[lld] [lld][WebAssembly] Don't export deps for unused stub symbols (PR #173422)

[Heejin Ahn via llvm-commits]

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@@ -16,6 +16,23 @@
 # RUN: wasm-ld %t.o %t/libfoo.a %p/Inputs/stub.so -o %t2.wasm
 # RUN: obj2yaml %t2.wasm | FileCheck %s
 
+## The function `foo` is declared in stub2.so and depends on `baz`, and both
+## `foo` and `baz` are defined in an LTO object. When `foo` and `baz` are
+## DCE'd and become undefined in the LTO process, wasm-ld should not try to
+## export the (nonexistent) `baz`.
+
+# RUN: llvm-mc -filetype=obj -triple=wasm32-unknown-unknown -o %t.o %s
+# RUN: mkdir -p %t
+# RUN: llvm-as %S/Inputs/foobaz.ll -o %t/foobaz.o
+# RUN: wasm-ld %t.o %t/foobaz.o %p/Inputs/stub2.so -o %t.wasm
+# RUN: obj2yaml %t.wasm | FileCheck %s --check-prefix=UNUSED
+
+## Run the same test but with foobaz.o inside of an archive file.
+# RUN: rm -f %t/libfoobaz.a
+# RUN: llvm-ar rcs %t/libfoobaz.a %t/foobaz.o
+# RUN: wasm-ld %t.o %t/libfoobaz.a %p/Inputs/stub2.so -o %t2.wasm
+# RUN: obj2yaml %t2.wasm | FileCheck %s --check-prefix=UNUSED
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aheejin wrote:

Then it can't be `foo` because `foo` is already being used in `stub.so` and I need a symbol that's not used anywhere. Anyway, I will remove `foo.ll` and create another file that contains all functions we need then.

https://github.com/llvm/llvm-project/pull/173422