#ifndef _MOVIT_FP16_H
#define _MOVIT_FP16_H 1
+#ifdef __F16C__
+#include <immintrin.h>
+#endif
+
// Code for converting to and from fp16 (from fp64), without any particular
// machine support, with proper IEEE round-to-even behavior (and correct
// handling of NaNs and infinities). This is needed because some OpenGL
namespace movit {
-typedef unsigned int fp32_int_t;
-typedef unsigned short fp16_int_t;
+// structs instead of ints, so that they are not implicitly convertible.
+struct fp32_int_t {
+ unsigned int val;
+};
+struct fp16_int_t {
+ unsigned short val;
+};
+
+#ifdef __F16C__
+
+// Use the f16c instructions from Haswell if available (and we know that they
+// are at compile time).
+static inline double fp16_to_fp64(fp16_int_t x)
+{
+ return _cvtsh_ss(x.val);
+}
+
+static inline fp16_int_t fp64_to_fp16(double x)
+{
+ // NOTE: Strictly speaking, there are some select values where this isn't correct,
+ // since we first round to fp32 and then to fp16.
+ fp16_int_t ret;
+ ret.val = _cvtss_sh(x, 0);
+ return ret;
+}
+
+#else
double fp16_to_fp64(fp16_int_t x);
fp16_int_t fp64_to_fp16(double x);
+#endif
+
// These are not very useful by themselves, but are implemented using the same
// code as the fp16 ones (just with different constants), so they are useful
// for verifying against the FPU in unit tests.
double fp32_to_fp64(fp32_int_t x);
fp32_int_t fp64_to_fp32(double x);
+// Overloads for use in templates.
+static inline double to_fp64(double x) { return x; }
+static inline double to_fp64(float x) { return x; }
+static inline double to_fp64(fp16_int_t x) { return fp16_to_fp64(x); }
+
+template<class T> inline T from_fp64(double x);
+template<> inline double from_fp64<double>(double x) { return x; }
+template<> inline float from_fp64<float>(double x) { return x; }
+template<> inline fp16_int_t from_fp64<fp16_int_t>(double x) { return fp64_to_fp16(x); }
+
+template<class From, class To>
+inline To convert_float(From x) { return from_fp64<To>(to_fp64(x)); }
+
+template<class Same>
+inline Same convert_float(Same x) { return x; }
+
} // namespace movit
#endif // _MOVIT_FP16_H