Re: [PATCH] lib/lz4: make arrays static const, reduces object code size

[Arnd Bergmann]

On Fri, Sep 22, 2017 at 1:11 AM, Colin Ian King
<colin.king@xxxxxxxxxxxxx> wrote:
> On 22/09/17 00:09, Christophe JAILLET wrote:
>> Le 22/09/2017 Ã 00:19, Colin King a Ãcrit :
>>> From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
>>>
>>> Don't populate the read-only arrays dec32table and dec64table on the
>>> stack, instead make them both static const.  Makes the object code
>>> smaller by over 10K bytes:
>> 10k? Wouaouh! This is way much more than what you usually win with such
>> patches.
>
> Yes, I had to triple check it because it was an unbelievable win.
>

I wonder whether this should be reported as a gcc bug. I tried reproducing
it here with gcc-7.1.1 and gcc-8.0.0, but I only see a 4K difference:

   text    data     bss     dec     hex filename
  18220     176       0   18396    47dc build/tmp/lib/lz4/lz4_decompress-after.o
  22297       0       0   22297    5719
build/tmp/lib/lz4/lz4_decompress-before.o

I tried x86 defconfig and allmodconfig on a slightly patched mainline kernel.

        Arnd