the `result` of the `visitor`, if the projected value does not escape.
   /// Returns nil, if the projected value escapes.
   ///
-  func visit<V: EscapeVisitorWithResult>(using visitor: V, _ context: some Context) -> V.Result? {
-    var walker = EscapeWalker(visitor: visitor, context)
+  func visit<V: EscapeVisitorWithResult>(using visitor: V,
+                                         complexityBudget: Int = Int.max,
+                                         _ context: some Context) -> V.Result? {
+    var walker = EscapeWalker(visitor: visitor, complexityBudget: complexityBudget, context)
     if walker.walkUp(addressOrValue: value, path: path.escapePath) == .abortWalk {
       return nil
     }

include/swift/SILOptimizer/Analysis/AliasAnalysis.h

@@ -206,6 +206,8 @@ class AliasAnalysis {
   /// Returns true if the address(es of) `addr` can escape to `toInst`.
   MemoryBehavior getMemoryBehaviorOfInst(SILValue addr, SILInstruction *toInst);
 
+  int getComplexityBudget(SILValue valueInFunction);
+
   /// Returns true if the object(s of) `obj` can escape to `toInst`.
   bool isObjectReleasedByInst(SILValue obj, SILInstruction *toInst);
 

include/swift/SILOptimizer/OptimizerBridging.h

@@ -32,9 +32,9 @@ struct BridgedAliasAnalysis {
   }
 
   typedef swift::MemoryBehavior (* _Nonnull GetMemEffectFn)(
-        BridgedPassContext context, BridgedValue, BridgedInstruction);
+        BridgedPassContext context, BridgedValue, BridgedInstruction, SwiftInt);
   typedef bool (* _Nonnull Escaping2InstFn)(
-        BridgedPassContext context, BridgedValue, BridgedInstruction);
+        BridgedPassContext context, BridgedValue, BridgedInstruction, SwiftInt);
   typedef bool (* _Nonnull Escaping2ValFn)(
         BridgedPassContext context, BridgedValue, BridgedValue);
   typedef bool (* _Nonnull Escaping2ValIntFn)(

lib/SILOptimizer/Analysis/AliasAnalysis.cpp

@@ -715,30 +715,24 @@ MemoryBehavior AliasAnalysis::getMemoryBehaviorOfInst(
             SILValue addr, SILInstruction *toInst) {
   if (getMemEffectsFunction) {
     return (MemoryBehavior)getMemEffectsFunction({PM->getSwiftPassInvocation()}, {addr},
-                                                 {toInst->asSILNode()});
+                                                 {toInst->asSILNode()},
+                                                 getComplexityBudget(addr));
   }
   return MemoryBehavior::MayHaveSideEffects;
 }
 
 bool AliasAnalysis::isObjectReleasedByInst(SILValue obj, SILInstruction *inst) {
   if (isObjReleasedFunction) {
-    return isObjReleasedFunction({PM->getSwiftPassInvocation()}, {obj}, {inst->asSILNode()}) != 0;
+    return isObjReleasedFunction({PM->getSwiftPassInvocation()}, {obj}, {inst->asSILNode()},
+                                 getComplexityBudget(obj)) != 0;
   }
   return true;
 }
 
 bool AliasAnalysis::isAddrVisibleFromObject(SILValue addr, SILValue obj) {
   if (isAddrVisibleFromObjFunction) {
-    // This function is called a lot from ARCSequenceOpt and ReleaseHoisting.
-    // To avoid quadratic complexity for large functions, we limit the amount
-    // of work what the EscapeUtils are allowed to to.
-    // This keeps the complexity linear.
-    //
-    // This arbitrary limit is good enough for almost all functions. It lets
-    // the EscapeUtils do several hundred up/down walks which is much more than
-    // needed in most cases.
-    SwiftInt complexityLimit = 1000000 / getEstimatedFunctionSize(addr);
-    return isAddrVisibleFromObjFunction({PM->getSwiftPassInvocation()}, {addr}, {obj}, complexityLimit) != 0;
+    return isAddrVisibleFromObjFunction({PM->getSwiftPassInvocation()}, {addr}, {obj},
+                                        getComplexityBudget(addr)) != 0;
   }
   return true;
 }
@@ -750,7 +744,14 @@ bool AliasAnalysis::canReferenceSameField(SILValue lhs, SILValue rhs) {
   return true;
 }
 
-int AliasAnalysis::getEstimatedFunctionSize(SILValue valueInFunction) {
+// To avoid quadratic complexity for large functions, we limit the amount
+// of work what the EscapeUtils are allowed to to.
+// This keeps the complexity linear.
+//
+// This arbitrary limit is good enough for almost all functions. It lets
+// the EscapeUtils do several hundred up/down walks which is much more than
+// needed in most cases.
+int AliasAnalysis::getComplexityBudget(SILValue valueInFunction) {
   if (estimatedFunctionSize < 0) {
     int numInsts = 0;
     SILFunction *f = valueInFunction->getFunction();
@@ -759,5 +760,5 @@ int AliasAnalysis::getEstimatedFunctionSize(SILValue valueInFunction) {
     }
     estimatedFunctionSize = numInsts;
   }
-  return estimatedFunctionSize;
+  return 1000000 / estimatedFunctionSize;
 }