[BUG] ’zext.h‘ is considered an illegal instruction.

Created by: youzi27

Is there an existing CVA6 bug for this?

• I have searched the existing bug issues

Bug Description

After enabling extensions rv64gc_zba_zbb_zbs_zbc_zicsr_zifencei, CVA6 cannot execute the 'zext.h' instruction correctly, resulting in an illegal instruction exception. This seems to indirectly explain the issues with issue #1758 (closed) and issue #1918 (closed).

The log is as follows ILLEGAL_INSTR exception @ 0x00000000800041d6