Revert "implement ManagerBuffer.reallocated to allow realloc'ing the storage" (swiftlang#21874)

* Revert "implement ManagerBuffer.reallocated to allow realloc'ing the storage"

Author: airspeedswift

stdlib/public/core/Builtin.swift

@@ -668,9 +668,6 @@ internal func _isUnique<T>(_ object: inout T) -> Bool {
   return Bool(Builtin.isUnique(&object))
 }
 
-@_silgen_name("_swift_reallocObject")
-internal func _reallocObject(_ object: UnsafeMutableRawPointer, _ newSizeInBytes: Int) -> UnsafeMutableRawPointer?
-
 /// Returns `true` if `object` is uniquely referenced.
 /// This provides sanity checks on top of the Builtin.
 @_transparent

stdlib/public/core/ManagedBuffer.swift

@@ -136,30 +136,6 @@ extension ManagedBuffer {
   }
 }
 
-@inline(never)
-public func tryReallocateUniquelyReferenced<Header, Element, Buffer: ManagedBuffer<Header, Element>>(
-  buffer: inout Buffer,
-  newMinimumCapacity: Int
-) -> Bool {
-  precondition(_isBitwiseTakable(Header.self))
-  precondition(_isBitwiseTakable(Element.self))
-  precondition(isKnownUniquelyReferenced(&buffer))
-
-  let newSizeInBytes = MemoryLayout<Header>.stride
-    + newMinimumCapacity * MemoryLayout<Element>.stride
-
-  return withUnsafeMutablePointer(to: &buffer) {
-    $0.withMemoryRebound(to: UnsafeMutableRawPointer.self, capacity: 1) {
-      if let reallocdObject = _reallocObject($0.pointee, newSizeInBytes) {
-        $0.pointee = reallocdObject
-        return true
-      } else {
-        return false
-      }
-    }
-  }
-}
-
 /// Contains a buffer object, and provides access to an instance of
 /// `Header` and contiguous storage for an arbitrary number of
 /// `Element` instances stored in that buffer.

stdlib/public/runtime/SwiftObject.h

@@ -88,11 +88,4 @@ NSString *getDescription(OpaqueValue *value, const Metadata *type);
 
 #endif
 
-namespace swift {
-
-SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_SPI
-HeapObject *_swift_reallocObject(HeapObject *obj, size_t size);
-
-}
-
 #endif

stdlib/public/runtime/SwiftObject.mm

@@ -82,24 +82,6 @@ static uintptr_t computeISAMask() {
 #endif
 }
 
-bool isObjCPinned(HeapObject *obj) {
-  #if SWIFT_OBJC_INTEROP
-    /* future: implement checking the relevant objc runtime bits */
-    return true;
-  #else
-    return false;
-  #endif
-}
-
-// returns non-null if realloc was successful
-SWIFT_CC(swift) SWIFT_RUNTIME_STDLIB_SPI
-HeapObject *swift::_swift_reallocObject(HeapObject *obj, size_t size) {
- if (isObjCPinned(obj) || obj->refCounts.hasSideTable()) {
-   return nullptr;
- }
- return (HeapObject *)realloc(obj, size);
-}
-
 #if SWIFT_OBJC_INTEROP
 
 /// \brief Replacement for ObjC object_isClass(), which is unavailable on

test/api-digester/Outputs/stability-stdlib-abi.swift.expected

@@ -1 +1,2 @@
 Class __SwiftNativeNSString has been removed
+Func tryReallocateUniquelyReferenced(buffer:newMinimumCapacity:) has been removed

test/api-digester/Outputs/stability-stdlib-source.swift.expected

@@ -1 +1 @@
-
+Func tryReallocateUniquelyReferenced(buffer:newMinimumCapacity:) has been removed

test/stdlib/ManagedBuffer.swift

@@ -40,7 +40,7 @@ extension ManagedBufferPointer
 
 struct CountAndCapacity {
   var count: LifetimeTracked
-  var capacity: Int
+  let capacity: Int
 }
 
 // An example of ManagedBuffer, very similar to what Array will use.
@@ -96,23 +96,6 @@ final class TestManagedBuffer<T> : ManagedBuffer<CountAndCapacity, T> {
     }
     self.count = count + 2
   }
-
-  class func tryGrow(_ buffer: inout TestManagedBuffer<T>, newCapacity: Int) -> Bool {
-    guard isKnownUniquelyReferenced(&buffer) else {
-      return false
-    }
-    guard newCapacity > buffer.capacity else {
-      return false
-    }
-
-    if tryReallocateUniquelyReferenced(buffer: &buffer,
-                                       newMinimumCapacity: newCapacity) {
-      buffer.header.capacity = newCapacity
-      return true
-    } else {
-      return false
-    }
-  }
 }
 
 class MyBuffer<T> {
@@ -258,35 +241,4 @@ tests.test("isKnownUniquelyReferenced") {
   _fixLifetime(s2)
 }
 
-tests.test("canGrowUsingRealloc") {
-  #if os(macOS) || os(iOS) || os(tvOS) || os(watchOS)
-  return // realloc currently unsupported on Darwin
-  #endif
-  func testGrow(_ buffer: inout TestManagedBuffer<LifetimeTracked>,
-                newCapacity: Int,
-                shouldSucceed: Bool = true) {
-    let s = TestManagedBuffer.tryGrow(&buffer, newCapacity: newCapacity)
-    expectEqual(s, shouldSucceed)
-    if shouldSucceed {
-      expectLE(newCapacity, buffer.myCapacity)
-      expectGE((newCapacity + 1) * 2, buffer.myCapacity)
-    }
-    repeat {
-      buffer.append(LifetimeTracked(buffer.count))
-    } while buffer.count < buffer.myCapacity - 2
-  }
-
-  var b = TestManagedBuffer<LifetimeTracked>.create(0)
-  // allow some over-allocation
-  expectLE(0, b.myCapacity)
-  expectGE(3, b.myCapacity)
-
-  testGrow(&b, newCapacity: 5)
-  testGrow(&b, newCapacity: 8)
-  testGrow(&b, newCapacity: 1000)
-  testGrow(&b, newCapacity: 16000)
-  var b2 = b
-  testGrow(&b, newCapacity: 2000, shouldSucceed: false)
-}
-
 runAllTests()