Re: [gentoo-user] world rebuild with gcc-6.3.0 - not completely there yet

[Rasmus Thomsen]

Hi,

unwind tables sounds really interesting, but does it affect the binary size when I compile with -O2 anyway?

Regards,
Rasmus

-------- Original Message --------
On 14 May 2017, 07:13, Walter Dnes wrote:
On Sat, May 13, 2017 at 10:21:19AM +0200, Helmut Jarausch wrote
>
> I have switched to gcc-6.3.0 at the end of last year.
> I have (re-)compiled all my packages including icewm-1.3.12-r1.
> Everything works just fine.
>
> I did have some segfaults (with gimp) until I recompiled each package
> with gcc-6.3.0
>
> I have
> CFLAGS="-mtune=native -O2 -msse3 -pipe -fPIC"
>
> in /etc/portage/make.conf

Why aren't you running "-march=native"? You're probably missing quite
a few features of your cpu. BTW, "-march=native" implies "-mtune=native"
and "-msse3" (if the cpu supports it). Out of sheer curiousity, what
does gcc report as your native cpu when you run...

gcc -c -Q -march=native --help=target | grep march=

> and quite a e few
> CFLAGS="-O3 -mtune=native -pipe -msse -msse2 -msse3 -msse4a -m3dnow"
> (for my aged AMD64 Phenom II machine)
>
> in /etc/portage/env/...

"-O3"... yikes! Not really recommended. If you want speedup, use
"-march=native" instead.

In make.conf, I have...

CFLAGS="-O2 -march=native -mfpmath=sse -fomit-frame-pointer -pipe -fno-unwind-tables -fno-asynchronous-unwind-tables"

The 2 "unwind_tables" flags reduce code bloat. See
http://comments.gmane.org/gmane.linux.busybox/36695 for details. The
guys at busybox do what they can to reduce code bloat. Knocking 15% off
the size of an executable or library helps. This results in faster
loading at startup (less to load), and less stuff in ram cuts down on
swapping.

--
Walter Dnes <waltdnes@××××××××.org>
I don't run "desktop environments"; I run useful applications