GCC update increased the file size by 4x on PowerPC port

[Felipe Gohring]

Thanks for the replies.


On Mon, Jan 7, 2019 at 12:23 PM Segher Boessenkool <
segher@kernel.crashing.org> wrote:

> Hi,
>
> On Mon, Jan 07, 2019 at 11:14:12AM -0500, Felipe Gohring wrote:
> > Now, my question is related to the generated code. When using V6.3, I had
> > files of about 10k. After upgrading to V8.2, the very same file has more
> > than 40k. Why is that? Please keep in mind that I am using exactly the
> same
> > compilation flags (*-m32 -mmfpgpr -mabi=spe -mfloat-gprs=double -nostdlib
> > -ffreestanding -fno-builtin -O0 -g3 -std=c11 -Wno-packed-bitfield-compat
> > -Wall -Werror*) and source code, the only thing changing is the compiler
> > version. I wouldn't mind having a memory footprint a bit bigger, but the
> > overhead added is beyond acceptable.
>
> If you care about code size, you want -O1 or -Os, not -O0.
>
> I don't, I was just surprised! But indeed, the difference was mostly due
to -g3 flag. Without debug flags the size is almos (>5%) the same.


> And why are you using -mmfpgpr?  That option doesn't do anything for
> anything
> targetting SPE, but for some reason many people use it?
>
> I assumed it was needed, in order for SPE to use the general purpose
registers properly. removed them.


> > Further, besides the crazy sizes, some applications are breaking when
> using
> > the updated compiler version, even though I am not having any warning
> > neither error (*-Wall -Werror)*. How come, as the ABI should not be
> broken
> > even with a different compiler version?
>
> Use -Wall -Wextra instead...  But your code may be doing many more things
> wrong than those warnings can detect.  You could try -fno-strict-aliasing
> for example.
>
> Using -Wall -Wextra a few new warnings were found and I have corrected
them already. Still, even with -fno-strict-aliasing applications do not
work with the new compiler version

>
> Segher
>


-- 
Felipe GM