<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/56733>56733</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            possible zext-related miscompile with global isel on AArch64
        </td>
    </tr>

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

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

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

<pre>
    hi folks, we're pretty sure this is a miscompile, since the argument/return register can contain junk in bits 1..7, right?

```
Johns-MacBook-Pro:~ regehr$ cat foo.ll
define i8 @f(i1 %0) {
  %2 = zext i1 %0 to i8
  ret i8 %2
}
Johns-MacBook-Pro:~ regehr$ ~/llvm-project/for-alive/bin/llc -global-isel foo.ll -o -
        .section        __TEXT,__text,regular,pure_instructions
        .build_version macos, 12, 0
        .globl  _f                              ; -- Begin function f
        .p2align        2
_f:                                     ; @f
        .cfi_startproc
; %bb.0:
        ret
        .cfi_endproc
                                        ; -- End function
.subsections_via_symbols
Johns-MacBook-Pro:~ regehr$ 
```

cc @ornata @nunoplopes @ryan-berger @nbushehri @aemerson
</pre>
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