Make sure the builtin use is inlined so it can statically see what's going on

Author: Catfish-Man

stdlib/public/core/ContiguousArrayBuffer.swift

@@ -274,7 +274,7 @@ internal struct _ContiguousArrayBuffer<Element>: _ArrayBufferProtocol {
          realMinimumCapacity._builtinWordValue, Element.self)
 
       let storageAddr = UnsafeMutableRawPointer(Builtin.bridgeToRawPointer(_storage))
-      if let allocSize = _mallocSize(ofAllocation: storageAddr) {
+      if let allocSize = _mallocSizeIfHeap(ofAllocation: storageAddr) {
         let endAddr = storageAddr + allocSize
         let realCapacity = endAddr.assumingMemoryBound(to: Element.self) - firstElementAddress
         _initStorageHeader(

stdlib/public/core/Shims.swift

@@ -37,9 +37,17 @@ internal let _fastEnumerationStorageMutationsPtr =
   UnsafeMutablePointer<CUnsignedLong>(Builtin.addressof(&_fastEnumerationStorageMutationsTarget))
 #endif
 
+
+
+
 @usableFromInline @_alwaysEmitIntoClient @_effects(readonly)
 internal func _mallocSize(ofAllocation ptr: UnsafeRawPointer) -> Int? {
-  return !Builtin.isOnStack(ptr) && _swift_stdlib_has_malloc_size() ?
-    _swift_stdlib_malloc_size(ptr) :
-    nil
+  return _swift_stdlib_has_malloc_size() ? _swift_stdlib_malloc_size(ptr) : nil
 }
+
+@inline(__always) @inlinable @_effects(readonly)
+internal func _mallocSizeIfHeap(ofAllocation ptr: UnsafeRawPointer) -> Int? {
+  if !Builtin.isOnStack(ptr) { return nil }
+  return _mallocSize(ofAllocation: ptr)
+}
+

stdlib/public/core/StringStorage.swift

@@ -206,7 +206,7 @@ fileprivate func _allocate<T: AnyObject>(
   let totalTailBytes = total - numHeaderBytes
 
   let object = tailAllocator(totalTailBytes)
-  if let allocSize = _mallocSize(ofAllocation:
+  if let allocSize = _mallocSizeIfHeap(ofAllocation:
     UnsafeRawPointer(Builtin.bridgeToRawPointer(object))) {
     _internalInvariant(allocSize % MemoryLayout<Int>.stride == 0)