<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/64435>64435</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [x86_64/GlobalISel] Returning `half` type causes error "Cannot emit physreg copy instruction"
        </td>
    </tr>

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

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

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

<pre>
    ## Description

Returning `half` type will crash the `x86_64` Global ISel backend with `LLVM ERROR: Cannot emit physreg copy instruction`.

The problem does not exist with `i686` or `aarch64`.
The problem also does not exist when not using Global ISel.

## Minimal Reproduction

https://godbolt.org/z/G1rszzf1n

### Code

```ll
define half @f(ptr %0) {
  %h = load half, ptr %0
 ret half %h
}
```

### Stack Trace

```console
LLVM ERROR: Cannot emit physreg copy instruction
PLEASE submit a bug report to https://github.com/llvm/llvm-project/issues/ and include the crash backtrace.
Stack dump:
0.      Program arguments: /opt/compiler-explorer/clang-assertions-trunk/bin/llc -o /app/output.s -x86-asm-syntax=intel -mtriple=x86_64 --global-isel <source>
1.      Running pass 'Function Pass Manager' on module '<source>'.
2.      Running pass 'Post-RA pseudo instruction expansion pass' on function '@f'
 #0 0x0000000003398418 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x3398418)
 #1 0x0000000003395d0c SignalHandler(int) Signals.cpp:0:0
 #2 0x00007f6d11af4420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #3 0x00007f6d115b700b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #4 0x00007f6d11596859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #5 0x0000000000695331 (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x695331)
 #6 0x00000000032ee9e8 (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x32ee9e8)
 #7 0x0000000001d4ef15 llvm::X86InstrInfo::copyPhysReg(llvm::MachineBasicBlock&, llvm::MachineInstrBundleIterator<llvm::MachineInstr, false>, llvm::DebugLoc const&, llvm::MCRegister, llvm::MCRegister, bool) const (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x1d4ef15)
 #8 0x0000000002937b38 llvm::TargetInstrInfo::lowerCopy(llvm::MachineInstr*, llvm::TargetRegisterInfo const*) const (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2937b38)
 #9 0x000000000253ff67 (anonymous namespace)::ExpandPostRA::runOnMachineFunction(llvm::MachineFunction&) ExpandPostRAPseudos.cpp:0:0
#10 0x0000000002680049 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#11 0x0000000002bf8bb9 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2bf8bb9)
#12 0x0000000002bf8df1 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2bf8df1)
#13 0x0000000002bf9612 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2bf9612)
#14 0x000000000075e092 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#15 0x000000000069a7e6 main (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x69a7e6)
#16 0x00007f6d11598083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#17 0x0000000000754a4e _start (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x754a4e)
Program terminated with signal: SIGSEGV
Compiler returned: 139
```
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJy8WF9v6joS_zTmxQI5zv8HHiiUcyud6lb06GrfkJNMEu9x7Mh2tnA-_cpJaBPKrrpn0a3aAvbkN7_54xkPzBheSYA1Ch9QuFuwztZKr_9gv857bupFporzGlEfUR_vwOSat5YricgOkc3w_wC205LLCqOI1EyUKCLYnlvAb1wInGtmamxrcNunJDpGgRP4JlTGBH56BYEzlv8EWeA3bmsn9f37X8_48XD484D8Dd4yKZXF0HCL2_psNFQ4V-0Zc2ms7vKeT0RWU04_asCtVpmABhcKDO4RTtzYdyU8SiJHRGn3iTGd1z2z1WcEJoz6BFOD7D92xpk-MWdGZHTdM5e8YQIfoNWqGDlPxGprW4P8DaJ7RPeVKjIl7ErpCtH9L0T33zxtfv0qPfkZ28FvVQGznYgMv0IMCwWUXAJ20cEoICWiSWs1RjQkiKYYxQ-DHHZLNUb-DgvFiv4BRLf4XXiQ0mBHLBrWo8p4d6X7NtVXy_Kf-Idm-W3GuZJGiXHvNxKhf-7l--Pm9RGbLnOyDGddhTW0SltsFb5yNrd1l61y1SC6F-Jfl5dlq9U_IbeI7rkxHRhE95jJAnOZi66APqWH5Hb5a51FY-gHG4uuaZ2WfsmlVfqiVaVZg5muugakdSQwonvVOi25alouQC_h1AqlQbs1wWS1ZMaAdtaZpdWd_InoPuOy55njpXIQrG0dUGfbzq4MXp6SaMlMszRnadkJ-TsuLQi8bKzmrQDk74ajiJfLqk_dJTcgMPK3RnU6B-Q_DsQ9R_zQyf6At8wYjGi872TvbfziFp6ZZJWjG2MlcaOKToCTmoHReHQOvQX4ooxdHja4NdAVahpQDKeWSePeOeFRSXkh4NT0-RyPqYmoTzA5kcuP76dJ4CW4j6y_Qf7GnM3w5kVzaftYDelIkw8hzd6OylgNrEE0ckeAS9sfFZr8nxFD9IGcRlqIph-8vSveYUFy_MorycQfTBbC4ScjjWHZrPLW5Rjp_96B6AgUl1HheawMAkrw8ajBWKXhqO1oheAZovshEZaCy-60rGQ3bLS21sCKlVEr0jP2HMqMrz9TE2YxIRnWjBv4An7ukKMeOfAJyWbIwRw5jZIwxSxTX2I-QaY0CdMZcjj1MYnS0Pe9e8V0QJupi2YhpQApJHdLoQFupi-e6vOKAEovnKT-P5LoyR2tJ1mqYcXVz5f6bA5QzfL_meU1l_DADM8fhMp_jqfgk0SP99C59HyyoJlVGvnb22IOoGTCDAVhCraDrKu-qxy78m8_69oeoOLGgv5v65lSwp2NHuNeXh6dOPNyMvUyTf0486cF5gfTFdgrRwv1Bnqr2vMtN4_e2cytG3AuFjqoi3s2dzdztGJmZjozM_TLMoqdPiaVPDeqM1iyBkzb18504PzoqnXhyvlhM1bSTv4pRzsvfeOWDz72ImfdFOil7wo3ip0rmrNqT6OEkCD9nKYXdNewJrxuErpigmiyapm2q_6qdAPvNq9ZNadZmWTZlNf-xT16aZ3_M6O7xHwg9R5zx5pesy5K7wusn_umPw_ruHRvxkXpzRj7V4zTyKMTxgIqlp_Hhv_B_alpxTv_v4O3ozXjHcw6URwCSSkedby7M6_ZUBeuSoO7GG-VtHCyI1Mh8tt5eN3xWAwRbhiX92t7DnJmW3TVvxOS-Ph4dM35aCzT9jgh8NVeHpDEn2mJrzwYsADwgH8v2wbQd62XC7wF3XDJLIwzq-lvY-42__r07fXx21-D-HZU7OalTksonITnp1cjz6JY-0Xqp2wBay9KPS8OSUAX9bpgZZGUJCRZ6WchpGWSsSQkNKYlCbIwXPA1JdQnCQm8xD2zStI4C8HzUhYmSeqFKCDQMC5WLnXcPLnoZ5l1FAR-uBAsA2H60Z9SCW-430SUonC30Ot-Csq6yqCACG6s-UCx3Ir-O4NxoKf7YQB28y8Kd_g_fyeQs86AwaC1G7wp_dJQR-mi02L9-4Nbb--_AwAA__9vgifc">