Index: tools/llvm-exegesis/lib/X86/Target.cpp =================================================================== --- tools/llvm-exegesis/lib/X86/Target.cpp +++ tools/llvm-exegesis/lib/X86/Target.cpp @@ -89,6 +89,12 @@ Op.getExplicitOperandInfo().OperandType == llvm::MCOI::OPERAND_PCREL) return llvm::make_error( "unsupported opcode: PC relative operand"); + for (const Operand &Op : Instr.Operands) + if (Op.isReg() && Op.isExplicit() && + Op.getExplicitOperandInfo().RegClass == + llvm::X86::SEGMENT_REGRegClassID) + return llvm::make_error( + "unsupported opcode: access segment memory"); // We do not handle second-form X87 instructions. We only handle first-form // ones (_Fp), see comment in X86InstrFPStack.td. for (const Operand &Op : Instr.Operands)