[llvm] [CodeGen][NFC] Add laneBitmask as new MachineOperand Type (PR #151944)

[Matt Arsenault via llvm-commits]

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@@ -2870,6 +2871,32 @@ bool MIParser::parseCustomRegisterMaskOperand(MachineOperand &Dest) {
   return false;
 }
 
+bool MIParser::parseLaneMaskOperand(MachineOperand &Dest) {
+  assert(Token.is(MIToken::kw_lanemask));
+
+  lex();
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arsenm wrote:

Should get MIR print/parse tests and cover the error cases too

https://github.com/llvm/llvm-project/pull/151944