Make Float16 available for macOS on Apple Silicon (#34821)

Due to an unstable (and undesirable) calling convention in the LLVM layer for x86, I had previously marked Float16 unconditionally unavailable on macOS. My hope was that Intel would stabilize the calling convention and we could make it available on both macOS platforms at the same time. Unfortunately, that hasn't happened, and we want to make the type available for macOS/arm users.

So, I am making the availability mirror Float80--the type will be unavailable for macOS on x86_64, and available on all other platforms (the other x86 platforms don't have a binary-stability guarantee to worry about). This isn't ideal. In particular, if/when the calling conventions for Float16 stabilize in LLVM, we would want to make the type available, but it would then have _different_ availability for different architectures of macOS, which the current availability system is not well-equipped to handle (it's possible, but not very ergonomic). Nonetheless, this seems like the best option.

The good news is that because the full API is already built in Swift (and simply marked unavailable), we can simply add macOS 11.0 availability for these API and it will work.

Author: stephentyrone

stdlib/public/core/CTypes.swift

@@ -56,11 +56,11 @@ public typealias CLong = Int
 /// The C 'long long' type.
 public typealias CLongLong = Int64
 
+#if !(os(macOS) && arch(x86_64))
 /// The C '_Float16' type.
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 public typealias CFloat16 = Float16
+#endif
 
 /// The C 'float' type.
 public typealias CFloat = Float

stdlib/public/core/Codable.swift

@@ -4730,9 +4730,8 @@ extension RawRepresentable where RawValue == Float, Self: Decodable {
   }
 }
 
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
+#if !(os(macOS) && arch(x86_64))
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 extension Float16: Codable {
   /// Creates a new instance by decoding from the given decoder.
   ///
@@ -4763,6 +4762,7 @@ extension Float16: Codable {
     try Float(self).encode(to: encoder)
   }
 }
+#endif
 
 extension Int: Codable {
   /// Creates a new instance by decoding from the given decoder.

stdlib/public/core/FloatingPointParsing.swift.gyb

@@ -42,13 +42,12 @@ internal func _isspace_clocale(_ u: UTF16.CodeUnit) -> Bool {
 
 % if bits == 80:
 #if !(os(Windows) || os(Android)) && (arch(i386) || arch(x86_64))
+% elif bits == 16:
+#if !(os(macOS) && arch(x86_64))
 % end
 
-//===--- Parsing ----------------------------------------------------------===//
 %if bits == 16:
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 %end
 extension ${Self}: LosslessStringConvertible {
   /// Creates a new instance from the given string.
@@ -136,7 +135,7 @@ extension ${Self}: LosslessStringConvertible {
   %if bits == 16:
     self.init(Substring(text))
   %else:
-    if #available(macOS 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
+    if #available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
       self.init(Substring(text))
     } else {
       self = 0.0
@@ -166,13 +165,7 @@ extension ${Self}: LosslessStringConvertible {
   // In particular, we still have to export
   // _swift_stdlib_strtoXYZ_clocale()
   // as ABI to support old compiled code that still requires it.
-%if bits == 16:
-  @available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-  @available(macOS, unavailable)
-  @available(macCatalyst, unavailable)
-%else:
-  @available(macOS 10.16, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-%end
+  @available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
   public init?(_ text: Substring) {
     self = 0.0
     let success = withUnsafeMutablePointer(to: &self) { p -> Bool in
@@ -196,7 +189,7 @@ extension ${Self}: LosslessStringConvertible {
   }
 }
 
-% if bits == 80:
+% if bits in [16,80]:
 #endif
 % end
 

stdlib/public/core/FloatingPointTypes.swift.gyb

@@ -40,7 +40,7 @@ RawSignificand = 'UInt' + str(SignificandSize)
 
 def Availability(bits):
     if bits == 16:
-        return '@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)\n@available(macOS, unavailable)\n@available(macCatalyst, unavailable)'
+        return '@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)'
     return ''
 
 if Self == 'Float16':
@@ -65,6 +65,8 @@ else:
 
 % if bits == 80:
 #if !(os(Windows) || os(Android)) && (arch(i386) || arch(x86_64))
+% elif bits == 16:
+#if !(os(macOS) && arch(x86_64))
 % end
 
 ${SelfDocComment}
@@ -1106,8 +1108,10 @@ extension ${Self} {
 %   srcBits = src_type.bits
 %   That = src_type.stdlib_name
 
-%   if (srcBits == 80) and (bits != 80):
+%   if srcBits == 80:
 #if !(os(Windows) || os(Android)) && (arch(i386) || arch(x86_64))
+%   elif srcBits == 16:
+#if !(os(macOS) && arch(x86_64))
 %   end
 
 %   if srcBits == bits:
@@ -1192,7 +1196,7 @@ extension ${Self} {
     }
   }
 
-%   if (srcBits == 80) and (bits != 80):
+%   if srcBits in [16,80]:
 #endif
 %   end
 % end
@@ -1343,12 +1347,12 @@ internal struct _${Self}AnyHashableBox: _AnyHashableBox {
 // Deprecated operators
 //===----------------------------------------------------------------------===//
 
-% if bits == 80:
+% if bits in [16,80]:
 #else
 
 ${SelfDocComment}
 @frozen
-@available(*, unavailable, message: "Float80 is not available on target platform.")
+@available(*, unavailable, message: "${Self} is not available on target platform.")
 public struct ${Self} {
   /// Creates a value initialized to zero.
   @_transparent

stdlib/public/core/IntegerTypes.swift.gyb

@@ -1129,6 +1129,8 @@ public struct ${Self}
 
 %     if FloatType == 'Float80':
 #if !(os(Windows) || os(Android)) && (arch(i386) || arch(x86_64))
+%     elif FloatType == 'Float16':
+#if !(os(macOS) && arch(x86_64))
 %     end
 
