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[Driver][SYCL] Remove object upon failure #18190

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Apr 30, 2025
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[Driver][SYCL] Remove object upon failure #18190

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[Driver][SYCL] Remove object upon failure
mdtoguchi Apr 25, 2025
eaa113d
clang format
mdtoguchi Apr 25, 2025
805770e
Update test, clean up predefine macro name, add -c and general test
mdtoguchi Apr 29, 2025
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6 changes: 5 additions & 1 deletion clang/lib/Driver/Driver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -2708,7 +2708,11 @@ int Driver::ExecuteCompilation(
// Remove result files if we're not saving temps.
if (!isSaveTempsEnabled()) {
const JobAction *JA = cast<JobAction>(&FailingCommand->getSource());
C.CleanupFileMap(C.getResultFiles(), JA, true);
// When performing offload compilations, the result files may not match
// the JobAction that fails. In that case, do not pass in the JobAction
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@srividya-sundaram srividya-sundaram Apr 25, 2025 •
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// When performing offload compilations, the result files may not match the JobAction that fails.

Can you add some details on why they don't match?
And also give an example Offload JobAction for this scenario?

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@mdtoguchi mdtoguchi Apr 29, 2025

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The generated result files are associated with a specific JobAction. One example here is with the old offloading model. Here, the output object from clang++ -fsycl file.cpp -o file.o is generated from the clang-offload-bundler call. Both the host and device compilations have temporary output files, so the JobAction associated with the actual fail (if one fails) including the output file do not match.

Here, the failing action is a BackendCompileJobAction but the file that needs to be removed is from the OffloadBundlingJobAction

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@srividya-sundaram srividya-sundaram Apr 29, 2025

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Here, the output object from clang++ -fsycl file.cpp -o file.o is generated from the clang-offload-bundler call.

clang++ -fsycl file.cpp -o file.o will trigger both compilation and linking at the same invocation and will not call clang-offload-bundler.

AFAIK, when compilation is separated from linking, the compilation step ends with engaging the offload bundler to generate "fat object" (<host object, device code IR> pair).

Both the host and device compilations have temporary output files, so the JobAction associated with the actual fail (if one fails) including the output file do not match

Can you clarify this?
If host or device compilation fails, there will be no host object or device object file generated right?

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@mdtoguchi mdtoguchi Apr 29, 2025

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Oh - yeah -c is needed in that compilation line. Thanks for pointing that out.

Can you clarify this?
If host or device compilation fails, there will be no host object or device object file generated right?

Yes, that is right, no object will be generated. The issue is an existing object that needs to be cleaned up. During the object compilation, the compiler is responsible for cleaning up the output file upon failure. Since the output file in those instances are temporary - there is no association with the actual output file pointed to with -o. The driver knows what the final output object file is, so we need to take the steps to clean up upon failure.

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@srividya-sundaram srividya-sundaram Apr 29, 2025 •
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Did I understand it correctly that if the host and device object files have been created, but the clang-offload-bundler fails to produce the fat object, we should still proceed with deleting the host and device object files?
In this case, the failing JobAction is OffloadBundlingJobAction but the host and device object files were created by a different JobAction.

Is it not possible to pass the JobAction associated with generating the host and device object files instead of not passing any JA at all?

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@mdtoguchi mdtoguchi Apr 29, 2025

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In this case, the failing JobAction is OffloadBundlingJobAction but the host and device object files were created by a different JobAction.

Is it not possible to pass the JobAction associated with generating the host and device object files instead of not passing any JA at all?

The JobAction associated with the host/device object generation is the the BackendCompileJobAction. The JobAction associated with the clang-offload-bundler call is the OffloadBundlingJobAction. Passing in the JobAction associated with the host and device compilation will not match the JobAction that is associated with the actual output file we want to remove, so ultimately the file will not be removed when we want it to be.

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@srividya-sundaram srividya-sundaram Apr 29, 2025

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the actual output file we want to remove

What is the actual output file we want to remove in the case where OffloadBundlingJobAction fails?
My understanding is we want to remove the host and device object files, since those will be the only ones created.

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@mdtoguchi mdtoguchi Apr 29, 2025

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If the OffloadBundlingJobAction fails, we still want to remove the resulting output file, which is the 'fat' object. This is the named object file.o from clang++ -c -fsycl file.cpp -o file.o

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@srividya-sundaram srividya-sundaram Apr 30, 2025

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If the OffloadBundlingJobAction fails, we still want to remove the resulting output file

I'm confused. You mentioned above that if a compilation fails, there will be no result/output file generated for that failed compilation.
So if OffloadBundlingJobAction fails, there will be no fat object created right?

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So if OffloadBundlingJobAction fails, there will be no fat object created right?

That's right. But we still need to remove the object if one existed before the compilation. This allows for matching behavior between clang++ -c a.cpp -o a.o and clang++ -fsycl -c a.cpp -o a.o if compilation fails in any way.

// to allow for the proper resulting file to be removed upon failure.
C.CleanupFileMap(C.getResultFiles(),
C.getActiveOffloadKinds() ? nullptr : JA, true);

// Failure result files are valid unless we crashed.
if (CommandRes < 0)
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26 changes: 26 additions & 0 deletions clang/test/Driver/sycl-obj-remove.cpp
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@@ -0,0 +1,26 @@
/// Verify object removal when the offload compilation fails.

// REQUIRES: system-linux

/// Force failure during device compilation
// RUN: touch %t.o
// RUN: not %clangxx -fsycl -Xsycl-target-frontend -DCOMPILE_FAIL=1 -c -o %t.o %s
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@srividya-sundaram srividya-sundaram Apr 30, 2025

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Can you share why -Xsycl-target-frontend option is needed here?

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@mdtoguchi mdtoguchi Apr 30, 2025

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The use of -Xsycl-target-frontend guides the next option to be specific to the device compilation. This allows to test a device only failure with the host side passing.

// RUN: not ls %t.o
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@srividya-sundaram srividya-sundaram Apr 30, 2025

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Could you explain how running the ls command can confirm that the object file has been successfully removed after a compilation failure?

If we try to ls a file that is not present, we would get
ls: cannot access 't.o': No such file or directory

Can you check for that message instead?

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@mdtoguchi mdtoguchi Apr 30, 2025

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ls as a tool will return a 0 or a 1 depending on if the command was successful. So running ls <file> will return a 0 if the file was found. If the file is not found, it will return a 1. So doing a not ls will allow for error codes to show pass or fail within the LIT testing infrastructure.


// RUN: touch %t.o
// RUN: not %clangxx --offload-new-driver -fsycl -Xsycl-target-frontend -DCOMPILE_FAIL=1 -c -o %t.o %s
// RUN: not ls %t.o

/// Force failure during compilation
// RUN: touch %t.o
// RUN: not %clangxx -fsycl -DCOMPILE_FAIL=1 -c -o %t.o %s
// RUN: not ls %t.o

// RUN: touch %t.o
// RUN: not %clangxx --offload-new-driver -fsycl -DCOMPILE_FAIL=1 -c -o %t.o %s
// RUN: not ls %t.o

void func(){};
#ifdef COMPILE_FAIL
#error FAIL
#endif // COMPILE_FAIL