[mips] Add empty scheduler info and `NoItinerary` to the `MipsAsmPseudoInst`

[atanasyan]

Summary

Set the hasNoSchedulingInfo flag for the`MipsAsmPseudoInst`. These pseudo-instructions are never used by codegen. This flag allows to reduce number of "No schedule information for" and "lacks information for" errors in case of marking a scheduler model as complete.

This patch is one of a series of patches. The goal is to make P5600 scheduler model complete and turn on the CompleteModel flag.

[Petar.Avramovic]

llvm/lib/Target/Mips/MipsInstrFormats.td

146

I looked only at CodeGenSchedModels::checkCompleteness()
We already have few pseudos with let hasNoSchedulingInfo = 1; and this has same effect (no error) in checkCompleteness as NoItinerary + empty Sched. Are there any advantages in using the latter?

[atanasyan]

llvm/lib/Target/Mips/MipsInstrFormats.td

146

Good point. The hasNoSchedulingInfo is enough. Thanks.

[atanasyan]

• Use hasNoSchedulingInfo flag

llvm/lib/Target/Mips/MipsInstrFormats.td

class PseudoSE<dag outs, dag ins, list<dag> pattern,
   MipsPseudo<outs, ins, pattern, itin> {
   let EncodingPredicates = [NotInMips16Mode];
 }
 
 // Pseudo-instructions for alternate assembly syntax (never used by codegen).
 // These are aliases that require C++ handling to convert to the target
 // instruction, while InstAliases can be handled directly by tblgen.
 class MipsAsmPseudoInst<dag outs, dag ins, string asmstr>:
   MipsInst<outs, ins, asmstr, [], IIPseudo, Pseudo> {
   let isPseudo = 1;
+  let hasNoSchedulingInfo = 1;
   let Pattern = [];
 }
 //===----------------------------------------------------------------------===//
 // Format R instruction class in Mips : <|opcode|rs|rt|rd|shamt|funct|>
 //===----------------------------------------------------------------------===//
 
 class FR<bits<6> op, bits<6> _funct, dag outs, dag ins, string asmstr,
          list<dag> pattern, InstrItinClass itin>: