[all-commits] [llvm/llvm-project] 404597: [OMPIRBuilder] - Make offloading input data persis...

[Pranav Bhandarkar via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 404597061f974470e8bd1198e44d024fac8319a1
      https://github.com/llvm/llvm-project/commit/404597061f974470e8bd1198e44d024fac8319a1
  Author: Pranav Bhandarkar <pranav.bhandarkar at amd.com>
  Date:   2025-06-16 (Mon, 16 Jun 2025)

  Changed paths:
    M llvm/include/llvm/Frontend/OpenMP/OMPIRBuilder.h
    M llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp
    M mlir/test/Target/LLVMIR/omptarget-depend.mlir
    M mlir/test/Target/LLVMIR/omptarget-nowait-llvm.mlir
    A mlir/test/Target/LLVMIR/omptarget-nowait.mlir
    M mlir/test/Target/LLVMIR/omptargetdata-nowait-llvm.mlir

  Log Message:
  -----------
  [OMPIRBuilder] - Make offloading input data persist for deferred target tasks (#133499)

When we offload to the target, the pointers to data used by the kernel
are passed in arrays created by `OMPIRBuilder`. These arrays of pointers
are allocated on the stack on the host. This is fine for the most part
because absent the `nowait` clause, the default behavior is that target
tasks are included tasks. That is, the host is blocked until the
offloaded target kernel is done. In turn, this means that the host's
stack frame is intact and accessing the array of pointers when
offloading is safe. However, when `nowait` is used on the `!$ omp
target` instance, then the target task is a deferred task meaning, the
generating task on the host does not have to wait for the target task
to finish. In such cases, it is very likely that the stack frame of the
function invoking the target call is wound up thereby leading to memory
access errors as shown below.
```
AMDGPU error: Error in hsa_amd_memory_pool_allocate: HSA_STATUS_ERROR_INVALID_ALLOCATION: The requested allocation is not valid.
AMDGPU error: Error in hsa_amd_memory_pool_allocate: HSA_STATUS_ERROR_INVALID_ALLOCATION: The requested allocation is not valid. "PluginInterface" error: Failure to allocate device memory: Failed to allocate from memory manager
fort.cod.out: /llvm/llvm-project/offload/plugins-nextgen/common/src/PluginInterface.cpp:1434: Error llvm::omp::target::plugin::PinnedAllocationMapTy::lockMappedHostBuffer(void *, size_t): Assertion `HstPtr && "Invalid pointer"' failed.
Aborted (core dumped)
```
This PR implements support in `OMPIRBuilder` to store these arrays of
pointers in the task structure that is passed to the target task thereby
ensuring it is available to the target task when the target task is
eventually scheduled.

---------

Co-authored-by: Sergio Afonso <safonsof at amd.com>



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