On 2011/1/25 04:22, Wolfgang Denk wrote:

Hello,

could you please provide some comments about the state of "-Os" (optimising for size) in the gcc 4.5.x versions of Linaro's tool chain?

It appears there are a number of issues with recent versions of GCC that get triggered when optimising for size, for example

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45052

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44392

Some other projects like the Linux Foundation driven Poky (resp. Yocto project) capitulated and stopped using -Os, see for example here: http://thread.gmane.org/gmane.linux.embedded.poky/2311/focus=2565

On the other hand, I can see that Linaro even adds improvements for "-Os", see for example here: http://thread.gmane.org/gmane.linux.linaro.toolchain/367

So I wonder what the state of these problems with "-Os" is in the Linaro tool chain? Have these issues been solved, and is "-Os" reliably working with the Linaro tool chain?

Well, a check of the ChangeLogs show that PR45052 should be fixed on the upstream 4.5 branch, which Linaro 4.5 has updated past by now.

PR44392 is fixed on trunk, though not backported to 4.5 yet. Ramana, I see this was fixed by you upstream, care to backport this? (maybe on upstream gcc-4_5-branch too)

Do you have any more specific cases/PRs, or is this all that's on your current list?

Thanks, Chung-Lin

On Tue, Jan 25, 2011 at 9:22 AM, Wolfgang Denk wd@denx.de wrote:

Hello,

could you please provide some comments about the state of "-Os" (optimising for size) in the gcc 4.5.x versions of Linaro's tool chain?

It appears there are a number of issues with recent versions of GCC that get triggered when optimising for size, for example

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=45052

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=44392

Some other projects like the Linux Foundation driven Poky (resp. Yocto project) capitulated and stopped using -Os, see for example here: http://thread.gmane.org/gmane.linux.embedded.poky/2311/focus=2565

On the other hand, I can see that Linaro even adds improvements for "-Os", see for example here: http://thread.gmane.org/gmane.linux.linaro.toolchain/367

So I wonder what the state of these problems with "-Os" is in the Linaro tool chain?  Have these issues been solved, and is "-Os" reliably working with the Linaro tool chain?

Hi Wolfgang. Linaro is an ARM performance branch of GCC so we aren't making improvements or actively fixing issues at -Os. We should be no worse than upstream for correctness and comparable in the final object size, and will fix any regressions that we introduce. Apart from that I'd recommend talking with the larger ARM community upstream.

-- Michael