[PATCH] D71989: [OpenMP][IRBuilder][WIP] Prototype `omp task` support

[Roger Ferrer Ibanez via Phabricator via llvm-commits]

rogfer01 added inline comments.


================
Comment at: openmp/runtime/src/kmp_tasking.cpp:1764
+    char *dest = static_cast<char *>(task->shareds);
+    memcpy(dest, shared_and_private_vars, sizeof_shared_and_private_vars);
+
----------------
Just double-checking here I understand what would happen here for C++ firstprivatized objects (sorry if I'm asking the obvious):

We would capture the copy onto an `alloc`ed memory and then we would copy that memory to the task struct?

So given something like

```lang=cpp
struct A {
  A(int x = 3);
  void bar();
};

void foo() {
  A a;
  #pragma omp task
  {
    a.bar();
  }
}
```

we'd do (in pseudo-C)

```lang=c
void foo() {
   struct task_env_0 { 
      char A_storage[sizeof(A)]; // properly aligned and all that
   } tenv_0;

   A::A(&tenv_0.A_storage, 3); // capture

   // This would happen (dynamically) inside __kmpc_task
   kmp_task_t* new_task = __kmp_omp_task_alloc( , sizeof(tenv_0), ... );
   memcpy(new_task->shareds, &tenv_0, sizeof(tenv_0));
   kmpc_omp_task(..., new_task).
   //
}
```

So we go from

 - create task
 - capture environment in the task context
 - queue task / run immediately for if0

to

  - capture environment in a local storage
  - allocate task + copy local environment to task environment if needed (for tasks that are not if0) + queue task / run immediately for if0

Did I get that right?

Thanks!


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https://reviews.llvm.org/D71989