Disable runtime cow verification for mutableSpan property

Author: meg-gupta

stdlib/public/core/Array.swift

@@ -355,6 +355,17 @@ extension Array {
     }
   }
 
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+  @inlinable
+  @_semantics("array.make_mutable")
+  @_effects(notEscaping self.**)
+  internal mutating func _makeMutableAndUniqueUnchecked() {
+    if _slowPath(!_buffer.beginCOWMutationUnchecked()) {
+      _buffer = _buffer._consumeAndCreateNew()
+    }
+  }
+#endif
+
   /// Marks the end of an Array mutation.
   ///
   /// After a call to `_endMutation` the buffer must not be mutated until a call
@@ -1737,8 +1748,15 @@ extension Array {
     @lifetime(&self)
     @_alwaysEmitIntoClient
     mutating get {
+      // _makeMutableAndUnique*() inserts begin_cow_mutation.
+      // LifetimeDependence analysis inserts call to end_cow_mutation_addr since we cannot schedule it in the stdlib for mutableSpan property.
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+      // We have runtime verification to check if begin_cow_mutation/end_cow_mutation are properly nested in asserts build of stdlib,
+      // disable checking whenever it is turned on since the compiler generated `end_cow_mutation_addr` is conservative and cannot be verified.
+      _makeMutableAndUniqueUnchecked()
+#else
       _makeMutableAndUnique()
-      // LifetimeDependence analysis inserts call to Builtin.endCOWMutation.
+#endif
       let pointer = unsafe _buffer.firstElementAddress
       let count = _buffer.mutableCount
       let span = unsafe MutableSpan(_unsafeStart: pointer, count: count)

stdlib/public/core/ArrayBuffer.swift

@@ -135,7 +135,22 @@ extension _ArrayBuffer {
 #endif
     return isUnique
   }
-  
+
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+   @_alwaysEmitIntoClient
+  internal mutating func beginCOWMutationUnchecked() -> Bool {
+    let isUnique: Bool
+    if !_isClassOrObjCExistential(Element.self) {
+      isUnique = _storage.beginCOWMutationUnflaggedNative()
+    } else if !_storage.beginCOWMutationNative() {
+      return false
+    } else {
+      isUnique = _isNative
+    }
+    return isUnique
+  }
+#endif
+
   /// Puts the buffer in an immutable state.
   ///
   /// - Precondition: The buffer must be mutable or the empty array singleton.

stdlib/public/core/ArraySlice.swift

@@ -1305,10 +1305,16 @@ extension ArraySlice {
     @lifetime(&self)
     @_alwaysEmitIntoClient
     mutating get {
+      // _makeMutableAndUnique*() inserts begin_cow_mutation.
+      // LifetimeDependence analysis inserts call to end_cow_mutation_addr since we cannot schedule it in the stdlib for mutableSpan property.
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+      // We have runtime verification to check if begin_cow_mutation/end_cow_mutation are properly nested in asserts build of stdlib,
+      // disable checking whenever it is turned on since the compiler generated `end_cow_mutation_addr` is conservative and cannot be verified.
+      _makeMutableAndUniqueUnchecked()
+#else
       _makeMutableAndUnique()
-      // NOTE: We don't have the ability to schedule a call to
-      //       ContiguousArrayBuffer.endCOWMutation().
-      //       rdar://146785284 (lifetime analysis for end of mutation)
+#endif
+      // LifetimeDependence analysis inserts call to Builtin.endCOWMutation.
       let (pointer, count) = unsafe (_buffer.firstElementAddress, _buffer.count)
       let span = unsafe MutableSpan(_unsafeStart: pointer, count: count)
       return unsafe _overrideLifetime(span, mutating: &self)

stdlib/public/core/ContiguousArray.swift

@@ -1247,10 +1247,15 @@ extension ContiguousArray {
     @lifetime(&self)
     @_alwaysEmitIntoClient
     mutating get {
+      // _makeMutableAndUnique*() inserts begin_cow_mutation.
+      // LifetimeDependence analysis inserts call to end_cow_mutation_addr since we cannot schedule it in the stdlib for mutableSpan property.
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+      // We have runtime verification to check if begin_cow_mutation/end_cow_mutation are properly nested in asserts build of stdlib,
+      // disable checking whenever it is turned on since the compiler generated `end_cow_mutation_addr` is conservative and cannot be verified.
+      _makeMutableAndUniqueUnchecked()
+#else
       _makeMutableAndUnique()
-      // NOTE: We don't have the ability to schedule a call to
-      //       ContiguousArrayBuffer.endCOWMutation().
-      //       rdar://146785284 (lifetime analysis for end of mutation)
+#endif
       let pointer = unsafe _buffer.firstElementAddress
       let count = _buffer.mutableCount
       let span = unsafe MutableSpan(_unsafeStart: pointer, count: count)

stdlib/public/core/ContiguousArrayBuffer.swift

@@ -818,6 +818,16 @@ internal struct _ContiguousArrayBuffer<Element>: _ArrayBufferProtocol {
     return false;
   }
 
+#if INTERNAL_CHECKS_ENABLED && COW_CHECKS_ENABLED
+ @_alwaysEmitIntoClient
+  internal mutating func beginCOWMutationUnchecked() -> Bool {
+    if Bool(Builtin.beginCOWMutation(&_storage)) {
+      return true
+    }
+    return false;
+  }
+#endif
+
   /// Puts the buffer in an immutable state.
   ///
   /// - Precondition: The buffer must be mutable or the empty array singleton.