[Kernel] Optimize rmsnorm cuda kernel

extensions/csrc/common/cuda_type_utils.h

@@ -0,0 +1,122 @@
+/*
+ * This code from NVIDIA FasterTransformer:
+ * https://github.com/NVIDIA/FasterTransformer/blob/main/src/fastertransformer/utils/cuda_type_utils.cuh
+ */
+
+#pragma once
+
+#include <cuda.h>
+#include <cuda_fp16.h>
+
+template <typename T>
+inline __device__ T add(T a, T b) {
+  return a + b;
+}
+
+template <>
+inline __device__ half2 add(half2 a, half2 b) {
+  return __hadd2(a, b);
+}
+
+template <>
+inline __device__ half add(half a, half b) {
+  return __hadd(a, b);
+}
+
+#if ENABLE_BF16
+template <>
+inline __device__ __nv_bfloat162 add(__nv_bfloat162 a, __nv_bfloat162 b) {
+  return bf16hadd2(a, b);
+}
+
+template <>
+inline __device__ __nv_bfloat16 add(__nv_bfloat16 a, __nv_bfloat16 b) {
+  return bf16hadd(a, b);
+}
+
+#endif  // ENABLE_BF16
+
+template <typename T>
+inline __device__ T mul(T a, T b, T c) {
+  return a * b * c;
+}
+
+template <>
+inline __device__ half2 mul(half2 a, half2 b, half2 c) {
+  return __hmul2(__hmul2(a, b), c);
+}
+
+#if ENABLE_BF16
+template <>
+inline __device__ __nv_bfloat16 mul(__nv_bfloat16 a, __nv_bfloat16 b,
+                                    __nv_bfloat16 c) {
+  return bf16hmul(a, b, c);
+}
+
+inline __device__ __nv_bfloat162 mul(__nv_bfloat162 a, __nv_bfloat162 b,
+                                     __nv_bfloat162 c) {
+  return bf16hmul2(a, b, c);
+}
+#endif  // ENABLE_BF16
+
+template <typename T_OUT, typename T_IN>
+__device__ inline T_OUT cuda_cast(T_IN val) {
+  return val;
+}
+
+template <>
+__device__ inline float2 cuda_cast<float2, int2>(int2 val) {
+  return make_float2(val.x, val.y);
+}
+template <>
+__device__ inline float2 cuda_cast<float2, float>(float val) {
+  return make_float2(val, val);
+}
+template <>
+__device__ inline float2 cuda_cast<float2, half2>(half2 val) {
+  return __half22float2(val);
+}
+template <>
+__device__ inline half2 cuda_cast<half2, float2>(float2 val) {
+  return __float22half2_rn(val);
+}
+template <>
+__device__ inline half2 cuda_cast<half2, float>(float val) {
+  return __float2half2_rn(val);
+}
+template <>
+__device__ inline half2 cuda_cast<half2, half>(half val) {
+  return __half2half2(val);
+}
+template <>
+__device__ inline float cuda_cast<float, half>(half val) {
+  return __half2float(val);
+}
+
+// Get type2 from type or vice versa (applied to half and bfloat16)
+template <typename T>
+struct TypeConverter {
+  using Type = half2;
+};  // keep for generality
+
+template <>
+struct TypeConverter<half2> {
+  using Type = at::Half;
+};
+
+template <>
+struct TypeConverter<at::Half> {
+  using Type = half2;
+};
+
+#if ENABLE_BF16
+template <>
+struct TypeConverter<__nv_bfloat162> {
+  using Type = at::BFloat16;
+};
+
+template <>
+struct TypeConverter<at::BFloat16> {
+  using Type = __nv_bfloat162;
+};
+#endif  // ENABLE_BF16