[clang] [compiler-rt] [llvm] [openmp] [PGO][Offload] Add GPU profiling flags to driver (PR #94268)

[Joel E. Denny via cfe-commits]

jdenny-ornl wrote:

For some codes, I get the following error for a gfx906:

```
LLVM ERROR: Relocation for CG Profile could not be created: unknown relocation name 
```

I see it for OpenMC, but the following is a simpler example:

```
$ cat test.c
#include <stdio.h>
#include <stdlib.h>
__attribute__((noinline))
double test(double x, int n) {
  double res = 1;
  for (int i = 0; i < n; ++i)
    res *= x;
  return res;
}
int main(int argc, char *argv[]) {
  double x = atof(argv[1]);
  unsigned n = atoi(argv[2]);
  #pragma omp target map(tofrom:x)
  x = test(x, n);
  printf("%f\n", x);
  return 0;
}

$ clang -O2 -g -fopenmp --offload-arch=native test.c -o test \
      -fprofile-generate -fprofile-generate-gpu

$ LLVM_PROFILE_FILE=test.profraw ./test 2 4
16.000000

$ llvm-profdata merge -output=test.profdata *.profraw

$ clang -O2 -g -fopenmp --offload-arch=native test.c -foffload-lto \
      -fprofile-use-gpu=test.profdata
```

I can prevent the error by lowering the last -O2 to -O1 or by removing
the `__attribute__((noinline))`.  Am I doing something wrong?

https://github.com/llvm/llvm-project/pull/94268