[cfe-dev] Documenting Clang: question about how best to deliver the doc
Morrison, Michael
Michael_Morrison at playstation.sony.com
Tue Aug 20 17:57:00 PDT 2013
Sorry for the delay in responding.
> Would you mind measuring this [increased size of the header file], at least approximately? If the performance penalty isn't substantial, I would lean towards this solution.
We don't have performance numbers yet. We can perform some measurements after the initial conversion from our base document to the new format is complete, so that we have real data in the header files to measure. We wouldn't be able to simply measure the performance impact with fake data and -Wdocumentation (which parses Doxygen comments and generates warnings for malformed and mismatched comments).
> It's not clear to me why you can't generate XML output if you use LLVM Doxygen style; do you just not have a tool that can do the appropriate conversion?
We don't have the appropriate tool yet, but we plan to create one. Our initial idea was to keep things in LLVM Doxygen style and then use a tool to convert to the Microsoft XML style. We expected the community to prefer 1a (straight Doxygen tagging) over 1b (Microsoft annotation grammar), but mentioned 1b for completeness’ sake. Using 1b would avoid the need for the extra conversion step (LLVM Doxygen style to XML), but this conversion is not necessarily difficult.
> Is generating MSVS Tooltip XML output a hard requirement for your use case?
Yes, generating the MSVS tooltip XML is a hard requirement for us.
> In what format is the documentation currently?
Currently, the documentation is in Microsoft Word format (required for our SDK). We have a tool that converts this document into an XML format that includes a lot of meaningless tags for Word styles. A new tool would convert to a more useful XML format.
> If so, can you estimate how much effort it is to convert to that format given each of these options?
In all cases, we will need to create a script to do an initial one-off conversion to a new format for any of the proposed solutions. After that, our estimations for the effort to implement solutions 1a and 1b are roughly on par with each other as relatively small efforts. Solution 1c requires a relatively larger effort because it requires changing how the intrinsics headers are generated and maintained. Solution 2 is fairly simple because we’d need to do much of the work for the one-off initial step in any case.
Our main concern is picking the path forward that is most preferred by the community. Given the discussion thus far, it sounds like the two front-runners are:
1a) Maintain the documentation in Doxygen. Any other formats required (HTML, XML, etc) can be generated on-the-fly from the Doxygen comments as needed.
2) Maintain the documentation in reST/Doxygen. Any other formats required can be generated on-the-fly from the reST as needed. (Also, it seems that Sphynx has good plugins and support for converting to other formats.)
Cheers,
Michael
From: Sean Silva [mailto:silvas at purdue.edu]
Sent: Monday, 19 August, 2013 18:35
To: Morrison, Michael
Cc: cfe-dev at cs.uiuc.edu; Rafael Ávila de Espíndola; me at filcab.net
Subject: Re: [cfe-dev] Documenting Clang: question about how best to deliver the doc
On Mon, Aug 19, 2013 at 5:39 PM, Morrison, Michael <Michael_Morrison at playstation.sony.com<mailto: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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