[RISCV] Remove unused Opcode field from RVInst16. NFC

Unlike RVInst which also has an Opcode field, all of the subclasseso
of RVInst16 assign Inst{1-0} directly.

Reviewed By: asb, wangpc

Differential Revision: https://reviews.llvm.org/D155791

diff --git a/llvm/lib/Target/RISCV/RISCVInstrFormatsC.td b/llvm/lib/Target/RISCV/RISCVInstrFormatsC.td
index 9575866..e14be7d 100644 (file)
--- a/llvm/lib/Target/RISCV/RISCVInstrFormatsC.td
+++ b/llvm/lib/Target/RISCV/RISCVInstrFormatsC.td
@@ -20,8 +20,6 @@ class RVInst16<dag outs, dag ins, string opcodestr, string argstr,
   // to build the decode table.
   field bits<16> SoftFail = 0;
   let Size = 2;
-
-  bits<2> Opcode = 0;
 }
 
 class RVInst16CR<bits<4> funct4, bits<2> opcode, dag outs, dag ins,