Exception: internal error: system should solve

[kkmonk]

I want to gen some illlegal instrctions in .S file, exception happens

Thu, 24 Feb 2022 17:43:37 lib.py:131   DEBUG    Traceback (most recent call last):
 File "/home/xuelai/riscv-dv/pygen/pygen_src/test/riscv_instr_base_test.py", line 38, in run
   self.run_phase(1)
 File "/home/xuelai/riscv-dv/pygen/pygen_src/test/riscv_instr_base_test.py", line 66, in run_phase
   self.asm.gen_program()
 File "/home/xuelai/riscv-dv/pygen/pygen_src/riscv_asm_program_gen.py", line 116, in gen_program
   self.main_program[hart].generate_instr_stream() #这个函数将指令序列转换成str序列
 File "/home/xuelai/riscv-dv/pygen/pygen_src/riscv_instr_sequence.py", line 247, in generate_instr_stream
   self.insert_illegal_hint_instr()
 File "/home/xuelai/riscv-dv/pygen/pygen_src/riscv_instr_sequence.py", line 293, in insert_illegal_hint_instr
   self.illegal_instr.randomize(solve_fail_debug=1)
 File "/home/xuelai/riscv-dv/dv_env/lib/python3.8/site-packages/vsc/rand_obj.py", line 162, in randomize
   Randomizer.do_randomize(
 File "/home/xuelai/riscv-dv/dv_env/lib/python3.8/site-packages/vsc/model/randomizer.py", line 597, in do_randomize
   r.randomize(ri, bounds_v.bound_m)
 File "/home/xuelai/riscv-dv/dv_env/lib/python3.8/site-packages/vsc/model/randomizer.py", line 213, in randomize
   self.create_diagnostics(active_randsets))
 File "/home/xuelai/riscv-dv/dv_env/lib/python3.8/site-packages/vsc/model/randomizer.py", line 444, in create_diagnostics
   raise Exception("internal error: system should solve")
Exception: internal error: system should solve