LifetimeDependenceDiagnostics; remove a bootstrapping hack.

This temporary hack was preventing diagnostics from kicking in. This could even
result in invalid SIL after the diagnostic failed to trigger.

Author: atrick

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/LifetimeDependenceDiagnostics.swift

@@ -199,21 +199,6 @@ private struct DiagnoseDependence {
     if function.hasUnsafeNonEscapableResult {
       return .continueWalk
     }
-    // FIXME: remove this condition once we have a Builtin.dependence,
-    // which developers should use to model the unsafe
-    // dependence. Builtin.lifetime_dependence will be lowered to
-    // mark_dependence [unresolved], which will be checked
-    // independently. Instead, of this function result check, allow
-    // isUnsafeApplyResult to be used be mark_dependence [unresolved]
-    // without checking its dependents.
-    //
-    // Allow returning an apply result (@_unsafeNonescapableResult) if
-    // the calling function has a dependence. This implicitly makes
-    // the unsafe nonescapable result dependent on the calling
-    // function's lifetime dependence arguments.
-    if dependence.isUnsafeApplyResult, function.hasResultDependence {
-      return .continueWalk
-    }
     // Check that the parameter dependence for this result is the same
     // as the current dependence scope.
     if let arg = dependence.scope.parentValue as? FunctionArgument,

SwiftCompilerSources/Sources/Optimizer/Utilities/LifetimeDependenceUtils.swift

@@ -225,16 +225,6 @@ extension LifetimeDependence {
     self.dependentValue = value
   }
 
-  var isUnsafeApplyResult: Bool {
-    if case let .owned(value) = scope {
-      if let apply = value.definingInstruction as? FullApplySite {
-        assert(!apply.hasResultDependence)
-        return true
-      }
-    }
-    return false
-  }
-
   /// Construct LifetimeDependence from mark_dependence [unresolved] or mark_dependence [nonescaping].
   ///
   /// For any LifetimeDependence constructed from a mark_dependence, its `dependentValue` will be the result of the

test/SIL/explicit_lifetime_dependence_specifiers.swift

@@ -8,6 +8,30 @@
 
 import Builtin
 
+@_unsafeNonescapableResult
+@lifetime(borrow source)
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, borrowing source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
+  dependent
+}
+
+@_unsafeNonescapableResult
+@lifetime(source)
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, copying source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
+  dependent
+}
+
 struct BufferView : ~Escapable {
   let ptr: UnsafeRawBufferPointer
 // CHECK-LABEL: sil hidden @$s39explicit_lifetime_dependence_specifiers10BufferViewVyACSWcfC : $@convention(method) (UnsafeRawBufferPointer, @thin BufferView.Type) -> @lifetime(borrow 0)  @owned BufferView {
@@ -22,7 +46,7 @@ struct BufferView : ~Escapable {
     } 
     self.ptr = ptr
   }
-  @_unsafeNonescapableResult
+  @lifetime(borrow ptr)
   init(independent ptr: UnsafeRawBufferPointer) {
     self.ptr = ptr
   }
@@ -71,7 +95,8 @@ func derive(_ x: borrowing BufferView) -> BufferView {
 // CHECK-LABEL: sil hidden @$s39explicit_lifetime_dependence_specifiers16consumeAndCreateyAA10BufferViewVADnF : $@convention(thin) (@owned BufferView) -> @lifetime(copy 0)  @owned BufferView {
 @lifetime(x)
 func consumeAndCreate(_ x: consuming BufferView) -> BufferView {
-  return BufferView(independent: x.ptr)
+  let bv = BufferView(independent: x.ptr)
+  return _overrideLifetime(bv, copying: x)
 }
 
 // CHECK-LABEL: sil hidden @$s39explicit_lifetime_dependence_specifiers17deriveThisOrThat1yAA10BufferViewVAD_ADtF : $@convention(thin) (@guaranteed BufferView, @guaranteed BufferView) -> @lifetime(copy 1, borrow 0)  @owned BufferView {
@@ -89,7 +114,8 @@ func deriveThisOrThat2(_ this: borrowing BufferView, _ that: consuming BufferVie
   if (Int.random(in: 1..<100) == 0) {
     return BufferView(independent: this.ptr)
   }
-  return BufferView(independent: that.ptr)
+  let bv = BufferView(independent: that.ptr)
+  return _overrideLifetime(bv, copying: that)
 }
 
 func use(_ x: borrowing BufferView) {}
@@ -123,12 +149,12 @@ struct Container : ~Escapable {
 // CHECK-LABEL: sil hidden @$s39explicit_lifetime_dependence_specifiers16getConsumingViewyAA06BufferG0VAA9ContainerVnF : $@convention(thin) (@owned Container) -> @lifetime(copy 0)  @owned BufferView {
 @lifetime(x)
 func getConsumingView(_ x: consuming Container) -> BufferView {
-  return BufferView(independent: x.ptr)
+  let bv = BufferView(independent: x.ptr)
+  return _overrideLifetime(bv, copying: x)
 }
 
