Extended Description

I noticed this on https://reviews.llvm.org/D86601, but it's a different bug:

define <2 x i16> @​rotate_v2i16(<2 x i16> %x, <2 x i16> %amt) nounwind {
%res = call <2 x i16> @​llvm.fshr.v2i16(<2 x i16> %x, <2 x i16> %x, <2 x i16> %amt)
ret <2 x i16> %res
}

declare <2 x i16> @​llvm.fshr.v2i16(<2 x i16>, <2 x i16>, <2 x i16>)

$ llc -o - rot.ll -mtriple=aarch64
.text
.file "rot.ll"
PLEASE submit a bug report to https://bugs.llvm.org/ and include the crash backtrace.
Stack dump:
0. Program arguments: ./llc -o - rot.ll -mtriple=aarch64

1. Running pass 'Function Pass Manager' on module 'rot.ll'.
2. Running pass 'AArch64 Instruction Selection' on function '@var_funnnel_v2i16'
   0 llc 0x000000010b9ef778 llvm::sys::PrintStackTrace(llvm::raw_ostream&, int) + 40
   1 llc 0x000000010b9ee508 llvm::sys::RunSignalHandlers() + 248
   2 llc 0x000000010b9efd8c SignalHandler(int) + 268
   3 libsystem_platform.dylib 0x00007fff6a6725fd _sigtramp + 29
   4 libsystem_platform.dylib 0x0000000000000010 _sigtramp + 18446603338731018800
   5 llc 0x000000010b773793 llvm::DAGTypeLegalizer::ReplaceValueWith(llvm::SDValue, llvm::SDValue) + 67
   6 llc 0x000000010b749e30 llvm::DAGTypeLegalizer::PromoteIntegerResult(llvm::SDNode*, unsigned int) + 784
   7 llc 0x000000010b772cd8 llvm::DAGTypeLegalizer::run() + 2808
   8 llc 0x000000010b7784ee llvm::SelectionDAG::LegalizeTypes() + 1438
   9 llc 0x000000010b885869 llvm::SelectionDAGISel::CodeGenAndEmitDAG() + 1897