On Windows, for a reason I don't fully understand boolean bits get extra
padding (even when asking for packed structures) in the structures that
messes the offsets between the compiler and the runtime.
Also, "weak" works differently on Windows than Linux (i.e., the "local"
routine has preference) which causes it to crash as we don't really have
an alternate implementation of __kmpc_omp_wait_deps. Given this, it
doesn't make sense to mark it as "weak" for Linux either.
This change adds support for saving full contents of attached Fortran
descriptors, and not just their pointee address, in the shadow-pointer
table.
With this, we now support:
* comparing full contents of descriptors to check whether a previous
shadow-pointer entry is stale;
* restoring the full contents of descriptors
And with that, we can now use ATTACH map-types (added in #149036) for
mapping Fortran pointer/allocatable arrays, and array-sections on them.
e.g.:
```f90
integer, allocatable :: x(:)
!$omp target enter data map(to: x(:))
```
as:
```
void* addr_of_pointee = allocated(x) ? &x(1) : nullptr;
int64_t sizeof_pointee = allocated(x) ? sizeof(x(:)) : 0
addr_of_pointee, addr_of_pointee, sizeof_pointee, TO
addr_of_descriptor, addr_of_pointee, size_of_descriptor, ATTACH
```
This patch introduces libomptarget support for the ATTACH map-type,
which can be used to implement OpenMP conditional compliant pointer
attachment, based on whether the pointer/pointee is newly mapped on a
given construct.
For example, for the following:
```c
int *p;
#pragma omp target enter data map(p[1:10])
```
The following maps can be emitted by clang:
```
(A)
&p[0], &p[1], 10 * sizeof(p[1]), TO | FROM
&p, &p[1], sizeof(p), ATTACH
```
Without this map-type, these two possible maps could be emitted by
clang:
```
(B)
&p[0], &p[1], 10 * sizeof(p[1]), TO | FROM
(C)
&p, &p[1], 10 * sizeof(p[1]), TO | FROM | PTR_AND_OBJ
````
(B) does not perform any pointer attachment, while (C) also maps the
pointer p, which are both incorrect.
In terms of implementation, maps with the ATTACH map-type are handled
after all other maps have been processed, as it requires knowledge of
which new allocations happened as part of the construct. As per OpenMP
5.0, an attachment should happen only when either the pointer or the
pointee was newly mapped while handling the construct.
Maps with ATTACH map-type-bit do not increase/decrease the ref-count.
With OpenMP 6.1, `attach(always/never)` can be used to force/prevent
attachment. For `attach(always)`, the compiler will insert the ALWAYS
map-type, which would let libomptarget bypass the check about one of the
pointer/pointee being new. With `attach(never)`, the ATTACH map will not
be emitted at all.
The size argument of the ATTACH map-type can specify values greater than
`sizeof(void*)` which can be used to support pointer attachment on
Fortran descriptors. Note that this also requires shadow-pointer
tracking to also support them. That has not been implemented in this
patch.
This was worked upon in coordination with Ravi Narayanaswamy, who has
since retired. Happy retirement, Ravi!
---------
Co-authored-by: Alex Duran <alejandro.duran@intel.com>
The following patch introduces a new interop interface implementation
with the following characteristics:
* It supports the new 6.0 prefer_type specification
* It supports both explicit objects (from interop constructs) and
implicit objects (from variant calls).
* Implements a per-thread reuse mechanism for implicit objects to reduce
overheads.
* It provides a plugin interface that allows selecting the supported
interop types, and managing all the backend related interop operations
(init, sync, ...).
* It enables cooperation with the OpenMP runtime to allow progress on
OpenMP synchronizations.
* It cleanups some vendor/fr_id mismatchs from the current query
routines.
* It supports extension to define interop callbacks for library cleanup.
In a nutshell, this moves our libomptarget code to populate the offload
subproject.
With this commit, users need to enable the new LLVM/Offload subproject
as a runtime in their cmake configuration.
No further changes are expected for downstream code.
Tests and other components still depend on OpenMP and have also not been
renamed. The results below are for a build in which OpenMP and Offload
are enabled runtimes. In addition to the pure `git mv`, we needed to
adjust some CMake files. Nothing is intended to change semantics.
```
ninja check-offload
```
Works with the X86 and AMDGPU offload tests
```
ninja check-openmp
```
Still works but doesn't build offload tests anymore.
```
ls install/lib
```
Shows all expected libraries, incl.
- `libomptarget.devicertl.a`
- `libomptarget-nvptx-sm_90.bc`
- `libomptarget.rtl.amdgpu.so` -> `libomptarget.rtl.amdgpu.so.18git`
- `libomptarget.so` -> `libomptarget.so.18git`
Fixes: https://github.com/llvm/llvm-project/issues/75124
---------
Co-authored-by: Saiyedul Islam <Saiyedul.Islam@amd.com>
