Print {z} decorator for instructions with zero-only mask mode

[flobernd]

Certain instructions like e.g. vpshufbitqmb use hardcoded zero masking.

Intel SDM says:

This instruction uses write masking (zeroing only).

Zydis correctly reflects this in the ZydisDecodedInstruction, but currently we do not print the {z} decorator for these cases.

Related to intelxed/xed#277

[flobernd]

I just found my own comment while working on it:

zydis/src/FormatterBase.c

Line 597 in 80d8d52

// Only print the zeroing decorator, if the instruction is not a "zeroing masking only"

@athre0z Can we compare against other disassemblers or assemblers?

[mappzor]

I'm aware of two cases:

• NASM: will not accept {z} decorator when assembling, ndisasm will not show it when disassembling
• capstone (cstool): fails to decode instruction completely ;)

[flobernd]

Thanks for checking!

I think in this case I will close this issue and don't print it as well. The .avx.mask_mode property will correctly contain ZYDIS_MASK_MODE_ZEROING or ZYDIS_MASK_MODE_CONTROL_ZEROING anyways, if somebody needs this information.