cuda : add softcap fusion (#14907)

ggml/src/ggml-cuda/softcap.cu

@@ -0,0 +1,34 @@
+#include "softcap.cuh"
+
+static __global__ void softcap_f32(const float * x, float * dst, const float scale, const float softcap, const int k) {
+    const int i = blockDim.x*blockIdx.x + threadIdx.x;
+
+    if (i >= k) {
+        return;
+    }
+
+    dst[i] = tanhf(scale * x[i]) * softcap;
+}
+
+static void softcap_f32_cuda(const float * x, float * dst, const float scale, const float softcap, const int k, cudaStream_t stream) {
+    const int num_blocks = (k + CUDA_SOFTCAP_BLOCK_SIZE - 1) / CUDA_SOFTCAP_BLOCK_SIZE;
+    softcap_f32<<<num_blocks, CUDA_SOFTCAP_BLOCK_SIZE, 0, stream>>>(x, dst, scale, softcap, k);
+}
+
+// fused GGML_OP_SCALE + GGML_UNARY_OP_TANH + GGML_OP_SCALE
+void ggml_cuda_op_softcap(ggml_backend_cuda_context & ctx, ggml_tensor * dst, ggml_tensor * src) {
+    const ggml_tensor * src0 = src->src[0];
+    const float * src0_d = (const float *)src0->data;
+    float * dst_d = (float *)dst->data;
+    cudaStream_t stream = ctx.stream();
+
+    GGML_ASSERT(src0->type == GGML_TYPE_F32);
+    GGML_ASSERT( dst->type == GGML_TYPE_F32);
+
+    float scale;
+    float softcap;
+    memcpy(&scale,   (float *) src->op_params + 0, sizeof(float));
+    memcpy(&softcap, (float *) dst->op_params + 0, sizeof(float));
+
+    softcap_f32_cuda(src0_d, dst_d, scale, softcap, ggml_nelements(src0), stream);
+}