Thumb2 code size improvements

Michael Hope michael.hope at linaro.org
Sun Sep 19 21:40:22 BST 2010


On Sat, Sep 18, 2010 at 3:00 AM, Dave Martin <dave.martin at linaro.org> wrote:
> Hi,
>
> On Fri, Sep 17, 2010 at 3:50 AM, Michael Hope <michael.hope at linaro.org> wrote:
>> It's only part of the puzzle, but I run speed benchmarks as part of
>> the continious build:
>>  http://ex.seabright.co.nz/helpers/buildlog
>>  http://ex.seabright.co.nz/helpers/benchcompare
>>  http://ex.seabright.co.nz/build/gcc-linaro-4.5-2010.09-1/logs/armv7l-maverick-cbuild4-pavo4/pybench-test.txt
>>
>> I've just modified this to build different variants as well.  ffmpeg
>> now builds as supplied (-O2 and others), with -Os, with hand-written
>> assembler turned off, and with -mfpu=neon.  corebench builds in -O2
>> and -Os.
>>
>> This might be one way to approach things.  It's simple to add other
>> programs into the mix.
>
> Could you easily add code size metrics?

The build currently runs 'size' on every executable file it can find.  See:
 http://ex.seabright.co.nz/build/gcc-linaro-4.5-2010.09-1/logs/armv7l-maverick-cbuild4-pavo4/benchnt-test.txt

for an example.

> It would be useful to watch those for regressions also, especially if
> there's an ongoing effort to make -Os better.

Yip.  I'm recording at the moment and hope to hand the reporting side
off to the Infrastructure team.

> It would be good to have more system-oriented metrics as well, such as
> boot, login and app launch times, and cache and TLB performance.
> Results of microbenchmarks can be quite misleading when it comes to
> the performance of the system as a whole.  I'm not sure the best way
> to approach that--- many variables affect performance, and you'd need
> to build many packages to get a system to benchmark.  It might be
> overkill; the toolchain can definitely influence these such metrics,
> but it may become a less-dominant factor once you're studying a large
> enough blob of software.

It's not wholly a toolchain issue but one I'm interested in.
Something we should talk about at Linaro at UDS...

-- Michael



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