<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJytVUuP2zYQ_jXyZWBBoh62Djrsxt0g6LYo0uRc8DGS2KVFgaS82f76Dml766TpIUkNeSTNkJ_m9Q2FVS_9hwkhoA8guUfgAaYQFp9Vdxl7oGvUPuSjDtMqcmmPpJn1k5Z0L0QzDLsdFztW7-u2RdGwRnVVjd1eCBTwPOEMbp0hTM6u4wRZWxgjYXtCp4eX7ZHLSc-oZx-cJxs49KsJHvQMHNIijQ7QOeuiP8UhK66yLS7X-ZVdLrjnCi64IK1C2gcfvZ5H4DOss8KBLAqW6cVryQ19MgZIX3mFOCNuYVhnGbSdIwL9nu1R8HA1Ck7bQRgrn6I9Y40QeQlCVPS8Lz7t6k5Jvs9Yd92RolxfEe8__np4_An0cTFa6rAlx0AhOZ-xWgcfeMCMvfncTibX3mrhSRuDaY9cvPvMFBcX_7HYNf9auo8ahWIdtxQUj26SvqzqMqvuKZPHRRt0Wxeo8EYLkp7POui_0P1B1iNFdasSOpxQBuvyiaItIKuLrPlhHFbUUVb_F1xDwd013492Gh1fpoTVMBJ7yJrD9X8tvF3Q8VlBfW6kr5fjq02d5IOzR2IS8fIdMZS4hMbEWgWirfZ-jZK62FDDKAg2wcJg-AiD_rQukUuL9WH7_g4MdTp4OaFaTWSEskQSsn9J-BuuG3O63raLs39S8uiV-j4mR7KBCVG0rdhXTVMqUQ2drJgqakWqgsuO1x1v1Q1OSuob4uVbjLn8_ewMHu7evktTIJfLkrHqsSyrbkuyqXJ4sC5FK4i-hhwOHs2QUmDH0eDPFLCPSSA6x4Q-k__AlfpgH_UJ3-NIoR0GbnwiVKxEBLOzeYHVp_hvwT1NnkSDW8JS_rWcotE_6WVBFZG8TRuRAM9zK9pDLFRUv84VUs420ExyT-Qc91SFE766cfksgXigYq3nSXXtjStIvlF9RZO14xu-hsm6Ps3gzepM_83FS03j6aFh-3K3mfpdVxS8YTW2u323wzjGy5qLYVADVRdxY7hA43viSMbYjM_nvqNn6vLNj3uge1awsmSsLLqaNXVeYEutU5ZdKXdt3QniJx65NnnEya0bN65PkFQmT8bY1_4fI_dejzNicpg8DDoY7H-5HArnY-Uy4dLRAnyIhfqNWPIFSdBtkq99cvRvRSVYoA>52817</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Machine verification error after PostRA list scheduler
        </td>
    </tr>

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

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

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

<pre>
    The test case at https://gist.github.com/nikic/0b5ff77ab7248466eb525d934e98bbeb when run through `llc -verify-machineinstrs` results in a verifier error:

```
*** Bad machine code: Using an undefined physical register ***
- function:    wombat
- basic block: %bb.1 bb3 (0x749dca8)
- instruction: BUNDLE implicit-def dead $itstate, implicit-def $r6, implicit killed $cpsr, implicit $r0, implicit killed $r5, implicit $r8, debug-location !341; compiler-rt/lib/sanitizer_common/sanitizer_bitvector.h:0 @[ compiler-rt/lib/sanitizer_common/sanitizer_bitvector.h:204:23 @[ compiler-rt/lib/sanitizer_common/sanitizer_bitvector.h:251:5 @[ compiler-rt/lib/sanitizer_common/sanitizer_bvgraph.h:52:8 ] ] ]
- operand 4:   implicit killed $r5
```

>From what I can tell, the issue is related to kill flag fixup in post-RA list scheduling done in https://github.com/llvm/llvm-project/blob/c2f2bb066b83551db3f9c32d04d6b80ac9a49a6d/llvm/lib/CodeGen/ScheduleDAGInstrs.cpp#L1139-L1153. For the bundle itself, toggleKills is called with addToLiveRegs=false, and the only use in the bundle is a debug instruction which is skipped, so the end result is that the register is not marked as live and the bundle ends up using a killed register.
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJytVUuP2zYQ_jXyZWBBoh62Djrsxt0g6LYo0uRc8DGS2KVFgaS82f76Dml746TJIW0NeSTNkB_n9Y2EVS_9hwkhoA8guUfgAaYQFp9Vdxl7oGvUPuSjDtMqcmmPpJn1k5Z0L0QzDLsdFztW7-u2RdGwRnVVjd1eCBTwPOEMbp0hTM6u4wRZWxgjYXtCp4eX7ZHLSc-oZx-cJxs49KsJHvQMHNIijQ7QOeuiP8UhK66yLS7X-ZVdLrjnCi64IK1C2gcfvZ5H4DOss8KBLAqW6cVryQ0dGQOkU14hzohbGNZZBm3niEC_Z3sUPFyNgtN2EMbKp2jPWCNEXoIQFT3vi0-7ulOS7zPWXXekKNdXxPuPvx4efwJ9XIyWOmzJMVBIzmes1sEHHjBjb760k8m1t1p40sZg2iMX774wxcXFdxa75h9L91GjUKzjloLi0U3Sl1VdZtU9ZfK4aINu6wIV3mhB0vNZB_0Xuj_IeqSoblVChxPKYF0-UbQFZHWRNf8ZhxV1lNX_BddQcHfNv0c7jY4vU8JqGIk9ZM3h-r8W3i7o-KygPjfSt8vxzaZO8sHZIzGJePmOGEpcQmNirQLRVnu_RkldbKhhFASbYGEwfIRBf1qXyKXF-rB9fweGOh28nFCtJjJCWSIJ2b8m_A3XjTldb9vF2T8pefRKfR-TI9nAhCjaVuyrpimVqIZOVkwVtSJVwWXH64636gYnJfUN8fItxlz-fnYGD3dv36UpkMtlyVj1WJZVtyXZVDk8WJeiFURfQw4Hj2ZIKbDjaPBnCtjHJBCdY0KfyX_gSn2wj_qE73Gk0A4DNz4RKlYigtnZvMDqU_y34J4mT6LBLWEp_1pO0eif9LKgikjepo1IgOe5Fe0hFiqqX-cKKWcbaCa5J3KOe6rCCV_duBxLIB6oWOt5Ul174wqSb1Rf0WTt-CboYLD_5TLhzjPyQtc0J4EP8dTfqORfVRzdZnWm_-Fipybz9NCwfbnbTH077JpW7TjreFm1O94UlWB1hzS-di22amO4QON74lTG2IzP5z6lZ2LFRvesYGXJWFl0NWvqvMCWGqUsu1Lu2roTxEY8cm3y6Edu3bhxfXKJiuLJGGPyn43cez3OiOk4wudrmKzr00dqkw7uk-N_AwmoQqE">