Disable _Float16 shims for relaxed operations on Intel.

The C type isn't available yet in clang on i386 or x86_64; once the calling conventions are stabilized in clang, we can reenable this.

Author: stephentyrone

Sources/RealModule/Float16+Real.swift

@@ -173,6 +173,9 @@ extension Float16: Real {
   }
   #endif
 
+  // TODO: once clang stabilizes the calling conventions for _Float16 on Intel,
+  // we can re-enable these; presently the type is disabled on the target.
+  #if !(arch(i386) || arch(x86_64))
   @_transparent
   public static func _mulAdd(_ a: Float16, _ b: Float16, _ c: Float16) -> Float16 {
     _numerics_muladdf16(a, b, c)
@@ -187,6 +190,7 @@ extension Float16: Real {
   public static func _relaxedMul(_ a: Float16, _ b: Float16) -> Float16 {
     _numerics_relaxed_mulf16(a, b)
   }
+  #endif
 }
 
 #endif

Sources/_NumericsShims/include/_NumericsShims.h

@@ -383,7 +383,7 @@ HEADER_SHIM long double libm_lgammal(long double x, int *signp) {
 #endif
 
 // MARK: - math inlines with relaxed semantics to support optimization.
-
+#if !(__i386__ || __x86_64__)
 /// a*b + c evaluated _either_ as two operations or fma, whichever is faster.
 HEADER_SHIM _Float16 _numerics_muladdf16(_Float16 a, _Float16 b, _Float16 c) {
 #pragma STDC FP_CONTRACT ON
@@ -403,6 +403,7 @@ HEADER_SHIM _Float16 _numerics_relaxed_mulf16(_Float16 a, _Float16 b) {
 #pragma clang fp reassociate(on) contract(fast)
   return a * b;
 }
+#endif
 
 /// a*b + c evaluated _either_ as two operations or fma, whichever is faster.
 HEADER_SHIM float _numerics_muladdf(float a, float b, float c) {