Merge pull request #81993 from atrick/62-fix-lifedep-indirect-closure

[6.2] LifetimeDependenceDiagnostics: diagnose indirect closure results.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LifetimeDependenceDiagnostics.swift

@@ -72,12 +72,16 @@ let lifetimeDependenceDiagnosticsPass = FunctionPass(
       markDep.settleToEscaping()
       continue
     }
-    if let apply = instruction as? FullApplySite {
-      // Handle ~Escapable results that do not have a lifetime dependence. This includes implicit initializers and
-      // @_unsafeNonescapableResult.
+    if let apply = instruction as? FullApplySite, !apply.hasResultDependence {
+      // Handle ~Escapable results that do not have a lifetime dependence. This includes implicit initializers, calls to
+      // closures, and @_unsafeNonescapableResult.
       apply.resultOrYields.forEach {
-        if let lifetimeDep = LifetimeDependence(unsafeApplyResult: $0,
-                                                context) {
+        if let lifetimeDep = LifetimeDependence(unsafeApplyResult: $0, apply: apply, context) {
+          _ = analyze(dependence: lifetimeDep, context)
+        }
+      }
+      apply.indirectResultOperands.forEach {
+        if let lifetimeDep = LifetimeDependence(unsafeApplyResult: $0.value, apply: apply, context) {
           _ = analyze(dependence: lifetimeDep, context)
         }
       }
@@ -237,10 +241,12 @@ private struct DiagnoseDependence {
     onError()
 
     // Identify the escaping variable.
-    let escapingVar = LifetimeVariable(dependent: operand.value, context)
+    let escapingVar = LifetimeVariable(usedBy: operand, context)
     if let varDecl = escapingVar.varDecl {
       // Use the variable location, not the access location.
-      diagnose(varDecl.nameLoc, .lifetime_variable_outside_scope, escapingVar.name ?? "")
+      // Variable names like $return_value and $implicit_value don't have source locations.
+      let sourceLoc = varDecl.nameLoc ?? escapingVar.sourceLoc
+      diagnose(sourceLoc, .lifetime_variable_outside_scope, escapingVar.name ?? "")
     } else if let sourceLoc = escapingVar.sourceLoc {
       diagnose(sourceLoc, .lifetime_value_outside_scope)
     } else {
@@ -263,7 +269,7 @@ private struct DiagnoseDependence {
 
   // Identify the dependence scope. If no source location is found, bypass this diagnostic.
   func reportScope() {
-    let parentVar = LifetimeVariable(dependent: dependence.parentValue, context)
+    let parentVar = LifetimeVariable(definedBy: dependence.parentValue, context)
     // First check if the dependency is limited to an access scope. If the access has no source location then
     // fall-through to report possible dependence on an argument.
     if parentVar.isAccessScope, let accessLoc = parentVar.sourceLoc {
@@ -310,7 +316,22 @@ private struct LifetimeVariable {
     return varDecl?.userFacingName
   }
 
-  init(dependent value: Value, _ context: some Context) {
+  init(usedBy operand: Operand, _ context: some Context) {
+    self = .init(dependent: operand.value, context)
+    // variable names like $return_value and $implicit_value don't have source locations.
+    // For @out arguments, the operand's location is the best answer.
+    // Otherwise, fall back to the function's location.
+    self.sourceLoc = self.sourceLoc ?? operand.instruction.location.sourceLoc
+      ?? operand.instruction.parentFunction.location.sourceLoc
+  }
+
+  init(definedBy value: Value, _ context: some Context) {
+    self = .init(dependent: value, context)
+    // Fall back to the function's location.
+    self.sourceLoc = self.sourceLoc ?? value.parentFunction.location.sourceLoc
+  }
+
+  private init(dependent value: Value, _ context: some Context) {
     guard let introducer = getFirstVariableIntroducer(of: value, context) else {
       return
     }

