diff --git a/llvm/lib/Target/ARM/ARMInstrInfo.td b/llvm/lib/Target/ARM/ARMInstrInfo.td
--- a/llvm/lib/Target/ARM/ARMInstrInfo.td
+++ b/llvm/lib/Target/ARM/ARMInstrInfo.td
@@ -5129,6 +5129,7 @@
 def TSB : AInoP<(outs), (ins tsb_opt:$opt), MiscFrm, NoItinerary,
                 "tsb", "\t$opt", []>, Requires<[IsARM, HasV8_4a]> {
   let Inst{31-0} = 0xe320f012;
+  let DecoderMethod = "DecodeTSBInstruction";
 }
 
 }
diff --git a/llvm/lib/Target/ARM/ARMInstrThumb2.td b/llvm/lib/Target/ARM/ARMInstrThumb2.td
--- a/llvm/lib/Target/ARM/ARMInstrThumb2.td
+++ b/llvm/lib/Target/ARM/ARMInstrThumb2.td
@@ -3561,6 +3561,7 @@
 def t2TSB : T2I<(outs), (ins tsb_opt:$opt), NoItinerary,
                 "tsb", "\t$opt", []>, Requires<[IsThumb, HasV8_4a]> {
   let Inst{31-0} = 0xf3af8012;
+  let DecoderMethod = "DecodeTSBInstruction";
 }
 }
 
diff --git a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
--- a/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
+++ b/llvm/lib/Target/ARM/Disassembler/ARMDisassembler.cpp
@@ -265,6 +265,8 @@
                                uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeAddrMode3Instruction(MCInst &Inst,unsigned Insn,
                                uint64_t Address, const void *Decoder);
+static DecodeStatus DecodeTSBInstruction(MCInst &Inst, unsigned Insn,
+                                         uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeSORegImmOperand(MCInst &Inst, unsigned Insn,
                                uint64_t Address, const void *Decoder);
 static DecodeStatus DecodeSORegRegOperand(MCInst &Inst, unsigned Insn,
@@ -2013,6 +2015,21 @@
   return S;
 }
 
+static DecodeStatus DecodeTSBInstruction(MCInst &Inst, unsigned Insn,
+                                         uint64_t Address,
+                                         const void *Decoder) {
+  DecodeStatus S = MCDisassembler::Success;
+
+  if (Inst.getOpcode() != ARM::TSB || Inst.getOpcode() != ARM::t2TSB)
+    return MCDisassembler::Fail;
+
+  // The "csync" operand is not encoded into the "tsb" instruction (as this is
+  // the only available operand), but LLVM expects the instruction to have one
+  // operand, so we need to add the csync when decoding.
+  Inst.addOperand(MCOperand::createImm(ARM_TSB::CSYNC));
+  return S;
+}
+
 static DecodeStatus
 DecodeAddrMode3Instruction(MCInst &Inst, unsigned Insn,
                            uint64_t Address, const void *Decoder) {