[SYCL][ESIMD][EMU] Atomic update

[dongkyunahn-intel]

• __esimd_svm_atomic0/1/2
• cmpxchng argument order fix (New value first, expected value second)
• atomic_add/sub/min/max/cmpxchg update

[dongkyunahn-intel]

'dword_atomic_smoke.cpp' from intel/llvm-test-suite fails with infinite looping. Still debugging.

[dongkyunahn-intel]

'dword_atomic_smoke.cpp' from intel/llvm-test-suite fails with infinite looping. Still debugging.

The test is disabled in intel/llvm-test-suite as the test fails for GPU as well - intel/llvm-test-suite#1185

[kbobrovs]

type __atomic_load_n (type *ptr, int memorder)
so AFAIU return __atomic_load_n((CmpxchgTy<Ty> *)ptr, __ATOMIC_SEQ_CST); does type conversion from CmpxchgTy<Ty> to Ty before returning the result, which is wrong. Do you have tests for this? They should have caught this problem.

Suggested change

	return __atomic_load_n((CmpxchgTy<Ty> *)ptr, __ATOMIC_SEQ_CST);
	return sycl::bit_cast<Ty>(__atomic_load_n((CmpxchgTy<Ty> *)ptr, __ATOMIC_SEQ_CST));

[dongkyunahn-intel]

I don't have a unit test for this. I'll put TODO comments with __ESIMD_UNSUPPORTED_ON_HOST.

[dongkyunahn-intel]

/verify with intel/llvm-test-suite#1259

[kbobrovs]

This is extremely dangerous, and can be a source of obscure bugs.
Emulator uses multiple threads to emulate GPU threads, so memory fence can't be a no-op.

[dongkyunahn-intel]

Fixed - built-in __atomic_thread_fence() is called.

[dongkyunahn-intel]

/verify with intel/llvm-test-suite#1274

[dongkyunahn-intel]

/verify with intel/llvm-test-suite#1274

[dongkyunahn-intel]

Failures from ESIMD_EMULATOR are already handled in intel/llvm-test-suite#1274

********************
Timed Out Tests (1):
  SYCL :: dword_atomic_cmpxchg.cpp

********************
Failed Tests (3):
  SYCL :: lsc/lsc_slm.cpp
  SYCL :: lsc/lsc_surf.cpp
  SYCL :: lsc/lsc_usm.cpp

********************
Unexpectedly Passed Tests (1):
  SYCL :: dword_atomic_smoke.cpp

[kbobrovs]

it looks strange that we need atomic_load as a part of atomic_store implementation, but that's how Gen ISA is :)
no action for this comment is needed

[kbobrovs]

Nit: strictly speaking, reinterpret_cast should be used. Can be fixed later.

[kbobrovs]

Here and in many more places:
Nit: sycl::bitcast should be used instead. Can be fixed later

[dongkyunahn-intel]

lsc_slm/surf/usm will be fixed once argument order for cmpxchg is confirmed.

Other failures are handled in intel/llvm-test-suite#1274.

********************
Timed Out Tests (1):
  SYCL :: dword_atomic_cmpxchg.cpp

********************
Failed Tests (3):
  SYCL :: lsc/lsc_slm.cpp
  SYCL :: lsc/lsc_surf.cpp
  SYCL :: lsc/lsc_usm.cpp

********************
Unexpectedly Passed Tests (1):
  SYCL :: dword_atomic_smoke.cpp

[dongkyunahn-intel]

/verify with intel/llvm-test-suite#1274

[dongkyunahn-intel]

/verify with intel/llvm-test-suite#1274

[dongkyunahn-intel]

Failures from 'SYCL / Linux / ESIMD Emu LLVM Test Suite (pull_request_target)'

********************
Timed Out Tests (1):
  SYCL :: dword_atomic_cmpxchg.cpp

********************
Unexpectedly Passed Tests (1):
  SYCL :: dword_atomic_smoke.cpp

These tests are modified in intel/llvm-test-suite#1274

[dongkyunahn-intel]

/verify