   /// Creates an integer from the given floating-point value, rounding toward
@@ -1152,9 +1154,7 @@ public struct ${Self}
   ///   `source` must be representable in this type after rounding toward
   ///   zero.
 %     if FloatType == 'Float16':
-  @available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-  @available(macOS, unavailable)
-  @available(macCatalyst, unavailable)
+  @available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 %     end
   @_transparent
   public init(_ source: ${FloatType}) {
@@ -1184,9 +1184,7 @@ public struct ${Self}
   ///
   /// - Parameter source: A floating-point value to convert to an integer.
 %     if FloatType == 'Float16':
-  @available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-  @available(macOS, unavailable)
-  @available(macCatalyst, unavailable)
+  @available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 %     end
   @_transparent
   public init?(exactly source: ${FloatType}) {
@@ -1206,7 +1204,7 @@ public struct ${Self}
     self._value = Builtin.fpto${u}i_FPIEEE${FloatBits}_${BuiltinName}(source._value)
   }
 
-%     if FloatType == 'Float80':
+%     if FloatType in ['Float16', 'Float80']:
 #endif
 %     end
 

stdlib/public/core/Runtime.swift

@@ -293,6 +293,7 @@ internal struct _Buffer72 {
   }
 }
 
+#if !(os(macOS) && arch(x86_64))
 // Note that this takes a Float32 argument instead of Float16, because clang
 // doesn't have _Float16 on all platforms yet.
 @_silgen_name("swift_float16ToString")
@@ -303,9 +304,7 @@ internal func _float16ToStringImpl(
   _ debug: Bool
 ) -> Int
 
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
 internal func _float16ToString(
   _ value: Float16,
   debug: Bool
@@ -317,6 +316,7 @@ internal func _float16ToString(
   }
   return (buffer, length)
 }
+#endif
 
 // Returns a UInt64, but that value is the length of the string, so it's
 // guaranteed to fit into an Int. This is part of the ABI, so we can't

stdlib/public/core/SIMDVectorTypes.swift.gyb

@@ -253,11 +253,10 @@ extension ${Self}: SIMDScalar {
 %end
 
 %for (Self, bits) in [('Float16',16), ('Float',32), ('Double',64)]:
-%if bits == 16:
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
-%end
+% if bits == 16:
+#if !(os(macOS) && arch(x86_64))
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
+% end
 extension ${Self} : SIMDScalar {
 
   public typealias SIMDMaskScalar = Int${bits}
@@ -299,5 +298,8 @@ extension ${Self} : SIMDScalar {
 
 % end
 }
+% if bits == 16:
+#endif
+% end
 
 %end

test/ClangImporter/simd.swift

@@ -22,12 +22,14 @@ let ll3_value: ll3 = makes_ll3()
 let ll8_value: ll8 = makes_ll8()
 let ull4_value: ull4 = makes_ull4()
 let ull16_value: ull16 = makes_ull16()
+#if !(os(macOS) && arch(x86_64))
 let half2_value: half2 = makes_half2()
 let half3_value: half3 = makes_half3()
 let half4_value: half4 = makes_half4()
 let half8_value: half8 = makes_half8()
 let half16_value: half16 = makes_half16()
 let half32_value: half32 = makes_half32()
+#endif
 let float2_value: float2 = makes_float2()
 let float3_value: float3 = makes_float3()
 let float4_value: float4 = makes_float4()
@@ -58,12 +60,14 @@ takes_ll3(ll3_value)
 takes_ll8(ll8_value)
 takes_ull4(ull4_value)
 takes_ull16(ull16_value)
+#if !(os(macOS) && arch(x86_64))
 takes_half2(half2_value)
 takes_half3(half3_value)
 takes_half4(half4_value)
 takes_half8(half8_value)
 takes_half16(half16_value)
 takes_half32(half32_value)
+#endif
 takes_float2(float2_value)
 takes_float3(float3_value)
 takes_float4(float4_value)

test/stdlib/PrintFloat.swift.gyb

@@ -345,11 +345,9 @@ let PrintTests = TestSuite("FloatingPointPrinting")
 
 % for FloatType in ['Float16', 'Float', 'Double', 'Float80']:
 % if FloatType == 'Float16':
-@available(iOS 14.0, watchOS 7.0, tvOS 14.0, *)
-@available(macOS, unavailable)
-@available(macCatalyst, unavailable)
-% end
-% if FloatType == 'Float80':
+#if !(os(macOS) && arch(x86_64))
+@available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *)
+% elif FloatType == 'Float80':
 #if !os(Windows) && (arch(i386) || arch(x86_64))
 % end
 
@@ -425,7 +423,7 @@ fileprivate func expectAccurateDescription(_ object: ${FloatType},
   // that the result is not closer.  Note this requires higher-precision
   // arithmetic.
 }
-% if FloatType == 'Float80':
+% if FloatType in ['Float16','Float80']:
 #endif
 % end
 % end
@@ -587,8 +585,8 @@ PrintTests.test("Printable_CDouble") {
   expectDescription("-1.0", CDouble(-1.0))
 }
 
-#if !os(macOS) && !(os(iOS) && targetEnvironment(macCatalyst))
-if #available(iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
+#if !(os(macOS) && arch(x86_64))
+if #available(macOS 11.0, iOS 14.0, watchOS 7.0, tvOS 14.0, *) {
 PrintTests.test("Printable_Float16") {
   func asFloat16(_ f: Float16) -> Float16 { return f }