<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/68770>68770</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            WebAssembly backend assertion failure with unreachable
        </td>
    </tr>

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

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

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

<pre>
    This code:
```llvm
target triple = "wasm32-unknown-unknown"

declare void @llvm.trap() cold noreturn nounwind
declare i32 @return_i32()
declare void @take_i32(i32)

define void @assert_fail() {
  %a = call i32 @return_i32()
  call void @llvm.trap()
  call void @take_i32(i32 %a)
  ret void
}
```
causes an assertion failure:
```
llc: /root/llvm-project/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp:168: void query(const llvm::MachineInstr&, bool&, bool&, bool&, bool&): Assertion `!MI.isTerminator()' failed.
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 <source>
1.      Running pass 'Function Pass Manager' on module '<source>'.
2.      Running pass 'WebAssembly Register Stackify' on function '@assert_fail'
 #0 0x00000000034145c8 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x34145c8)
 #1 0x0000000003411cfc SignalHandler(int) Signals.cpp:0:0
 #2 0x00007f9f6cda2420 __restore_rt (/lib/x86_64-linux-gnu/libpthread.so.0+0x14420)
 #3 0x00007f9f6c86500b raise (/lib/x86_64-linux-gnu/libc.so.6+0x4300b)
 #4 0x00007f9f6c844859 abort (/lib/x86_64-linux-gnu/libc.so.6+0x22859)
 #5 0x00007f9f6c844729 (/lib/x86_64-linux-gnu/libc.so.6+0x22729)
 #6 0x00007f9f6c855fd6 (/lib/x86_64-linux-gnu/libc.so.6+0x33fd6)
 #7 0x0000000001ac853e query(llvm::MachineInstr const&, bool&, bool&, bool&, bool&) WebAssemblyRegStackify.cpp:0:0
 #8 0x0000000001ac924f isSafeToMove(llvm::MachineOperand const*, llvm::MachineOperand const*, llvm::MachineInstr const*, llvm::WebAssemblyFunctionInfo const&, llvm::MachineRegisterInfo const&) (.isra.0) WebAssemblyRegStackify.cpp:0:0
 #9 0x0000000001acc728 (anonymous namespace)::WebAssemblyRegStackify::runOnMachineFunction(llvm::MachineFunction&) WebAssemblyRegStackify.cpp:0:0
#10 0x00000000026f1e21 llvm::MachineFunctionPass::runOnFunction(llvm::Function&) (.part.0) MachineFunctionPass.cpp:0:0
#11 0x0000000002c70009 llvm::FPPassManager::runOnFunction(llvm::Function&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2c70009)
#12 0x0000000002c70241 llvm::FPPassManager::runOnModule(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2c70241)
#13 0x0000000002c70a62 llvm::legacy::PassManagerImpl::run(llvm::Module&) (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x2c70a62)
#14 0x0000000000760e52 compileModule(char**, llvm::LLVMContext&) llc.cpp:0:0
#15 0x000000000069ec46 main (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x69ec46)
#16 0x00007f9f6c846083 __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24083)
#17 0x00000000007577ee _start (/opt/compiler-explorer/clang-assertions-trunk/bin/llc+0x7577ee)
Program terminated with signal: SIGSEGV
Compiler returned: 139
```
[Godbolt link](https://godbolt.org/#g:!((g:!((g:!((h:codeEditor,i:(filename:'1',fontScale:14,fontUsePx:'0',j:1,lang:llvm,selection:(endColumn:25,endLineNumber:7,positionColumn:25,positionLineNumber:7,selectionStartColumn:25,selectionStartLineNumber:7,startColumn:25,startLineNumber:7),source:'target+triple+%3D+%22wasm32-unknown-unknown%22%0A%0Adeclare+void+@llvm.trap()+cold+noreturn+nounwind%0Adeclare+i32+@return_i32()%0Adeclare+void+@take_i32(i32)%0A%0Adefine+void+@assert_fail()+%7B%0A++%25a+%3D+call+i32+@return_i32()%0A++call+void+@llvm.trap()%0A++call+void+@take_i32(i32+%25a)%0A++ret+void%0A%7D'),l:'5',n:'0',o:'LLVM+IR+source+%231',t:'0')),k:28.102455380752453,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:compiler,i:(compiler:llc-assertions-trunk,deviceViewOpen:'1',filters:(b:'0',binary:'1',binaryObject:'1',commentOnly:'0',debugCalls:'1',demangle:'0',directives:'0',execute:'1',intel:'0',libraryCode:'0',trim:'1'),flagsViewOpen:'1',fontScale:14,fontUsePx:'0',j:2,lang:llvm,libs:!(),options:'___+',overrides:!(),paneName:'+llc+wasm',selection:(endColumn:1,endLineNumber:1,positionColumn:1,positionLineNumber:1,selectionStartColumn:1,selectionStartLineNumber:1,startColumn:1,startLineNumber:1),source:1),l:'5',n:'0',o:'+llc+wasm',t:'0')),k:24.857851593775443,l:'4',n:'0',o:'',s:0,t:'0'),(g:!((h:output,i:(compilerName:'llc+(assertions+trunk)',editorid:1,fontScale:14,fontUsePx:'0',j:2,wrap:'1'),l:'5',n:'0',o:'Output+of+llc+(assertions+trunk)+(Compiler+%232)',t:'0')),k:47.03969302547212,l:'4',n:'0',o:'',s:0,t:'0')),l:'2',n:'0',o:'',t:'0')),version:4)

