linux-kernel - Re: huge gcc 4.1.{0,1} _

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Message-ID: <20080501233038.GA20601@linux-os.sc.intel.com>
Date:	Thu, 1 May 2008 16:30:39 -0700
From:	Venki Pallipadi <venkatesh.pallipadi@...el.com>
To:	Tom Rini <trini@...nel.crashing.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Venki Pallipadi <venkatesh.pallipadi@...el.com>,
	torvalds@...ux-foundation.org, bunk@...nel.org,
	davem@...emloft.net, mingo@...e.hu, tglx@...utronix.de,
	hpa@...or.com, linux-kernel@...r.kernel.org,
	suresh.b.siddha@...el.com
Subject: Re: huge gcc 4.1.{0,1} __weak problem

On Thu, May 01, 2008 at 04:21:16PM -0700, Tom Rini wrote:
> On Thu, May 01, 2008 at 03:42:38PM -0700, Andrew Morton wrote:
> 
> [snip]
> > Is there some vaguely maintainable workaround we can do?  If the problem
> > only affects completely-empty weak functions then we could put something in
> > them to make them non-empty?
> 
> My memory is a tiny bit hazy (it was a while ago), but no, it's not just
> empty functions (again, I _think_ I hit it with a generic vs arch weak
> function).
> 

Other thing we observed was: this does not just depend on the __weak
function definition. It also depends on where the function is called from.

__weak function with single return statement, did not get inlined when called
from say

caller()
{
	function();
}

but got inlined when called as in

caller()
{
	for (;;) {
		function();
	}
}

Thanks,
Venki

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