llvm dev - Feb 2018 - Adding comments to 'MachineInstruction'

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?

 

Thanks,

 

            MartinO

 

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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> 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?
>  
> Thanks,
>  
>             MartinO
>  
> _______________________________________________
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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,

 

            MartinO

 

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?

 

Thanks,

 

            MartinO

 

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