[llvm-bugs] [Bug 50938] New: [WebAssembly] imports not de-duplicated between different languages

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=50938

            Bug ID: 50938
           Summary: [WebAssembly] imports not de-duplicated between
                    different languages
           Product: lld
           Version: unspecified
          Hardware: All
                OS: All
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: wasm
          Assignee: unassignedbugs at nondot.org
          Reporter: fitzgen at gmail.com
                CC: llvm-bugs at lists.llvm.org, sbc at chromium.org

## Steps to Reproduce

* Ensure you have Rust toolchain that can target `wasm32-wasi`:

  ```
  $ rustup target add wasm32-wasi
  ```

* Ensure you have a C toolchain that can target `wasm32-unknown-wasi`. Multiple
ways to do this, easiest is via
[wasi-sdk](https://github.com/WebAssembly/wasi-sdk).

* Clone https://github.com/fitzgen/lld-dupe-import and `cd` into it.

* Build:

  ```
  $ CC=path/to/wasi-sdk/bin/clang \
    SYSROOT=path/to/wasi-sdk/share/wasi-sysroot \
    RANLIB=path/to/wasi-sdk/bin/ranlib \
    cargo build --target wasm32-wasi
  ```

* Inspect the built `.wasm` file's imports:

  ```
  $ wasm-objdump -x -j Import target/wasm32-wasi/debug/lld_dupe_import.wasm
  ```

## Expected Results

`"wasi_snapshot_preview1" "fd_write"` is imported once.

## Actual Results

`"wasi_snapshot_preview1" "fd_write"` is imported twice (functions 0 and 5):

```
lld_dupe_import.wasm:   file format wasm 0x1

Section Details:

Import[8]:
 - func[0] sig=7
<_ZN4wasi13lib_generated22wasi_snapshot_preview18fd_write17h133cd9fedd86597bE>
<- wasi_snapshot_preview1.fd_write
 - func[1] sig=0 <__wasi_proc_exit> <- wasi_snapshot_preview1.proc_exit
 - func[2] sig=3 <__wasi_environ_sizes_get> <-
wasi_snapshot_preview1.environ_sizes_get
 - func[3] sig=3 <__wasi_environ_get> <- wasi_snapshot_preview1.environ_get
 - func[4] sig=8 <__wasi_fd_seek> <- wasi_snapshot_preview1.fd_seek
 - func[5] sig=7 <__wasi_fd_write> <- wasi_snapshot_preview1.fd_write
 - func[6] sig=9 <__wasi_fd_close> <- wasi_snapshot_preview1.fd_close
 - func[7] sig=3 <__wasi_fd_fdstat_get> <- wasi_snapshot_preview1.fd_fdstat_get
```

## Additional Information

This test case links C into a Rust project. I've also reproduced this by
linking Rust into a C project. I assume other languages linked together with
`wasm-ld` would have the same issue?

I can't find any `wasm-ld` CLI flags that seem to control this.
Enabling/disabling LTO and GC sections, for example, doesn't make a difference.

I assume that this is not specific to WASI imports, but I haven't tried
reproducing without WASI.

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