diff --git a/opcodes/riscv-opc.c b/opcodes/riscv-opc.c
index aeef09146d8..b34d541b8ea 100644
--- a/opcodes/riscv-opc.c
+++ b/opcodes/riscv-opc.c
@@ -368,7 +368,7 @@ const struct riscv_opcode riscv_opcodes[] =
 {"call",        0, INSN_CLASS_I, "c",         (X_RA << OP_SH_RS1)|(X_RA << OP_SH_RD), (int) M_CALL, match_never, INSN_MACRO },
 {"tail",        0, INSN_CLASS_I, "c",         (X_T1 << OP_SH_RS1), (int) M_CALL, match_never, INSN_MACRO },
 {"jump",        0, INSN_CLASS_I, "c,s",       0, (int) M_CALL, match_never, INSN_MACRO },
-{"nop",         0, INSN_CLASS_C, "",          MATCH_C_ADDI, 0xffff, match_opcode, INSN_ALIAS },
+{"nop",         0, INSN_CLASS_C, "",          MATCH_C_NOP, MASK_C_NOP, match_opcode, INSN_ALIAS },
 {"nop",         0, INSN_CLASS_I, "",          MATCH_ADDI, MASK_ADDI|MASK_RD|MASK_RS1|MASK_IMM, match_opcode, INSN_ALIAS },
 {"lui",         0, INSN_CLASS_C, "d,Cu",      MATCH_C_LUI, MASK_C_LUI, match_c_lui, INSN_ALIAS },
 {"lui",         0, INSN_CLASS_I, "d,u",       MATCH_LUI, MASK_LUI, match_opcode, 0 },
@@ -496,7 +496,7 @@ const struct riscv_opcode riscv_opcodes[] =
 {"sw",          0, INSN_CLASS_I, "t,A,s",     0, (int) M_SW, match_never, INSN_MACRO },
 {"fence",       0, INSN_CLASS_I, "",          MATCH_FENCE|MASK_PRED|MASK_SUCC, MASK_FENCE|MASK_RD|MASK_RS1|MASK_IMM, match_opcode, INSN_ALIAS },
 {"fence",       0, INSN_CLASS_I, "P,Q",       MATCH_FENCE, MASK_FENCE|MASK_RD|MASK_RS1|(MASK_IMM & ~MASK_PRED & ~MASK_SUCC), match_opcode, 0 },
-{"fence.i",     0, INSN_CLASS_ZIFENCEI, "",   MATCH_FENCE_I, MASK_FENCE|MASK_RD|MASK_RS1|MASK_IMM, match_opcode, 0 },
+{"fence.i",     0, INSN_CLASS_ZIFENCEI, "",   MATCH_FENCE_I, MASK_FENCE_I|MASK_RD|MASK_RS1|MASK_IMM, match_opcode, 0 },
 {"fence.tso",   0, INSN_CLASS_I, "",          MATCH_FENCE_TSO, MASK_FENCE_TSO|MASK_RD|MASK_RS1, match_opcode, 0 },
 {"rdcycle",     0, INSN_CLASS_I, "d",         MATCH_RDCYCLE, MASK_RDCYCLE, match_opcode, INSN_ALIAS },
 {"rdinstret",   0, INSN_CLASS_I, "d",         MATCH_RDINSTRET, MASK_RDINSTRET, match_opcode, INSN_ALIAS },
@@ -924,7 +924,7 @@ const struct riscv_opcode riscv_opcodes[] =
 {"c.lw",       0, INSN_CLASS_C,   "Ct,Ck(Cs)", MATCH_C_LW, MASK_C_LW, match_opcode, INSN_DREF|INSN_4_BYTE },
 {"c.swsp",     0, INSN_CLASS_C,   "CV,CM(Cc)", MATCH_C_SWSP, MASK_C_SWSP, match_opcode, INSN_DREF|INSN_4_BYTE },
 {"c.sw",       0, INSN_CLASS_C,   "Ct,Ck(Cs)", MATCH_C_SW, MASK_C_SW, match_opcode, INSN_DREF|INSN_4_BYTE },
-{"c.nop",      0, INSN_CLASS_C,   "",          MATCH_C_ADDI, 0xffff, match_opcode, INSN_ALIAS },
+{"c.nop",      0, INSN_CLASS_C,   "",          MATCH_C_NOP, MASK_C_NOP, match_opcode, INSN_ALIAS },
 {"c.nop",      0, INSN_CLASS_C,   "Cj",        MATCH_C_ADDI, MASK_C_ADDI|MASK_RD, match_opcode, INSN_ALIAS },
 {"c.mv",       0, INSN_CLASS_C,   "d,CV",      MATCH_C_MV, MASK_C_MV, match_c_add_with_hint, 0 },
 {"c.lui",      0, INSN_CLASS_C,   "d,Cu",      MATCH_C_LUI, MASK_C_LUI, match_c_lui_with_hint, 0 },