[tremor] Tremor on strongarm CPU

[Nicolas Pitre]

On Mon, 9 Sep 2002, dilb wrote:

> On Monday 9 September 2002 18:25, Nicolas Pitre wrote:
> 
> > If applying the same set of compiler flags to Tremor that I used in my own
> > version, I also get that 5% or more improvement as well.  Would you mind
> > posting your assembly version (or making it available somewhere if too big)
> > and I could compare the performance gain as well?
> I did play with compiler flags too, and so far, my best combination is:
> CFLAGS = -O2 -D_ARM_ASSEM_ -fsigned-char  -D_REENTRANT -ffast-math 
> -mcpu=strongarm1100 -fomit-frame-pointer -fthread-jumps  -fregmove 
> -DUSE_MEMORY_H
> when using gcc 2.95.4

You should try the following:

CFLAGS=	-O1 -fforce-mem -fforce-addr -fthread-jumps -fcse-follow-jumps \
        -fcse-skip-blocks -fexpensive-optimizations -fregmove \
        -fschedule-insns2 -finline-functions -fsigned-char \
        -fomit-frame-pointer -march=armv4 -mtune=strongarm \
        -D_ARM_ASSEM_ -D_REENTRANT -DUSE_MEMORY_H

Surprisingly, using -O1 with the above specific optimization flags produces
better code and performances than with -O2.  I bet that the 5% gain from
your own assembly mdct will then vanish.  Please confirm if this is the
case.

> > So far, inspecting the generated assembly from a recent gcc (currently
> > testing with gcc 3.2), the compiler is increasingly doing a pretty good job
> > out of plain C code.  It just looks like writing assembly code is less
> > worth it than it was before.
> did you compile as a cross-compiler ? If so, is the pakage available 
> somewhere ?

No, built it from source myself.

> Do you know if profiling is working on this version ?

Never used gproff on that version yet, only inspected the generated 
assembly.

<p>Nicolas

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