<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126943>126943</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [RISCV] Miscompile caused by #126108 (Decompose single source shuffles (without exact VLEN))
        </td>
    </tr>

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

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

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

<pre>
    There's active discussion on #126108, so this issue is written with some haste to provide a clear reproducer an doesn't have in-depth analysis and hasn't further reduced the input.

The simplest reproducer:
```
wget https://raw.githubusercontent.com/llvm/llvm-test-suite/refs/heads/main/SingleSource/Regression/C/gcc-c-torture/execute/20050826-2.c
$HOME/llvm-project/build/stage1/bin/clang \
  --target=riscv64-linux-gnu \
  -fuse-ld=lld \
 --sysroot=$HOME/rvsysroot \
  -O3 \
  -march=rva23u64 -mllvm -force-tail-folding-style=data-with-evl -mllvm -prefer-predicate-over-epilogue=predicate-else-scalar-epilogue \
 20050826-2.c
export QEMU_LD_PREFIX="$HOME/rvsysroot"
export QEMU_CPU="rv64,zba=true,zbb=true,zbc=false,zbs=true,zfhmin=true,v=true,vext_spec=v1.0,zkt=true,zvfhmin=true,zvbb=true,zvkt=true,zihintntl=true,zicond=true,zimop=true,zcmop=true,zcb=true,zfa=true,zawrs=true,rvv_ta_all_1s=true,rvv_ma_all_1s=true,rvv_vl_half_avl=true"
```
</pre>
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