Re: -ffunction-sections and -fdata-sections documentation

[Hi-Angel <hiangel999 at gmail dot com>]

On 13 October 2017 at 17:02, David Edelsohn <dje.gcc@gmail.com> wrote:
> On Fri, Oct 13, 2017 at 3:06 AM, Sebastian Huber
> <sebastian.huber@embedded-brains.de> wrote:
>> Hello,
>>
>> I would like to update the documentation of these compiler flags and have
>> some questions.  The -ffunction-sections and -fdata-sections documentation
>> is currently:
>>
>> "Place each function or data item into its own section in the output file if
>> the target supports arbitrary sections. The name of the function or the name
>> of the data item determines the section’s name in the output file.
>>
>> Use these options on systems where the linker can perform optimizations to
>> improve locality of reference in the instruction space. Most systems using
>> the ELF object format and SPARC processors running Solaris 2 have linkers
>> with such optimizations. AIX may have these optimizations in the future.
>>
>> Only use these options when there are significant benefits from doing so.
>> When you specify these options, the assembler and linker create larger
>> object and executable files and are also slower. You cannot use |gprof| on
>> all systems if you specify this option, and you may have problems with
>> debugging if you specify both this option and -g."
>>
>> The end-of-life of Solaris 2.6 was 2006. Is it worth to mention this here?
>>
>> This "AIX may have these optimizations in the future." is there since at
>> least 1996. What is the current AIX status?
>>
>> Is the "Only use these options when there are significant benefits from
>> doing so. When you specify these options, the assembler and linker create
>> larger object and executable files and are also slower. You cannot use
>> |gprof| on all systems if you specify this option, and you may have problems
>> with debugging if you specify both this option and -g." still correct on the
>> systems of today?
>>
>> Do these options affect the code generation?
>
> Out of date documentation in GCC?  What a surprise!
>
> -ffunction-sections and -fdata-sections are available on AIX.  The AIX
> linker rearranges sections (CSECTs) based on the call graph.  The
> performance impact varies.
>
> I'm not certain what the central question of the email message is.
>
> Thanks, David

I think they're asking:
1. Is it worth removing the note about Solaris, given it get EOLed in 2006.
2. Does AIX's linker perform optimization "to improve locality of
reference in the instruction space"
3. Does options still cause problems with debugging(when used with -g)
and with gprof?