CPU OpenCL runtime: Apparent miscompilation of conditional

[inducer]

Running this snippet:

import numpy as np
import pyopencl as cl
import pyopencl.array

src = """
#define lid(N) ((int) get_local_id(N))
#define gid(N) ((int) get_group_id(N))

__kernel void __attribute__ ((reqd_work_group_size(16, 1, 1))) actx_special_cos(__global double const *__restrict__ inp0, int const inp0_offset, int const n0, int const n1, __global double *__restrict__ out, int const out_offset)
{
  if (-1 * lid(0) + n1 >= 0) // CRASHES/WRONG OUTPUT ON INTEL
  //if (n1 >= lid(0))  // NO FAILURE ON INTEL
  {
      out[(1 + n1) * gid(0) + lid(0)] = cos(inp0[(1 + n1) * gid(0) + lid(0)]);
  }
}
"""


def main():
    ctx = cl._csc()
    queue = cl.CommandQueue(ctx)

    inp = cl.array.zeros(queue, (3, 4), dtype=float)
    out = cl.array.zeros_like(inp)
    prg = cl.Program(ctx, src).build()
    knl = prg.actx_special_cos
    knl(
            queue, (16*3,), (16,), inp.data, np.int32(0),
            np.int32(inp.shape[0]-1), np.int32(inp.shape[1]-1),
            out.data, np.int32(0))

    c = out.get()
    print(c)
    good = (c == 1)
    assert good.all(), np.where(good)

main()

on the CPU runtime version oclcpuexp-2020.10.6.0.4_rel distributed from this release page gives me

[[0. 0. 0. 1.]
 [1. 1. 1. 1.]
 [1. 1. 1. 1.]]
Traceback (most recent call last):
  File "testac2.py", line 38, in <module>
    main()
  File "testac2.py", line 36, in main
    assert good.all(), np.where(good)
AssertionError: (array([0, 1, 1, 1, 1, 2, 2, 2, 2]), array([3, 0, 1, 2, 3, 0, 1, 2, 3]))
double free or corruption (out)

• Oclgrind has no complaints about this kernel.
• Every other OpenCL implementation with which I try this kernel gives me what I'd view as the correct output:

  [[1. 1. 1. 1.]
   [1. 1. 1. 1.]
   [1. 1. 1. 1.]]
  

• Uncommenting the (IMO) equivalent rewrite of the conditional at the top and commenting the other version makes the Intel CPU runtime behave the same as all other CL implementations.

x-ref: https://gitlab.tiker.net/inducer/meshmode/-/merge_requests/80#note_49286

[AlexeySachkov]

@fzou1, @woshiyifei, @turinevgeny: FYI

[github-actions]

This issue is stale because it has been open 180 days with no activity. Remove stale label or comment or this will be automatically closed in 30 days.

[inducer]

I just verified that this is still an issue with release 2021-09.

[isuruf]

@napetrov, this is an issue with the new conda package as well.

[zhaomaosu]

@inducer, thank you for reporting the issue. And the issue will be fixed in the next release of oneAPI.

[inducer]

Does not appear fixed in https://github.com/intel/llvm/releases/tag/2022-WW13.

[cdai2]

The fix for this issue is already merged to code base but targeted next release. @inducer

[zhaomaosu]

@inducer, this issue should be fixed in https://github.com/intel/llvm/releases/tag/2022-WW33. I verified locally, the case provided by you is passed now.

[inducer]

I can confirm that this is fixed. Thanks!

[inducer]

Here's the next bug: #6607