cuda-samples/Samples/2_Concepts_and_Techniques/inlinePTX/inlinePTX.cu

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/*
 * Demonstration of inline PTX (assembly language) usage in CUDA kernels
 */

// System includes
#include <stdio.h>
#include <assert.h>

// CUDA runtime
#include <cuda_runtime.h>

// helper functions and utilities to work with CUDA
#include <helper_functions.h>
#include <helper_cuda.h>

__global__ void sequence_gpu(int *d_ptr, int length)
{
    int elemID = blockIdx.x * blockDim.x + threadIdx.x;

    if (elemID < length)
    {
        unsigned int laneid;
        //This command gets the lane ID within the current warp
        asm("mov.u32 %0, %%laneid;" : "=r"(laneid));
        d_ptr[elemID] = laneid;
    }
}


void sequence_cpu(int *h_ptr, int length)
{
    for (int elemID=0; elemID<length; elemID++)
    {
        h_ptr[elemID] = elemID % 32;
    }
}

int main(int argc, char **argv)
{
    printf("CUDA inline PTX assembler sample\n");

    const int N = 1000;

    int dev = findCudaDevice(argc, (const char **) argv);

    if (dev == -1)
    {
        return EXIT_FAILURE;
    }

    int *d_ptr;
    checkCudaErrors(cudaMalloc(&d_ptr, N * sizeof(int)));

    int *h_ptr;
    checkCudaErrors(cudaMallocHost(&h_ptr, N * sizeof(int)));

    dim3 cudaBlockSize(256,1,1);
    dim3 cudaGridSize((N + cudaBlockSize.x - 1) / cudaBlockSize.x, 1, 1);
    sequence_gpu<<<cudaGridSize, cudaBlockSize>>>(d_ptr, N);
    checkCudaErrors(cudaGetLastError());
    checkCudaErrors(cudaDeviceSynchronize());

    sequence_cpu(h_ptr, N);

    int *h_d_ptr;
    checkCudaErrors(cudaMallocHost(&h_d_ptr, N *sizeof(int)));
    checkCudaErrors(cudaMemcpy(h_d_ptr, d_ptr, N *sizeof(int), cudaMemcpyDeviceToHost));

    bool bValid = true;

    for (int i=0; i<N && bValid; i++)
    {
        if (h_ptr[i] != h_d_ptr[i])
        {
            bValid = false;
        }
    }

    printf("Test %s.\n", bValid ? "Successful" : "Failed");

    checkCudaErrors(cudaFree(d_ptr));
    checkCudaErrors(cudaFreeHost(h_ptr));
    checkCudaErrors(cudaFreeHost(h_d_ptr));

    return bValid ? EXIT_SUCCESS: EXIT_FAILURE;
}