linux-kernel - Re: [Bug 8501] udivdi3 absence with gcc-4.3.0 on kernels 2.6.20.11 & 2.6.22.-rc1

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Date:	Sat, 19 May 2007 01:12:23 +0200
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	"bugme-daemon@...nel-bugs.osdl.org" 
	<bugme-daemon@...zilla.kernel.org>, linux-kernel@...r.kernel.org,
	malitzke@...ronets.com,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [Bug 8501] udivdi3  absence with gcc-4.3.0 on kernels
	2.6.20.11 & 2.6.22.-rc1

On Fri, 2007-05-18 at 15:29 -0700, Andrew Morton wrote:
> We use the above idiom in several places.  A suitable fix might be to hunt
> down those various sites and then make them call a helper function which
> does
> 
> 	if (unlikely(ns >= NSEC_PER_SEC)) {
> 		do_div(...)
> 	}
> 
> (Better would be to inline the comparison and to uninline the do_div(),
> if it's a 32-bit arch.  Doing all this in a backportable fashion may
> prove tricky)

A suitable fix would be to slap the gcc maintainers with a large trout
to fix this nonsense. At least they should provide a command line option
to prevent this extra intelligent optimization.

	tglx


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