[PATCHv2 0/5] OpenMP/PTX: improve correctness in SIMD regions

[Alexander Monakov <amonakov@ispras.ru>]

Hello,

This patchset implements privatization of addressable variables in OpenMP SIMD
regions lowered for SIMT targets (i.e. NVPTX) via the approach identified in
the review of the previous submission.

Now instead of explicitly privatizing those variables as fields of an
allocated struct up front, we keep them as normal variables in the IR until
after IPA passes.  After that, the ompdevlow pass rewrites the IR to make
privatization explicit (patch 3/5).

Inlining is taught to privatize variables this way (patch 4), and when a
variable no longer has its address taken, it can be promoted to a gimple
register and no longer be subject to special privatization (patch 5).

Post-omplow IR looks like this:

  void *simtrec;
  int priv1 __attribute__((omp simt private));

  simduid.n_2 = GOMP_SIMT_ENTER (simduid.n_1, &priv1, &priv2, ...);
  simtrec = GOMP_SIMT_ENTER_ALLOC (simduid.n_2);

  for (...) { foo (&priv1); }

  priv1 = {CLOBBER};
  GOMP_SIMT_EXIT (simtrec);

And post-ompdevlow IR looks like this:

  struct {
    int priv1;
  } *simtrec;
  int priv1 [value-expr: simtrec->priv1];
  /* priv1 is no longer itself present in IR */

  simduid.n_2 = simduid.n_1;
  simtrec = GOMP_SIMT_ENTER_ALLOC (sizeof *simtrec, alignof *simtrec);

  for (...) { foo (&simtrec->priv1); }

  *simtrec = {CLOBBER};
  GOMP_SIMT_EXIT (simtrec);

Thanks.
Alexander