SwiftCompilerSources/Sources/Optimizer/Utilities/LifetimeDependenceUtils.swift

@@ -165,16 +165,12 @@ extension LifetimeDependence {
   //
   // This is necessary because inserting a mark_dependence placeholder for such an unsafe dependence would illegally
   // have the same base and value operand.
-  //
-  // TODO: handle indirect results
-  init?(unsafeApplyResult value: Value, _ context: some Context) {
+  init?(unsafeApplyResult value: Value, apply: FullApplySite, _ context: some Context) {
     if value.isEscapable {
       return nil
     }
-    if (value.definingInstructionOrTerminator as! FullApplySite).hasResultDependence {
-      return nil
-    }
-    assert(value.ownership == .owned, "unsafe apply result must be owned")
+    assert(!apply.hasResultDependence, "mark_dependence should be used instead")
+    assert(value.ownership == .owned || value.type.isAddress, "unsafe apply result must be owned")
     self.scope = Scope(base: value, context)
     self.dependentValue = value
     self.markDepInst = nil
@@ -578,8 +574,8 @@ extension LifetimeDependenceDefUseWalker {
     }
     let root = dependence.dependentValue
     if root.type.isAddress { 
-      // The root address may be an escapable mark_dependence that guards its address uses (unsafeAddress), or an
-      // allocation or incoming argument. In all these cases, it is sufficient to walk down the address uses.
+      // The root address may be an escapable mark_dependence that guards its address uses (unsafeAddress), an
+      // allocation, an incoming argument, or an outgoing argument. In all these cases, walk down the address uses.
       return walkDownAddressUses(of: root)
     }
     return walkDownUses(of: root, using: nil)
@@ -974,7 +970,8 @@ extension LifetimeDependenceDefUseWalker {
 
   private mutating func visitAppliedUse(of operand: Operand, by apply: FullApplySite) -> WalkResult {
     if let conv = apply.convention(of: operand), conv.isIndirectOut {
-      return leafUse(of: operand)
+      // This apply initializes an allocation.
+      return dependentUse(of: operand, dependentAddress: operand.value)
     }
     if apply.isCallee(operand: operand) {
       return leafUse(of: operand)

test/SILOptimizer/lifetime_dependence/verify_diagnostics.swift

@@ -49,6 +49,17 @@ struct Holder {
   var c: C? = nil
 }
 
+// Generic non-Escapable for indirect values.
+struct GNE<T> : ~Escapable {
+  let t: T
+  @lifetime(borrow t)
+  init(t: borrowing T) { self.t = copy t }
+}  
+
+@_silgen_name("forward")
+@lifetime(copy arg)
+func forward<T>(_ arg: GNE<T>) -> GNE<T>
+
 @_silgen_name("getGeneric")
 @lifetime(borrow holder)
 func getGeneric<T: ~Escapable>(_ holder: borrowing Holder, _: T.Type) -> T
@@ -156,3 +167,26 @@ func testClosureCapture1(_ a: HasMethods) {
     }
    */
 }
+
+// =============================================================================
+// Indirect ~Escapable results
+// =============================================================================
+
+@lifetime(copy arg1)
+func testIndirectForwardedResult<T>(arg1: GNE<T>) -> GNE<T> {
+  forward(arg1)
+}
+
+@lifetime(copy arg1)
+func testIndirectNonForwardedResult<T>(arg1: GNE<T>, arg2: GNE<T>) -> GNE<T> {
+  // expected-error @-1{{lifetime-dependent variable 'arg2' escapes its scope}}
+  // expected-note  @-2{{it depends on the lifetime of argument 'arg2'}}
+  forward(arg2) // expected-note {{this use causes the lifetime-dependent value to escape}}
+}
+
+func testIndirectClosureResult<T>(f: () -> GNE<T>) -> GNE<T> {
+  f()
+  // expected-error @-1{{lifetime-dependent variable '$return_value' escapes its scope}}
+  // expected-note  @-3{{it depends on the lifetime of argument '$return_value'}}
+  // expected-note  @-3{{this use causes the lifetime-dependent value to escape}}
+}