[ARM][MVE] Enable VMOVN for tail predication

[samparker]

Summary

These instructions also don't change lanes, so make them legal too.

[SjoerdMeijer]

LGTM

llvm/lib/Target/ARM/ARMInstrMVE.td

class MVE_VxMOVxN<string iname, string suffix, bit bit_28, bit bit_17,
   let Inst{21-20} = 0b11;
   let Inst{19-18} = size;
   let Inst{17} = bit_17;
   let Inst{16} = 0b1;
   let Inst{12} = T;
   let Inst{8} = 0b0;
   let Inst{7} = !if(!eq(bit_17, 0), 1, 0);
   let Inst{0} = 0b1;
+  let validForTailPredication = 1;
 }
 
 multiclass MVE_VxMOVxN_halves<string iname, string suffix,
                               bit bit_28, bit bit_17, bits<2> size> {
   def bh : MVE_VxMOVxN<iname # "b", suffix, bit_28, bit_17, size, 0b0>;
   def th : MVE_VxMOVxN<iname # "t", suffix, bit_28, bit_17, size, 0b1>;
 }
 

llvm/unittests/Target/ARM/MachineInstrTest.cpp

auto IsValidTPOpcode = [](unsigned Opcode) {
     case MVE_VLDRWU32_qi_pre:
     case MVE_VLDRWU32_rq:
     case MVE_VLDRWU32_rq_u:
     case MVE_VMOVimmf32:
     case MVE_VMOVimmi16:
     case MVE_VMOVimmi32:  
     case MVE_VMOVimmi64:
     case MVE_VMOVimmi8: 
+    case MVE_VMOVNi16bh:
+    case MVE_VMOVNi16th:
+    case MVE_VMOVNi32bh:
+    case MVE_VMOVNi32th:
     case MVE_VMULLBp16:
     case MVE_VMULLBp8:
     case MVE_VMULLBs16:
     case MVE_VMULLBs32:
     case MVE_VMULLBs8:
     case MVE_VMULLBu16:
     case MVE_VMULLBu32:
     case MVE_VMULLBu8:
auto IsValidTPOpcode = [](unsigned Opcode) {
     case MVE_VQDMULL_qr_s32th:
     case MVE_VQDMULLs16bh:
     case MVE_VQDMULLs16th:
     case MVE_VQDMULLs32bh:
     case MVE_VQDMULLs32th:
     case MVE_VQNEGs16:
     case MVE_VQNEGs32:
     case MVE_VQNEGs8:
+    case MVE_VQMOVNs16bh:
+    case MVE_VQMOVNs16th:
+    case MVE_VQMOVNs32bh:
+    case MVE_VQMOVNs32th:
+    case MVE_VQMOVNu16bh:
+    case MVE_VQMOVNu16th:
+    case MVE_VQMOVNu32bh:
+    case MVE_VQMOVNu32th:
+    case MVE_VQMOVUNs16bh:
+    case MVE_VQMOVUNs16th:
+    case MVE_VQMOVUNs32bh:
+    case MVE_VQMOVUNs32th:
     case MVE_VQRSHL_by_vecs16:
     case MVE_VQRSHL_by_vecs32:
     case MVE_VQRSHL_by_vecs8:
     case MVE_VQRSHL_by_vecu16:
     case MVE_VQRSHL_by_vecu32:
     case MVE_VQRSHL_by_vecu8:
     case MVE_VQRSHL_qrs16:
     case MVE_VQRSHL_qrs32: