)]}'
{
  "commit": "670d37f4653c5374d43809800cdfbab2a6d9c4fa",
  "tree": "d3b0dbc2db9c00392aa6c2605a66b9e680718217",
  "parents": [
    "edc6da7c161d0ceedbda45df61532651d111a0d3"
  ],
  "author": {
    "name": "Slava Zakharin",
    "email": "szakharin@nvidia.com",
    "time": "Fri Aug 28 15:01:46 2026 -0700"
  },
  "committer": {
    "name": "Copybara-Service",
    "email": "copybara-worker@google.com",
    "time": "Fri Aug 28 15:10:29 2026 -0700"
  },
  "message": "[flang][OpenACC] Changed memory management for private POINTERs. (#219052)\n\nThe motivating example:\n```\n!$acc parallel loop private(ptr) present(target_data)\n  do i \u003d 1, 128\n     ptr \u003d\u003e target_data(i)%array\n     ptr(...) \u003d ...\n```\n\nThe OpenACC privatization recipe was allocating private data\nfor `ptr`, storing it in `ptr` private descriptor and then\ntrying to deallocate `ptr-\u003ebase_addr` at the end of the region.\n\n`ptr-\u003ebase_addr` is pointing to `target_data(i)%array` that is allocated\nin device global memory and it is illegal to `free()` it in the device\ncode.\n\nThe `destroy` part of the recipe can only `free()` the private data\nthat was originally allocated in the `init` part.\n\nThis approach works well for the two most common case.\n\nCase 1: `ptr` is originally unassociated and it is used to point\nto some target data (the example above).\nCase 2: `ptr` is originally associated and it is used as a normal\nprivate variable for storing something into it without reassociating\n`ptr` to some other data.\n\nThis change, on the other hand, breaks the following case:\n```\nallocate(ptr(10))\n!$acc parallel private(ptr)...\ndeallocate(ptr)\nptr \u003d\u003e ...\n```\n\nThe private memory for `ptr` data may be allocated from the host\nusing CUDA runtime or driver API, and it is illegal to deallocate\nit via `free()` which flang-rt\u0027s implementation is using.\nMoreover, flang-rt\u0027s implementation of `DEALLOCATE` assumes\nthere is an 8-byte footer after the data payload that it uses\nto verify whether a `POINTER` deallocation is valid. OpenACC\nprivatization recipe uses `fir.allocmem` that does not create\nthe footer, so flang-rt may read past the allocated data\nand crash the kernel.\n\nThe reference compiler implements `DEALLOCATE` as `free()`, so\nthe compute-sanitizer reports invalid `free()` errors, though,\nw/o the sanitizer the kernel silently passes.\n\nFlang\u0027s implementation either fails in `DEALLOCATE` runtime with\n`DEALLOCATE of a pointer that is not the whole content of a pointer\nALLOCATE`\nerror or crashes the kernel due to accessing past the allocated memory.\n\nOpenACC spec does not explicitly specify what should happen in this\ncase,\nso I suggest that Flang\u0027s implementation always reports a runtime error\nwhen program tries to deallocate the private data. This is left for\nfuture improvement.\n\nAssisted-by: Cursor\nGitOrigin-RevId: 02c5537c2569b54ee0eb6d0c25dcb9b485fb7406\n",
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