 // CHECK-LABEL: sil hidden @$s39explicit_lifetime_dependence_specifiers16getBorrowingViewyAA06BufferG0VAA9ContainerVF : $@convention(thin) (@guaranteed Container) -> @lifetime(borrow 0)  @owned BufferView {
 @lifetime(borrow x)
 func getBorrowingView(_ x: borrowing Container) -> BufferView {
   return BufferView(independent: x.ptr)
 }
-

test/SIL/implicit_lifetime_dependence.swift

@@ -5,11 +5,27 @@
 
 // REQUIRES: swift_feature_LifetimeDependence
 
+@_unsafeNonescapableResult
+@lifetime(borrow source)
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, borrowing source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
+  dependent
+}
+
 @_unsafeNonescapableResult
 @lifetime(source)
-func unsafeLifetime<T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable>(
-  dependent: consuming T, dependsOn source: borrowing U)
-  -> T {
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, copying source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
   dependent
 }
 
@@ -21,7 +37,7 @@ struct BufferView : ~Escapable {
     self.ptr = ptr
     self.c = c
   }
-  @_unsafeNonescapableResult
+  @lifetime(borrow ptr)
   init(independent ptr: UnsafeRawBufferPointer, _ c: Int) {
     self.ptr = ptr
     self.c = c
@@ -74,7 +90,8 @@ func derive(_ unused: Int, _ x: borrowing BufferView) -> BufferView {
 
 // CHECK-LABEL: sil hidden @$s28implicit_lifetime_dependence16consumeAndCreateyAA10BufferViewVADnF : $@convention(thin) (@owned BufferView) -> @lifetime(copy 0)  @owned BufferView {
 func consumeAndCreate(_ x: consuming BufferView) -> BufferView {
-  return BufferView(independent: x.ptr, x.c)
+  let bv = BufferView(independent: x.ptr, x.c)
+  return _overrideLifetime(bv, copying: x)
 }
 
 func use(_ x: borrowing BufferView) {}
@@ -175,7 +192,7 @@ struct GenericBufferView<Element> : ~Escapable {
         count: bounds.upperBound.distance(to:bounds.lowerBound) / MemoryLayout<Element>.stride
       )
       // assuming that bounds is within self
-      return unsafeLifetime(dependent: result, dependsOn: self)
+      return _overrideLifetime(result, copying: self)
     }
   }
 }

test/SIL/lifetime_dependence_generics.swift

@@ -21,12 +21,12 @@ extension P {
 }
 
 public struct View: ~Escapable {
-  // TODO: dependsOn(immortal)
-  @_unsafeNonescapableResult
+  @lifetime(immortal)
   init() { }
 }
 
 public struct PView: P {
+  @lifetime(immortal)
   borrowing func getE() -> View { return View() }
 }
 
@@ -36,7 +36,7 @@ public func test(pview: borrowing PView) -> View {
 
 // CHECK-LABEL: sil hidden @$s28lifetime_dependence_generics1PPAAE10getDefault1EQzyF : $@convention(method) <Self where Self : P> (@in_guaranteed Self) -> @lifetime(borrow 0)  @out Self.E {
 
-// CHECK-LABEL: sil hidden @$s28lifetime_dependence_generics5PViewV4getEAA4ViewVyF : $@convention(method) (PView) -> @lifetime(borrow 0)  @owned View {
+// CHECK-LABEL: sil hidden @$s28lifetime_dependence_generics5PViewV4getEAA4ViewVyF : $@convention(method) (PView) -> @lifetime(immortal) @owned View {
 
 // CHECK-LABEL: sil private [transparent] [thunk] @$s28lifetime_dependence_generics5PViewVAA1PA2aDP4getE1EQzyFTW : $@convention(witness_method: P) (@in_guaranteed PView) -> @lifetime(borrow 0)  @out View {
 

test/SIL/lifetime_dependence_span_lifetime_attr.swift

@@ -5,6 +5,30 @@
 // REQUIRES: swift_in_compiler
 // REQUIRES: swift_feature_LifetimeDependence
 
+@_unsafeNonescapableResult
+@lifetime(borrow source)
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, borrowing source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
+  dependent
+}
+
+@_unsafeNonescapableResult
+@lifetime(source)
+internal func _overrideLifetime<
+  T: ~Copyable & ~Escapable, U: ~Copyable & ~Escapable
+>(
+  _ dependent: consuming T, copying source: borrowing U
+) -> T {
+  // TODO: Remove @_unsafeNonescapableResult. Instead, the unsafe dependence
+  // should be expressed by a builtin that is hidden within the function body.
+  dependent
+}
+
 // TODO: Use real Range
 public struct FakeRange<Bound> {
   public let lowerBound: Bound
@@ -128,10 +152,11 @@ extension Span {
   public subscript(bounds: FakeRange<SpanIndex<Element>>) -> Self {
   @lifetime(self)
     get {
-      Span(
+      let span = Span(
         start: bounds.lowerBound,
         count: bounds.upperBound.distance(to:bounds.lowerBound) / MemoryLayout<Element>.stride
       )
+      return _overrideLifetime(span, copying: self)
     }
   }
 

test/SILOptimizer/lifetime_dependence/lifetime_dependence_borrow_fail.swift

@@ -31,13 +31,17 @@ struct NC : ~Copyable {
     BV(p, i)
   }
 
+  // @lifetime(borrow self)
   borrowing func getEmpty() -> Empty {
     Empty()
   }
 }
 
 // Test dependencies on an empty struct.
-public struct Empty: ~Escapable {}
+public struct Empty: ~Escapable {
+  @lifetime(immortal)
+  init() {}
+}
 
 func use(e: Empty) {}