Added half type

src/half.h

@@ -0,0 +1,28 @@
+#ifndef HALF_H
+#define HALF_H
+
+#define __STDC_WANT_IEC_60559_TYPES_EXT__
+
+#include <float.h>
+
+/* _Float16 and __fp16 are not supported on x86_64 with GCC 11 */
+#if defined(__is_identifier)
+#if __is_identifier(_Float16)
+#define FLT16_SUPPORT
+#endif
+#elif defined(FLT16_MAX)
+#define FLT16_SUPPORT
+#endif
+
+#ifdef FLT16_SUPPORT
+#define half _Float16
+#define HALF_MAX FLT16_MAX
+#else
+#define half uint16
+#define HALF_MAX 65504
+#endif
+
+#define PG_GETARG_HALF(n)  DatumGetHalf(PG_GETARG_DATUM(n))
+#define PG_RETURN_HALF(x)  return HalfGetDatum(x)
+
+#endif