[llvm-dev] Making llvm-xyz -help useful

[Serge Guelton via llvm-dev]

Thanks James for the pointer - I'm still amazed by LLVM's pandora box
colloquially  named tablegen!
You're pointing at a right problem, which is independent of the actual
engine used to specify tool options: To what extent are the options of
liked libraries relevant to the tool. And only tool maintainer can answer
that question, so a per-tool approach is probably the better option here.

On Fri, May 10, 2019 at 11:33 AM James Henderson <
jh7370.2008 at my.bristol.ac.uk> wrote:

> Hi Serge,
>
> I'm all for any approach that hides irrelevant options from the individual
> tools. This is one method. Another method might be to switch to using
> tablegen, like we do with LLD or llvm-objcopy, which will have other
> benefits too relating to command-line option handling. However, it is
> important that we don't lose options that ARE relevant to the tool by any
> such switch. I cannot comment on which options those are for some tools,
> but at least for the tools that I've been working on recently, I'm happy to
> review (and indeed have done for some in the past).
>
> James
>
> On Thu, 9 May 2019 at 17:24, Serge Guelton via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> Hi folks,
>>
>> today, I wanted to concatenate two .ll, and naively typed:
>>
>>     $ llvm-cat -help
>>
>> This is the not-so-helpful output I had:
>>
>>     OVERVIEW: Module concatenation
>>     USAGE: llvm-cat [options] <input  files>
>>
>>     OPTIONS:
>>
>>     General options:
>>
>>       -aarch64-neon-syntax                              - Choose style of
>> NEON code to emit from AArch64 backend:
>>         =generic                                        -   Emit generic
>> NEON assembly
>>         =apple                                          -   Emit
>> Apple-style NEON assembly
>>       -amdgpu-dump-hsa-metadata                         - Dump AMDGPU HSA
>> Metadata
>>       -amdgpu-enable-merge-m0                           - Merge and hoist
>> M0 initializations
>>       -amdgpu-sdwa-peephole                             - Enable SDWA
>> peepholer
>>     [...]
>>
>> Surely, the style of NEON code to emit from AArch64 backend is not the
>> information I was looking for...
>>
>> I've implemented a straight-forward patch for llvm-cat here
>> https://reviews.llvm.org/D61740, and the result becomes:
>>
>>     OVERVIEW: Module concatenation
>>     USAGE: llvm-cat [options] <input  files>
>>
>>     OPTIONS:
>>
>>     Generic Options:
>>
>>       --help        - Display available options (--help-hidden for more)
>>       --help-list   - Display list of available options
>> (--help-list-hidden for more)
>>       --version     - Display the version of this program
>>
>>     llvm-cat Options:
>>
>>       -b            - Whether to perform binary concatenation
>>       -o=<filename> - Output filename
>>
>>
>> Depending on the tools, the filtering imposed by
>> llvm::cl::HideUnrelatedOptions may be too harsh, but there's still
>> -help-hidden for the curious!
>>
>> Any thoughts on that approach? Should I go on that way for other tools?
>> If so, anyone willing to be auto-added as a reviewer?
>>
>> ++
>> Serge
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>
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