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How to handle undocumented opcodes
- From: Arnold Metselaar <arnold dot metselaar at planet dot nl>
- To: binutils at sources dot redhat dot com
- Date: Sat, 01 Oct 2005 17:38:12 +0200
- Subject: How to handle undocumented opcodes
Hello
I have written Z80-backends for gas and objdump. The Z80 has a
lot of undocumented instructions. Many but not all of them are
legal instructions on the R800, a successor also supported by
my backend.
I use different machine numbers to distinguish between z80 code
with and without undocumented instructions. My current naming
scheme for processor variants is:
z80strict - only documented Z80 instructions
z80 - adds support for undocumented instructions that are
legal on R800
z80full - all Z80 instructions
r800 - documented r800 instructions
I'm not completely satisfied with this scheme as it may be too
finegrained, and "z80" should probably refer to the documented
instructions only.
Do you have any comments?
Are there any standards or conventions I should adhere to?
Kind regards,
Arnold Metselaar