From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jamie Lokier <lk@tantalophile.demon.co.uk>
To: gcc@gcc.gnu.org, Linus Torvalds <torvalds@transmeta.com>
Cc: Andrew Morton <akpm@zip.com.au>, Alan Cox <alan@lxorguk.ukuu.org.uk>, lkml <linux-kernel@vger.kernel.org>
Subject: GCC still keeps empty loops?  (was: [patch 4/21] fix ARCH_HAS_PREFETCH)
Date: Sun, 11 Aug 2002 13:07:00 -0000
Message-id: <20020811210718.B3206@kushida.apsleyroad.org>
References: <3D56B13A.D3F741D1@zip.com.au> <Pine.LNX.4.44.0208111203520.9930-100000@home.transmeta.com>
X-SW-Source: 2002-08/msg00637.html

Linus Torvalds wrote:
> I thought that special case was removed long ago, because it is untenable 
> in C++ etc (where such empty loops happen due to various abstraction 
> issues, and not optimizing them away is just silly).
> 
> But testing shows that you're right at least for 2.95 and 2.96. Argh

Unbelievably, 3.1 doesn't remove empty loops either.
I think there's a case for a compiler flag, `-fremove-empty-loops'.

Empty loop delays aren't portable acrosss compilers in general.  If you
_really_ want an empty loop that must always work with GCC, it's easy
enough to write:

	for (i = 0; i < 100000; i++)
		__asm__ __volatile__ ("");

-- Jamie