[llvm-bugs] [Bug 49113] New: Tiny program crashes "X86 DAG->DAG Instruction Selection", likely related to AVX512

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=49113

            Bug ID: 49113
           Summary: Tiny program crashes "X86 DAG->DAG Instruction
                    Selection", likely related to AVX512
           Product: libraries
           Version: 10.0
          Hardware: PC
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: Backend: X86
          Assignee: unassignedbugs at nondot.org
          Reporter: wenzel.jakob at epfl.ch
                CC: craig.topper at gmail.com, llvm-bugs at lists.llvm.org,
                    llvm-dev at redking.me.uk, pengfei.wang at intel.com,
                    spatel+llvm at rotateright.com

Dear all,

I've run into a persistent LLVM crash during instruction selection that
bugpoint was able to narrow down to the following few lines. FWIW this is with
LLVM 10.0.0. Interestingly, the problem disappears when changing the target
from "skylake-avx512" to just "skylake".

-----------------------------

; ModuleID = 'bugpoint-reduced-simplified.bc'
source_filename = "test.ll"
target triple = "x86_64-pc-linux-gnu"

define void @func() #0 {
entry:
  %p1_0 = load <8 x i8>, <8 x i8>* undef, align 8
  %p1 = trunc <8 x i8> %p1_0 to <8 x i1>
  %p3 = select <8 x i1> %p1, <8 x i1> zeroinitializer, <8 x i1> %p1
  %p3_e = zext <8 x i1> %p3 to <8 x i8>
  store <8 x i8> %p3_e, <8 x i8>* undef, align 8
  unreachable
}

attributes #0 = { "target-cpu"="skylake-avx512" }

-----------------------------

Stack dump:                                                                     
0.      Program arguments: llc-10 bugpoint-reduced-simplified.ll                
1.      Running pass 'Function Pass Manager' on module
'bugpoint-reduced-simplified.ll'.                                               
2.      Running pass 'X86 DAG->DAG Instruction Selection' on function '@func'   
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm3sys15PrintStackTraceERNS_11raw_ostreamE+0x1f)[0x7fd0356c54ff] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm3sys17RunSignalHandlersEv+0x50)[0x7fd0356c37b0] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(+0x981ac5)[0x7fd0356c5ac5]                
/lib/x86_64-linux-gnu/libpthread.so.0(+0x153c0)[0x7fd034d363c0]                 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZNK4llvm3EVT23isExtendedScalarIntegerEv+0x4)[0x7fd035af6514] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(+0x275550c)[0x7fd03749950c]               
/lib/x86_64-linux-gnu/libLLVM-10.so.1(+0xdc4125)[0x7fd035b08125]                
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm12SelectionDAG7CombineENS_12CombineLevelEPNS_9AAResultsENS_10CodeGenOpt5LevelE+0x939)[0x7fd035b069f9] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm16SelectionDAGISel17CodeGenAndEmitDAGEv+0xe2)[0x7fd035ca9ea2] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm16SelectionDAGISel20SelectAllBasicBlocksERKNS_8FunctionE+0x1957)[0x7fd035ca9a07] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm16SelectionDAGISel20runOnMachineFunctionERNS_15MachineFunctionE+0x796)[0x7fd035ca7396] 
/lib/x86_64-linux-gnu/libLLVM-10.so.1(+0x26b4e18)[0x7fd0373f8e18]               
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm19MachineFunctionPass13runOnFunctionERNS_8FunctionE+0x118)[0x7fd0359605e8]
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm13FPPassManager13runOnFunctionERNS_8FunctionE+0x466)[0x7fd0357cad76]
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm13FPPassManager11runOnModuleERNS_6ModuleE+0x33)[0x7fd0357caff3]
/lib/x86_64-linux-gnu/libLLVM-10.so.1(_ZN4llvm6legacy15PassManagerImpl3runERNS_6ModuleE+0x3c0)[0x7fd0357cb4a0]
llc-10[0x4196e7]
llc-10(main+0x3fd)[0x416acd]
/lib/x86_64-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0x7fd03480b0b3]
llc-10(_start+0x2e)[0x415a7e]

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