2025.02 llvm-objdump fails to disassemble some custom xxldsp instructions

[dongyasun]

llvm-objdump cannot recognize DSP instructions, whereas gcc's objdump can recognize them correctly, so no 'unknown' instructions appear.

> /home/share/devtools/toolchain/nuclei_gnu/linux64/newlibc/2025.10/gcc/bin/llvm-objdump -d dsp_test.elf | grep unknown | head
800003b6: c0e3177f 02a68333 02a693b3    <unknown>
800003c2: c067177f 00179513 01f75693    <unknown>
8000040e: c0e5157f 02c68633 00c49703    <unknown>
8000041e: c0c5157f 00f71613 41f75693    <unknown>
8000042a: c0c5157f 813d05c6 2ca18d4d    <unknown>
800004e0: c0891a7f fb568c13 038a3bb3    <unknown>
800004f2: c58a9bff 038a0b33 c2eb177f    <unknown>
80000512: c4a71aff 02a68a33 01f45693    <unknown>
8000052e: c127197f 04b68713 02e936b3    <unknown>
8000053e: c4e99bff 02e90b33 c0ab197f    <unknown>
>  /home/share/devtools/toolchain/nuclei_gnu/linux64/glibc/2025.10/gcc/bin/llvm-objdump -d dsp_test.elf | grep unknown | head
800003b6: c0e3177f 02a68333 02a693b3    <unknown>
800003c2: c067177f 00179513 01f75693    <unknown>
8000040e: c0e5157f 02c68633 00c49703    <unknown>
8000041e: c0c5157f 00f71613 41f75693    <unknown>
8000042a: c0c5157f 813d05c6 2ca18d4d    <unknown>
800004e0: c0891a7f fb568c13 038a3bb3    <unknown>
800004f2: c58a9bff 038a0b33 c2eb177f    <unknown>
80000512: c4a71aff 02a68a33 01f45693    <unknown>
8000052e: c127197f 04b68713 02e936b3    <unknown>
8000053e: c4e99bff 02e90b33 c0ab197f    <unknown>
> riscv64-unknown-elf-objdump -d dsp_test.elf | grep unknown | head

[dongyasun]

LLVM performs a bitwise AND operation between the instruction encoding and specific binary masks to determine whether to parse the instruction as 32-bit or 16-bit.
However, some custom xxldsp instruction encodings do not fall into the above categories, resulting in parsing failures.
This issue has been fixed in version 2025.10.