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Writing MCR instruction

Senthil Ramakrishnan over 12 years ago

Senthil Ramakrishnan over 12 years ago
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Senthil Ramakrishnan over 12 years ago

Note: This was originally posted on 2nd March 2010 at http://forums.arm.com

Those are great inputs, Isogen - Writing some custom command processor to convert my commands to assembler functions
as required. Im thinking about something like that as a long time solution for this.

Thanks again,
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Peter Harris over 12 years ago

Note: This was originally posted on 26th February 2010 at http://forums.arm.com

My usual approach for this type of build problem would be to have a custom "preprocessor" which takes in an "almost assembler" and outputs the "real assembler" file which actually gets assembled. You could then insert some custom instructions which your preprocessor translates, but leave the rest of the file untouched.
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Jacob Bramley over 12 years ago

Note: This was originally posted on 25th February 2010 at http://forums.arm.com

There's no easy way to do what you ask. If you think about it, it's similar to asking if you can programmatically choose the arguments to something like an "ADD" instruction.

Given that MCR instructions are generally rare, it's not too much of an overhead to write out ten or twenty instruction to dump the information that you want.

I agree that it would be best to try to avoid the self-modifying code route; there is much to consider and in many cases it tends to get very messy, even before you start trying to debug it. I have a blog post [url="http://blogs.arm.com/software-enablement/caches-and-selfmodifying-code/"]here[/url] which may be of interest if you go down this route. It may be more efficient (in execution time) to use a switch-case style selector, unless you want a lot of options.

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Out of interest, what exactly are you trying to do? I've never found that I've needed generic access as you describe.
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