[cfe-dev] Documenting Clang: question about how best to deliver the doc

[Sean Silva]

On Mon, Aug 19, 2013 at 5:39 PM, Morrison, Michael <
Michael_Morrison at playstation.sony.com> wrote:

>  As some of you know, we at Sony Computer Entertainment America have been
> working on various aspects of LLVM, including Clang and its toolchain.  As
> part of our work, we have created documentation for our customers about
> using Clang, and we would like to share the fruits of our work with the
> Clang and LLVM communities.****
>
> ** **
>
> As our first documentation submission, we plan to provide our *CPU
> Intrinsics Guide*, which documents the Clang intrinsics for x86intrin.h,
> along with several builtin and sync types.  I've included a sample of what
> we document for one of the intrinsics below.****
>
> ** **
>
> Our question for the community is:  what documentation format is most
> helpful and desired for this information?  We currently have two main
> possibilities in mind (with three variants for the first option):****
>
> ** **
>
> 1) Add the documentation for each intrinsic to the header file:****
>
> ** **
>
> - 1a) Using Doxygen tagging.  One benefit of this approach is that the
> documentation is available for the developer within a
> code-development/editing system.  One potential difficulty with this
> approach is that the intrinsics header file becomes much larger, which
> could increase compile times.
>

As Eli mentioned, it would be nice to get some performance numbers.

****
>
> ** **
>
> - 1b) Using Microsoft's annotation grammar.  We might be able to contain
> this annotation grammar within Doxygen tagging that deviates somewhat from
> the LLVM Doxygen style.  This approach allows us to generate XML output for
> the Microsoft Visual Studio Tooltip class.  The benefit of this approach is
> that the documentation is available for the developer within Visual Studio,
> without his or her having to open the specific header file.  Like option
> (1a), one potential difficulty with this approach is that the intrinsics
> header file becomes much larger, which could increase compile times.
>

Is generating MSVS Tooltip XML output a hard requirement for your use case?
If so, can you estimate how much effort it is to convert to that format
given each of these options? My suspicion is that keeping this info in reST
or even just a structured XML file converted to reST with a Sphinx plugin
for docs generation will be the easiest solution; in both cases, it should
be a fairly straightforward Python script to slurp in the file and spit out
XML (the `docutils` library that Sphinx is based on and that reads in the
reST has a nice XML-based internal representation of the reST document).


> ****
>
> ** **
>
> - 1c) Using TblGen to maintain both the intrinsics definitions and their
> documentation, from which we generate the header file with both.  With this
> approach, we could implement either option (1a), (1b), or both, and have a
> single point of maintenance.  This option has the same benefits and
> drawbacks as (1a) and (1b).****
>
> ** **
>
> 2) Add the documentation in reST and Sphynx format (to match existing
> Clang and LLVM documentation) to the Clang Web site.  The main benefit of
> this approach is that the documentation is available to anyone on the Web.
> ****
>
> ** **
>
> ** **
>
> Thus, we come to you today to ask your opinion on which approach we should
> take.  We're open to providing one or more of the formats, as desired, or
> considering a different option that one of you might make.
>

In what format is the documentation currently?

-- Sean Silva


> ****
>
> ** **
>
> ** **
>
> Sample intrinsic documentation (ASCII formatted for forum viewing)****
>
> -------------------------------****
>
> ** **
>
> _mm256_round_ps****
>
> ** **
>
> SYNOPSIS****
>
> #include <x86intrin.h>****
>
> __m256 _mm256_round_ps(__m256 v, const int m);****
>
> ** **
>
> INSTRUCTION****
>
> VROUNDPS****
>
> ** **
>
> DESCRIPTION****
>
> Rounds the values stored in a packed 256-bit vector [8 x float] as
> specified by the byte operand. The source values are rounded to integer
> values and returned as floating point values.****
>
> ** **
>
> PARAMETERS****
>
> v              A 256-bit vector of [8 x float] values.****
>
> m            An immediate byte operand specifying how the rounding is to
> be performed.****
>
>                 Bits [7:4] are reserved.****
>
>                 Bit [3] is a precision exception value:****
>
>                                 0: A normal PE exception is used****
>
>                                 1: The PE field is not updated****
>
>                 Bit [2] is a rounding control source:****
>
>                                 0: MXCSR:RC****
>
>                                 1: Use the RC field value****
>
>                 Bit [1:0] contain the rounding control definition:****
>
>                                 00: Nearest****
>
>                                 01: Downward (toward negative infinity)***
> *
>
>                                 10: Upward (toward positive infinity)****
>
>                                 11: Truncated****
>
> ** **
>
> RETURNS****
>
> A 256-bit vector of [8 x float] containing the rounded values.****
>
> ** **
>
> -------------------------------****
>
> ** **
>
> ** **
>
> Cheers,****
>
> Michael****
>
> △○×□    お疲れ様です****
>
> ** **
>
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>
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