<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/95928>95928</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang-19 crashed: fatal error: error in backend: Stack realignment in presence of dynamic allocas is not supported withthis calling convention.
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          iamanonymouscs
      </td>
    </tr>
</table>

<pre>
    Clang-19 crashed when attribute `preserve_none` is enabled and compiled with `-fsanitize=address`.

Compiler explorer(assertion trunck): https://godbolt.org/z/sar6bcP3d
```
$cat mutant.c
void a();
__attribute__((preserve_none)) int b() {
  int c;
  a(&c);
}

$clang-19 -fsanitize=address mutant.c
mutant.c:4:4: warning: passing arguments to 'a' without a prototype is deprecated in all versions of C and is not supported in C23 [-Wdeprecated-non-prototype]
    4 |   a(&c);
      | ^
mutant.c:5:1: warning: non-void function does not return a value [-Wreturn-type]
    5 | }
      | ^
fatal error: error in backend: Stack realignment in presence of dynamic allocas is not supported withthis calling convention.
clang-19: error: clang frontend command failed with exit code 70 (use -v to see invocation)
Ubuntu clang version 19.0.0 (++20240301064251+dd426fa5f931-1~exp1~20240301184412.1845)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-19/bin
clang-19: note: diagnostic msg: 
********************

PLEASE ATTACH THE FOLLOWING FILES TO THE BUG REPORT:
Preprocessed source(s) and associated run script(s) are located at:
clang-19: note: diagnostic msg: /tmp/mutant-e3f4cd.c
clang-19: note: diagnostic msg: /tmp/mutant-e3f4cd.sh
clang-19: note: diagnostic msg: 

********************
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzEVU1v2zgT_jX0ZSBDoj4sHXyw46gtELwp2hQ9BiNyJPOtRAok5SQ99LcvKNlut-kCi-0CGyiyOOR8Pc8MB51TnSbasnzP8sMKJ380dqtwQG30y2AmJ9yqMfJle9Oj7qKkAmHRHUnC05E0oPdWNZMnYEU8WnJkT_SojSZWxKAckMamJwmoJQgzjCosnpQ_BoWodaiVV1-JpQeU0pJzrIjXLD6weLe8bxYlC_Q89saSZbxE58h6ZTR4O2nxhfGKpTs4ej86lu4YrxmvOyMb0_u1sR3j9VfGa4e2aMT7VJ7tF_H5WZY8E-hhmDxqvxaL8GSUBGS8nF3sF-Hj4zXtx8d5r_xz6rxivAKlPTSLKrDNWRdmsbjagrP1QvzogW0OP2IQQrvA_yvMfgr6ukp32fkfntBqpbvwOQbWdQdou2kg7R14A4xvkPHNTI2ZPCCM1njjX0YKNEoaLQn0JEFpwL6HE1mnjHZgWriZ6VUOtPHgpnE09nzyhqfA8n30-buBSBsdXY2z_HABAiADtrmBX0MC81_YZ_ntqzxzlu6Sn_IMfmb-2kmLuVqkoSVGS36yGhBO2E-0RLjIoldB5YvTzeEv42jRYw9krbHB7_wRkm9QfCEtg-yjR_EFLGGvOh1AD_tz0WhBAUL5onFQIkBrBLrXYAZi_FE5ENj3gT5h9Il0yOvcL5cSucYQPmYhtNZoT0sLDoGrFr83Ij0rD8JIgk0MjJeTI4hOoSgcESh9MgKDm8DG7OhTM2k_nU2f6wCSah2vZ33G94zvecyzOI2TuMh4njC-lzLjRYt5W6VJlHyj5zH5djmUlFmW8HVSZvnVywPajnzI4bksHossGkXUKz09R52ezkeOllDCYCT1c2Ubp56XrXfaeex7kgc148B4PTnLeN2rJrz70xCg4nWj9Gv4tPEUfqXCThvnlYDBzUV1acjfeH5o7Pd3t7uPt7B7eNjdvIWHt7dQ39_d3X9-9783UL-7u_0ID_ezeP_pDXy4fX__4SHcb4uupdEaQc6RBGcmK4jx0oXbJjCMzhmh5o61kwYnrBr99YAlCHUWdtFfTf5NCHjth5Hxeum_iNI2E_Jy-fyWDXf8B1z8W4xcxsFKblNZpRWuaJtsknKTlFWRrI7bpC1ku8E2ydMy3eQVNpIyLKjiWCRN3q7Udi7oIimTNC_iZC3yPMkykRaSGlmgZFlMA6p-HeovTKaVcm6ibZVXvFz12FDv5lnMuaYnmDcZ52E02-1cs83UOZbFvXLefbfile_p1YgOGP3nd9Nqsv32p8ms_HFq1sIM5068NORozf9JeMbrOXPHeL0gc9ryPwIAAP__I8Km2g">