It seems like [this line in WebAssemblyRegStackify::runOnMachineFunction calls isSafeToMove()](https://github.com/llvm/llvm-project/blob/bccf2c8468e2f364f8c364d613ffb78d61b67ceb/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp#L878C44-L878C44)
which [calls query() in two places](https://github.com/llvm/llvm-project/blob/bccf2c8468e2f364f8c364d613ffb78d61b67ceb/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp#L399C3-L399C8)
which has the line [`assert(!MI.isTerminator());`](https://github.com/llvm/llvm-project/blob/bccf2c8468e2f364f8c364d613ffb78d61b67ceb/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp#L168C25-L168C25)
which trips over the fact that unreachable (what `@llvm.trap()` is compiled to) [is defined as a terminator](https://github.com/llvm/llvm-project/blob/bccf2c8468e2f364f8c364d613ffb78d61b67ceb/llvm/lib/Target/WebAssembly/WebAssemblyInstrControl.td#L109C9-L109C9)
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzUWVtz4ygW_jXkhbJLAl0f8hA7ndlUdSapTu_sowshZDNBoAWUy7_fAmRHsuWeZKZ3a2dqOjJwOOc7Fz4BIsbwrWTsEqQrkF5fkN7ulL5sye9kRy4qVb9dft9xA6mqGcBXILoG0RXIovC_EM9t6LJEb5mFVvNOMAjwNQQIvRDTYrTo5ZNUL3L_BAgNavzfmlFBNIPPitcQJF7n0mrSAVQAVEKqRA2l0sz2WkKpevnCZT2dyzFyU4PMhmMU5s4bsOSJDTL-bzlF03D5LkuMYdpuGsLFAAfkqyAJIUAp8a5SIsSPMcAgc8bHWZkpTG9sJKqZ9ZID9vz6KDOhSUlvmIFEwuAIVxI6X3o9k8zQFIICfAUButFKWYBuHNZFp9XvjO6b7sErgG6--6wDdPMvVl0Zw9pKvE1b39j20RL6xJu3Je06gK_irHAGvJv_7pl-A6igShoLvWp8BfDVHaE7LtmtNFYDlAG0hpVS4mM_S6f-6uCv8wzFd7dLbr4z3XJJrNJD3FHuw8HqZXD-4euXq8cv0PRVyy0ksOq3ULNOaQutgjtrO-MAohuAbrbc7vpqSVU7iso0VtyYnhmAbiCRNeSSir5m0O4YpJqYHawIfbKaUDaY95GCdd92h-xESxCVD1ptNWkh0du-ZdKaIUOqc1aoajsumF6w104ozbTrE0RuF4ekm4XVvXwC6Kbi0uOkcKGcCtJ1TlFvu94uDVy8FtmCmHZh3qQlrwBfc2mZgACvjeo1ZQB_CcBiB-xbLyWXW9gRYyBA-U0vqQ_6g-u4I5JsHZwcKglbVfeOGlA-UYbywXk0p3BUSfAb23JjmYb7ghoUN3ujTvXRks2H9QIQjmD0Gu3_w0mcpLQYlZx5M-HHg-bSehPfXWoAKt6FNHnZKGM1I-1QdVxazwqunv5SPgBaRa8DrPd1DhCOj3DHtKHwkW8lEf8gshZOfzHACN1mWGmR_3dQhAZFeVM2Ga0JSlAENxvNjFWabbQdvAhL-7XINlmyEFz2r4ut7MNAZ3eakXpp1DLyiOMkQdEEL56YKbI0iiqoCTfsA_qp05x5zQmOomqiOZlqTpIiLSGp1IeQjzQjVKTlRHN6rDk_5PTDOnM01ZlNdaZpU2ef04lxU2cTnfm4FmJCixSzA4nO0yf03Pp5EoU_JPGj0iqOcJUoaSA3j6Rh39WdemZz8O47ph0vDgCvnP0_JzRx9Ehk5MaenW5loyZhOVG4p5ojSV8TS240cdX_uRCVRyGiOSqcOiKVfGtVb6AkLTOdp5zyBPtI_0BFvbyXA9y9Y3NRfh_7VFYd8UwYE2VNzFB8Gqu9AUf5I2izmI7AuGh2RNsQzRl987gmjIhoHkVROcJ18-Cm7l8-n0b0M3h8APW-t0Q4RseoURJ_APWdf21OMzt0_WzEKIkniPExYpKhEWLBtoQO1TjCftt24oD_f4KbZGiCOxnjjvIsYimCg41DOOmOaE8WR3zx9etvd2slLXvdr3kh6HwdphM7WcloksGWcPmznAsqJ74dvVWSLCow3Gzci2NjLNF2MwLw0XdXEhV4YiWfRjDNc8Zg0P-zfAtKD1b3W1w7bNFZDV-43UHjdzRuv_t4-8vjl19-C-LrwTAMxy1WO4kYl7NHGpCuflF1pYSFgssnkF4DVBxt5sP4Uumt78BbPxR7Z4vzjR3AV-5o_KXm_lSx5n60aLhgjs99K4_dRhStGyXtIyXC9cbJ0PFPwx5eg1gUxH53wwCtXRzdMvNHi7VhggWm8gaYrNdK9K1rohSgNZP1Vy7Zr31bef5wmjpluJsyldz3nogfTDy6RE8nTcdOp87MmBMs3cCw93cu2-EAuQoXBwCtAErxdXiev0BIEQIodbWaHs73AK38gRitZg7YaEWVcGP7iwT_c7hKmCrxR-7V3En-nLHTC4URtobLqfTJlUJwNl8Ns1aD8-64f4gGJUL8IbYwdxD9QSzOix57cgAynqV9wsKk4Gd-7SvXJVeEvKahlOWksFVoOYYFaHX7DaDVUAvBEB7WiR3PKoPeJ1dWxTKOUJKmuIjyFCUpfjeY_MBgaBhP3qfa1_NrOvDL-4o-9LgVSWf4bV2zZ07Zb5y93HdMTlc-F5bpQDdFNcFYcUn020Q6dN1X_hZhPEBV647_91K8TXTUrOq3ayKEmYjXrCVyK9hUlmu3kJ-ZmXSzV0Z7O-Urf_SfSAleaaLf1sNl4KHfat6Op7qwNoJszXw0Ps6D6IQHBa_MKFvOkup8IsLkzWbjy8nn_5lpzWt2PKEjkv16YGeAVuGl5NhmqJXzZBvPcG08x7XxOaqNz1Pt6dDpzNMJc3IToo0_vDZnYnF2NSbLIs2LNE5LnOdpkvz3VmO4njpdi-85DKDdceqwLv1Lxa_Mcihx_47m9RC2T1bhiyPQoxL_QEDvB-gr1Rxiex6mG1ofqCeQIjo4cC4TSb6McJmVOEJpkqMY_YxEjPxDf6hkbvIz0yasoOTojv3WQsNYa6DgTwyCdGV33DUkg1yeOaGeP_T6W3NzfNvgTM7t8_740rYSyu2aK0ob5DbYBUMNzpKmoDhL6izGTVPlRZ3FVZZTVv31K3GEvxZ5sU6SxfA8hOtlx-nOBSi4uL_ocYcSLqF9UbAThDLzN_IUl-UaL_yjOPJzR4y_G_eFANIVyIa9knf53A1-CbCT_BuFIM6KNUoXw_MoCG4fbKB7cflYNIRaaHfEwl5qRuiOVP4OvXhxfc7v0_1dFkH_wc7TSA2t8sftdMUNDNvRGhIDyeGopfT_a_D8vZ47jGsllrb2wYvKdbkID4DKi_oS1yUuyQW7jLMyj6KijOOL3WUV06QoG5bHaVOmtM7qNGZVmaZN3URJUV7wSxQhHEdxHOUoTuNlFaOYVVlVNFmBCUUgiVhLuFj6-Cq9vfCfcy6zIs-jC0EqJoz_aoqQZC_QDwKEQHp9oS99pKp-a1x-uLHmXYvlVrDL8YeNitAnJuvTb3ThCDzK_EWvxeWf_wzlof8nAAD__-n_5CI">