[HOWTO] Intel C++ Compiler and per-package CFLAGS

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

I've rewritten Gentoo-Wiki's HOWTO on using the Intel C++ Compiler.

http://gentoo-wiki.com/HOWTO_Intel_C_Compiler

The old guide was terribly written and horribly messy.

It also made Portage compile with icc unless you explicitly told it to use gcc. This is bad. Far too many packages don't work with icc to use this behavior. My guide makes Portage compile only specified packages with icc and all others with gcc which will save a few headaches in the long run. It also will give your system the ability to use per-package CFLAGS for gcc and icc!

Need feedback on the guide. Suggestions are welcome.

Etal · Veteran Joined: 15 Jul 2005 Posts: 1932

Thanks, that looks interesting.

Is the change in performance noticeable, though? For example, if I bzip an archive or encode a video in x264, how much faster would it be than if I use gcc 4.1 on a Core2 processor?
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mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

easy target · Tux's lil' helper Joined: 09 Jan 2008 Posts: 134

deno · Guru Joined: 13 Sep 2006 Posts: 411

Here faac fails with error:

paluszak · Posted: Mon Feb 18, 2008 5:08 pm Post subject:

I have just compiled x11-themes/qtcurve, x11-themes/gtk-engines-curve and app-mobilephone/obex-data-server, they all seem to work fine. Is there a place where we could make a list of packages that compile fine with ICC?

Another thing is that it pays to read the ICC docs, there are some optimization options that could be considered, for instance, my flags on Pentium4 look like this:

deno · Guru Joined: 13 Sep 2006 Posts: 411

I have just compiled firefox, but it wont run. I get:

deno · Guru Joined: 13 Sep 2006 Posts: 411

my specs: core due t 2250, icc version 10.1

e17 (everything below) and all modules build fine

from other apps i compiled those also build and run fine:

all these are ~x86 at the moment.

edit:

I am writing this with firefox beta 3

compiled with -xP -Os -gcc-version=420 -ipo -fomit-frame-pointer -parallel.

deno · Guru Joined: 13 Sep 2006 Posts: 411

@paluszak

From icc man page:

paluszak · Posted: Wed Feb 20, 2008 8:24 am Post subject:

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

scronkey · n00b Joined: 19 Jan 2004 Posts: 31

Good effort on your clean and well written HOWTO.

I installed icc a little while ago, not using portage though. I've just been experimenting with it but I was wondering if the set up described in your article could still be used, without me re-installing the compiler through portage.

From the looks of it I'd say it would work but I'm not sure whether the /etc/portage/bashrc file and the ICCCFLAGS would still be adhered to by portage. I really like the clean separation of what is compiled with what and I want to get Python compiled with icc but considering how central Python is to Gentoo I don't want to go in blindly (Been there before. You're not really a Gentoo until you've borked your Python install!).

Any tips or caveats you're aware of? Is the /etc/portage/bashrc used for other parts of portage or is it something you've implemented?

deno · Guru Joined: 13 Sep 2006 Posts: 411

@|mattst88|

Thanks for your replay. Have just compiled libtheora, but faac still fails. I have experimented with flags and it always fails. I have tried:

edit:

faac compiles with 'media-libs/faac -mtune=pentium4 -O2 -gcc-version=420'. the same is a must here for libvorbis.

deno · Guru Joined: 13 Sep 2006 Posts: 411

splashutils now fails (with gcc-4.2.3, probably because of freetype been compiled with icc) error:

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

deno,

I experienced this also. My solution was to compile libpng with gcc. Alternatively, compile freetype, libpng, and splashutils with gcc, and following, recompile libpng and freetype with icc. That's a bit of a headache though.

kaethorn · Posted: Thu Mar 06, 2008 6:50 pm Post subject:

Hello everyone and thanks for the HOWTO. I've followed the steps mentioned and it seems to work fine for app-arch/bzip2, but that's about it. As soon as I try any package which includes limits.h, compilation fails:

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

I experienced this problem for the first time today on my laptop. I can compile the same ebuild on my server with no problems.

I'll investigate and see if I can find a solution.

kaethorn · Posted: Sun Mar 09, 2008 3:21 pm Post subject:

OK, I found out how to get around the error. I've recently compiled gcc-4.3 (4.3.0-pre20080302 to be precise) from the dirtyepic overlay and set it as the default compiler. Setting it back to 4.2.3 did the trick:

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

This is odd.

My laptop cannot compile php which includes limits.h with icc. I'm using gcc-4.2.3 (no multislot), icc-10.1.012. No other versions of either compiler are installed.

My server can compile php with icc. Here, I'm using gcc-4.1.2 (no multislot), and icc-10.1.012. No other versions of either compiler are installed.

What could be going on?

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423

It appears to me that AMD64 systems are effected by the limits.h mess. My Core 2 Duo laptop, my AMD64 Sempron desktop, and your AMD64 box exhibit this behaviour while my 32-bit x86 server does not.

richardpku · n00b Joined: 18 May 2008 Posts: 1

Add '-fno-builtin' to CFLAGS and they will compile.

Probably it's a bug of ICC. I have also encountered packages that don't compile unless ipo is disabled.

deno · Guru Joined: 13 Sep 2006 Posts: 411

You meant ICCCFLAGS, thanks for reply, I'll try it.

AzraelNewtype · n00b Joined: 07 May 2007 Posts: 22

I'm having a particularly bizarre problem with icc since installing using the wiki. Occasionally, programs not listed in /etc/portage/package.icc are getting compiled with icc, sometimes only certain lines of the make process. What's worse though is that it isn't picking up the ICCCFLAGS with the change of compiler, so these compilations break as soon as the switch happens. The last one I noticed it with is subversion, but the error is a little burried so I'll show the output of samba instead:

deno · Guru Joined: 13 Sep 2006 Posts: 411

Yup. It's because of python. I have recompiled it with gcc and subversion compiled then.

mattst88 · Developer Joined: 28 Oct 2004 Posts: 423