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Michael Giacomelli 5d8ce62b45 codecs: link libarm_support for its division routines 
lib/arm_support/support-arm.S was written to replace libgcc's
division for ARM, and bff5a35c3c (FS#10943, 2010) added it to the
core, the plugin library and the codec library alike.  When
1501df045f (2013) replaced EXTRA_LIBS with explicit lists, plugins
kept it and codecs did not, and they have taken their division from
libgcc since.

With the gcc 4.4 toolchain that cost little: its libgcc had a
routine that used clz.  With gcc 9.5 libgcc has no soft-float ARMv5
variant, so ARMv5 targets get the ARMv4 routine, a shift and
subtract loop of about 130 cycles a division.

Monkey's Audio divides two or three times a sample in its range
decoder and, without codec IRAM, does it in C.  On a Clip+ it is
11% to 21% slower than 3.14 was, with over half of -c1000's decode
in __udivsi3.  MP2 is 4% to 7% slower.

Put libarm_support back, ahead of libgcc.  In perfsim's model of
the Clip+ a division falls to 44 cycles, Monkey's Audio by 38%, 30%
and 22% at -c1000, -c2000 and -c3000 (60.9 to 37.9 MHz at -c1000),
and MP2 by 3% to 7%; nothing else moves by more than 0.6%.  A Clip+
decodes -c1000 with the same checksum as before.

A division by zero in a codec goes to __div0 again, and so to the
firmware's handler, as it did with support-arm.S and with the old
libgcc (3.14's ape.codec calls it).  The gcc 9.5 libgcc returns
from its own stub instead.

Change-Id: I6a9a79ce8e85bca69870349a5c0823f392a578b6
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
2026-10-05 07:46:37 -04:00
android chore: Get rid of *all* vestigal CVS '$Id:$' tags 2026-06-01 16:01:18 -04:00
apps radio: redraw the FM screen after the autoscan question 2026-10-05 10:03:20 +02:00
backdrops ap80max: New hosted port 2026-08-13 17:55:06 -07:00
bootloader h1x0/h3x0: Get rid of redundant cut-down bidi_l2v() function 2026-09-29 10:16:26 -04:00
docs docs: Fix case of "iPod" in area name and history 2026-10-01 17:32:24 -04:00
firmware YP-CP3: simulator 2026-10-02 16:42:34 +02:00
fonts chore: Get rid of *all* vestigal CVS '$Id:$' tags 2026-06-01 16:01:18 -04:00
icons chore: Get rid of *all* vestigal CVS '$Id:$' tags 2026-06-01 16:01:18 -04:00
lib codecs: link libarm_support for its division routines 2026-10-05 07:46:37 -04:00
manual manual: Fix case of "iPod" 2026-09-30 07:58:19 -04:00
packaging 3ds: Port refactor. 2026-09-01 08:39:07 -04:00
tools buildzip: install wps/ subfolders with a dot in their name 2026-10-05 10:03:20 +02:00
uisimulator YP-CP3: simulator 2026-10-02 16:42:34 +02:00
utils Fix case of "iPod" in docs and CLI tools help 2026-10-01 17:32:24 -04:00
wps cabbiev2: 400x240 FM screen, sharing the WPS backdrop 2026-10-05 10:03:20 +02:00
.gitattributes Add a gitattributes file for the migration. 2011-12-01 14:14:59 +00:00
.gitignore misc: Update gitignore to cover a bunch of utils/* binaries 2026-06-17 13:56:29 -04:00
.gitreview misc: Add a .gitreview file for better gerrit integration 2021-06-24 07:22:19 -04:00

docs/README 

               __________               __   ___.
     Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
     Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
     Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
     Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
                       \/            \/     \/    \/            \/

Build Your Own Rockbox

1. Clone 'rockbox' from git (or extract a downloaded archive).

   $ git clone git://git.rockbox.org/rockbox

     or

   $ tar xJf rockbox.tar.xz

2. Create a build directory, preferably in the same directory as the firmware/
   and apps/ directories. This is where all generated files will be written.

   $ cd rockbox
   $ mkdir build
   $ cd build

3. Make sure you have mips/m68k/arm-elf-gcc and siblings in the PATH. Make sure
   that you have 'perl' in your PATH too. Your gcc cross compiler needs to be
   a particular version depending on what player you are compiling for. These
   can be generated using the rockboxdev.sh script in the /tools/ folder of the
   source.

   $ which arm-elf-eabi-gcc
   $ which perl

4. In your build directory, run the 'tools/configure' script and enter what
   target you want to build for and if you want a debug version or not (and a
   few more questions). It'll prompt you. The debug version is for making a
   gdb version out of it. It is only useful if you run gdb towards your target
   Archos.

   $ ../tools/configure

5. *ploink*. Now you have got a Makefile generated for you.

6. Run 'make' and soon the necessary pieces from the firmware and the apps
   directories have been compiled, linked and scrambled for you.

   $ make
   $ make zip

7. unzip the rockbox.zip on your music player, reboot it and
   *smile*.

If you want to build for more than one target, just create several build
directories and create a setup for each target:

   $ mkdir build-fuzeplus
   $ cd build-fuzeplus
   $ ../tools/configure

   $ mkdir build-xduoox3
   $ cd build-xduoox3
   $ ../tools/configure

Questions anyone? Ask on the mailing list or on IRC. We'll be happy to help you!