[UnitTests] Add initial set of tests with multiple early exits.

[fhahn]

Extend the single-early exits tests (#264) to also test loops with multiple exits.

Depends on #264 (included in PR)

[Meinersbur]

I took the initiative to approve #264 even though I am not in the reviewer list since none of the revierer's remarks seem to have been resolved. It will be much easier to review this one when I can see the actual diff.

[fhahn]

Rebased and simplified a bit

[Meinersbur]

Suggested change

	, A, B, C, for (unsigned I = 0; I < N; I++) {
	if (A[I] == 0)
	return I;
	if (A[I] == B[I])
	return I + 1000;
	} return -1;);
	, A, B, C, { for (unsigned I = 0; I < N; I++) {
	if (A[I] == 0)
	return I;
	if (A[I] == B[I])
	return I + 1000;
	} return -1;});

braces may help clang-format to format this better as code:

DEFINE_SCALAR_AND_VECTOR_EARLY_EXIT_2(int A[N]; int B[N]; int C[N];, A, B, C, {
  for (unsigned I = 0; I < N; I++) {
    if (A[I] == 0)
      return I;
    if (A[I] == B[I])
      return I + 1000;
  }
  return -1;
});

[Meinersbur]

Suggested change

	// N_ODD is not divisible by common VFs (4, 8, 16) to test scalar epilogue.
	/// N_ODD is not divisible by common VFs (4, 8, 16) to test scalar epilogue.

[Meinersbur]

Suggested change

	// N_SMALL is a small trip count divisible by common VFs, allowing the compiler
	// to potentially eliminate the scalar remainder loop entirely.
	/// N_SMALL is a small trip count divisible by common VFs, allowing the compiler
	/// to potentially eliminate the scalar remainder loop entirely.

[Meinersbur]

It it is worth extracting out the constant, also give it a description of where it is used?