CLongDouble should map to Float128 (which is yet supported) on arm64, and trivial copy ctor is yet available even on 14

Author: michael-yuji

include/swift/AST/AutoDiff.h

@@ -422,7 +422,7 @@ class DerivativeFunctionTypeError
   Kind kind;
 
   /// The type and index of a differentiability parameter or result.
-  /// std::pair does not have a trivial copy constructor on FreeBSD <= 14 for
+  /// std::pair does not have a trivial copy constructor on FreeBSD for
   /// ABI reasons, so we have to define our own type here instead
   struct TypeAndIndex {
     Type first;

include/swift/SILOptimizer/Differentiation/DifferentiationInvoker.h

@@ -71,7 +71,7 @@ struct DifferentiationInvoker {
 
     /// The parent `apply` instruction and the witness associated with the
     /// `IndirectDifferentiation` case.
-    /// Note: This used to be a std::pair, but on FreeBSD <= 14, libc++ is
+    /// Note: This used to be a std::pair, but on FreeBSD, libc++ is
     /// configured with _LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR
     /// and hence does not have a trivial copy constructor
     struct IndirectDifferentiation {

stdlib/public/core/CTypes.swift

@@ -114,12 +114,10 @@ public typealias CLongDouble = Double
 #error("CLongDouble needs to be defined for this OpenBSD architecture")
 #endif
 #elseif os(FreeBSD)
+// On FreeBSD, long double is Float128 for arm64, which we don't have yet in
+// Swift
 #if arch(x86_64) || arch(i386)
 public typealias CLongDouble = Float80
-#elseif arch(arm64)
-public typealias CLongDouble = Double
-#else
-#error("CLongDouble needs to be defined for this FreeBSD architecture")
 #endif
 #elseif $Embedded
 #if arch(x86_64) || arch(i386)