SWDEV-379007 - use avx instruction for bf16 cvt

AMD CPUs have had avx512_bf16 support for quite some time now (from
consumer Ryzen 7000 series to enterprise grade CPUs). This
patch should allow users to use the hardware bf16 unit when running the
__host__ variants of the function. This can be enabled via `hipcc ...
-mavx512vl -mavx512bf16`.

Change-Id: I67c377afc95ddfe8d45a048dce078a247d4a1878


[ROCm/clr commit: 49349f168c]

projects/clr/hipamd/include/hip/amd_detail/amd_hip_bf16.h

@@ -116,6 +116,20 @@
 #define __BF16_DEVICE_STATIC__ __BF16_DEVICE__ static inline
 #define __BF16_HOST_DEVICE_STATIC__ __BF16_HOST_DEVICE__ static inline
 
+#if defined(__AVX512VL__) and defined(__AVX512BF16__) and not defined(__HIP_DEVICE_COMPILE__)
+// Enable with -mavx512vl -mavx512bf16
+#if defined(__MINGW64__)
+#include <intrin.h>
+#else
+#include <immintrin.h>
+#endif
+#define HIP_BF16_AVX512_OP 1
+static_assert(sizeof(__bf16) == sizeof(unsigned short),
+              "sizeof __bf16 should match sizeof unsigned short");
+#else
+#define HIP_BF16_AVX512_OP 0
+#endif
+
 #define HIPRT_ONE_BF16 __float2bfloat16(1.0f)
 #define HIPRT_ZERO_BF16 __float2bfloat16(0.0f)
 #define HIPRT_INF_BF16 __ushort_as_bfloat16((unsigned short)0x7F80U)
@@ -140,7 +154,6 @@ typedef struct __attribute__((aligned(2))) {
   unsigned short x;
 } __hip_bfloat16_raw;
 
-
 /**
  * \ingroup HIP_INTRINSIC_BFLOAT162_RAW
  * \brief represents raw bfloat16x2 vector type
@@ -159,14 +172,29 @@ typedef struct __attribute__((aligned(4))) {
 struct __attribute__((aligned(2))) __hip_bfloat16 {
  private:
   __BF16_HOST_DEVICE_STATIC__ float bfloatraw_2_float(unsigned short val) {
+#if HIP_BF16_AVX512_OP
+    union {
+      unsigned short us;
+      __bf16 bf16;
+    } u = {val};
+    return _mm_cvtsbh_ss(u.bf16);
+#else
     unsigned int uval = val << 16;
     union {
       unsigned int u32;
       float fp32;
     } u = {uval};
     return u.fp32;
+#endif
   }
   __BF16_HOST_DEVICE_STATIC__ unsigned short float_2_bfloatraw(float f) {
+#if HIP_BF16_AVX512_OP
+    union {
+      __bf16 bf16;
+      unsigned short us;
+    } u = {_mm_cvtness_sbh(f)};
+    return u.us;
+#else
     union {
       float fp32;
       unsigned int u32;
@@ -201,7 +229,9 @@ struct __attribute__((aligned(2))) __hip_bfloat16 {
       u.u32 |= 0x10000;  // Preserve signaling NaN
     }
     return static_cast<unsigned short>(u.u32 >> 16);
+#endif
   }
+
   __BF16_HOST_DEVICE_STATIC__ unsigned short double_2_bfloatraw(double d_in) {
     union {
       float fp32;
@@ -393,6 +423,7 @@ struct __attribute__((aligned(4))) __hip_bfloat162 {
   __hip_bfloat16 x; /*! \brief raw representation of bfloat16 */
   __hip_bfloat16 y; /*! \brief raw representation of bfloat16 */
 
+
  public:
   /*! \brief create __hip_bfloat162 from __hip_bfloat162_raw */
   __BF16_HOST_DEVICE__ __hip_bfloat162(const __hip_bfloat162_raw& h2r)
@@ -422,22 +453,34 @@ struct __attribute__((aligned(4))) __hip_bfloat162 {
 
   /*! \brief return a float2 */
   __BF16_HOST_DEVICE__ operator float2() const {
+#if HIP_BF16_AVX512_OP
+    union {
+      __hip_bfloat162_raw raw2;
+      __bf16 bf162[2];
+      static_assert(sizeof(__bf16[2]) == sizeof(__hip_bfloat162_raw));
+    } u;
+    u.raw2 = *this;
+    __m128bh pbf16{u.bf162[0], u.bf162[1], 0, 0};
+    __m128 pf32 = _mm_cvtpbh_ps(pbf16);
+    float2 ret(pf32[0], pf32[1]);
+#else
     float2 ret(x, y);
+#endif
     return ret;
   }
 
   /*! \brief assign value from __hip_bfloat162_raw */
   __BF16_HOST_DEVICE__ __hip_bfloat162& operator=(const __hip_bfloat162_raw& h2r) {
-    x = __hip_bfloat16(__hip_bfloat16{h2r.x});
-    y = __hip_bfloat16(__hip_bfloat16{h2r.y});
+    x = __hip_bfloat16(__hip_bfloat16_raw{h2r.x});
+    y = __hip_bfloat16(__hip_bfloat16_raw{h2r.y});
     return *this;
   }
 
   /*! \brief assign value from __hip_bfloat162 */
   __BF16_HOST_DEVICE__ __hip_bfloat162& operator=(const __hip_bfloat162& src) {
     __hip_bfloat162_raw hr = src;
-    x = __hip_bfloat16(__hip_bfloat16{hr.x});
-    y = __hip_bfloat16(__hip_bfloat16{hr.y});
+    x = __hip_bfloat16(__hip_bfloat16_raw{hr.x});
+    y = __hip_bfloat16(__hip_bfloat16_raw{hr.y});
     return *this;
   }
 };
@@ -466,9 +509,8 @@ __BF16_HOST_DEVICE_STATIC__ __hip_bfloat16 __float2bfloat16(float f) {
  * \brief Converts and moves bfloat162 to float2
  */
 __BF16_HOST_DEVICE_STATIC__ float2 __bfloat1622float2(const __hip_bfloat162 a) {
-  __hip_bfloat162_raw hr = a;
-  return float2{__bfloat162float(__hip_bfloat16(__hip_bfloat16_raw{hr.x})),
-                __bfloat162float(__hip_bfloat16(__hip_bfloat16_raw{hr.y}))};
+  float2 ret = a;
+  return ret;
 }
 
 /**
@@ -576,7 +618,7 @@ __BF16_HOST_DEVICE_STATIC__ __hip_bfloat16 __low2bfloat16(const __hip_bfloat162
  */
 __BF16_HOST_DEVICE_STATIC__ __hip_bfloat162 __low2bfloat162(const __hip_bfloat162 a) {
   __hip_bfloat162_raw hr = a;
-  return __hip_bfloat162(__hip_bfloat162{hr.x, hr.x});
+  return __hip_bfloat162(hr.x, hr.x);
 }
 
 /**