Re: [PATCH] wireless: iwlegacy: make const array static to shink object code size Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 8bit

From: Joe Perches
Date: Fri Sep 22 2017 - 06:46:42 EST

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On Fri, 2017-09-22 at 12:06 +0200, Julia Lawall wrote:
>
> On Fri, 22 Sep 2017, Colin Ian King wrote:
>
> > On 22/09/17 11:03, Joe Perches wrote:
> > > On Fri, 2017-09-22 at 09:23 +0200, Julia Lawall wrote:
> > > >
> > > > On Thu, 21 Sep 2017, Colin King wrote:
> > > >
> > > > > From: Colin Ian King <colin.king@xxxxxxxxxxxxx>
> > > > >
> > > > > Don't populate const array ac_to_fifo on the stack in an inlined
> > > > > function, instead make it static. Makes the object code smaller
> > > > > by over 800 bytes:
> > > > >
> > > > > text data bss dec hex filename
> > > > > 159029 33154 1216 193399 2f377 4965-mac.o
> > > > >
> > > > > text data bss dec hex filename
> > > > > 158122 33250 1216 192588 2f04c 4965-mac.o
> > > > >
> > > > > (gcc version 7.2.0 x86_64)
> > > >
> > > > Gcc 7 must be much more aggressive about inlining than gcc 4. Here is the
> > > > change that I got on this file:
> > > >
> > > > text data bss dec hex filename
> > > > - 76346 1494 152 77992 130a8 drivers/net/wireless/intel/iwlegacy/4965-mac.o
> > > > + 76298 1494 152 77944 13078 drivers/net/wireless/intel/iwlegacy/4965-mac.o
> > > > decrease of 48
> > >
> > > More likely different CONFIG options.
> > >
> > > e.g. allyesconfig vs defconfig with wireless
> > >
> >
> > yup, I used allyesconfig
>
> Mine is also allyesconfig.

Odd.

Here is what I get: (Sorry, no gcc-7)

gcc4: gcc-4.9 (Ubuntu 4.9.4-2ubuntu1) 4.9.4
gcc5: gcc-5 (Ubuntu 5.4.1-8ubuntu1) 5.4.1 20170304
gcc6: gcc-6 (Ubuntu 6.3.0-12ubuntu2) 6.3.0 20170406

$ size drivers/net/wireless/intel/iwlegacy/4965-mac.o*
   text    data     bss     dec     hex filename
118559    1766     152 120477   1d69d drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc4.allyesconfig.new
118623    1766     152 120541   1d6dd drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc4.allyesconfig.old
51595    1156       0   52751    ce0f drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc4.defconfig.new
51659    1156       0   52815    ce4f drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc4.defconfig.old
141956   29790    1216 172962   2a3a2 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc5.allyesconfig.new
142671   29702    1216 173589   2a615 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc5.allyesconfig.old
51733    1156       0   52889    ce99 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc5.defconfig.new
51813    1156       0   52969    cee9 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc5.defconfig.old
152991   29790    1216 183997   2cebd drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc6.allyesconfig.new
153722   29702    1216 184640   2d140 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc6.allyesconfig.old
51813    1156       0   52969    cee9 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc6.defconfig.new
51893    1156       0   53049    cf39 drivers/net/wireless/intel/iwlegacy/4965-mac.o.gcc6.defconfig.old