Drop precision requirements for host math built-ins

[AlexeySachkov]

KhronosGroup/SYCL-Docs#511 essentially removed any precision guarantees for math built-ins invoked on host and this PR aligns CTS with that direction.

[keryell]

Thanks.

[AerialMantis]

SYCL WG call:

• One approval, looks good to merge.

[hvdijk]

Hi, is it intentional that this still checks for inf vs. non-inf? With DPC++ commit 557df1aa57c810732f1635abb85045f407c5d0f3, SYCL-CTS commit 3197f43, I'm seeing, for instance,

/home/harald/SYCL-CTS/tests/math_builtin_api/math_builtin.h:196: FAILED:
  CHECK( verify(log, hostRes, ref, -1, comment) )
with expansion:
  false
with message:
  tests case: 4000523. Correctness check failed on host.

/home/harald/SYCL-CTS/util/logger.cpp:41: warning:
  value: inf [7f800000], reference: 0 [0]

/home/harald/SYCL-CTS/util/logger.cpp:41: warning:
  Expected accuracy in ULP: -1

for the test case

{

        sycl::marray<float, 5> inputData_0(0.1958509433f,0.2681012382f,0.2765018591f,0.2239653187f,0.5127045541f);
        int inputData_1(7348);

        sycl_cts::resultRef<sycl::marray<float, 5>> ref = reference::ldexp(inputData_0,inputData_1);

  check_function<4000523, sycl::marray<float, 5>>(log,
      [=]{

        sycl::marray<float, 5> inputData_0(0.1958509433f,0.2681012382f,0.2765018591f,0.2239653187f,0.5127045541f);
        int inputData_1(7348);

        static_assert(std::is_same_v<decltype(sycl::ldexp(inputData_0, inputData_1)), sycl::marray<float, 5>>,
            "Error: Wrong return type of sycl::ldexp(sycl::marray<float, 5>, int), not sycl::marray<float, 5>");

        static_assert(std::is_same_v<decltype(sycl::ldexp<decltype(inputData_0)>(inputData_0, inputData_1)), decltype(sycl::ldexp(inputData_0, inputData_1))>,
            "Error: sycl::ldexp(sycl::marray<float, 5>, int) definition does not use the required template arguments.");

        return sycl::ldexp(inputData_0, inputData_1);

      }, ref, 0);
}

[AlexeySachkov]

@hvdijk, that is a good question and I'm not sure if I know the right answer.

Strictly speaking, the SYCL 2020 specification poses no requirements on host built-ins precision and therefore there are no guarantees about the result. However, I would expect that an implementation would return at least somewhat reasonable result and therefore I left checks for inf/non-inf in place.