Introduce PAL function table #10675

GregoryComer · 2025-05-04T07:46:17Z

Summary:
This is part 1 of the implementation of the PAL changes described in #10432. This PR introduces a struct (pal_table) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism.

I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. In the following PR, I update ET callers to do this.

Differential Revision: D74121895

pytorch-bot · 2025-05-04T07:46:21Z

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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/10675

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facebook-github-bot · 2025-05-04T07:46:32Z

This pull request was exported from Phabricator. Differential Revision: D74121895

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

facebook-github-bot · 2025-05-21T05:45:39Z

This pull request was exported from Phabricator. Differential Revision: D74121895

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

facebook-github-bot · 2025-05-21T06:03:23Z

This pull request was exported from Phabricator. Differential Revision: D74121895

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

runtime/platform/platform.h

runtime/platform/test/executor_pal_override_test.cpp

GregoryComer · 2025-05-21T06:17:17Z

runtime/platform/platform.h

+ *
+ * Returns true if the registration was successful, false otherwise.
+ */
+bool register_pal(pal_table impl);


This API is returning bool primarily because using Error would introduce a circular header dependency and there's no current way for this call to fail. I'm open to switching to error, but would require a little bit of a header refactor.

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

GregoryComer · 2025-05-29T10:41:33Z

Trying to repro the size test failure locally to investigate. For some reason, I'm only seeing a 64-byte increase in size between this PR and the base revision, which is more in line with what I'd expect. I am on Clang 14 locally vs 12 in CI. Maybe that's related?

Main:

-rwxr-xr-x  1 gregory gregory   51664 May 29 03:34 size_test
-rwxr-xr-x  1 gregory gregory 1915080 May 29 03:33 size_test_all_ops
-rwxr-xr-x  1 gregory gregory   70872 May 29 03:34 size_test_unstripped 

PR:

-rwxr-xr-x  1 gregory gregory   51728 May 29 03:38 size_test
-rwxr-xr-x  1 gregory gregory 1915840 May 29 03:37 size_test_all_ops
-rwxr-xr-x  1 gregory gregory   71936 May 29 03:37 size_test_unstripped

Edit: Interestingly, it does seem to be reproducible on Clang 12:

Main:

-rwxr-xr-x  1 gregory gregory   47560 May 29 03:57 size_test
-rwxr-xr-x  1 gregory gregory 1748816 May 29 03:57 size_test_all_ops
-rwxr-xr-x  1 gregory gregory   66504 May 29 03:57 size_test_unstripped

PR:

-rwxr-xr-x  1 gregory gregory   51720 May 29 03:55 size_test
-rwxr-xr-x  1 gregory gregory 1749880 May 29 03:54 size_test_all_ops
-rwxr-xr-x  1 gregory gregory   71664 May 29 03:55 size_test_unstripped

runtime/platform/platform.h

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

GregoryComer · 2025-06-03T06:46:46Z

.github/workflows/pull.yml

@@ -371,7 +371,7 @@ jobs:
        size=${arr[4]}
        # threshold=48120 on devserver with gcc11.4
        # todo(lfq): update once binary size is below 50kb.
-        threshold="51408"
+        threshold="55584"


Note that the "true" size increase is around ~80 bytes, due to some instability in the size test on older toolchains. See https://github.com/pytorch/executorch/pull/11217/files. This is confirmed with manual builds on newer toolchains and Meta app build size checks.

GregoryComer · 2025-06-03T06:47:38Z

.github/workflows/pull.yml

@@ -406,7 +406,7 @@ jobs:
        output=$(ls -la cmake-out/test/size_test)
        arr=($output)
        size=${arr[4]}
-        threshold="47560"
+        threshold="51720"


Similar to above, note that the "true" size increase is around ~64 bytes. See https://github.com/pytorch/executorch/pull/11217/files.

facebook-github-bot · 2025-06-03T07:27:42Z

@GregoryComer has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

Summary: This is the implementation of the PAL changes described in pytorch#10432. This PR introduces a struct (`pal_table`) to hold function pointers to the PAL function implementations. There is a singleton instance of this struct, which is initialized with the weak/strong et_pal_ functions - maintaining backwards compatibility with the existing override mechanism. I've then added wrapper functions for the PAL into the executorch::runtime namespace which dispatch through the function table. It is intended that callers use these functions instead of the "raw" et_pal_ methods in order to correctly dispatch through the function table. I also update ET callers to do this. Differential Revision: D74121895

facebook-github-bot · 2025-06-05T04:48:35Z

@GregoryComer has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

### Summary The recent PAL changes (#10675) increased runtime size slightly. This was approved and size targets were updated for the main size jobs. However, I missed the Cortex-M job and am updating here. ### Test plan CI

### Summary Update PAL docs in using-executorch-runtime-integration.md to describe the new PAL override mechanism introduced in #10675. I've left the docs in for the weak symbol override mechanism, as well, though I've recommended use of the runtime APIs. ### Test plan I built the docs locally to validate form and content.

### Summary Update PAL docs in using-executorch-runtime-integration.md to describe the new PAL override mechanism introduced in pytorch#10675. I've left the docs in for the weak symbol override mechanism, as well, though I've recommended use of the runtime APIs. ### Test plan I built the docs locally to validate form and content.

GregoryComer requested review from JacobSzwejbka, lucylq and swolchok as code owners May 4, 2025 07:46

facebook-github-bot added the CLA Signed This label is managed by the Facebook bot. Authors need to sign the CLA before a PR can be reviewed. label May 4, 2025

facebook-github-bot added the fb-exported label May 4, 2025

GregoryComer added the release notes: runtime Changes related to the core runtime which loads the program methods, initializes delegates, and runs label May 4, 2025

GregoryComer force-pushed the export-D74121895 branch from 84a8e89 to 24a7b2e Compare May 21, 2025 05:45

GregoryComer requested a review from larryliu0820 as a code owner May 21, 2025 05:45

GregoryComer requested review from manuelcandales, tarun292, Gasoonjia, digantdesai and mcr229 as code owners May 21, 2025 05:45

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GregoryComer commented May 21, 2025

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GregoryComer merged commit 60929cf into pytorch:main Jun 5, 2025
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zingo mentioned this pull request Jun 5, 2025

Arm backend: Replace asserts with exceptions in passes #11394

Merged

This was referenced Jun 5, 2025

Provide an alternative PAL override mechanism #11142

Closed

Update Cortex-M Size target #11399

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larryliu0820 mentioned this pull request Jun 11, 2025

install_executorch.sh --clean should remove buck-out/ #11564

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GregoryComer mentioned this pull request Jun 17, 2025

Update PAL override docs for new APIs #11747

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