<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/83403>83403</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [X86] Failure to create load-ext + trunc-store on avx512 target
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            backend:X86,
            missed-optimization
      </td>
    </tr>

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

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

<pre>
    ```ll
define void @cast_i16x4_to_u8x4(ptr %a0, ptr %a1) {
  %1 = load <4 x i16>, ptr %a1
  %2 = trunc <4 x i16> %1 to <4 x i8>
  store <4 x i8> %2, ptr %a0
  ret void
}
```
llc -mcpu=x86-64-v4
```asm
cast_i16x4_to_u8x4:                     # @cast_i16x4_to_u8x4
        vmovq   (%rsi), %xmm0                   # xmm0 = mem[0],zero
        vpmovwb %xmm0, %xmm0
        vmovd   %xmm0, (%rdi)
        retq
```
This could be performed as:
```asm
cast_i16x4_to_u8x4:                     # @cast_i16x4_to_u8x4
        vpmovsxwd       (%rsi), %xmm0
 vpmovdb %xmm0, (%rdi)
        retq
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy8VEFzmzwQ_TXLRYNHLAjDgYMdPl--W9tDbxmBZFutZDmSIDS_voOwkzh1Lj1U4xkj6e3bfW94cO_V4SRlA2wLrE34EI7WNV_-_6qMPSWdFb8aKOny0xpoC3Qj5F6dJBmtEgQK2nMfHlVWTsVjsI9DNRWA1Tk4Asg4BXwg100GWBNYbxcaMp9lBPKWaMsFgfyhIBNRWQn5f7dlb3iM-OCGU39bsJAF-3pazSyXQh-skzc3ket9E3rFOhmitGUP6_bycHVh2Wrdk9T05wHydqrKtCzSsfiA5N4sJ3ccyjfk3gLMP7H0Mt2yRmPHpwivAJnzCrCexQCyyRj6CXG8mu0z0gDbUmAt4MOLdPYD-9nY8bm7sr0j_nMKEbnf4eJAIg50A3YyPN118ttRedLbQQvSSXKWbm-dkYJwD_nm3zk6a_bTs3gtu-vspSiiRffXyhPR5KLOa57IJlvTGimymibHhnJeZNjJer_mjPWU8p7tiz3N8n1d9IIlqkGKBUWsM4o1o6uy67BeZ1itu7KnlYSCSsOVXmk9mpV1h0R5P8imyguaJ5p3UvuYdsSO9z_lSUC--V6VgHMcANEo76VI7Tkoo154UPY037E2cc3MmXbDwUNBtfLBv3UJKuj4GZm5WEt2XOnByTmRvZM8yBjyVE6BAG6XBKdLLu2J8HFiGZLA3UGGZHC6OYZwjm8A7gB3BxWOQ7fqrQHczT0vf-nZ2R-yD4C7KNMD7qLS3wEAAP__SYxSvQ">