[RISC-V] Mark C_MV as a move instruction

[luismarques]

LGTM.

llvm/lib/Target/RISCV/RISCVInstrInfoC.td

522

I was wondering if it made sense to have both isMoveReg and isAsCheapAsMove, since the former should imply the latter. Unfortunately, that doesn't seem to be handled automatically, so I guess we need both.

llvm/lib/Target/RISCV/RISCVInstrInfoC.td

def C_JR : RVInst16CR<0b1000, 0b10, (outs), (ins GPRNoX0:$rs1),
                       "c.jr", "$rs1">, Sched<[WriteJmpReg]> {
   let isBranch = 1;
   let isBarrier = 1;
   let isTerminator = 1;
   let isIndirectBranch = 1;
   let rs2 = 0;
 }
 
-let hasSideEffects = 0, mayLoad = 0, mayStore = 0 in
+let hasSideEffects = 0, mayLoad = 0, mayStore = 0, isMoveReg = 1,
+    isAsCheapAsAMove = 1 in
 def C_MV : RVInst16CR<0b1000, 0b10, (outs GPRNoX0:$rs1), (ins GPRNoX0:$rs2),
                       "c.mv", "$rs1, $rs2">,
            Sched<[WriteIALU, ReadIALU]>;
 
 let rs1 = 0, rs2 = 0, hasSideEffects = 1, mayLoad = 0, mayStore = 0 in
 def C_EBREAK : RVInst16CR<0b1001, 0b10, (outs), (ins), "c.ebreak", "">, Sched<[]>;
 
 let hasSideEffects = 0, mayLoad = 0, mayStore = 0,