[Bug target/61578] [4.9 regression] Code size increase for ARM thumb compared to 4.8.x when compiling with -Os

[vmakarov at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61578

--- Comment #24 from Vladimir Makarov <vmakarov at gcc dot gnu.org> ---
(In reply to Fredrik Hederstierna from comment #23)
> Thanks for your patch, I tried it out, and it solves the small example fine,
> the code now is similar to GCC 4.8 for this particular example.
> 
> Though when I ran the full CSiBE benchmark, the code size unfortunately grew
> approx +150 bytes overall for the full suite. So the patch did not solve the
> generic root problem with code size increase unfortunately.
> 
> This is strange and I'm thinking of how to continue from here, this issue
> has diverged a bit too much (mostly because of my own fault) with several
> examples etc. Do you think we should create separate issues for different
> small examples that compiles bad perhaps? but on the same time we need to
> keep track on the 'generic' overall code size issue as eg. CSiBE points out.
> 

Either way will work for me.  The most important is to have test cases
somewhere in Bigzilla on which I could work.

I did not expect that the patch solves CSiBE code size degradation.  Therefore
I wrote "a patch for" instead of "patch solving the problem".

I expect it will be a long work to solve the problem.

> Here's is another small example I tested yesterday that also gives
> unnecessary moves, both for arm7tdmi, arm966e-s and cortex-m0 tested.
> 

Thanks.  I'll will investigate it.