Re: [PATCH] modpost.c: Add .text.unlikely to TEXT_SECTIONS

Tom Rini
2013-04-29T13:14:52Z

On 04/28/2013 10:59 PM, Rusty Russell wrote:
> Tom Rini <trini@ti.com> writes:
>
>> Recent gcc's may place functions into the .text.unlikely section and we
>> need to check this section as well for section mismatches now otherwise
>> we may have false negatives for this test.
>
> Hmm, I don't think it's all that recent, is it? I can find it back to
> gcc 4.0.4:
>
> `-freorder-functions'
> Reorder functions in the object file in order to improve code
> locality. This is implemented by using special subsections
> `.text.hot' for most frequently executed functions and
> `.text.unlikely' for unlikely executed functions. Reordering is
> done by the linker so object file format must support named
> sections and linker must place them in a reasonable way.
>
> Also profile feedback must be available in to make this option
> effective. See `-fprofile-arcs' for details.
>
> Enabled at levels `-O2', `-O3', `-Os'.
>
> The comment is the same in in gcc 4.7.
>
> So is your real issue that this section is generated with
> -fprofile-arcs, or has something changed with gcc 4.8, or...?

I've started seeing this with Linaro based 4.7 toolchains. I can go
back through their releases and see when it starts showing up there if
it helps. I didn't add .text.hot as I didn't have that section at all,
fwiw.

--
Tom