llvm dev - May 2017 - I want to update WritingAnLLVMBackend document

Hi LLVM developers,

As one of the maintainers of AVR target, I want to update 
WritingAnLLVMBackend document to be familiar with the development of 
backend, because:

1. The structure of LLVMTargetMachine 
https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-machine
has been changed a lot!

2. LLVMInitializeSparcTargetInfo 
https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-registration
not mentioned the directory structure: TargetInfo/SparcTargetInfo.cpp

3. There is the Sparc target example in the document, but we could add 
AVR target as another example

Please give me some advice, thanks a lot!

-- 
Regards,
Leslie Zhai - a LLVM hacker https://reviews.llvm.org/p/xiangzhai/

2017-05-03 17:23 GMT+08:00 Leslie Zhai via llvm-dev <llvm-dev at
lists.llvm.org
>:
> Hi LLVM developers,
>
> As one of the maintainers of AVR target, I want to update
> WritingAnLLVMBackend document to be familiar with the development of
> backend, because:
>
> 1. The structure of LLVMTargetMachine https://github.com/llvm-mirror
> /llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-machine has been
> changed a lot!
>
> 2. LLVMInitializeSparcTargetInfo https://github.com/llvm-mirror
> /llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-registration not
> mentioned the directory structure: TargetInfo/SparcTargetInfo.cpp
>
> 3. There is the Sparc target example in the document, but we could add AVR
> target as another example
>
> Please give me some advice, thanks a lot!

​Although contribution always welcome, personally I prefer making the
document as consistent as possible.
I don't know if it's a good idea interleaving different backend
implementation
​s​
in
​one​
 document.

​Anyway, I think you can write a RFC (request for comment)​
​
​ mail, describing what/where you feel unsatisfied
about current document, giving a draft to show us how you would improve the
document. I think that will make
the discussion more concrete.

HTH,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Homepage: https://people.cs.nctu.edu.tw/~chenwj
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您好 Chen :)

I'm the maintainer for LLVM AVR backend wanted to update 
WritingAnLLVMBackend document. My apologies for the delay in responding.

I respect the document's original authors! Sorry for breaking consistent.

At the very beginning: SparcV8 skeleton 
https://github.com/llvm-mirror/llvm/commit/e785e531f4495068ee46cabd926939eec15a565a#diff-6998035da03f58a8c7e0ac3de7d21276

It was very close to the SPARC target example:

- similar constructor's variables

- similar get*Info methods

But the structure of backends and related components often be changed:

- https://reviews.llvm.org/D30879

- https://reviews.llvm.org/D31875

So doc might be out-of-date, but never mind, I can read the source code 
directly :)


在 2017年05月03日 20:36, 陳韋任 写道:
>
> 2017-05-03 17:23 GMT+08:00 Leslie Zhai via llvm-dev 
> <llvm-dev at lists.llvm.org <mailto:llvm-dev at
lists.llvm.org>>:
>
>     Hi LLVM developers,
>
>     As one of the maintainers of AVR target, I want to update
>     WritingAnLLVMBackend document to be familiar with the development
>     of backend, because:
>
>     1. The structure of LLVMTargetMachine
>    
https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-machine
>    
<https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-machine>
>     has been changed a lot!
>
>     2. LLVMInitializeSparcTargetInfo
>    
https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-registration
>    
<https://github.com/llvm-mirror/llvm/blob/master/docs/WritingAnLLVMBackend.rst#target-registration>
>     not mentioned the directory structure: TargetInfo/SparcTargetInfo.cpp
>
>     3. There is the Sparc target example in the document, but we could
>     add AVR target as another example
>
>     Please give me some advice, thanks a lot!
>
>
> ​Although contribution always welcome, personally I prefer making the 
> document as consistent as possible.
> I don't know if it's a good idea interleaving different backend 
> implementation
> ​s​
> in
> ​one​
>  document.
>
> ​Anyway, I think you can write a RFC (request for comment)​
> ​
> ​ mail, describing what/where you feel unsatisfied
> about current document, giving a draft to show us how you would 
> improve the document. I think that will make
> the discussion more concrete.
>
> HTH,
> chenwj
>
> -- 
> Wei-Ren Chen (陳韋任)
> Homepage: https://people.cs.nctu.edu.tw/~chenwj 
> <https://people.cs.nctu.edu.tw/%7Echenwj>
-- 
Regards,
Leslie Zhai - a LLVM hacker https://reviews.llvm.org/p/xiangzhai/
�)

On 3 May 2017, at 13:36, 陳韋任 via llvm-dev <llvm-dev at lists.llvm.org>
wrote:
> 
> ​Although contribution always welcome, personally I prefer making the
document as consistent as possible.
> I don't know if it's a good idea interleaving different backend
implementation​s​ in ​one​ document.
I believe that this is a necessary evil.  I don’t think that we have a single
back end that uses all of the target-agnostic codegen features, or hits all of
the important corner cases of back-end development, and so a good document would
necessarily cover multiple cases.

That said, I’m not sure that AVR is sufficiently different from SPARC that it
makes a good example here.

David