[lld] [lld-macho] Implement ObjC category merging (-objc_category_merging) (PR #82928)

[via llvm-commits]

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+# REQUIRES: aarch64
+# RUN: rm -rf %t; split-file %s %t && cd %t
+
+## Create a dylib to link against(a64_file1.dylib) and merge categories in the main binary (file2_merge_a64.exe)
+# RUN: llvm-mc -filetype=obj -triple=arm64-ios-simulator -o a64_file1.o a64_file1.s
+# RUN: ld64.lld a64_file1.o -o a64_file1.dylib -dylib -arch arm64 -platform_version ios-simulator 14.0 15.0
+
+# RUN: llvm-mc -filetype=obj -triple=arm64-ios-simulator -o a64_file2.o a64_file2.s
+# RUN: ld64.lld -o a64_file2_no_merge.exe a64_file1.dylib a64_file2.o -arch arm64 -platform_version ios-simulator 14.0 15.0
+# RUN: ld64.lld -o a64_file2_merge.exe -objc_category_merging a64_file1.dylib a64_file2.o -arch arm64 -platform_version ios-simulator 14.0 15.0
+
+# RUN: llvm-objdump --objc-meta-data --macho a64_file2_no_merge.exe | FileCheck %s --check-prefixes=NO_MERGE_CATS
+# RUN: llvm-objdump --objc-meta-data --macho a64_file2_merge.exe | FileCheck %s --check-prefixes=MERGE_CATS
+
+
+MERGE_CATS: __OBJC_$_CATEGORY_MyBaseClass_$_(Category02|Category03)
+MERGE_CATS: instanceMethods
+MERGE_CATS-NEXT: 24
+MERGE_CATS-NEXT: 4
+MERGE_CATS: classMethods
+MERGE_CATS-NEXT: 24
+MERGE_CATS-NEXT: 4
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alx32 wrote:

TODO: add more checks

https://github.com/llvm/llvm-project/pull/82928