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Add frontend options to write SIL and LLVM IR as additional compilation output #84392

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rjmansfield
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This change introduces two new frontend options that enable writing intermediate representations as additional outputs during compilation:

-sil-output-path : Outputs SIL to the specified path
-ir-output-path : Outputs LLVM IR to the specified path

These options can be useful for debugging and analysis tools workflows that need the IR forms without requiring separate compiler invocations.

rdar://160297898

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@swift-ci please test

@aschwaighofer
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Can you add tests showing this working for multi threaded wmo?

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Can you add tests showing this working for multi threaded wmo?

Ah yeah, I see the issue in performParallelIRGeneration now. I guess in multithreaded WMO we'll need one path per source file then

cachemeifyoucan
cachemeifyoucan reviewed Sep 22, 2025
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The added frontend logics LGTM. The test should be frontend test instead (direct swift-frontend invocation, rather than swift driver invocation, reasons below).

Driver code is optional since the legacy driver is deprecated. If you intended to make this a driver flag, please implement the logic in the new swift-driver.

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Can you add tests showing this working for multi threaded wmo?

Ah yeah, I see the issue in performParallelIRGeneration now. I guess in multithreaded WMO we'll need one path per source file then

Isn't there an IR linking phase, or does that not create a single IR module to print? It's going to be really tricky to deal with one path per source file in build systems when there is only a single object file that's emitted at the end.

DougGregor
DougGregor approved these changes Sep 23, 2025
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Looks good to me, but I'd like to have a solution to the multi-threaded WMO issue. That's a fairly common configuration.

artemcm
artemcm reviewed Sep 23, 2025
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include/swift/Option/FrontendOptions.td
HelpText<"Output semantic info of current module to <path>">;

def sil_output_path
: Separate<["-"], "sil-output-path">, MetaVarName<"<path>">,
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Since these are being modeled as additional supplementary outputs they also need a flag SupplementaryOutput:

swift/include/swift/Option/Options.td

Line 58 in 391a18d

def SupplementaryOutput : OptionFlag;

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@DougGregor In multi-thread WMO, there will be one LLVM Module (.ll file) per source file and also one final product (.o/.bc) file per source file.

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@DougGregor In multi-thread WMO, there will be one LLVM Module (.ll file) per source file and also one final product (.o/.bc) file per source file.

That's tough for this feature, because our output file map is going to have just a single entry (since there's one output file, e.g., .o).

I have a very silly idea! In this case, can we print some split-file-like thing so that there's just one output .ll file, but we break it up with, e.g.,

; --- <source-file-name-1>.ll
first source file IR
; --- <source-file-name-2>.ll
second source file IR

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Ok, I'll explore that. I have a patch that emits separate .ll files, but doesn't address the issue @DougGregor pointed out with supplementary output filemaps. I'll update the current diff in case it solicited further feedback.

@rjmansfield rjmansfield mentioned this pull request Sep 29, 2025
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@swift-ci please test

@rjmansfield rjmansfield force-pushed the sil-ir-extra-outputs branch from 3ad7231 to a17d73d Compare October 1, 2025 13:31
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@swift-ci please smoke test

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Please test with following pull request:

swiftlang/llvm-project#11558

@swift-ci Please test

@rjmansfield rjmansfield force-pushed the sil-ir-extra-outputs branch from a17d73d to 7c4614a Compare October 6, 2025 13:19
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Please test with following pull request:

swiftlang/llvm-project#11558

@swift-ci Please test

@rjmansfield
Add frontend options to write SIL and LLVM IR as additional compilati…
ba0ce8a 
…on output.

This commit adds -sil-output-path and -ir-output-path frontend options that
allow generating SIL and LLVM IR files as supplementary outputs during normal
compilation.

These options can be useful for debugging and analysis tools
workflows that need access to intermediate compilation artifacts
without requiring separate compiler invocations.

Expected behaviour:

Primary File mode:
 - SIL: Generates one .sil file per source file
 - IR: Generates one .ll file per source file

Single-threaded WMO mode:
 - SIL: Generates one .sil file for the entire module
 - IR: Generates one .ll file for the entire module

Multi-threaded WMO mode:
 - SIL: Generates one .sil file for the entire module
 - IR: Generates separate .ll files per source file

File Maps with WMO:
 - Both SIL and IR outputs using first entry's naming, which is
   consistent with the behaviour of other supplementary outputs.

rdar://160297898
@rjmansfield rjmansfield force-pushed the sil-ir-extra-outputs branch from 7c4614a to ba0ce8a Compare October 6, 2025 19:46
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Please test with following pull request:

swiftlang/llvm-project#11558

@swift-ci Please test

@rjmansfield
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Please test with following pull request:

swiftlang/llvm-project#11558

@swift-ci Please smoke test

@rjmansfield rjmansfield mentioned this pull request Oct 7, 2025
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