optimize rtn

include/ck/utility/data_type.hpp

@@ -965,47 +965,21 @@ inline __host__ __device__ constexpr float type_convert<float, bhalf_t>(bhalf_t
 }
 
 // convert fp32 to bfp16
+struct uint16_t_2{
+    ushort x;
+    ushort y;
+};
+
 template <>
 inline __host__ __device__ constexpr bhalf_t type_convert<bhalf_t, float>(float x)
 {
     union
     {
         float fp32;
-        uint32_t int32;
+        uint16_t_2 int32;
     } u = {x};
 
-    // When the exponent bits are not all 1s, then the value is zero, normal,
-    // or subnormal. We round the bfloat16 mantissa up by adding 0x7FFF, plus
-    // 1 if the least significant bit of the bfloat16 mantissa is 1 (odd).
-    // This causes the bfloat16's mantissa to be incremented by 1 if the 16
-    // least significant bits of the float mantissa are greater than 0x8000,
-    // or if they are equal to 0x8000 and the least significant bit of the
-    // bfloat16 mantissa is 1 (odd). This causes it to be rounded to even when
-    // the lower 16 bits are exactly 0x8000. If the bfloat16 mantissa already
-    // has the value 0x7f, then incrementing it causes it to become 0x00 and
-    // the exponent is incremented by one, which is the next higher FP value
-    // to the unrounded bfloat16 value. When the bfloat16 value is subnormal
-    // with an exponent of 0x00 and a mantissa of 0x7f, it may be rounded up
-    // to a normal value with an exponent of 0x01 and a mantissa of 0x00.
-    // When the bfloat16 value has an exponent of 0xFE and a mantissa of 0x7F,
-    // incrementing it causes it to become an exponent of 0xFF and a mantissa
-    // of 0x00, which is Inf, the next higher value to the unrounded value.
-    bool flag0 = ~u.int32 & 0x7f800000;
-
-    // When all of the exponent bits are 1, the value is Inf or NaN.
-    // Inf is indicated by a zero mantissa. NaN is indicated by any nonzero
-    // mantissa bit. Quiet NaN is indicated by the most significant mantissa
-    // bit being 1. Signaling NaN is indicated by the most significant
-    // mantissa bit being 0 but some other bit(s) being 1. If any of the
-    // lower 16 bits of the mantissa are 1, we set the least significant bit
-    // of the bfloat16 mantissa, in order to preserve signaling NaN in case
-    // the bfloat16's mantissa bits are all 0.
-    bool flag1 = !flag0 && (u.int32 & 0xffff);
-
-    u.int32 += flag0 ? 0x7fff + ((u.int32 >> 16) & 1) : 0; // Round to nearest, round to even
-    u.int32 |= flag1 ? 0x10000 : 0x0;                      // Preserve signaling NaN
-
-    return uint16_t(u.int32 >> 16);
+    return u.int32.y + ((u.int32.x & 0x8000) >> 15);
 }
 
 // convert fp16 to bf16