[PATCH] sparc all BSPs: Use function and data sections

[Chris Johns]

On 26/10/2013 1:28 am, Joel Sherrill wrote:
>
> I would love to do this across all BSPs but it can also
> break a BSP. The first SPARC executables I got were 0x80
> bytes because I was missing some KEEP() and ENTRY() directives
> in the linker script.
>
> In addition, this isn't a big deal on many BSPs. I would
> love to see it used on low memory BSPs. IMO it should be
> universal on the ARM given that many of them are low memory
> and we already have shared linker scripts.
>

Do you have any metrics on the link time on large code bases ? I assume this approach places extra pressure on linker because the number of sections it needs to manage increases.

The RSB has an option --targetcflags which lets you supply flags like the ones you have added so I decided to see what it did. I am surprised by the results.

This is the size output for the samples using the current git master with your patch built with gcc-4.8.2 and newlib-18-Oct-2013 [1]:

   ../source-builder/sb-set-builder --log=log_sparc --prefix=/Users/chris/development/rtems/4.11 \
        --trace 4.11/rtems-sparc

chris at huia sis $ arm-rtems4.11-size $(find . -name \*.exe)
   text    data     bss     dec     hex filename
  93344    1648    4336   99328   18400 ./sparc-rtems4.11/c/sis/testsuites/samples/base_sp/base_sp.exe
 196480    2112    6160  204752   31fd0 ./sparc-rtems4.11/c/sis/testsuites/samples/capture/capture.exe
 193504    2176   20896  216576   34e00 ./sparc-rtems4.11/c/sis/testsuites/samples/cdtest/cdtest.exe
 466848    5184   15280  487312   76f90 ./sparc-rtems4.11/c/sis/testsuites/samples/fileio/fileio.exe
  69632    1440    4000   75072   12540 ./sparc-rtems4.11/c/sis/testsuites/samples/hello/hello.exe
 396944    6336   26576  429856   68f20 ./sparc-rtems4.11/c/sis/testsuites/samples/iostream/cxx_iostream.exe
 260752    6080    8752  275584   43480 ./sparc-rtems4.11/c/sis/testsuites/samples/loopback/loopback.exe
  36544    1056    3552   41152    a0c0 ./sparc-rtems4.11/c/sis/testsuites/samples/minimum/minimum.exe
 103120    1712    4368  109200   1aa90 ./sparc-rtems4.11/c/sis/testsuites/samples/nsecs/nsecs.exe
 161264    1984    4992  168240   29130 ./sparc-rtems4.11/c/sis/testsuites/samples/paranoia/paranoia.exe
 420160   12112   36112  468384   725a0 ./sparc-rtems4.11/c/sis/testsuites/samples/pppd/pppd.exe
  98368    1712    4368  104448   19800 ./sparc-rtems4.11/c/sis/testsuites/samples/ticker/ticker.exe
  94864    1584    7840  104288   19760 ./sparc-rtems4.11/c/sis/testsuites/samples/unlimited/unlimited.exe

And here are the results with the gcc runtime and newlib built with the extra flags. The executables are larger.

  ../source-builder/sb-set-builder --log=log_sparc --prefix=/Users/chris/development/rtems/4.11 \
        --targetcflags="-ffunction-sections -fdata-sections" --trace 4.11/rtems-sparc

chris at huia sis $ arm-rtems4.11-size $(find . -name \*.exe)
   text    data     bss     dec     hex filename
  99472    1616    4336  105424   19bd0 ./sparc-rtems4.11/c/sis/testsuites/samples/base_sp/base_sp.exe
 210400    2080    6160  218640   35610 ./sparc-rtems4.11/c/sis/testsuites/samples/capture/capture.exe
 217280    2144   20896  240320   3aac0 ./sparc-rtems4.11/c/sis/testsuites/samples/cdtest/cdtest.exe
 522176    5136   15248  542560   84760 ./sparc-rtems4.11/c/sis/testsuites/samples/fileio/fileio.exe
  72992    1456    4000   78448   13270 ./sparc-rtems4.11/c/sis/testsuites/samples/hello/hello.exe
 455184    6304   26560  488048   77270 ./sparc-rtems4.11/c/sis/testsuites/samples/iostream/cxx_iostream.exe
 270368    6048    8752  285168   459f0 ./sparc-rtems4.11/c/sis/testsuites/samples/loopback/loopback.exe
  37152    1056    3552   41760    a320 ./sparc-rtems4.11/c/sis/testsuites/samples/minimum/minimum.exe
 113952    1680    4368  120000   1d4c0 ./sparc-rtems4.11/c/sis/testsuites/samples/nsecs/nsecs.exe
 176752    1952    4992  183696   2cd90 ./sparc-rtems4.11/c/sis/testsuites/samples/paranoia/paranoia.exe
 445696   12080   36096  493872   78930 ./sparc-rtems4.11/c/sis/testsuites/samples/pppd/pppd.exe
 106608    1680    4368  112656   1b810 ./sparc-rtems4.11/c/sis/testsuites/samples/ticker/ticker.exe
 100800    1552    7840  110192   1ae70 ./sparc-rtems4.11/c/sis/testsuites/samples/unlimited/unlimited.exe

I have not looked into why and do not have the time. I feel extending this to other BSPs will require more investigation.

Note, the sparc stdc++ libraries are built with these flags by default.

Chris

[1] All tools built on MacOS 10.9 (Maverick) using clang (linked gcc).