<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/90403>90403</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [WebAssembly] Support `tailcc` calling convention in wasm backend
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          8051Enthusiast
      </td>
    </tr>
</table>

<pre>
    Currently, llvm's wasm backend does not support the `tailcc` calling convention even when tail calls are supported.
I thought about making a PR that just adds it to the `callingConvSupported` function, but then I wasn't sure if it should handle the absense of the tail-call feature or fast-isel not emitting tail calls.

Example program:
```
target triple = "wasm32-unknown-unknown"
declare tailcc void @void_nullary()

define void @tailcc_tail_call_void_nullary() {
  tail call tailcc void @void_nullary()
  ret void
}
```
`llc` output:
```
error: <unknown>:0:0: in function tailcc_tail_call_void_nullary void (): WebAssembly doesn't support language-specific or target-specific calling conventions yet
```
</pre>
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