Bug #98848 Subopt implementation of integer load/store InnoDB functions for big-endian arch

• Submitted: 6 Mar 2020 5:28
• Modified: 27 Mar 2020 10:54
• Reporter: Dmitry Shulga
• Status: Closed
• Category: MySQL Server: InnoDB storage engine
• Severity: S4 (Feature request)
• OS: Any
• CPU Architecture: Any

[6 Mar 2020 5:28] Dmitry Shulga

Description:
InnoDB has its own inline functions to load/store integer values from/to
memory. These functions make conversion between a host byte order and the
big-endian representation because the InnoDB on-disk format is big-endian.
Unfortunately, implementation of these functions could be translated by
compiler to not optimal assembler code. The following Godbolt link
https://godbolt.org/z/Bvm4hx shows how optimized and not-optimized functions
look like after compiler generated assembler code.

The following commit
https://github.com/mysql/mysql-server/commit/f717e0567457e8a0d513ac17ff63d62e3dc0670d
and its follow-up
https://github.com/mysql/mysql-server/commit/7c24e9bd619304dd7655f4fee4ef52a238d25d13
provide functions to convert 2-bytes and 4-bytes integers to/from big-endian
format.

Unfortunately, similar functions are missed for 3-bytes, 5-bytes, 6-bytes,
7-bytes and 8-bytes integers. Moreover, mi_*() macros and inlined functions
located in the file include/myisampack.h use own implementation to load/store
integer in big-endian format. Additionally, implementation of functions
mach_read_from_*, mach_write_to_* use direct manipulation with bytes array
instead of calling the load*be()/store*be() functions to store/load integers
in big-endian representation. That leads to code duplication and code bloating
in the mysqld binary.

This bug report is to make optimization of source code for loading/storing
integers in big-endian format and to refactor source code for storing/loading
integers in big-endian format to avoid code duplication.

How to repeat:
Do code analysis and look to Godbolt output https://godbolt.org/z/Bvm4hx

[6 Mar 2020 13:34] MySQL Verification Team

Hi Mr. Shulga,

Thank you for your bug report.

However, this is not a bug. At best, this is a feature request.

Also, your description of how to make the improvements for those conversions is not quite clear. We need more specific advise. You could make it clear by providing a source for at least one of those functions. Then, we could proceed further.

[27 Mar 2020 10:54] Dmitry Shulga

Contribution was submitted for the new bug report 
https://bugs.mysql.com/bug.php?id=99097

[27 Mar 2020 13:53] MySQL Verification Team

Thank you, very much, Mr. Shulga for your contribution.

However, you do not need to create a new bug report when you make a contribution.