[llvm-bugs] [Bug 26483] New: CUDA __device__ lambdas generating incorrect code

[via llvm-bugs]

https://llvm.org/bugs/show_bug.cgi?id=26483

            Bug ID: 26483
           Summary: CUDA __device__ lambdas generating incorrect code
           Product: clang
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: justin.lebar at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

The following CUDA code, which passes a __device__ functor to a kernel,
compiles fine but does not give the correct output.

When I compile and run it, I get the following output:

Error 3: invalid device function
Error: 0 2883584
Error: 1 0
Error: 2 2883584
Error: 3 0
Error: 4 3105024
Error: 5 0
Error: 6 0
Error: 7 0
Error: 8 0
Error: 9 0
Error: 10 0
Error: 11 0
Error: 12 0
Error: 13 0
Error: 14 0
Error: 15 0

The "error 3 invalid device function" is probably the root of the problem; it
seems like we may not be running any device code at all.

#include <cuda_runtime.h>
#include <cuda.h>
#include <cstdio>

template<class Functor>
__global__ void foo(const Functor f) {
   f(blockIdx.x*blockDim.x+threadIdx.x);
}

template<class Functor>
void run(const Functor& f) {
 foo<Functor> <<<256,256>>> (f);   
}


int main() {
  int* h_a = new int[256*256];

  int d_c = 9;
  int* d_a;
  cudaMalloc(&d_a,256*256*sizeof(int));

  run([=] (int i) __device__ {
    d_a[i] = d_c;
  });

  cudaMemcpy(h_a,d_a,256*256*sizeof(int),cudaMemcpyDeviceToHost);
  printf("Error 3: %s\n",cudaGetErrorString(cudaGetLastError()));

  for(int i=0;i<16;i++)
    if(h_a[i]!=d_c)
     printf("Error: %i %i\n",i,h_a[i]); 
}

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