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d514ee9282
Cuts realtime decode on the Sansa e200v1 from 52.1 MHz to 50.8 MHz. clt_mdct_backward was the largest remaining item at 13.5% of decode. Only the three inner loops move to assembly. The setup stays in C, so mdct.c remains readable and the assembly needs no knowledge of mdct_lookup. What the compiled loops lose is registers. Each needs more live values than gcc can hold, so it spills the loop-invariant pointers, strides and limits and reloads them every pass: five stack accesses per iteration in the post-rotation alone. Holding the twiddle as a 16-bit value and accumulating the product pair with smull/smlal is what makes the bookkeeping fit, needing seven live registers where the shifted MULT16_32_Q15 form needs nine. ldm/stm helps only where the addressing allows. The post-rotation walks the buffer from both ends and so reads and writes contiguous pairs. The pre-rotation reads the spectrum through a runtime stride and writes through the bitrev table, so only its 8-byte output pair merges, and the TDAC mirror merges nothing. Over 160 ms of stereo music, traced under qemu: clt_mdct_backward 1,037,962 -> 900,982 -13.2% whole decode 7,695,876 -> 7,558,896 -1.8% loads 650,157 -> 611,667 -5.9% stores 350,605 -> 323,605 -7.7% multiplies 337,493 -> 337,493 unchanged Accuracy improves substantially, because all three loops keep 32 bits of each Q15 product where MULT16_32_Q15_armv4 drops the low bit, and the backward MDCT applies three such rounds per sample. The rounding SNR of the backward transform rises about 9.5 dB, and its worst case error falls from 708 to 186. Decoded output differs from the previous build in 90 of 15,360 samples, each by one LSB. Build with OPUS_ARM_NO_MDCT_ASM to select the C loops instead. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Change-Id: I3c4404b4dbe581d8bcf1f357266a658a068fdb50 |
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| android | ||
| apps | ||
| backdrops | ||
| bootloader | ||
| docs | ||
| firmware | ||
| fonts | ||
| icons | ||
| lib | ||
| manual | ||
| packaging | ||
| tools | ||
| uisimulator | ||
| utils | ||
| wps | ||
| .gitattributes | ||
| .gitignore | ||
| .gitreview | ||
__________ __ ___.
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!