[OpenMP] offload linking undesired entanglement

[ye-luo]

Using the reproducer

$ clang++ -fopenmp --offload-arch=sm_80 main.cpp -foffload-lto -O3 -ffast-math -v
...
nvlink info    : Function properties for '__omp_offloading_10307_18c6188_main_l9':
nvlink info    : used 28 registers, 8 stack, 40 bytes smem, 360 bytes cmem[0], 0 bytes lmem

Once I comment the second offload region

nvlink info    : Function properties for '__omp_offloading_10307_18c606c_main_l9':
nvlink info    : used 16 registers, 0 stack, 12 bytes smem, 360 bytes cmem[0], 0 bytes lmem

register count, stack, smen all changed. The first offload kernel generation should not be affected by other kernels. There are undesired entanglement.

reproducer main.cpp

#include <unistd.h>
#include <cstdio>

#define N 100

int main()
{
  int a[N];
  #pragma omp target teams distribute parallel for map(a)
  for(int i=0; i<N; i++)
  { a[i]=i; }

  int b = 0;
  #pragma omp target teams distribute parallel for map(a) reduction(+:b)
  for(int i=0; i<N; i++)
  { a[i]+=1; b+=a[i]; }
}

[llvmbot]

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