[llvm-dev] Adding comments to 'MachineInstruction'

Martin J. O'Riordan via llvm-dev llvm-dev at lists.llvm.org
Mon Feb 5 11:31:58 PST 2018

Thanks Matthias,


It looks like the comments that do exist are emitted are pre-cooked and depend on some other attribute of the MI or the context of the MI.  Curiously enough, a couple of years ago I had thought about this, but I wanted to have different comments used for instructions selected by the TableGen pattern matcher versus those crafted directly in the C++ code which would be very useful when debugging obscure code-generation issues.


All the best,




From: mbraun at apple.com [mailto:mbraun at apple.com] 
Sent: 05 February 2018 17:08
To: Martin J. O'Riordan <MartinO at theheart.ie>
Cc: LLVM Developers <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] Adding comments to 'MachineInstruction'


There is no generic mechanism as far as I know. You can look at AsmPrinter.cpp/emitComments() to see what situations trigger comments at the moment.


- Matthias

On Feb 3, 2018, at 4:40 AM, Martin J. O'Riordan via llvm-dev <llvm-dev at lists.llvm.org <mailto:llvm-dev at lists.llvm.org> > wrote:


When I am constructing sequences of instructions during custom lowering, I would like to be able to also add a comment that appears in the generated assembly with ‘-S -fverbose-asm’.  There is a large set of ‘add*’ functions to attach additional information to the MI, but I don’t see one for adding comments.


Is there a method I can call to attach an arbitrary string (‘StringRef’, ‘const char*’, ‘Twine’) to an MI with ‘BuildMI’ or after?






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