http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0068b/CIHBJEHG.html
 says that "Rd cannot be the same as Rm."
http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.dui0068b/CIHBJEHG.html
 says that "RdLo, RdHi, and Rm must all be different registers."
This means that some of the early clobbers I removed really should
 have been there (to prevent aliasing Rd, RdLo, or RdHi with Rm).
It also means that we should reverse some of the operands in the
 FFT's complex multiplies.
This should only affect the ARMv4 optimizations.

Thanks to Nils Wallménius for the report.

While we're here, audit the commutative pair flags again, since I
 screwed up at least one of them, and eliminate some dead code.

Original patch by Aurélien Zanelli <aurelien.zanelli@parrot.com>:
 http://lists.xiph.org/pipermail/opus/2013-May/002078.html

Revised version:
- Add autconf detection (ported from libtheora).
- Rename ARM5E to ARMv5E (an ARM5 is not the same thing as ARMv5!).
- Use actual macros so they can still be selectively overridden.
- Split out ARMv4 parts and add a few more ARMv4 macros.
- Label blocks to make them easy to find in generated assembly.
- Fix MULT16_32_Q15() so we can pass make check.
  The MDCT test passes in values larger than 2**30 for b.
  The new version should be just as fast (or faster, since it's
   easier to merge the shift with following instructions), and
   there's no appreciable impact on accuracy (FFT/MDCT SNR actually
   goes up in most cases).
- Fix register constraints.
  We were using early-clobber flags in a bunch of places that
   didn't need them, and commutative-pair flags in a bunch of
   places that weren't actually commutative.
  This was Jean-Marc's fault (the original code came from Speex).
- Simplify silk_CLZ16().
- Port over iFFT C_MULC asm by Andree Buschmann
   <AndreeBuschmann@t-online.de> from Rockbox.
- Speed up the C_MULC asm by using LDRD, allowing more flexible
   addressing, re-ordering instructions to avoid some stalls,
   allowing more flexible register allocation, and getting things
   out of the inline asm block so the compiler can schedule them
   better.
- Add C_MUL and C_MUL4 asm for the FFT to the encoder based, on the
   new C_MULC.

In total, this patch gives a 22.3% speed-up on test_opus_encoder on
 a 600 MHz Cortex A8 using gcc 4.2.1,
When restricted to ARMv4 optimizations, it gives a 9.6% speed-up
 on the same processor/compiler.
On the conformance test vectors:
 Average mono quality is 97.0583 %
 Average stereo quality is 97.775 %

This reverts commit 9f407afa.

Also reformat some, but by no means all, of the opus
code for line length and three-character indents.

Gregory Maxwell authored 13 years ago and Jean-Marc Valin committed 13 years ago

non-ascii characters from the source.

Got authorization from all copyright holders

by POSIX. The other _t types that are not part of the API are still there
for now. Also, got rid of all that was left of the 64-bit types.

This involved adding kfft_single.[ch] that redefines kiss_fft a second time
with a different prefix. All this is still a bit of a mess now. The mask
had to be converted to 16-bit input, but we're still using floats to apply it.

float)

different precision for twiddles and data.

"inverse" flag from the state so it can be shared between the forward and
inverse transforms.