[llvm] [Object][COFF][NFC] Document writeImportLibrary. (PR #81600)

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llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-binary-utilities

Author: Jacek Caban (cjacek)

<details>
<summary>Changes</summary>

As suggested in #<!-- -->81426.

 CC @<!-- -->zmodem

---
Full diff: https://github.com/llvm/llvm-project/pull/81600.diff


1 Files Affected:

- (modified) llvm/include/llvm/Object/COFFImportFile.h (+12) 


``````````diff
diff --git a/llvm/include/llvm/Object/COFFImportFile.h b/llvm/include/llvm/Object/COFFImportFile.h
index 23c3e6a1f0784a..f4671d7405dbda 100644
--- a/llvm/include/llvm/Object/COFFImportFile.h
+++ b/llvm/include/llvm/Object/COFFImportFile.h
@@ -135,6 +135,18 @@ struct COFFShortExport {
   }
 };
 
+/// Writes a COFF import library containing entries described by the Exports
+/// array.
+///
+/// For hybrid targets such as ARM64EC, additional native entry points can be
+/// exposed using the NativeExports parameter. When NativeExports is used, the
+/// output import library will expose these native ARM64 imports alongside the
+/// entries described in the Exports array. Such a library can be used for
+/// linking both ARM64EC and pure ARM64 objects, and the linker will pick only
+/// the exports relevant to the target platform.
+///
+/// For non-hybrid targets, the NativeExports parameter should not be used.
+/// Instead, pass std::nullopt or an empty array to this parameter.
 Error writeImportLibrary(StringRef ImportName, StringRef Path,
                          ArrayRef<COFFShortExport> Exports,
                          ArrayRef<COFFShortExport> NativeExports,

``````````

</details>


https://github.com/llvm/llvm-project/pull/81600